Interpolymer complexes and miscible blends of poly(p-vinyl phenol) and poly(ethylene imine)

Interpolymer complexation between poly(p-vinyl phenol) (PVPh) and poly(ethylene imine) (PEI) in various solvents was studied. By mutual mixing of solutions of PVPh and PEI, precipitates of PVPh/PEI complexes were prepared from methanol, ethanol, cyclohexanone, N,N-dimethylformamide and N,N-dimethylacetamide. However, only polymer blends were obtained from N-methyl-2-pyrrolidone (NMP). It has been found that solvent molecules also participate in hydrogen-bonding interactions, either as donors or accepters, with a component polymer; the nature of the solvent assumes a profound influence on the degree of the interpolymer association. The glass transition (T-g) behavior of the complexes and the blends were studied by DSC. Both the complex and the blend showed one composition-dependent T-g, indicating its single-phase nature, and the PVPh/PEI blends prepared by casting from NMP are miscible over the entire composition range. The complexes showed higher T(g)s in comparison with those of the blends having the same compositions and positive deviations of T-g were observed for the complexes, suggesting that the strength of the interactions between the components in the complex is much higher than that in the blend. FT-IR study revealed that there are hydrogen-bonding interactions between hydroxyl groups of PVPh and N-H groups of PEI in the blends cast from NMP and that the average strength of the hydrogen bond between the hydroxyl groups of PVPh and the N-H groups of PEI in the blend is much higher than that between hydroxyl groups in pure PVPh. A fluorescence study confirmed that there are stronger interactions between PVPh and PEI in ethanol than in NMP. The interpolymer complexation of PVPh with PEI in ethanol reduces the possibility of the formation of excimer between the structural units of PVPh. (C) 1997 Elsevier Science Ltd. All rights reserved.