Conformational inversion of polyethylene-polyvinyl acetate graft copolymerin selective solvents by viscometry

Viscometric measurements were performed for a low molecular weight polyethy lene (LMWPE) and the LMWPE grafted vinyl acetate (E-g-VA) copolymer in a se ries of binary solvent mixtures. consisting of a polar and a non-polar solv ents. The degree of grafting (DG) or VA content dependence of the intrinsic viscosity [eta]. Huggins constant k(H) and the critical association concen tration CA. Of the polymers are investigated in the 1,2-dichloroethane (DCE )/cyclohexane (CYH) solvent mixtures, especially in phi (c) = 0.3 and phi ( c) = 0.9 (phi (c) is the volume fraction of CYH in solvent mixtures). The o pposite variations of [eta], k(H) and C-A With the increasing of DG of the polymers studied at 30 degreesC were observed in different solvent mixtures of phi (c) = 0.3 and phi (c) = 0.9 respectively. Moreover, the inversion v ariation of [eta] of E-g-VA graft copolymer acid its parent polymer (LMWPE) occurred with the change of the composition of the solvent mixtures. A lar ge difference of the viscous flow energy of the E-g-VA graft copolymers fro m two different kinds of solvent mixtures of phi (c) = 0.3 and phi (c) = 0. 9 respectively was also found. These phenomena can be accounted for by the conformational inversion of the E-g-VA graft copolymer in the selective sol vents. (C) 2001 Elsevier Science Ltd. All rights reserved.