Viscoelastic behavior and submolecular level dynamic heterogeneity of hydrogen‐bonded polymer blends probed by dynamic FTIR spectroscopy

Viscoelastic behavior and submolecular (functional group) level dynamic heterogeneity of hydrogen‐bonded poly(vinyl phenol)/poly(methyl acrylate) (PVPh/PMA) blends were investigated by using dynamic FTIR spectroscopy. It has been found that the viscoelastic behaviors of the blends, measured by the dynamic (in‐phase and quadrature) spectra of both “free” and hydrogen‐bonded carbonyl groups are dependent on the compositions, i.e., the T_g of the blends, and the degree of hydrogen bonding between the two components. In all the blends studied, elastic response of the hydrogen‐bonded carbonyl groups to the applied strain has been found. The free carbonyl groups respond differently to the applied strain in these blends. Essentially, elastic response of the free carbonyl groups to the applied strain is observed in blends with both a high T_g and a higher fraction (～ 40%) of intermolecular hydrogen bonding between PVPh and PMA, and the submolecular level dynamic heterogeneity is suppressed. The free carbonyl group has a viscous component to its response, in blends having a lower fraction (～ 20%) of hydrogen bonds, even at temperatures well below the thermal T_g of the blends, suggesting that there is a degree of submolecular level dynamic heterogeneity in these blends. Almost entirely viscous response of the free carbonyl group is found in blends whose T_g is close to room temperature and fraction of PVPh/PMA hydrogen bonds is very low. The results reported here suggest that dynamic FTIR has considerable potential for studying specific interactions and viscoelastic behaviors in hydrogen‐bonded polymer blends on submolecular level. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009