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Development of Living Radical Emulsion Polymerization

活性自由基乳液聚合的进展

基本信息

批准号：
12555260
负责人：
FUKUDA Takeshi
金额：
$ 3.84万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

It is theoretically predicted that the degenerative chain transfer-mediated living radical polymerization (LRP) carried out in an emulsion or dispersion polymerization system under specific conditions will provide an elongated radical lifetime and an increased frequency of degenerative chain transfer. In other words, LRP carried out in the inhomogeneous system is predicted to give longer chains with a lower polydispersity and a higher fraction of chain end activity (livingness) than LRP carried out in a homogeneous system. In order to test these theoretical predictions, polymerization of methyl methacrylate (MMA) and styrene were carried out in an emulsion and a dispersion system. Notable results obtained in the dispersion system will be reported below.Optimization of the aqueous-phase solvent (75% ethanol), dispersant (polyacrilic acid), and temperature (70℃), resulted in PMMA with a number-average molecular weigh about 1.0 x 10^5 and a polydispersity index M_w/M_n about 1.1, verifying the theory. However, some mutual adhesion of the PMMA particles was observed, which remains to be a problem to be solved. In the styrene polymerization, in which polyvinyl pyrrolidone was used as a dispersant, no such adhesion of the particles was observed. The polymerization gave polystyrene particles of controllable and homogeneous size (typically 2μm) composed of well defined polystyrene. For both MMA and styrene, the polymerization was completed in a short time, meaning that the effective radical concentration was exceptionally high, and thus increasing the performance, and making better use, of the degenerative chain transfer type of LRP.

理论上预测，在特定条件下在乳液或分散聚合体系中进行的退化链转移介导的活性自由基聚合（LRP）将提供延长的自由基寿命和增加的退化链转移频率。换句话说，与在均相系统中进行的 LRP 相比，在非均相系统中进行的 LRP 预计会产生更长的链，具有较低的多分散性和较高的链端活性（活性）分数。为了检验这些理论预测，在乳液和分散体系中进行了甲基丙烯酸甲酯（MMA）和苯乙烯的聚合。下面将报道分散体系中获得的显着结果。通过对水相溶剂（75%乙醇）、分散剂（聚丙烯酸）和温度（70℃）的优化，得到的PMMA数均分子量约为1.0 x 10^5，多分散指数M_w/M_n约为1.1，验证了理论。然而，观察到PMMA颗粒之间存在一些相互粘附，这仍然是一个有待解决的问题。在使用聚乙烯吡咯烷酮作为分散剂的苯乙烯聚合中，没有观察到这种颗粒的粘附。聚合反应产生由明确的聚苯乙烯组成的可控且均匀尺寸（通常为2μm）的聚苯乙烯颗粒。对于MMA和苯乙烯来说，聚合反应在短时间内完成，这意味着有效自由基浓度异常高，从而提高了退化链转移型LRP的性能并更好地利用。