Hydrogen Bonding Interaction and Miscibilization of Ternary Blends of Poly(2‐vinylpyridine), Poly(N‐vinyl‐2‐pyrrolidone), and 4,4′‐(1,4‐Phenylenediisopropylidene)bisphenol

The interaction energy densities of poly(2‐vinylpyridine) (P2VPy)/4,4′‐(1,4‐phenylenediisopropylidene)bisphenol (PDIPBP) blend and poly(N‐vinyl‐2‐pyrrolidone) (PVP)/PDIPBP blend were determined using melting point depression method. The interaction between PVP and PDIPBP is stronger than that between P2VPy and PDIPBP. Wide‐angle X‐ray diffraction study revealed that PDIPBP crystallizes out from the polymer/PDIPBP blends at high PDIPBP contents. The phase equilibrium calculation supports that the single‐T_g behavior is a result of miscibilization rather than an overlap of two close T_g's of two separated phases. The critical miscibilization content of PDIPBP obtained from spinodal phase boundary calculation is lower than the saturation content, and therefore, there is enough PDIPBP in the amorphous phase to miscibilize P2VPy and PVP. Scanning electron microscopy showed a drastic reduction in domain size in single‐T_g blends.

Ternary phase diagram of P2VPy/PVP/PDIPBP blends. (○) miscible blends; (?) immiscible blends; (— × —) calculated phase boundary (Coordinate in volume fraction).