Synthesis of isotactic polystyrene in hydrocarbons by initiation with t-BuLi in the presence of sodium dodecylbenzenesulfonate

Isotactic rich polystyrene was synthesized at 30 °C by the t-BuLi initiated polymerization in the presence of sodium dodecylbenzenesulfonate (SDBS) in hexane or cyclohexane. The polymerization rates at 30 °C were very fast and typically gave quantitative conversions. At SDBS/t-BuLi molar ratios between 0.5 and 1.0, the unfractionated polystyrene had almost the same stereoregularity, with triad and pentad contents of about 45% and 19%, respectively. The polymers could be fractionated into a more isotactic PS (mm = 0.77) and other fractions with lower isotactic content. The influence on the stereochemistry of lithium and potassium dodecylbenzenesulfonates or other sulfonate derivatives, reaction temperature and solvent have also been investigated. Density functional theory (DFT) was used to simulate the reactive sites using 1-lithio-1,3-diphenylbutane and 4-methylbenzenesulfonate (SBS) were used as simplified models of polystyryllithium and SDBS respectively. DFT calculation results indicated that unlike the simpler LDPB model and LDPB-styrene complexes, the pro-m-SBS-LDPB-styrene complexes were the preferred stereochemical configuration consistent with the formation of long isotactic pentad sequences.