ATOMISTIC MODELS OF AMORPHOUS POLYBUTADIENES .2. POLY(1,4-TRANS-BUTADIENE), POLY(1,2-BUTADIENE), AND A RANDOM COPOLYMER OF 1,4-TRANS-BUTADIENE, 1,4-CIS-BUTADIENE, AND 1,2-BUTADIENE

Atomistic models of amorphous poly(1,4-trans-butadiene) and isotactic poly(1,2-butadiene) have been obtained at bulk density by carrying out molecular mechanics and molecular dynamics calculations under periodi c boundary conditions, along the lines of the previous study of poly(1 ,4-cis-butadiene). In addition, a model structure has also been obtain ed for a random copolymer of the trans (55%), cis (35%) and vinyl (10% ) units. From the equilibrated structures, the cohesive energy and sol ubility parameter are calculated. The characteristic intermolecular pa cking is discussed in detail for these amorphous structures in terms o f the pair correlation functions, along with that of poly(1,4-cis-buta diene), which turns out to be significantly different for all four str uctures. The calculation of conformational statistics of the pure tran s structure reveals that it retains the properties predicted by the ro tational isomeric state (RIS) theory. Also provided here are the resul ts of conformational analysis on the vinyl structure, for which no tho rough RIS analysis has been done. The conformational analysis of the m ixed structure shows no significant deviation from the results obtaine d for the pure trans, cis, or vinyl structures.