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Ab Initio Batch Emulsion Thiol–Ene Photopolymerization
Macromolecules ( IF 5.5 ) Pub Date : 2020-04-01 , DOI: 10.1021/acs.macromol.0c00265
Cuong Minh Quoc Le 1, 2 , Marc Schmutz 3 , Abraham Chemtob 1, 2
Affiliation  

Very few step polymer latexes have been produced by aqueous emulsion polymerization and never with a clear picture of the operating mechanism. Therefore, finding new means to expand this widely used process industrially beyond chain radical polymerization is highly desirable. Herein, we report the successful photo-initiated thiol–ene radical polyaddition of an emulsion based on two bifunctional monomers diallyl phthalate and 2,2-(ethylenedioxy)diethanedithiol. After 20 min of irradiation (λmax = 385 nm, 3.7 mW cm–2), polymerization resulted in a conversion above 99%, a coagulum-free poly(thioether) latex with a solid content of 10 wt %, a number-average molecular weight of 14 kDa, and an average particle diameter of 60 nm. Reaction kinetics, particle size distribution, and molecular weight progress have been studied in detail. To clarify the mechanism dictating particle formation, the number of particles per unit volume of water has been determined depending on reaction time and surfactant and initiator concentration. The nucleation mode is found to depart significantly from conventional chain radical emulsion polymerization. Polymer particle formation mainly proceeds through the precipitation of oligo-radicals (homogeneous nucleation) even when the concentration of the surfactant exceeds its critical micelle concentration. The end of nucleation (interval I) occurs until a monomer conversion of about 95%. The dispersion’s solid content can reach as high as 40%, and the molecular weights remain reasonable (>4 kDa) even if the functional groups are stoichiometrically imbalanced. In contrast to conventional thermally induced polymerization, temporal control is demonstrated through sequential “on”/“off” cycles, and tuning of molecular weights is achieved by precise energetic dosage of radiation. This new step photopolymerization in emulsion thus opens an avenue for the synthesis of linear polysulfide latexes without high energy homogenization and at low irradiance.

中文翻译:

从头开始批量乳液硫醇-烯光聚合

通过水乳液聚合已经生产了极少的步骤聚合物胶乳,并且从来没有清楚的操作机理图。因此,迫切需要寻找新的方法来将该工业上广泛使用的方法扩展到链自由基聚合之外。在这里,我们报道了基于两种双官能单体邻苯二甲酸二烯丙基酯和2,2-(乙烯二氧基)二乙烷二硫醇的乳液的光引发硫醇-烯基自由基加成反应。照射20分钟后(λmax = 385 nm,3.7 mW cm –2),聚合导致高于99%的转化率,固体含量为10wt%,数均分子量为14kDa,平均粒径为60nm的无凝结的聚(硫醚)胶乳。已详细研究了反应动力学,粒度分布和分子量变化。为了阐明决定颗粒形成的机理,已经根据反应时间以及表面活性剂和引发剂浓度确定了每单位体积的水的颗粒数。发现成核模式明显不同于常规的链自由基乳液聚合。即使表面活性剂的浓度超过其临界胶束浓度,聚合物颗粒的形成也主要通过低聚自由基的沉淀(均相成核)进行。成核的结束(间隔I)发生直到单体转化率达到约95%为止。分散体的固体含量可高达40%,并且即使官能团在化学计量上不平衡,分子量仍保持合理(> 4 kDa)。与传统的热引发聚合相反,通过顺序的“开” /“关”循环证明了时间控制,并且通过精确的高能辐射剂量实现了分子量的调节。乳液中的这一新的光聚合步骤因此为合成线性多硫化物胶乳开辟了一条途径,这种合成方法无需高能量均质化和低辐照度。即使这些官能团在化学计量上是不平衡的,仍然是4 kDa)。与传统的热引发聚合相反,通过顺序的“开” /“关”循环证明了时间控制,并且通过精确的高能辐射剂量实现了分子量的调节。乳液中的这一新的光致聚合步骤因此为合成线性多硫化物胶乳开辟了一条途径,这种合成方法无需进行高能量均化和低辐照度。即使这些官能团在化学计量上是不平衡的,仍然是4 kDa)。与传统的热引发聚合相反,通过顺序的“开” /“关”循环证明了时间控制,并且通过精确的高能辐射剂量实现了分子量的调节。乳液中的这一新的光致聚合步骤因此为合成线性多硫化物胶乳开辟了一条途径,这种合成方法无需进行高能量均化和低辐照度。
更新日期:2020-04-24
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