悬浮聚合制备大尺寸梭形聚苯乙烯粒子新方法及机理研究

利用氢氧化钾对苯乙烯-马来酸酐交替共聚物(SMA)进行水解,所得中等皂化程度的SMA水解产物(SMAA)在水溶液中具有刚性棒状直链构型;将此特殊结构的大分子作为分散剂用于苯乙烯悬浮聚合,通过控制搅拌速度和油水比,可得到梭形聚苯乙烯粒子;在优化条件下,粒子平均长度6.8 mm,宽度1.4 mm,厚度0.5 mm,长径比约5.0.其可能的机理为,中等皂化程度的刚棒直链型SMAA在聚合物"软粒子"表面能形成难以"回复"的有效保护层,使由剪切形成的变形聚合物"软粒子"在聚合过程中能保持形状和尺寸的稳定,从而得到梭形聚合物粒子.

PREPARATION OF MACRO-SCALE SPINDLE POLYSTYRENE PARTICLES BY SUSPENSION POLYMERIZATION AND THEIR FORMATION MECHANISM

Poly(styrene-alt-maleic anhydride)(SMA) was prepared by solution polymerization of styrene(St) and(MAH).SMA was saponified with KOH to get SMAA,and the resulting SMAA then served as polymeric surfactant for the suspension polymerization of St.The influence of ionization degree of SMAA,rotation speed and weight ratio of St to water on the size and morphology of the obtained PS particles has been studied in detail by optical microscopy and SEM.When ionization degree of the SMAA was 50%,the SMAA was partially saponified product containing both carboxylic acid and carboxylate groups.By using this SMAA as polymeric surfactant,spindle PS particles were prepared at high ratios of St to water(3.0∶3.5~3.0∶4.5) and medium rotation speeds.At optimum reaction conditions,the average size of the particles was 6.8 mm in length,1.4 mm in width,0.5 mm in thickness and the ratio of length to width was 5.0.With increasing rotation speed,the size of the particles decreased gradually and the ratio of length to width became higher.Based on these experiment results,the formation mechanism of the PS nonspherical particles by suspension polymerization in the presence of SMAA was preliminarily proposed.