Structure of polybutadienes synthesised with a new catalyst system, 3 -: Random copolymers of trans-1,4-and 1,2-polybutadiene

The structure and phase composition of random copolymers based on mesomorphic trans-1,4-polybutadiene containing a different amount of vinyl units (2-41 were studied at various temperatures by X-ray analysis and differential scanning calorimetry, As the amount of 1,2-units in the polymer increases, temperatures of the phase transitions crystal-mesophase and meso-phase-melt decrease, thus leading to a more narrow temperature range corresponding; to aa existence of the mesomorphic state, At a concentration of alien units of abut. 30 mol-%, the copolymer loses the ability to form a mesophase. Upon a further increase of 1,2-unit content (35-40 mol-%), the copolymer no longer crystallizes. The phase diagram of the copolymer is discussed in relation of temperature of phase transitions versus composition. It was shown that the destruction of the regular structure of the mesophase polymer by incorporation of alien units in its main chain leads to substantial decrease of the tendency of the material to mesomorphism, even more strongly than its ability to crystallize.