writer：Feng Bai, Bo Huang, Xinlin Yang*, Wenqiang Huang
keywords：Poly(methacrylic acid) microsphere; Hydrogen-bonding interaction; Distillation–precipitation polymerization; Growth mechanism
source：期刊
specific source：Eur. Polym. J., 43 (9), 3923-3932 (2007). DOI: 10.1016/j/europolymj.2007.06.024
Issue time：2007年

Monodisperse poly(methacrylic acid) (PMAA) microspheres were prepared by distillation–precipitation polymerization in acetonitrile with 2,20-azobisisobutyronitrile (AIBN) as initiator. The polymeric microspheres were formed simultaneously via a precipitation polymerization manner during the distillation of the solvent out of the reaction system in the absence of any surfactant and crosslinker. Monodisperse PMAA microspheres with spherical shape and smooth surface were synthesized with diameters ranging from 60 to 290 nm below the glass transition temperature of PMAA without any stabilizer. The particle size increased with increasing monomer concentration, which may be resulted from the higher molecular weight for the polymerization. To investigate the growth procedure of PMAA microspheres, the morphology of microspheres over the distillated acetonitrile volume was conducted by monitoring the morphologies with TEM. GPC and FTIR provide key insights into the particle growth mechanism. The PMAA microspheres may be formed by an internal contraction due to the marginal solvency of the continuous phase with the aid of the hydrogen-bonding interaction
between the carboxylic acid unit, in which the particles were stabilized by the steric effect of the pendent chains and surface gel as well as the electrostatic repulsion from the carboxylic acid group.