2-DIMENSIONAL NMR-STUDIES OF MOLECULAR-WEIGHT AND CONCENTRATION EFFECTS ON POLYMER POLYMER INTERACTIONS

Two-dimensional (2D) NMR experiments are used to measure the effects of molecular weight and concentration on polymer-polymer interaction for polystyrene-poly(vinyl methyl ether) mixtures in toluene. Through-space dipolar interactions lead to exchanges of magnetization that can be observed as cross peaks in a 2D nuclear Overhauser effect experiment. Concentration-dependent intrachain transfer is observed for both polymers, and specific polymer-polymer interchain transfer is observed between the polystyrene phenyl protons and the poly(vinyl methyl ether) methoxyl protons. For mixtures with polyvinyl methyl ether) of 72 000 molecular weight, interchain transfer is similar for polystyrenes of 110 000 and 35 000 molecular weight. Transfer is diminished in 17 500 and 9000 molecular weight mixtures and disappears when the polystyrene molecular weight decreases below 4000. Interchain magnetization transfer is independent of polymer tacticity, and intrachain dipolar interactions are shown to be sensitive to chain entanglement. © 1990, American Chemical Society. All rights reserved.