The establishment of a broad base of fundamental information on the thermodynamics of polyolefin mixtures in the melt state will be accomplished by a combination of small-angle neutron scattering (SANS) measurements of the liquid mixtures and equation-of-state (EOS) measurements on the pure component liquids. Model homopolymers and copolymers, synthesized by anionic polymerization of dienes and subsequent hydrogenation, will be used in the initial stages of the work. Labelled samples, needed for SANS, will be obtained by using deuterium in place of the hydrogen. The highly uniform structure of these model materials, and a judicious selection of copolymer pairings, should provide single-phase liquid mixtures for samples in the polymeric size range and a relatively clean analysis of the SANS data. The EOS measurements will permit the use of liquid-state theory to interpret and generalize the results. The influences of copolymer sequence distribution and co-mer size will be studied, and bridging to commercial polyolefins will be started. Aside from supplying thermodynamic data for an extremely important class of polymeric materials, the proposed work will provide tests of current theories for polymer mixtures where the local interactions are simple and the local structures are well defined. It also provides the essential basis and appropriate model materials for studies on the dynamics of phase separation, leading to the design of solid-state morphologies in amorphous and semicrystalline polymer blends.
