Preparation and glass transition temperature of hyperbranched poly[allyl methyl maleate-co-N-propyl maleimide]

The kinetics and molecular weight averages of the hyperbranched polymers formed by the alternating copolymerization of equimolar allyl methyl maleate (AMM) and N-n-propyl maleimide (PMI) were investigated. The yields, molecular weight averages, and polydispersity indices as well as the branching degrees of the produced copolymers increased with increasing initiator concentrations and prolonged polymerization time. The trends of the experimental molecular weights as determined by size exclusion chromatography were in good agreement with the theoretical predictions. The molecular weight distribution indices fit the curve given by Mw/Mn = 1/(1-xD), and the molecular weights fit the curve given by Mw = 4076/(1-xD)2, where xD was the conversion of vinyl groups. DSC studies demonstrated a nonlinear relation of Tg values to the reciprocal of molecular weight (M), and Tg values decreased with the increase of molecular weight. For the Tg values of highly branched polymers in high molecular weight range, a relation of Tg = T[stack g\(infinity)0 ] + k/M was obtained, where T[stack g(infinity)0 ] was obtained by extrapolating to infinite molecular weight and k was a constant. T[stack g(infinity)0 ] was 136(degree)C, and k = 2.9 for this work.