Won Seok Lyoo, Jin Woo Kwak, Jeong Hyun Yeum, Byung Chul Ji, Chul Joo Lee and Seok Kyun Noh
The particle size distributions of poly(vinyl pivalate) (PVPi) produced from low-temperature suspension polymerization of vinyl pivalate (VPi) using 2,2′azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMDMVN) as an initiator have been studied. By controlling vaious synthesis parameters, near-monodisperse PVPi microspheres from 100 μm to 400 μm were obtained, which are expected to be a precursor of near-monodisperse syndiotactic poly(vinyl alcohol) (PVA) microspheres for biomedical embolic applications. The mean particle diameter follows the relationship: the volume average diameter, Dvad∝Y0.26[VPi]0.52[AMDMVN]−0.25[PVA]0.40T−8.35Rpm−0.67, where Y, [VPi], [AMDMVN], [PVA], T, and Rpm are the fractional conversion, concentrations of VPi, AMDMVN, and suspending agent, polymerization temperature, and agitation speed during polymerization of VPi, respectively. Ultrahigh molecular weight PVPi and PVA (number-average degrees of polymerization of PVPi (25,000–32,000) and PVA (14,000–17,500), of high syndiotactic diad content (63%), and of high ultimate conversion of VPi into PVPi (85–95%) were obtained by suspension polymerization at 10 °C followed by saponification.