MISCIBILITY IN BLENDS OF MODEL POLYOLEFINS AND CORRESPONDING DIBLOCK COPOLYMERS - THERMAL-ANALYSIS STUDIES

The miscibility of polymers that are models for polyolefins was examin ed by thermal analysis in this work. Analogs of ethylene-propylene cop olymer (PEP) were made by the hydrogenation of polyisoprenes; similarl y, atactic polypropylene models (APP) were produced from poly(2-methyl -1,3-pentadiene)s. PEP-APP diblocks were made from the corresponding p olydiene block polymers. Blends of the homopolymers and blocks were ma de over a broad enough range of molecular weights so that the low mole cular weight varieties were single phase and the higher ones showed tw o phases. From the Flory-Huggins-Staverman theory of blends and Leible r's model of block polymers a value of 3.52 X 10(-3) for chi could be found for these polymers. Also, the addition of a single-phase APP-PEP diblock, to a two-phase APP/PEP blend was shown to greatly alter the thermal behavior of the blend and even to convert it into a one-phase system at high enough concentrations.