Orientation of uniaxially stretched poly(vinyl phenol)/poly(vinyl methyl ether) blends

Orientation of poly(vinyl phenol) (PVPh)-poly(vinyl methyl ether) (PVME) am orphous miscible blends has been studied using FTIR spectroscopy. Blends of 33, 42, 53 and 66% (mol/mol) in PVPh were uniaxially stretched at 0.1 s(-1 ) and T-g + 15. Both polymers showed similar orientation values in the blen d. Whereas, at high PVPh concentration, the orientation function <P-2> is l inear with deformation, at intermediate compositions a non-linear relations hip was observed, attributed to a fast relaxation. Orientation of both poly mers increases with PVME concentration up to 48 mol% (40 wt%) composition. For blends richer in PVME, orientation decreases. It is proposed that the m aximum in orientation is related to the presence of strong intermolecular P VPh-PVME hydrogen bonds, which hinder relaxation and increase the friction coefficient. Comparison with PVPh-poly(methyl methacrylate) and PVPh-poly(e thylene oxide) blends, which are both hydrogen bond containing systems, sug gest that hydrogen bonds hinder relaxation and could favor cooperativity. M oreover, comparison to poly(styrene)-poly(vinyl methyl ether) blends, a sim ilar system that does not present hydrogen bonds and that was studied by va rious groups previously, shows that the maximum in orientation is related t o interaction fluctuations. (C) 2001 Elsevier Science Ltd. All rights reser ved.