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Stabilizer‐Free Dispersion Copolymerization of Maleic Anhydride and Vinyl Acetate. II. Polymerization Features
Author(s) -
Xing ChangMin,
Yu Yong,
Yang WanTai
Publication year - 2006
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200500527
Subject(s) - copolymer , dispersion polymerization , polymer chemistry , polymerization , monomer , vinyl acetate , maleic anhydride , dispersion (optics) , chemistry , materials science , polymer , organic chemistry , physics , optics
Summary: The polymerization features of the novel stabilizer‐free dispersion copolymerization of MAn and VAc were studied. It was found that the dispersion copolymerization of MAn/VAc is a fairly rapid process, which starts from a slow solution polymerization (below 10% conversion, Stage I) and follows a drastic increase of polymerization rate (10–80% conversion, Stage II) due to the known gel effect. Such process was accompanied by the increase of molecular weight of the copolymer formed ( $\overline M _{\rm n}$ from 1.2 × 10 4 to 3.8 × 10 4 g · mol −1 ) and the broadening of the molecular weight distribution ( $\overline M _{\rm w} /\overline M _{\rm n}$ from 2.4 to 8.0). E a of Stage I was determined to be 76.7 kJ · mol −1 , while the value of Stage II was 64.7 kJ · mol −1 . The lower E a in Stage II than that in Stage I suggests that there exists a shift of polymerization locus from the solution phase to the particle phase. Moreover, we found that the initial rate of polymerization increased with monomer concentration as well as initiator concentration, following the relationship ( R p ) i ∝ [MAn + VAc] o 0.92 · [BPO] o 0.57 . This further implies that the dispersion copolymerization mainly proceeds as a solution polymerization in the very early stage.Evolutions of the stabilizer‐free dispersion copolymerization of MAn and VAc with butyl acetate as reaction medium and the solution copolymerization with methyl propyl ketone as solvent.