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

Orientation of poly(vinyl phenol) (PVPh)–poly(vinyl methyl ether) (PVME) amorphous 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 Tg+15. Both polymers showed similar orientation values in the blend. Whereas, at high PVPh concentration, the orientation function 〈P2〉 is linear with deformation, at intermediate compositions a non-linear relationship was observed, attributed to a fast relaxation. Orientation of both polymers increases with PVME concentration up to 48 mol% (40 wt%) composition. For blends richer in PVME, orientation decreases. It is proposed that the maximum in orientation is related to the presence of strong intermolecular PVPh–PVME hydrogen bonds, which hinder relaxation and increase the friction coefficient. Comparison with PVPh–poly(methyl methacrylate) and PVPh–poly(ethylene oxide) blends, which are both hydrogen bond containing systems, suggest that hydrogen bonds hinder relaxation and could favor cooperativity. Moreover, comparison to poly(styrene)–poly(vinyl methyl ether) blends, a similar system that does not present hydrogen bonds and that was studied by various groups previously, shows that the maximum in orientation is related to interaction fluctuations.