Characterization and Thermal Rearrangement Investigation of 1,4-Polybutadiene by Nuclear Magnetic Resonance Spectroscopy
Microstructural investigation of low molecular weight 1,4-polybutadiene (1,4-PBD) was studied by 1H and 13C nuclear magnetic resonance spectroscopy (NMR). The isomer contents of 1,4-cis, 1,4-trans and 1,2- vinyl in polybutadiene microstructure were determined. The number average molecular weight for low molecular weight polybutadiene was measured by NMR techniques and comparison was made with gel permeation chromatography (GPC) results. Due to the presence of methyl end group and considering the repeating units in 1,4-PBD microstructure, the number average molecular weight was calculated by NMR techniques. This study was accomplished by obtaining cis-trans isomerization in non-pyrolytic anaerobic conditions at 200 to 250oC. The results showed that increase in heat treatment time increased the trans isomer and decreased the cis isomer contents respectively. The presence of 1,2-vinyl isomers increased the average molecular weights by heat treatment time at 250oC and did not lead to any chain scission in 1,4-PBD.