扩散控制无皂乳液聚合法制备纳米聚合物微球

Preparation of nanoparticles via diffusion-controlled soap-free emulsion polymerization

在不添加任何乳化剂的条件下,将甲基丙烯酸(MAA)和苯乙烯(St)单体进行无皂乳液聚合,制备纳米聚合物微球。由于采用的搅拌速率较低,单体相和水相呈现层状分布,聚合反应速率由单体扩散速率控制。跟传统的动力学控制乳液聚合法相比,扩散控制所得产物粒径较小,最小可达35nm,且乳液稳定性较好。采用傅里叶变换红外光谱仪(FTIR)、动态激光光散射(DLS)、核磁(1 HNMR)、扫描电镜(SEM)对其进行表征。并研究了反应温度、引发剂用量、单体摩尔配比对乳液稳定性和微球粒径的影响,发现反应温度在80℃,引发剂的占单体质量百分数为25%,单体摩尔配比1:2.5的时候乳液稳定,微球最小粒径35nm,57.7%的粒子小于100nm。

Nanoparticle formation by soap-free emulsion polymerizations of two monomers including styrene and methacrylic acid were carried out under highly diffusion-controlled conditions. The monomers were placed on top of an aqueous solution of an initiator, while being gently stirred. Polymerization occurred by diffusion of monomer from the monomer phase via the interface to the aqueous solution. The results were compared with those obtained with a high rate of agi- tation which allowed kinetics of polymerization to become the rate determinant. Nanopartieles as small as 35nm were produced as a result of reduced particle growth. Nanoparticles were characterized by FTIR, DIS, 1H-NMR snd SEM. Emulsion stability and particle size influenced by temperature, initiatorand monomers was studied. Emulsion was well stability, the smallest particle size was 35nm, 58 percent of particles were smaller than 100nm when the temperature was 80℃, the weight of initiator was 25 % （mass percent of monomers）, monomers mole ratio（MAA/St）was 1：2. 5.