The effect of solvent on the microstructure, nature of hydroxyl end groups and kinetics of polymerization reaction in synthesize of hydroxyl terminated polybutadiene

Hydroxyl terminated polybutadiene was synthesized by solution radical polymerization of 1,3-butadiene in the presence of hydrogen peroxide as initiator and 2-propanol,dioxane, ethylene glycol ethyl ether and also the mixtures of them as solvents. Obtained HTPBs in the presence of various solvents were characterized by NMR spectroscopy. It was observed that the microstructure of the back-bone as well as the chemical structure of hydroxyl end groups of HTPBs depended on the type of solvent used in polymerization reaction. A HTPB with microstructure of 45/22/33 (trans/vinyl/cis) was synthesized in the presence of ethylene glycol ethyl ether whereas a microstructure of 56/22/22 and 51/22/27 were obtained for 2-propanol and dioxane, respectively. As molar ratio of 2-propanol to ethylene glycol ethyl ether was changed, the secondary hydroxyl end groups were increased. The kinetic studies showed that the type and amount of solvent affected the rate of reaction seriously. It is noteworthy that the polymerization reaction is the first-order in all solvents but the rate of polymerization reactions in presence of dioxane, ethylene glycol ethyl ether and 2-propanol were obtained different. In 2-propanol, the rate coefficient increased as the amount of initial molar ratio of solvent to monomer decreased.