| Abstract: | Significant drift in the compositions of copolymer and of unreacted monomer mixture is predicted to occur during the bulk copolymerization of N-vinyl-2-pyrrolidone (VP) with butyl acrylate (BA), when the inital feed mixture contains 75 wt.-% VP. The drift in copolymer composition has been confirmed by 1 the optical appearance and glass transition (Tg) behaviour of the products of the γ-ray initiated copolymerization at various fractional conversions (C) and 2 the Tg behaviour of low-conversion samples of poly(VP-co-BA) blended in propertions so as to simulate the overall composition of material that would be present cumulatively at selected values of C during an actual copolymerization. The compositions of unreacted monomer mixtures co-existing with copolymer at selected conversions have been calculated and intrinsic viscosities [η] of blends dissolved in these VP/BA mixtures have been measured. Theta conditions for the blends have been established turbidimetrically in chloroform/heptane and the corresponding values of [η]Θ measured. The chain expansion factors thereby derived from [η] and [η]Θ show a decreasing affinity of copolymer for residual monomer during the course of copolymerization. |
