Miscibility and Hydrogen Bonding in Blends of Poly(vinylphenol-co-methyl methacrylate) with Poly(ethylene oxide)

Blends of poly(vinylphenol-co-methyl methacrylate) (PVPh-co-PMMA) with poly(ethylene oxide) (PEO) were prepared by solution casting from tetrahydrofuran (THF) solution. The miscibility behavior and hydrogen bonding of blends were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (NMR). Experimental results indicate that PEO was miscible with PVPh-co-PMMA as shown by the existence of single composition-dependent glass transition temperatures over the entire composition range by DSC. In addition, a negative polymer-polymer interaction energy density "B" was calculated based on the melting depression of PEO using the Nishi-Wang equation. Solid-state NMR reveals single-exponential decay of proton spin-lattice relaxation times in the rotating frame (T1F H ) in the amorphous PVPh-co- PMMA phase. Furthermore, FTIR and solid-state NMR results reveal that at least three competing equilibria are present in the blend; self-association of PVPh-co-PMMA copolymer (hydroxyl-hydroxyl and hydroxyl-carbonyl) and hydroxyl-ether interassociation between PVPh and PEO. Quantitative results show that although the hydroxyl-ether interassociation is favored at room temperature, the hydroxyl-carbonyl self-association dominates at higher temperatures (>70 °C). The Painter-Coleman association model (PCAM) can predict three interacting functional groups based on our experimental results at various temperatures.