Mixing enthalpies of polymers with mesomorphic properties and mesogenic plasticizers

Abstract

AbstractMixtures of polymers of mesomorphic properties with mesogenic plasticizers were investigated by differential scanning calorimetry (DSC). The nature of the mesomorphic structure of the polymers could be identified by studying the concentration dependence of such thermal processes as glass transition, mutual solution of the phases and formation of eutectic melts. Mixtures of polymers with a supposed nematic structure such as poly(phenyl‐p‐acryloyloxy‐benzoate) (pPAB), poly(p‐butoxy‐phenyl‐p‐acryloyloxy‐benzoate) (pBPAB), poly(p‐methoxy‐phenyl‐p‐methacryloyloxy‐ethoxy‐benzoate) (pMPMEB), and one copolymer of p‐methyl‐p'‐acryloyloxy‐azoxy‐benzene (MAAB) and cholesteryl‐vinyl‐succinate (CVS) and of nematogenic materials as terephthal‐bis‐butyl‐aniline (TBBA), p‐butoxy‐phenyl‐p‐propionyloxy‐benzoate (BPPB) and the monomers of the copolymer were investigated. None of the systems was found fully miscible with nematic structure. The enthalpies of melting at the clearing points were found proportional to the polymer content of the mixtures. The mixing enthalpies in the liquid state are too small to be measured by DSC. The mixing enthalpies of the solid components resulting in solid plasticized polymer are found proportional to the melting enthalpies of the plasticizers and to their saturation concentration in the polymer. The anisotropy of the bulk polymer originated from the anisometric geometrical shape of the macromolecules themselves, which is in good agreement with the structural concept introduced earlier.