Synthesis of micrometer-sized poly(vinyl acetate) particles through microsuspension iodine transfer polymerization: effect of iodine species in a water medium

Microsuspension iodine transfer polymerization (ms ITP) of vinyl acetate (VAc) was demonstrated for the first time with simulation of the polymerization rate in the aqueous phase (Rw(p)). The high polymerization temperature induced the degradation of poly(vinyl acetate) with an iodine end group (PVAc-I) and the formation of a crosslinking structure, which was worsened by the presence of the dispersant-poly(vinyl alcohol) (PVA) used in this work. Furthermore, the increase in the molecular weight distribution (M-w/M-n) with the monomer conversion was attributed to PVAc-I degradation and iodine hydrolysis. Upon considering the effect of iodine species, the mechanism of ITP in an aqueous system was further clarified. The micrometer-sized particles consisting of well-defined poly(vinyl acetate) (PVAc) were finally achieved by performing the ms ITP using iodoform (CHI3) as the chain transfer agent and 2,2 '-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as the initiator at a low polymerization temperature of 30 degrees C, where the particle size was 22.3 mu m and the molecular weight (M-n = 26 000, M-n,M-th = 26 900) was effectively controlled. The prepared PVAc was further successfully hydrolyzed into PVA with a desired molecular weight and narrow molecular weight distribution.

Automated summary

The study demonstrated the microsuspension iodine transfer polymerization of vinyl acetate for the first time, investigating the influences of polymerization temperature, dispersant, and iodine species on the properties of the polymer products. Effective control of polymer molecular weight and distribution was achieved in the process.