Effect of polyethylene glycol surface modified nanodiamond on properties of polylactic acid nanocomposite films

doi:10.1016/j.diamond.2020.108092

Diamond and Related Materials

Volume 109, November 2020, 108092

https://doi.org/10.1016/j.diamond.2020.108092 Get rights and content

Highlights

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Polydopamine (PDA) coating was applied on nanodiamond (ND) as the first step of ND surface modification.
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The hydroxyl groups on polyethylene glycol (PEG) and PDA were covalently linked by isocyanate groups.
•
PEG functionalized ND (ND-PEG) was successfully prepared by a novel method.
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ND-PEG exhibits excellent dispersibility and compatibility in polylactic acid (PLA) matrix.
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The incorporation of ND-PEG into PLA matrix improves the mechanical properties and thermal stability of PLA.

Abstract

Nanodiamond (ND) was surface modified by polyethylene glycol (PEG) to improve the interfacial adhesion between ND and the polylactic acid (PLA) matrix and achieve uniform nanoparticle dispersion in the matrix. PEG functionalized ND (ND-PEG) was successfully prepared by a novel and scalable modification method. Firstly, the ND particles oxidized by air was treated with dopamine, and then the hydroxyl groups on PEG and polydopamine (PDA) were covalently linked by isocyanate groups. The Fourier Transform Infrared spectroscopy, Thermogravimetric analysis and X-ray photoelectron spectroscopy reveal that PEG has been covalently boned on the surface of ND. Compared with those of pure PLA film, the tensile strength, tensile modulus and elongation at break of the nanocomposite films with PEG modified ND increase by 66.64%, 37.6% and 187.43%, respectively. In the meantime, the degradation temperature at the initial stage and the temperature at the maximum weight loss rate of the nanocomposite films are significantly increased. It is suggested that the incorporation of ND-PEG into PLA matrix is an effective method to improve the mechanical properties and thermal stability of PLA.

Graphical abstract

Introduction

Polylactic acid (PLA) is a kind of environmentally friendly material, which is made from renewable plant resources and has good biodegradability [1]. It has mechanical properties similar to those of commercial polymers and has excellent biocompatibility [2]. Initially, PLA was mainly used in biomedical and packaging fields for its biodegradability. Nowadays, due to the depletion of petroleum resources, it has been regarded as one of substitutes of petrochemical-based polymers, and its value in long-term applications such as automobiles and electronics is increasingly prominent [3]. Therefore, PLA is playing an important role in biopolymer market, being one of the most promising candidates for further developments [4]. However, inherent brittleness and poor thermal stability of PLA have limited its wide applications in high-performance areas [5]. Therefore, it is necessary to ameliorate the toughness of PLA, improve its thermal stability, and in the meantime increase its strength and modulus. Nanofillers have been added into PLA matrix to give nanocomposite materials with excellent properties. In previous studies, researchers have prepared PLA nanocomposite materials with graphene [6], carbon nanotube (CNTs) [7], halloysite nanotubes [8], cellulose nanocrystals [9], etc.

Nanodiamond (ND) is non-toxic and has excellent biocompatibility, mechanical properties and thermal stability [10]. Accordingly, the addition of ND within PLA matrix has been considered to be an effective method to improve the thermal stability and mechanical strength of PLA. A large number of research work shows that the properties of polymer nanocomposites can be improved significantly by adding nanofillers, even if the content of nanofillers is very low [3]. Delavar and Shojaei [11] demonstrated that the tensile strength and tensile modulus of chitosan were significantly improved by incorporating 1.5 wt% thermally oxidized ND. Nevertheless, the commercialized NDs are mainly produced by detonation method and have many oxygen-containing functional groups on its surface [12,13]. The hydrogen bond and van der Waals force between oxygen-containing functional groups make ND particles easy to form aggregates, which seriously affects the role of ND in PLA matrix [11,14].

Therefore, surface modification is employed to obtain good dispersion of ND particles in the PLA matrix. Traditional methods, including carboxylation with strong oxidizing acid mixtures [15], hydrogenation with hydrogen at elevated temperatures [16], fluorination with fluorine and hydrogen gases [17] and hydroxylation using Fenton chemistry [18], have been used to treat the surface of ND particles. However, most of these methods for surface modification of ND [[19], [20], [21], [22]] either require strong oxidizing and corrosive solvents or need expensive experimental equipments, which are not environmentally friendly and not economical. Polydopamine (PDA) coating has drawn much attention [23,24], since it is not only biodegradable and environmentally friendly, but also is simple and easy to prepare. Qin et al. [25] employed polydopamine chemistry to surface modify ND in order to ensure the homogeneous dispersion of ND and the good interface interaction between ND and the polyimide matrix. Dopamine can easily convert to PDA by self-polymerization and has the ability to adhere to various materials [26,27]. Generally, PDA needs to react with specific substances containing amine and/or thiol groups on their surface through Michael addition and/or Schiff base reactions [26]. However, the surface of PDA contains a great quantity of hydroxyl groups [28], thus PDA can be used as a platform for grafting modification through the hydroxyl on its surface. On the other hand, polyethylene glycol (PEG) is a frequently-used plasticizer for PLA matrix [29], and has the advantages of nontoxicity, good biocompatibility and good solubility in various common solvents [30].

Based on above research, in this paper PDA coating was applied on ND as the first step of ND surface modification. Then PEG was attached by covalent bonds to the PDA coated ND to prepare PEG functionalized ND via grafting-to method, to improve the agglomerates of ND in the PLA matrix and enhance the interfacial interaction between nanoparticles and polymer. In this study, PLA nanocomposite films with different contents of functionalized NDs were prepared via solvent casting technology, and the effects of the PEG functionalized ND on the properties of PLA matrix were investigated. The influences of ND-PEG nanoparticles or pristine ND particles on the fracture morphology, mechanical properties and thermal stability of PLA nanocomposite films were also studied.

Section snippets

Materials

Pristine nanodiamond (ND, purity ≥ 95% and mean size 25 nm) was manufactured by detonation technique and provided by Henan Hengxiang Diamond Abrasive, China. PEG with M_n = 2000 g/mol and 1, 6-hexamethylene diisocyanate (HDI, the purity ≥ 99%) were supplied by Aladdin Industrial Corporation, China. PLA (4032D) was purchased from Dongguan ZhanYan Industrial Co. Ltd. Dopamine hydrochloride (98%) and tris(hydroxymethyl)-aminomethane (Tris, 99%) was purchased from Shanghai Dibai Chemical Technology

FTIR analysis

The FTIR spectra of pristine ND, ND-PDA and ND-PEG are presented in Fig. 1. The spectrum of pristine ND particles shows a broad absorption band at 3440 cm⁻¹, which is ascribed to the stretching vibrations of hydroxyl and carbonyl groups on the surface of ND. The absorption peaks at 1802 cm⁻¹ and 1635 cm⁻¹ correspond to the stretching vibration of carbonyl and the deformation vibration of hydroxyl. In comparison with that of pristine ND particles, the band of ND-PDA at around 3435 cm⁻¹ becomes

Conclusions

As a kind of carbon-based nanoparticles with good biocompatibility, ND has superior mechanical properties and thermal properties, which make ND becomes an excellent filler for nanocomposite materials. In order to improve the elongation at break of PLA and ameliorate its thermal stability, a novel method was used to functionalize ND with PDA and PEG successively. It can be observed that a homogeneous dispersion of ND-PEG in PLA matrix and a good interfacial compatibility between ND and PLA

CRediT authorship contribution statement

Xiaoyu Shi: Conceptualization, Formal analysis, Writing - original draft, Writing - review & editing
Shengnan Bai: Investigation, Validation
Yuanyuan Li: Visualization
Kimiyoshi Naito: Data curation
Xiaoyan Yu: Project administration, Funding acquisition
Qingxin Zhang: Resources, Supervision, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The author would like to gratefully acknowledge the financial support from the National Natural Science Foundation of China (51573037) and Natural Science Foundation of Hebei Province, China (B2017202281, E2019202348).

References (48)

E. Castro-Aguirre et al.
Poly(lactic acid)-mass production, processing, industrial applications, and end of life
Adv. Drug Deliv. Rev.
(2016)
J.-M. Raquez et al.
Polylactide (PLA)-based nanocomposites
Prog. Polym. Sci.
(2013)
M. Murariu et al.
PLA composites: from production to properties
Adv. Drug Deliv. Rev.
(2016)
S. Farah et al.
Physical and mechanical properties of PLA, and their functions in widespread applications - a comprehensive review
Adv. Drug Deliv. Rev.
(2016)
Y. Zhou et al.
Preparation and characterization of polylactic acid (PLA) carbon nanotube nanocomposites
Polym. Test.
(2018)
Z. Wang et al.
Improvement of polylactic acid film properties through the addition of cellulose nanocrystals isolated from waste cotton cloth
Int. J. Biol. Macromol.
(2019)
P. Karami et al.
Polymer/nanodiamond composites - a comprehensive review from synthesis and fabrication to properties and applications
Adv. Colloid Interf. Sci.
(2019)
Z. Delavar et al.
Enhanced mechanical properties of chitosan/nanodiamond composites by improving interphase using thermal oxidation of nanodiamond
Carbohydr. Polym.
(2017)
C. Shuai et al.
Surface modification of nanodiamond: toward the dispersion of reinforced phase in poly-L-lactic acid scaffolds
Int. J. Biol. Macromol.
(2019)
M. Khan et al.
Reinforcement effect of acid modified nanodiamond in epoxy matrix for enhanced mechanical and electromagnetic properties
Diam. Relat. Mater.
(2017)

D. Mitev et al.

Surface peculiarities of detonation nanodiamonds in dependence of fabrication and purification methods

Diam. Relat. Mater.

(2007)

B.V. Spitsyn et al.

The physical–chemical study of detonation nanodiamond application in adsorption and chromatography

Diam. Relat. Mater.

(2010)

H. Tinwala et al.

Production, surface modification and biomedical applications of nanodiamonds: a sparkling tool for theranostics

Mater. Sci. Eng. C

(2019)

S. Kumar et al.

Nanodiamonds: emerging face of future nanotechnology

Carbon

(2019)

S. Xiong et al.

Poly(ε-caprolactone)-grafted polydopamine particles for biocomposites with near-infrared light triggered self-healing ability

Polymer

(2016)

N.D. Mao et al.

Polyethylene glycol functionalized graphene oxide and its influences on properties of poly(lactic acid) biohybrid materials

Compos. Part B

(2019)

J. Wang et al.

A facile approach of fabricating proton exchange membranes by incorporating polydopamine-functionalized carbon nanotubes into chitosan

Int. J. Hydrog. Energy

(2019)

C. Liu et al.

Facile fabrication of superhydrophobic polyurethane sponge towards oil-water separation with exceptional flame-retardant performance

Sep. Purif. Technol.

(2019)

R. Liu et al.

Synthesis of biopolymer-grafted nanodiamond by ring-opening polymerization

Diam. Relat. Mater.

(2014)

Y. Li et al.

Enhancing water permeability and fouling resistance of polyvinylidene fluoride membranes with carboxylated nanodiamonds

J. Membr. Sci.

(2018)

L. Zhu et al.

Preparation and characterization of dopamine-decorated hydrophilic carbon black

Appl. Surf. Sci.

(2012)

M. Varga et al.

Templated diamond growth on porous carbon foam decorated with polyvinyl alcohol-nanodiamond composite

Carbon

(2017)

N. Wang et al.

Influence of carbon black on the properties of plasticized poly(lactic acid) composites

Polym. Degrad. Stab.

(2008)

S.A. Rakha et al.

Comparison of mechanical properties of acid and UV ozone treated nanodiamond epoxy nanocomposites

J. Mater. Sci. Technol.

(2014)

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Effect of polyethylene glycol surface modified nanodiamond on properties of polylactic acid nanocomposite films

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

FTIR analysis

Conclusions

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgements

Adv. Drug Deliv. Rev.

Prog. Polym. Sci.

Adv. Drug Deliv. Rev.

Adv. Drug Deliv. Rev.

Polym. Test.

Int. J. Biol. Macromol.

Adv. Colloid Interf. Sci.

Carbohydr. Polym.

Int. J. Biol. Macromol.

Diam. Relat. Mater.

Diam. Relat. Mater.

Diam. Relat. Mater.

Mater. Sci. Eng. C

Carbon

Polymer

Compos. Part B

Int. J. Hydrog. Energy

Sep. Purif. Technol.

Diam. Relat. Mater.

J. Membr. Sci.

Appl. Surf. Sci.

Carbon

Polym. Degrad. Stab.

J. Mater. Sci. Technol.