MEASUREMENTS OF THE FLORY-HUGGINS INTERACTION PARAMETER FOR POLYSTYRENE-POLY(4-VINYLPYRIDINE) BLENDS

We have measured the Flory-Huggins interaction parameter (chi) for ble nds of polystyrene (PS) and poly(4-vinylpyridine) (P4VP) by three diff erent methods. First, we measured the micelle spacings in microphase-s eparated films of PS-P4VP diblock copolymers by secondary ion mass spe ctrometry and atomic force microscopy. Second, we measured the contact angle of droplets of homopolymer PS on P4VP homopolymer film. Finally we determined the interfacial width between homopolymer layers of dPS and P4VP by neutron reflectometry. From each of these experiments chi was calculated using mean field theory in the strong segregation limi t. These values of chi are much larger than those of other nonionic po lymer pairs. Pie discuss the importance of this findings.