This review details the challenges with the canonical polymer swelling theory in its ability to accurately estimate realistic polymer swelling behavior. It is important to quantify this behavior since the development of new and hybrid materials with dynamic environmental response is expected to drive rapid growth and innovation in markets including biomedicine, electronics, pharmaceuticals, building and infrastructure, and aerospace. As many of these markets require high precision and controlled dynamic response, hydrogels are being investigated to help address some of the heat transfer and fluid flow challenges found in these applications. Stimuli-responsive materials usually respond to one stimulus (e.g., light, temperature, etc.) However, hybrid polymer materials that respond to multiple stimuli can be developed through the mixing of monomer chains with differing behaviors. For these materials, the synthesis conditions influence the polymer behavior in changing environmental conditions, and it is imperative to develop a deeper understanding of how the preparation of the polymer networks impacts the viscoelastic nature of the polymer. The work also discusses the influence that synthesis conditions have on the behavior of thermo-responsive Poly(N-isopropylacrylamide) (PNIPAAm). Lastly, the paper describes an inferential, nested regression model developed to highlight the dependence the swelling has on the synthesis technique used.

Stretchable and tough hydrogels have attracted a lot of attention due to their great potential in applications such as wound healing, drug delivery, tissue culture, etc. They can also be paired with electronic components to create artificial skin, wearable electronics, and patches. To promote the development of more hydrogels, we will summarize methods and materials that have been used to develop these gels, and then we will compare the performance of these gels in an aim to guide the future development of gels for superior performance, especially for specific applications.

In this paper we review the literature on electrospinning of porous fibers of micron and nanoscale diameters. Selection of an appropriate polymer-solvent system can yield porous fibers due to phase separation, and different types of porosity are generated by different phase separation mechanisms. In comparison with porous polymeric fibers, production of porous inorganic fibers is much more complex: small molecules or atoms cannot be directly electrospun into continuous fibers and so polymer precursors are required and subsequently removed. Inorganic porous fibers can be generated based on a range of materials: carbon, silica and numerous metal oxides and mixed metal oxides. Some of the many applications of electrospun porous fibers are discussed: applications ranging from tissue engineering and drug delivery, to water treatment, sensors, photocatalysis and lithium-ion batteries.

Interlaminar fracture toughness had been the subject of great interest for several years and is still interesting to the research community. In this article, a comprehensive analysis of fracture toughness in FRP laminates is presented. Primarily, toughness studies are undertaken on glass and carbon fiber reinforced composites under mode-I and mode-II loading conditions. The fracture behavior and its failure pattern depend on a number of parameters: fiber sizing/coating, matrix modification, insert film, fiber volume fraction, stacking sequence, specimen geometry, loading rate and temperature change. In fact, a state-of-the-art process enables increasing fracture resistance with “matrix toughening by carbon nanotubes (CNT) inclusion”. It enables production of materials having ultra-high strength and low weight. The present study has highlighted the available techniques of CNT incorporation: mechanical mixing, grafting and interleaving. Other aspects, such as the dispersion level, matrix viscosity, fiber surface roughness, loading weight %, bonding strength with epoxy, height and density of grown CNT, energy absorption mechanism during delamination, etc., have been examined as well. Although a clear correlation of all these parameters with fracture toughness is hard to establish, there is growing understanding of the surface-grown CNTs and interleaving processes as they ensure significant increase in fracture toughness.

A high number of sport injuries result in damage to articular cartilage, a tissue type with poor self-healing capacity. Articular cartilage tissue is a sophisticated hydrogel, which contains 80% water and possesses strong mechanical properties. For this reason, synthetic hydrogels are thought to be an optimal material for cartilage regeneration. In the last decade, more than 2,000 research papers pertaining to “hydrogel and cartilage” have been published. Due to its biomimetic properties and user-friendly nature, especially in the field of minimal invasive surgery, intelligent injectable hydrogel have gradually become a focal point in cartilage research in recent years. In this review, we systematically summarize current “state-of-the-art” manufacture technologies of injectable hydrogels including ion-induced, thermo-induced, non-induced chemical, and light-induced crosslinking. We also review current strategies for designing intelligent injectable hydrogels, such as component-based, mechanical property-based and structure-based intelligent design to simulate the natural articular cartilage. Lastly, the applications of intelligent injectable hydrogels for cartilage regeneration are presented, and their outlooks for future clinical translation is dicussed.

Phase Changing Materials (PCM) portrays proficiency to liberate perceptible amount of latent heat on the course of phase transformation between liquid-solid or solid-liquid, thereby creating momentary warmth or cooling effect. PCM has been utilized in garments for introducing thermoregulating effect to diminish thermal discomfort of clothing. Assimilation of thermal energy by PCM causes delay in upsurge of microclimate temperature and results in substantial diminution of moisture release from skin thereby leading to inhibition of heat stress conditions and enhancement of thermo-physiological wearing comfort. Simultaneously, the insulating characteristic of such garment can also avert wearer from certain pivotal corollaries like hypothermia or heat syncope, keeping the individual in consolation owing to their automatic acclimatizing attribute in accordance with body and ecological temperature. As the assimilation of PCM into various textile materials have been extensively studied by researchers, an attempt has been made to explicate the recent existing literatures that have successfully integrated and implemented PCM in textile, concentrating on characteristics of PCMs integrated into fibers, and fabrics for potential industrial applications. Finally, various methodologies like coating, spinning & lamination being utilized for applying PCMs onto textiles for developing thermoregulated clothing have been discussed & concludes with challenges & future prospects.

Materials based on polymer-inorganic nanostructures, e(Polym/INS), produced by combining functional polymers with inorganic nanostructured compounds represent a major area of research with many applications. This review provides a summary of the most relevant polymer-inorganic nanostructured systems found in the literature over the last decade. Then the most relevant and specific features of these systems are described. Finally, we summarize the progress made over the last decade in the development of polymer-inorganic electrospun hybrid materials with various morphologies, compositions and applications in environmental remediation, sensors, catalysts, energy area and biomedical uses.

Stereoregular fused thiophenes (SFTs: especially thieno[3,2-b]thiophene (TT) and dithieo[3,2-b:2′,3′-d]thiophene (DTT)), as stable conjugated structures deriving from thiophene ring enlargement, possess outstanding properties and special configuration, such as the superior carrier transfer efficiency and a high degree backbone of planarity. In comparison to stand-alone SFTs structures, oligomers and polymers containing different heteroaromatic units have been much widely researched and used in many fields. In decade, several important reviews have summarized the broad field of fused thiophenes including SFTs, and their synthesis and optoelectronic applications. Here, we critically present the structure–performance relationships and application of oligomers and polymers containing SFTs (exhibiting thiophene ring number from 2 to 7) units. First, the basic structures and properties of SFTs are briefly stated. Then, oligomers classified by extra conjugated heterocyclic attachments are carefully discussed, focusing on the structure–performance relationships for their optoelectronic applications including organic photovoltaic cells and organic field-effect transistors. Moreover, such relationships in polymers have been applied in much wider fields such as organic light-emitting diodes, electrochromic devices, thermoelectric devices, and supercapacitors are discussed. Finally, a summary and prospect are given. Through this review, instruction for molecular design and novel ideas for the future development of SFTs-contained are provided.

This review paper provides an overview of chromogenic polymers and their classifications, mechanisms, chemistry, synthesis procedures, and potential applications with a focus on packaging. Commonly and academically accepted classifications derived from chemical engineering, material science, and packaging science are used. Furthermore, recent progress and outputs aligned with chromogenic polymers for overcoming the common challenges are discussed. Finally, future prospects, market trends and academic investigations are described, including challenges related to chromogenic polymers.

Waterborne polyurethanes (WPUs), owing to their environmental friendliness and non-flammability, are considered as a green class of materials for a wide spectrum of applications, like adhesives, coatings, drug delivery, and tissue engineering. However, to strengthen their thermal stability, water resistance, mechanical properties, and introduce new peculiarities to these polymers, the incorporation of different types of (nano) fillers within their molecular state, emerged novel opportunities and challenges in material sciences. This approach provides new vitality to these materials since the strong interactions between WPU matrices and fillers facilitate the formation of desired WPU composites (WPUCs). Therefore, WPUCs have greatly promoted the construction and designing of novel materials, like hyperbranched WPUs and their nanocomposites. Thus, the aim of the present article is to deeply overview the properties and application of WPUCs in the various realm. The review also provides a brief discussion on the design and synthesis of WPUs, WPUCs, hyperbranched WPUs, and their nanocomposites along with the implementation of naturally derived materials for the development of sustainable WPUCs.

The outstanding performance of conventional thermosets arising from their covalently cross-linked networks directly results in a limited recyclability. The available commercial or close-to-commercial techniques facing this challenge can be divided into mechanical, thermal, and chemical processing. However, these methods typically require a high energy input and do not take the recycling of the thermoset matrix itself into account. Rather, they focus on retrieving the more valuable fibers, fillers, or substrates. To increase the circularity of thermoset products, many academic studies report potential solutions which require a reduced energy input by using degradable linkages or dynamic covalent bonds. However, the majority of these studies have limited potential for industrial implementation. This review aims to bridge the gap between the industrial and academic developments by focusing on those which are most relevant from a technological, sustainable and economic point of view. An overview is given of currently used approaches for the recycling of thermoset materials, the development of novel inherently recyclable thermosets and examples of possible applications that could reach the market in the near future.

In last two decades, acid doped polybenzimidazole as polymer electrolyte membrane (PEM) has been widely recognized and envisioned as “ideal” proton conducting materials for application in high temperature PEM fuel cell (HT-PEMFC). The majority of research and developmental work is mainly focused on poly (2,2´-m-phenylene-5,5´-bibenzimidazole), However, it is neither easy-processed nor inexpensive component of the respective family. On the other hand, among the various members belonging to benzimidazole family, poly (2,5-benzimidazole) is unique because it possesses a cost-attractive, single-step synthesis process, high extent of doping as well as good chemical and thermal stability. In the recent years this material has proved its potency in the earlier research. Thus this review puts special emphasis on poly (2,5-benzimidazole) and epitomizes the on-going breath-taking progress and achievements on the fabrication of poly (2,5-benzimidazole) based membranes. The write-up describes the effect of blending, cross-linking, ionic liquids and incorporation organic/inorganic nano-fillers. In addition, incorporating other protonic dopants such as heteropoly acids into the chain of poly (2,5-benzimidazole) molecular skeleton is also overviewed. Moreover, the critical interpretation of different causes responsible for earlier degradation and their effect towards the fabrication of high temperature membrane electrode assembly are visualized herein. Highlights Current developments and existing challenges of ABPBI in PEMFC have been reviewed. PEM Modification and addition of protonic dopants has been discussed. Proton migration, permeability, stability and reliability are thoroughly illustrated. Different ABPBI-based membranes and their performance are comparatively analyzed.

Bacterial cellulose (BC) is an extracellular natural polymer produced by many microorganisms and its properties could be tailored via specific fabrication methods and culture conditions. There is a growing interest in BC derived materials due to the main features of BC such as porous fibrous structure, high crystallinity, impressive physico-mechanical properties, and high water content. However, pristine BC lacks some features, limiting its practical use in varied applications. Thus, fabrication of BC composites has been attempted to overcome these constraints. This review article overviews most recent advance in the development of BC composites and their potential in biomedicine including wound dressing, tissue engineering scaffolds, and drug delivery. Special emphasis is placed on the fabrication and applications of BC-containing nanofibrous composites for biomedical usage. It summarizes electrospinning of BC-based nanofibers and their surface modification with an outline on challenges and future perspective.

The present article provides a review on the nonlinear mechanical behavior of polymer matrix composites (PMCs). Initially, essential mechanisms driving the nonlinear response of PMCs under different loading conditions are discussed. Rate-dependence, tension-compression asymmetry, viscous behavior, unloading characteristics, interaction between stress components and effects of environmental factors on mechanical properties are briefly reviewed. This is followed by a review of major approaches and constitutive models for predicting stress–strain behavior of PMCs. Following an increasing degree of complexity, models are categorized into four major classes: nonlinear elasticity models, elastic-plastic models, elastic-plastic-viscous models and Damage-Plasticity models. The vast number of existing models is mainly due to the anisotropy and inhomogeneity of PMCs. In brief, this review focuses on informing the reader of major frameworks, rather than addressing all the models in detail.

Epoxy resin will continue to be in the forefront of many thermoset applications due to its versatile properties. However, with advancement in manufacturing, changing societal outlook for the chemical industries and emerging technologies that disrupt conventional approaches to thermoset fabrication, there is a need for a multifunctional epoxy resin that is able to adapt to newer and robust requirements. Epoxy resins that behave both like a thermoplastic and a thermoset resin with better properties are now the norm in research and development. In this paper, we viewed multifunctionality in epoxy resins in terms of other desirable properties such as its toughness and flexibility, rapid curing potential, self-healing ability, reprocessability and recyclability, high temperature stability and conductivity, which other authors failed to recognize. These aspects, when considered in the synthesis and formulation of epoxy resins will be a radical advance for thermosetting polymers, with a lot of applications. Therefore, we present an overview of the recent finding as to pave the way for varied approaches towards multifunctional epoxy resins.

Responsive polymeric materials that are sensitive to biological stimuli including temperature, pH, enzymes, or redox conditions have attracted research interest in recent years. Among these, reactive oxygen species (ROS)-responsive polymers are particularly appealing because of the special role of ROS in living organisms. ROS are the indicator and cause of certain diseases, and they are also important signaling molecules. ROS-responsive polymers could possess the following functions: drug carriers, ROS probes, or medications for certain ROS-related diseases. In this review, we analyze the progress about ROS-responsive polymers made in recent years and predict the future trends of ROS-responsive polymers from the above mentioned perspectives. Due to the limited scope of this review, some older articles are not covered here and are left for more comprehensive reviews.

Poly(vinyl alcohol) (PVA) is a biodegradable, water-soluble membrane that has low methanol permeation and reactive chemical functionalities. Modification of these features makes PVA an attractive proton exchange membrane (PEM) alternative to NafionTM. However, the pristine PVA membrane is a poorer proton conductor than the NafionTM membrane due to the absence of negatively charged ions. Hence, modification of PVA matrixes whilst complying with the requirements of projected applications has been examined extensively. Generally, three modification methods of PVA membranes have been highlighted in previous reports, and these are (1) grafting copolymerization, (2) physical and chemical crosslinking, and (3) blending of polymers. The use of each modification method in different applications is reviewed in this study. Although the three modification methods can improve PVA membranes, the mixed method of modification provides another attractive approach. This review covers recent studies on PVA-based PEM in different fuel cell applications, including (1) proton-exchange membrane fuel cells and (2) direct-methanol fuel cells. The challenges involved in the use of PVA-based PEM are also presented, and several approaches are proposed for further study.

Thiol chemistry is an efficient tool to manipulate the microstructure of aliphatic polyesters and open the way to different applications. Synthetic strategies that aim to synthesize thiol-functionalized aliphatic polyesters are reviewed herein. The introduction of thiol-editable groups on aliphatic polyesters can occur both at chain ends and along the chains, enabling diverse modifications of the polymeric chains and imparting new properties and functions. The use of thiol chemistry for postpolymerization modification of this class of polymers and the (co)polymerizations of monomers bearing thiol groups has also been described herein.

In last two decades, acid doped polybenzimidazole as polymer electrolyte membrane (PEM) has been widely recognized and envisioned as “ideal” proton conducting materials for application in high temperature PEM fuel cell (HT-PEMFC). The majority of research and developmental work is mainly focused on poly (2,2´-m-phenylene-5,5´-bibenzimidazole), However, it is neither easy-processed nor inexpensive component of the respective family. On the other hand, among the various members belonging to benzimidazole family, poly (2,5-benzimidazole) is unique because it possesses a cost-attractive, single-step synthesis process, high extent of doping as well as good chemical and thermal stability. In the recent years this material has proved its potency in the earlier research. Thus this review puts special emphasis on poly (2,5-benzimidazole) and epitomizes the on-going breath-taking progress and achievements on the fabrication of poly (2,5-benzimidazole) based membranes. The write-up describes the effect of blending, cross-linking, ionic liquids and incorporation organic/inorganic nano-fillers. In addition, incorporating other protonic dopants such as heteropoly acids into the chain of poly (2,5-benzimidazole) molecular skeleton is also overviewed. Moreover, the critical interpretation of different causes responsible for earlier degradation and their effect towards the fabrication of high temperature membrane electrode assembly are visualized herein. Highlights Current developments and existing challenges of ABPBI in PEMFC have been reviewed. PEM Modification and addition of protonic dopants has been discussed. Proton migration, permeability, stability and reliability are thoroughly illustrated. Different ABPBI-based membranes and their performance are comparatively analyzed.

Many modern technologies rely on materials with controlled surface properties. A key property in many of these applications is surface energy; specifically a low surface energy is often desired so as to impart low adhesive behavior to the materials. The fluorine–carbon bond displays low polarizability, and so fluorocarbons show high resistance to interactions with both polar and non-polar molecules. Thus the commodity fluoropolymers within the PFTE family have been used widely in applications where low adhesion and solvent resistance are important. For several decades scientists have included perfluorinated or partly-fluorinated segments into specialty polymers in attempts to achieve low fouling behavior, and modification of virtually every class of macromolecule has been explored. Notably, over the past several decades, advances in polymerization techniques, specifically controlled radical polymerization, have made possible the creation of polymers with highly-specific and unique structures, for example, block and well-defined network copolymers. Accordingly, this review discusses traditional partly-fluorinated materials but primarily focuses on recent progress in the design of partly-fluorinated polymeric materials with low surface energy. The objective of the review is to provide a concise summary of the approaches taken to date, and to demonstrate, though example, areas with high potential for innovation in the future.

Strategies to design biostable polyurethanes are briefly reviewed to understand the effect of the polyurethane chemical structure on mechanical properties and resistance to degradation based on reported in vitro and in vivo data. In vitro test methods developed to simulate the biological environment and their suitability to screen new materials for oxidative stability are discussed. Major part of the review is devoted to the family of siloxane-based polyurethanes since materials from this family have advanced to clinical application with demonstrated long-term biostability in cardiovascular devices. The morphology and surface properties of siloxanepolyurethanes are also discussed along with a brief overview of reported studies to evaluate comparative stability of polyurethanes formulated using different strategies.

Interference and chaos among different electromagnetic signals become the prime challenge of the current era which relies on wireless communication. Effective shielding of electromagnetic interference (EMI) waves with advanced materials thus emerges as major research field to prevent cross-talking among electronic devices. This article reviews the current research status of polymer-based EMI shielding materials with a particular focus on a high-performance hybrid with diverse nanomaterials filler. Compatibility and synergist of polymer host with filler materials have been illuminated in this article. Developments of polymer-based EMI hybrid with carboneous, metallic, magnetic and nano/micro materials have been summarized in detail. Emphasis has been given to discuss the role of nano/micro materials size and shape, their electronic, mechanical, chemical properties in tuning the EMI shielding effectiveness (EMI SE) of polymer hybrid. A specific correlation of surface chemical modification/doping of filler materials with EMI SE of their polymer hybrid have been summarized. In the last section, future research direction has been proposed to overcome the existing technological bottlenecks to realize most advanced EMI shielding materials for future use.

Carboxymethyl cellulose (CMC) has attracted considerable scientific attention, thanks to its enhanced water solubility and wide range of possible chemical reactions. In the present review, we attempt to summarize the current knowledge on chemical modifications of CMC, focusing specifically on the derivatization of its carboxyl functions, through “grafting onto” strategies. CMC derivatives, obtained by grafting of small molecules and/or polymers, can be engineered as peculiar assembled architectures (e.g., conjugates, nanoparticles, hydrogels), particularly suitable for the development of drug delivery systems or scaffolds for tissue engineering. The potential of the resulting CMC derivatives in biomedical applications is, therefore, discussed in detail.

Amphiphilic monomer units contain both hydrophobic and hydrophilic groups. They are characterized by affinity and antagonism simultaneously to both polar and nonpolar solvents, tend to settle themselves at solvent interfaces rather than in the bulk of the solvent and, thus, possess effective surface activity. For this reason, in selective solvents the macromolecules with amphiphilic monomer units self-assemble to complex morphologies with enlarged surface which could be similar to those formed by low-molecular surfactants, lipids and amphiphilic diblock-copolymers. In literature, macromolecules with amphiphilic monomer units are also referred to as polymer amphiphiles. When they consist of identical amphiphilic monomer units, they are called amphiphilic homopolymers. The article aims to review the macromolecular self-assembly driven by amphiphilicity of monomer units containing both solvophobic and solvophilic (hydrophobic and hydrophilic) groups. The particular attention is paid to the situation when such macromolecules assemble into the hollow and vesicle-like particles being especially prospective for different applications. We present the current state of experimental, computational and analytical research in this field and reveal the conditions favoring the formation of vesicles with thin (mono-, bi- or multilayer) membranes.

Air-filtration has played an increasingly important role in keeping desired indoor air quality in spite of the heavily polluted air that has worsened by human being’s activities. Because the compositions of the pollutants present in the air are so complex and uncontrollable, traditional air-filtering materials produced from non-degradable plastics or glass fibers are facing a big challenge of effectively removing not only the particulate pollutants, such as PM2.5, but also gaseous pollutants, including toxic chemicals, and bacteria and so forth. These materials are also non-degradable and end up in landfills. As a result, development of new multi-functional filtering materials to satisfy the fast-growing community of air-filtration is currently in a critical need. Natural materials that are well known for their richness in functional groups and suitability for many applications represent a promising material solution for high-performance air-filtration. In addition, these materials are sustainable, and their inherent bio-degradability makes them a green solution. In this review, we summarize the significant studies on using polymeric materials for air-filtration with an emphasis on natural biomaterials. In specific, the characteristics of polluted air, the air filter types and filtering materials are briefly summarized. The advantages of developing green air filters from natural polymers as well as the challenges are highlighted.

Fused deposition modeling (FDM) is one of the most widely used 3D printing techniques that utilizes polymers to create models, prototypes or even end products. Since 2009, the demand for FDM has been increasing at an incredible rate from one year to the next, and many experts believe that this technology has the potential to revolutionize manufacturing in many sectors. The main advantages of FDM technology are that the technique offers a simpler fabrication process and a more cost-effective method compared to other prominent 3D printing techniques, and yet, it is still capable of manufacturing complex geometries and cavities with reasonable dimensional accuracy. However, there are still some limitations and shortcomings that have been identified, especially pertaining to the lower mechanical properties exhibited in FDM parts compared to the parts produced by conventional methods such as injection and compression techniques. Therefore, this review article focused on recent developments and progress in the FDM technique in an attempt to improve the end performance of 3D-printed parts, along with current challenges and the future direction.

In recent decades, there has been a growing interest in block copolymer with broad dispersity. Previous studies showed that increasing polydispersity influences the self-assembly behavior of block copolymers; however, disagreements between experimental and computational studies remained on key issues including the extent of domain swelling with increasing block dispersity and the effects of polydispersity on order–disorder and order–order transitions in block copolymers. Furthermore, while polydispersity stabilized complex microdomain morphologies and macrophase separation were suggested by a number of computational reports, experimental evidences on the topic were rare. Building on these earlier studies, new advances have been made on the synthesis and characterization of polydisperse block copolymers. These recent studies resolve the existing controversies in the field and bring new insights on polydisperse block copolymer phase behavior. Here, we highlight studies on polydisperse block copolymers published in the past ten years.

Environmental pollution is a global concern due to the rapidly increasing population and industrialization. In this context, there is a strong need to develop green separation techniques to isolate pollutants from different sources. Polymer assemblies or hydrogel polymers are water-swollen and crosslinked polymeric materials capable of retaining large amounts of water in their 3D networks. Hydrogels function as excellent adsorbents in pollutant removal processes by binding heavy metal ions and/or organic compounds due to the presence of various functional groups in their polymeric networks (e.g., amide, amine, and carboxylic acid). Hydrogels have the benefits of simplicity, high adsorption, and easy recovery compared to other adsorbent materials that involve activated carbon, zeolites, silica gel, biomass, and inorganic mineral. For these reasons, hydrogels have received increased interest for environmental remediation applications over the past few decades. The objective of this review is to describe the issues related to the preparation of different hydrogels, their characterization process, their adsorption characteristics for various pollutants, and the technical viability of some applications.

Being commercialized in 1992, poly (lactic acid) (PLA) has been considered for biomedical applications and as a reliable substitute for a wide range of commodity and engineering applications where noncompostable petroleum-based polymers are currently being used. However, PLA suffers from series of drawbacks and it would not be applicable unless these shortcomings resolve somewhat. Besides the PLA’s brittleness and low toughness which originate from its higher glass transition temperature, the major shortcomings which negatively influence the other features of PLA are its low melt strength and slow crystallization kinetics. These weaknesses limit the processability, formability and foamability of PLA, and hence, the manufacturing of PLA based products. In this context, the improvement of rheological and viscoelastic properties of PLA is of a great importance as it enhances the melt strength. To control the PLA’s rheological and viscoelastic properties, various attempts such as varying the D-lactide content in PLA molecules, increasing the PLA’s molecular weight, the use of chain extender and branching, controlling the PLA’s crystallization, compounding with micro-/nano-sized fillers and blending with other polymers have been considered. This article critically reviews these studies that have been conducted so far on rheological investigations of various PLA-based systems.

Air-filtration has played an increasingly important role in keeping desired indoor air quality in spite of the heavily polluted air that has worsened by human being’s activities. Because the compositions of the pollutants present in the air are so complex and uncontrollable, traditional air-filtering materials produced from non-degradable plastics or glass fibers are facing a big challenge of effectively removing not only the particulate pollutants, such as PM2.5, but also gaseous pollutants, including toxic chemicals, and bacteria and so forth. These materials are also non-degradable and end up in landfills. As a result, development of new multi-functional filtering materials to satisfy the fast-growing community of air-filtration is currently in a critical need. Natural materials that are well known for their richness in functional groups and suitability for many applications represent a promising material solution for high-performance air-filtration. In addition, these materials are sustainable, and their inherent bio-degradability makes them a green solution. In this review, we summarize the significant studies on using polymeric materials for air-filtration with an emphasis on natural biomaterials. In specific, the characteristics of polluted air, the air filter types and filtering materials are briefly summarized. The advantages of developing green air filters from natural polymers as well as the challenges are highlighted.

In recent decades, there has been a growing interest in block copolymer with broad dispersity. Previous studies showed that increasing polydispersity influences the self-assembly behavior of block copolymers; however, disagreements between experimental and computational studies remained on key issues including the extent of domain swelling with increasing block dispersity and the effects of polydispersity on order–disorder and order–order transitions in block copolymers. Furthermore, while polydispersity stabilized complex microdomain morphologies and macrophase separation were suggested by a number of computational reports, experimental evidences on the topic were rare. Building on these earlier studies, new advances have been made on the synthesis and characterization of polydisperse block copolymers. These recent studies resolve the existing controversies in the field and bring new insights on polydisperse block copolymer phase behavior. Here, we highlight studies on polydisperse block copolymers published in the past ten years.

This article focuses on providing a systematic review on various fundamental properties of composite based on poly(α-hydroxy esters) and hydroxyapatite (HAp) for application in bone tissue engineering. Poly(α-hydroxy esters), a well-known synthetic biopolymer has attracted considerable interest to be employed for synthesis of bone graft substitute material with HAp mainly due to its bioresorbability, variable biodegradation rate and melt-processibility. Such features are simultaneously attractive for both biomedical application and industrial-scale productions. Besides the main function of hydroxyapatite as bioactive ceramic filler in composite to induce new bone formation upon polymer bioresorption, HAp can also serve as reinforcement for matrix polymer by providing sufficient mechanical support for cell attachment. Moreover, HAp plays a significant role in determining other composite properties, such as resistance to ingress of body fluid, body temperature ageing, relaxation movement of polymer segment, and in vivo biodegradation. These properties constitute as the fundamental requirements in field of bone tissue regeneration which is desirable to be achieved by unique composite system based on poly(α-hydroxyesters) and HAp particles.

Compared to conventional porous materials with a uniform pore size distribution, hierarchical ones containing interconnected macro-, meso-, and micropores have greatly enhanced material performance due to the increased specific surface area and mass transfer. Copolymer is a good candidate used for construction of such hierarchically porous structures, resulting from its tunable segment composition, unique phase separation, and self-assembly, etc. Hierarchically porous materials derived from copolymers can be served as a versatile support for many reactive molecules. Furthermore, hierarchically porous carbon materials (HPCMs) can also be prepared by carbonization of copolymers, one segment of which is converted to carbon while the other segment is responsible for the pore formation after its removal by pyrolysis. The obtained hierarchically porous copolymers or carbon materials have promising electrochemical applications especially in energy conversion and storage. In the present review, recent advances in preparation of hierarchically porous materials (HPMs) derived from copolymers are reviewed, and their electrochemical applications in supercapacitors, lithium-ion batteries, fuel cells, electrochemical biosensors, and electrocatalysis are also introduced. The rational design and control for the hierarchically porous microstructures are described deeply from the molecular level. Also, the relationship between the micro-structure and the electrochemical performance is revealed. This review can provide us a better understanding of both theory and experiment for the preparation of hierarchically porous organic materials and their electrochemical applications.

Secondary flow (also termed as stagnation flow, dead space, recirculation zone, and vortex) is rheological phenomenon occurring during flow of polymer melts through abrupt contraction channels as result of flow separation from solid boundary leading to accelerating flow regime with recirculating material in corners. Polymer melt captured in secondary flow slowly rotates in direction opposite to main flow direction and simultaneously moves in third direction through helical motion. This may first reduce flow stability and second increase residence time initiating highly undesirable thermal degradation of polymer melt. Since the first visual experimental observation performed by Tordella and preliminary theoretical prediction made by Langlois and Rivlin at the end of the 1950s, this phenomenon represents one of the most fundamental rheological problems ever with many practical and theoretical impacts discussed here. This comprehensive review written in historical perspective summarizes key factors (Newtonian viscosity, shear thinning, viscoelasticity, flow geometry, and extensional viscosity) influencing secondary entry flows for polymer melts and provides deep and critical discussion of the most important experimental and theoretical works on this topic (such as branched low-density polyethylene, LDPE, linear low-density polyethylene, LLDPE, high-density polyethylene, HDPE, polystyrene, PS, isotactic polypropylene, PP, polymethyl methacrylate, PMMA, polyamide, Nylon PA 66, or polybutadiene, BR).

Strategies to design biostable polyurethanes are briefly reviewed to understand the effect of the polyurethane chemical structure on mechanical properties and resistance to degradation based on reported in vitro and in vivo data. In vitro test methods developed to simulate the biological environment and their suitability to screen new materials for oxidative stability are discussed. Major part of the review is devoted to the family of siloxane-based polyurethanes since materials from this family have advanced to clinical application with demonstrated long-term biostability in cardiovascular devices. The morphology and surface properties of siloxanepolyurethanes are also discussed along with a brief overview of reported studies to evaluate comparative stability of polyurethanes formulated using different strategies.

Polysulfide polymers as an important class of polymers are used in different applications as sealants, adhesives, etc. They are usually synthesized by reaction of disodium polysulfides with dihalo compounds to yield liquid or solid polymers. Their most important advantages are excellent adhesion to different surfaces, creation of no defect in sealant under stress and pressure, resistance against to fuels and solvents, very low gas and steam permeability, and high resistance to ozone and UV. This article aims to review methods of synthesis, properties, and applications of polysulfide polymers. Also, polysulfide-based nanocomposites and blends are also briefly discussed.

Thermoplastic and thermoset polymers in use today have fire risk and fire hazard associated with them that is not always well known to the public or material scientists. Recent events in the United Kingdom and California show that, if not considered carefully, use of flammable materials can result in catastrophic losses of both life and property. Further, current understanding has shown that simply adding flame retardant chemicals to polymers to address fire hazard and risk is not sufficient, as there is an increased demand from consumers, government, and industry for improved durability, recyclability, fire safety, and reduced environmental impact. These new requirements are beginning to change flame retardant chemistry for polymers, which has been mostly unchanged for the past 50 years. Existing flame retardant chemical technology will be briefly reviewed to show what is available today, followed by a discussion of potential future flame retardant approaches. Future possibilities such as polymeric, reactive, inorganic, and transition metal chemistries will be surveyed and discussed, with emphasis on what is not fully understood or validated for commercial use or future research and development investment. Current unmet fire safety needs of polymers, based upon current information and technological trends, will also be discussed.

Polymer/clay aerogel composites fabricated using the freeze-drying method and water as solvent has drawn extensive attentions during the past decade. Such aerogels possess layered or network microstructures, low thermal conductivities, and good thermal stabilities; of special interest, they generally have very low flammability, which could be influenced by the composition and microstructure of the aerogel composites. The fire performance of the aerogels can be further improved with flame retardant modifications. Polymer/clay aerogel composites can also serve as effective flame retardant coatings. The mechanisms of the flame retardancy of polymer/clay aerogel composites are also discussed herein. The thorough survey of the current literatures offers useful information to realize potential of polymer/clay aerogels and help guidance to design novel high-performance polymer/clay aerogel composites.

High performance and high temperature polymers are a class of polymeric materials exhibiting high thermal stability and their resistance to fire makes them valuable assets for many applications. Those applications include as typical examples high temperature gas separation membranes, automotive and aerospace industry as well as the construction industry. The high performance polymers have been synthesized since the early 1960s, and have developed rapidly over the past few decades. Most high performance polymers comprise a highly aromatic backbone, linear chains, and strong inter-chain interactions. This review deals mostly with commercial polymeric materials. Studies regarding their thermal behavior, degradation mechanism and their reaction to fire have been synthetically combined in order to bring out potential insight concerning the effect of the thermal decomposition and thermal behavior on the fire properties of those polymers.

Intrinsically conducting polymers (ICP) and conductive fillers incorporated conductive polymer-based composites (CPC) greatly facilitate the research in electromagnetic interference (EMI) shielding because they not only provide excellent EMI shielding but also have advantages of electromagnetic wave absorption rather than reflection. In this review, the latest developments in ICP and CPC based EMI shielding materials are highlighted. In particular, existing methods for adjusting the morphological structure, electric and magnetic properties of EMI shielding materials are discussed along with the future opportunities and challenges in developing ICP and CPC for EMI shielding applications.

This review focuses on poly(2-oxazoline) containing triblock copolymers and their applications. A detailed overview of the synthetic techniques is provided. Triblock copolymers solely based on poly(2-oxazoline)s can be synthesized by sequential monomer addition utilizing mono- as well as bifunctional initiators for the cationic ring-opening polymerization of 2-oxazolines. Crossover and coupling techniques enable access to triblock copolymers comprising, e.g., polyesters, poly(dimethylsiloxane)s, or polyacrylates in combination with poly(2-oxazoline) based segments. Besides systematic studies to develop structure property relationships, these polymers have been applied, e.g., in drug delivery, as (functionalized) vesicles, in segmented networks or as nanoreactors.

Nanofibers have attracted extensive interest over the few decades due to their unique physicochemical properties. Tremendous efforts have been made to explore their applications, and many articles have been published in the literature to date. These studies of nanofibers have focused on two main issues, that is, how to make nanofibers and how they can be used. This review summarizes the current status of nanofiber fabrication and applications of nanofibers. In the fabrication area, we focused on recently developed methods for fabricating nanofibers, which is based on mechanical force. This approach has accelerated the development of new types of nanofibers, and it has made commercial opportunities available for the hundreds of ideas that have been developed in academic fields. This review also presents information concerning the current applications and potential applications of nanofibers in medical engineering, the generation of energy, and the remediation of areas affected by environmental pollution. We have introduced the concept and technology for achieving target applications of nanofibers in the various fields, and this is followed by discussing several highlighted works. We believe that this review could help advance the progress in the development of strategies for the synthesis of nanofibers and broaden their academic and commercial applications.

Three-dimensional (3D) printing technologies enable not only faster bioconstructs development but also on-demand and customized manufacturing, offering patients a personalized biomedical solution. This emerging technique has a great potential for fabricating bioscaffolds with complex architectures and geometries and specifically tailored for use in regenerative medicine. The next major innovation in this area will be the development of biocompatible and histiogenic 3D printing materials with bio-based printable polymers. This review will briefly discuss 3D printing techniques and their current limitations, with a focus on novel bio-based polymers as 3D printing feedstock for clinical medicine and tissue regeneration.

The miniaturization of electronics has been following Moore's Law for decades and has resulted in the development of sequentially evolutionized multifunctional nanoengineered devices. The conventional electronic devices are processed over planar hierarchically nanopatterned substrates having mechanical rigidity and stiffness which limit the degree of utility due to its inability to interface with soft curvilinear morphology, brittle nature, and inferior optical transparency. However, flexible substrates assembled over polymeric framework would, therefore, play a key role by offering light weighted thin film architecture, wearability, improved optical transparency, and morphological configuration to curvilinearity. The flexibility of substrate is defined when the material is processed such that individual component complies to a comparable degree of bending without deterioration of electronic/optoelectronic performance. Since the fabricated structure is pliable, the mechanical integrity of the structure governs the electromechanical performance of flexible electronic devices. The structure may undergo delamination, which occurs due to the stress field gradient developed due to the coefficient of thermal expansion, thereby generating a built-in strain potentially capable of breaking the adhering bonds. This article provides a consolidated review of numerous processing techniques to fabricate flexible electronics ranging from printing, sol-gel, chemical vapor deposition to chemical synthesis route, etc. and their applications in thin-film transistors, solar cells, sensors, health monitoring e-skins, optical devices, etc. along with a theoretical mechanical two layer film substrate model.

Particle coagulation, in conjunction with nucleation and growth, plays a significant role in determining the evolution of particle size distribution in emulsion polymerizations. Therefore, many modelling and experimental studies have been carried out to have a better understanding and control of the particle coagulation phenomenon in order to achieve high-quality as well as highly efficient industrial production. This article presents a review of modelling and experimental studies focused on the particle coagulation phenomenon in emulsion polymerizations. The state-of-art of particle coagulation modelling pertaining to emulsion polymerizations is discussed. Experimental studies concerned with latex coagulation processes are summarized next. The review finishes by discussing outstanding problems that need attention and sharing our perspectives on future developments.

Development and commercialization of alternative energy harnessing and storing devices are most necessarily required in today's world. Progressive increase in consumption of energy by the ever-increasing human population, coupled with depletion in conventional non- renewable energy reserves of the world, demands development of renewable energy production. Fuel cells have projected themselves as prospective renewable energy devices. Microbial fuel cells (MFCs) represent a category of polymer electrolyte membrane fuel cells (PEMFCs), which are comparatively new entities in the field of fuel cell devices. MFCs are unique in such manner that they can produce electricity from industrial and domestic wastewaters while efficiently carry out wastewater purification in the course of this operation; therefore, they can be viewed as dual-utility devices. An MFC often comprises a polymeric ion-exchange membrane as an employed electrolyte. Proper functioning of this membrane is critical toward the overall performance of the cell. Commercial Nafion membranes have found use in majority of the MFC devices reported. However, certain drawbacks of Nafion membranes have recently led to the development of alternative materials for the purpose of fabricating polymer electrolyte membranes (PEMs). This review highlights the various PEMs developed so far for application in MFCs.

This review outlines latest developments in the field of self-healing rubbers and elastomers, analyzing their potential application to natural rubber (NR). Different validated healing concepts are presented and the possibilities of applying them to NR are discussed. Research in this field should aim at modifying the chemical structure of NR as to enhance physical or chemical reversible interactions either intermolecular or intramolecular. The realization of better mechanical properties at relevant working conditions and with milder healing conditions remains a challenge for all self-healing rubbers. This overview should be seen as setting the conceptual framework for new developments with a more clearly defined industrial focus.

Elastomers are materials showing exceptional elasticity and are used for numerous applications. However, their low stiffness as well as their insulating behavior can be limiting so the incorporation of graphene-based materials can help and improve drastically their properties. With high Young's modulus, high electrical and thermal conductivities, graphene and graphene-like fillers seem ideal fillers to effectively tune elastomers properties. With low graphene-like loadings, most elasticity properties of elastomers could be preserved while increasing or adding new properties to the composites to enable new applications. Herein, we focus on the effects of “graphene” incorporation into elastomers and we will highlight the key parameters to effectively monitor the changes.

This paper is an overview of current understanding in the areas of composites made from biodegradable thermoplastics and wood fillers. The review finds that the composite properties depend on the type of wood filler, the choice of polymer matrix, the wood filler content, the compatibilization technique used and the processing parameters. The extent of interfacial adhesion and the filler morphology are identified as the underlying factors that control the composite properties. Future research needs are identified, including establishment of fundamental relationships between quantified interfacial adhesion and end-use properties and advanced modelling of biodegradation processes.

This review aims to provide a comprehensive overview about various innovative strategies that have been employed by recent researchers to overcome with the shortcomings associated with traditional microspheres. Essentially, optimization strategies from structural aspects have been widely investigated to improve the properties (e.g., enhanced hydrophilicity, reduced initial burst release, etc.) of the pristine microspheres. These include bulk alteration, surface modification as well as the formation of sophisticated microsphere design such as core-shell structures. Other than that, various microencapsulation techniques and novel technologies such as spray drying, supercritical fluid technique, membrane, and microfluidics emulsification also have been explored in this review. Additionally, the impact of formulation-related aspects on the drug encapsulation efficiency, particles size and particles size distribution during double emulsification method will also be discussed and reviewed extensively based on the recent literatures reported.

Glycosylated materials have attracted special attention in biomedical field because of the unique properties of the individual carbohydrates in recognition mechanisms in many biological events. Sugar residues decorating a polymer surface can be regarded as multivalent ligands for interaction with various glycoproteins. This phenomenon provides the basis for several biomedical applications; of these, ligand-based targeted therapy is the most frequently cited. Materials functionalized with individual carbohydrates can be used for the selective binding of lectin proteins. Carbohydrate–lectin interactions underpin the development of diverse biosensor devices and bioassays aimed at pathogen detection. Because of the high content of hydroxyl groups and the consequent high hydrophilicity, saccharide-based monomers are perfect candidates for incorporation into hydrogels. Such functionalization allows synthetic materials to acquire unique properties and enhance their performance. This review covers developments over the past 15 years in the field of the synthesis of chemically crosslinked nano-, micro- and bulk hydrogels with covalently incorporated mono-, di- or trisaccharides. A brief view on the potential biomedical applications of these unique hydrogels is provided with particular emphasis on carriers for delivery of bioactive molecules, bioactivated materials for cell culture and tissue engineering as well as capture systems for pathogenic microorganisms.

The gas barrier properties of ethylene vinyl alcohol copolymer (EVOH) against oxygen, carbon dioxide and water vapor have been widely investigated in relation to different material characteristics, environmental conditions and new processing technologies. Recently, EVOH is gaining more attention as a barrier material against other gases and organic substances such as aromas, flavors, fuels, chemicals (e.g., BTEX), and as a functional barrier, e.g., to avoid mineral oil migration. This review contains an update on permeability data of EVOH emphasizing its potential as a barrier material for new and versatile applications in food and pharmaceutical packaging, agriculture, construction, automotive, etc.

Polysaccharides and proteins are abundantly found in nature and are highly recommended for developing eco-friendly materials due to their special properties (biodegradability, biocompatibility, non-toxicity, low cost, etc.). However, they sometimes fail to meet specific requirements due to poor mechanical and physical properties. Poly(vinyl alcohol) (PVA) is one of the promising synthetic polymers with superior properties that can be blended with natural polymers for obtaining novel biomaterials with improved performances. This review addresses recent advance in PVA/polysaccharides and PVA/proteins biocomposites design and fabrication, mainly for the past two decades.

By surrounding small droplets with a coating, one can obtain micrometer-size capsules (microcapsules), and combine multiple properties into a single system. This technology has allowed the design of advanced and functional materials. Amino resins are composed principally of urea and/or melamine and formaldehyde, and exhibit advantages as wall-forming materials, such as high mechanical strength and chemical resistance. In this review, a general description of the encapsulation process by in situ polymerization of amino resins is given. Characterization methods, and the influence of the physical and design parameters are discussed. A mechanistic description and some of the promising avenues of research are also presented.

Seven series of polyimides have been analyzed and compared with regard to the correlation between their conformational rigidity parameters, such as the Kuhn segment, the characteristic ratio, the Van der Waals volume and free volume, and some physical properties, such as glass transition temperature, dielectric permittivity, and permeability to different gases. This review concentrates on the author's own work, placed in the context of the broader field. The conformational rigidity parameters were calculated by using the Monte Carlo method, while the values of physical properties were taken from published articles.

Hypercrosslinked polymers (HCPs) represent a class of nanoporous materials with a wide range of practical and potential applications such as gas sorption and separation, heterogeneous catalysis, drug delivery, and chromatographic separation. First introduced by Davankov and Tsyurupa in the early 1970s, HCPs have developed rapidly over the past few decades. Mostly based on Friedel-Crafts chemistry, HCP materials can be prepared from the post-crosslinking of polystyrene-type precursors in their swollen state, or from the condensation of small building blocks. HCP materials manifest numerous important advantages, including moderate synthetic conditions, an enormous stockroom of inexpensive monomers, robust structures, and good thermal and chemical stabilities. This review article aims to provide an overview of recent publications on HCPs, and the emphasis is positioned on the synthetic approaches, theoretical studies, characterizations, structure-property relationships, and applications of these HCP materials.

Benzimidazoles are commonly used as an electron acceptor unit in the synthesis of donor acceptor donor type conjugated polymers. This review offers an overview of the utility of benzimidazole derivatives in the synthesis of various donor acceptor donor type of conjugated polymers, covering the research trends in experimental studies. The selected molecules in this overview have been limited with the donor-acceptor-donor type of conjugated polymers including benzimidazole as an acceptor unit and the corresponding studies up to 2016 have been shown. The polymers examined in this paper are discussed in two sections. The first section includes the studies about the effect of benzimidazole unit on the optical feature of resulting donor-acceptor type polymers. The second section illustrates the benzimidazole-based donor-acceptor-donor type conjugated polymers which are utilized in photovoltaic applications.

Stable emulsions are frequently encountered in oil production and cause a series of environmental and operational issues. Chemical demulsification is widely used for the separation of oil from water or removal of water from oil. The chemicals used in the demulsification process have a strong affinity to the oil-water interface. This review presents the various types of chemical demulsifiers used for the demulsification of water-in-oil and oil-in-water emulsions. The review covers the relevant properties of polymeric surfactants such as polyether, dendrimers, and natural biodegradable polymeric surfactants. In addition, emerging alternatives like nanoparticles-based demulsifiers and ionic liquids are also reviewed. The factors affecting the demulsification efficiency of these demulsifiers and structure-property relationships are discussed. Copolymers with high hydrophilic content and molecular weight are more efficient demulsifiers. Similarly, the position isomerism (same carbon skeleton and functional groups but a different location of functional groups) strongly affects the HLB and demulsification performance. Generally, dendrimers show better performance compared to linear polymeric surfactants due to their relatively higher interfacial activity, better penetrability, and a larger number of reactive terminal groups. Techniques used to evaluate the performance of demulsifiers are also covered. The review also highlights the current developments and future prospects of chemical demulsifiers.

Cellulose has been used as a raw material for the manufacture of membranes and fibers for many years. This review gives the background of the most recent methods of treating or dissolving cellulose, and its derivatives to form polymer films or membranes for a variety of applications. Indeed, some potential applications of bacterial cellulose, nanofibrillar cellulose (NFC) for films showing enhanced barrier characteristics are reviewed as well as the utilization of cellulose nanonocrystals (CNC) for production of highly oriented super strong films or thin films is discussed. Because of the success of the Lyocell process as well as the amine/metal thiocyanate solvent blends of cellulose and other polysaccharides like starch, chitosan, and other natural polymers. Consequently, the use of cellulose (or its derivatives) and another polysaccharide dissolved as a blend is also elaborated. It is our hope that the reader will want to follow up and investigate these new systems and use them to develop end use materials for all sorts of applications, from medical to water filtration, or electrogels for use in batteries.

Polycaprolactone (PCL) is a bioresorbable and biocompatible polymer that has been widely used in long-term implants and controlled drug release applications. However, when it comes to tissue engineering, PCL suffers from some shortcomings such as slow degradation rate, poor mechanical properties, and low cell adhesion. The incorporation of calcium phosphate-based ceramics and bioactive glasses into PCL has yielded a class of hybrid biomaterials with remarkably improved mechanical properties, controllable degradation rates, and enhanced bioactivity that are suitable for bone tissue engineering. This review presents a comprehensive study on recent advances in the fabrication and properties of PCL-based composite scaffolds containing calcium phosphate-based ceramics and bioglasses in terms of porosity, degradation rate, mechanical properties, in vitro and in vivo biocompatibility and bioactivity for bone regeneration applications. The fabrication routes range from traditional methods such as solvent casting and particulate leaching to novel approaches including solid free-form techniques.