Microstructure‐thermal property relationship of high <i>trans</i>‐1,4‐poly(butadiene) produced by anionic polymerization of 1,3‐butadiene using an initiator composed of alkyl aluminum, <i>n</i>‐butyl lithium, and barium alkoxide

Abstract

Abstract This article deals with the characterization of high trans ‐1,4‐poly(butadiene) (TPBD) prepared by means of an anionic polymerization using an initiator composed of alkyl aluminum, n ‐butyl lithium, and barium alkoxide. By controlling both initiator composition and polymerization temperature, a set of TPBD was prepared with well‐known number of 1,4‐trans units, molecular weight distribution, and average molecular weight. Analyses by differential scanning calorimetry and diffraction of wide‐angle X‐rays showed a direct relationship between the microstructure of the polymer and its thermal properties. By increasing the number of 1,4‐trans units (70–90%), the crystallinity of the polymer was increased (10–30%); polymers with less than 65% of 1,4‐trans units were amorphous, whereas TPBD with a number of 1,4‐trans units greater than 80% were polymorphous and presented two endothermic transitions. Summing up, the results presented in this article indicate that cyclohexane solutions of alkyl aluminum, n ‐butyl lithium, and barium alkoxide allow produce polybutadienes with enough amount of 1,4‐trans units to display a regular microstructure that makes them susceptible to experience‐induced crystallization, likewise at a reaction rate similar to that observed for the commercial production of poly(butadiene) with n ‐butyl lithium. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers