原子转移自由基聚合合成聚乙烯胺大分子单体及其共聚反应研究

以水为反应介质, 采用原子转移自由基聚合(ATRP), 在70 ℃下合成了末端为溴原子的聚丙烯酰胺预聚体(PAM-Br). 利用水相凝胶渗透色谱(GPC)对PAM-Br的相对分子质量和分子量分布进行了表征, 结果表明: 单体浓度、单体与引发剂物质的量之比和反应时间对PAM-Br的分子量及其分布有较大的影响, 在较低AM单体与引发剂物质的量比条件下, 其聚合过程符合ATRP的基本规律. 进而使PAM-Br预聚体末端的溴原子与甲基丙烯酸(MAA)进行亲核取代反应, 得到了末端带有不饱和双键的大分子单体(MAA-PAM). 并利用霍夫曼降解制备出了部分胺解的聚乙烯胺(MAA-PVAm)大分子单体, 其结构由傅里叶变换红外(FTIR)和核磁共振仪(NMR)的表征得到了确定. 以得到的大分子单体为反应性分散稳定剂, 与苯乙烯在乙醇/水的混合介质中进行分散共聚反应, 制得了聚苯乙烯接枝MAA-PVAm (PS-g-PVAm)复合微球, 由扫描电子显微镜(SEM)观察发现: 微球保持规整的球形结构, 粒径分布均一, 有较好的单分散性.

Synthesis of Polyvinylamine Macromonomer by Atom Transfer Radical Polymerization and Its Copolymerization

Polyacrylamide with a bromine atom end group (PAM-Br) was synthesized by atom transfer radical polymerization (ATRP) of acrylamide (AM) in water at 70 ℃. The molecular weight and molecular weight distribution of the PAM-Br were characterized by aqueous gel permeation chromatography (GPC). It was found that the molecular weight and molecular weight distribution of PAM-Br were affected by changing concentration of AM, ratio of AM monomer to initiator and reaction time. The reaction process contributed to the basic rule of ATRP under a low molar ratio of AM]∶EPN-Br]＝25∶1. Furthermore, the polyacrylamide macromonomers (MAA-PAM) with vinyl double end groups were successful prepared by the nucleophilic substitution reaction of bromine atom to methacrylic acid (MAA). Then polyvinylamine macromonomers (MAA-PVAm) were obtained by Hofmann degradation reaction of MAA-PAM at 0 ℃. The structure of MAA-PVAm was characterized by using FTIR and NMR spectra. The polymeric microspheres were also prepared by dispersion copolymerization of MAA-PVAm macromonomers with styrene using 2,2’-azobisisobutyronitrile as an initiator in ethanol/water mixed solvent. The polymeric microspheres have sphere morphology and uniformity of diameters based on the observation of scanning electron microscopy.