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The intermolecular interactions responsible for miscibility in 1,2-polybutadiene/cis-polyisoprene blends have been investigated using solid-state two-dimensional (2D) NMR. We find that highresolution proton spectra can be obtained at temperatures above Tg using magic-angle spinning and that intermolecular association can be probed using nuclear Overhauser effect spectroscopy. The results reveal the existence of weak intermolecular interactions between the polyisoprene methyl group and the 1,2polybutadiene vinyl side chain. These studies demonstrate the large effect that weak intermolecular interactions can have on the phase structure of polymer blends.

Fast magic-angle spinning solid-state proton NMR has been used to study the structure and dynamics of poly(ethyl acrylate) in bulk and polymerized in a Vycor glass with 40 Å pores. Bulk poly(ethyl acrylate) is a low-T g material, and high-resolution solid-state proton NMR spectra are observed at ambient temperature because the dipolar interactions are averaged by the combination of chain motion and fast magic-angle sample spinning. The spectrum of the poly(ethyl acrylate)/Vycor composite shows signals in addition to those of the polymer that are assigned to water and surface hydroxyl groups in the porous glass. Integration of the composite and bulk poly(ethyl acrylate) signals reveals that the volume fraction of polymer in the pores is 0.56 and that the polymer occupies the central 30 Å in a 40 Å pore. Spin diffusion studies demonstrate that filling of the poly(ethyl acrylate)/Vycor is incomplete, and a fraction of the water in the pores is isolated from the polymer. Multiple-quantum NMR studies reveal a large difference in chain dynamics between the bulk poly(ethyl acrylate) and the porous glass composite, and 2D wide line separation NMR shows that the polymer is restricted at the surface of the pores but has bulklike mobility in the center of the pore.

This paper reports a deuterium effect involving poly (styrene-co-methyl methacrylate) alternating copolymer/poly(methyl methacrylate) homopolymer blends, AB/A, in which deuteration of the methyl methacrylate (MMA) monomer unit influences blend miscibility. Two blend compositions were investigated, 35 % /65 % and 50%/50%, using DSC and TEM. Perdeuteration of the MMA units of the copolymer promotes miscibility, perdeuteration of the MMA units of the homopolymer reduces miscibility, and the absence of perdeuteration exhibits intermediate miscibility. These results are interpreted using the concept that intramolecular repulsion within a copolymer can promote copolymer/homopolymer miscibility. Using the sequence-independent models for copolymer/homopolymer blends, we have determined xps,d-pmma > XPSfl-PMMA, which is consistent with measurements of these interaction parameters by others.

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