A LATTICE MODEL FOR DYNAMICS IN A MIXED POLYMER DILUENT GLASS

A lattice model is developed to interpret NMR lineshape and relaxation data on polymer-diluent systems. The lattice is used to count nearest-neighbor contacts which are assumed to influence local dynamics. When applied to the polymer chain, the presence of one diluent-polymer repeat unit contact is considered to suppress sub-glass transition motion through improved packing. Polymer repeat units in contact with more than one diluent molecule on the lattice are presumed to have enhanced mobility. Polymer repeat units surrounded by other polymer repeat units are thought to have no change in their sub-glass transition dynamics. When applied to the diluent, isotropic rotational motion of diluent surrounded by polymer is considered to commence at the apparent thermal glass transition. For those diluent molecules in contact with other diluent molecules on the lattice, sub-glass transition rotational motion occurs at a temperature determined by the intrinsic mobility of the diluent. The motions of the chain and the diluent are reflected in the modulus and are traditionally discussed in terms of plasticization and antiplasticization.