Synthesis Of Star LCBR And Star Comb (SI)_n By Anionic Polymerization

In this thesis, based on the previous researches, star-shaped low-cis polybutadiene rubber(LCBR) and novel structure star-comb polystyrene-isoprene was successfully synthesized via anionic polymerization in the methord of arm-first and coupling reaction.Taking cyclohexane as solvent, n-BuLi as initiator, and silicon tetrachloride(SiCl4) as coupling agent, S-LCBR had been successfully synthesized. FT-IR,’H-NMR and GPC were used to analyze molecular weight and their distribution, microstructure content of S-LCBR. The best conditions of polymerization and coupling reaction were determined. The optimum reaction conditions are as follows:polymerization temperature is50℃, polymerization time is4hours, n(THF/n-BuLi)0.48-0.9, coupling time temperature is70℃, coupling time is2hours. The relationship between molecular parameters and the Mooney viscosity (ML), toluene solution viscosity (SV) were studied. The ML and5%SV increases with increasing molecular weight. In order to obtained the optimum ML and SV, the arm molecular weight should match coupling efficiency. The mold test products have stable quality, gel content and volatile are very low. The HIPS and ABS prapared by mold test products have better impact performance than those toughened by similar product.Taking cyclohexane as solvent, n-BuLi as initiator, and epoxidized star polybutadiene (ESPB) as coupling agent, a series of pure star-comb styrene-isoprene block copolymer (SC-(SI)n) were obtained by living anionic polymerization and precipitation fractionation. The results show that, the coupling efficiency increases with the increasing coupling agent amount and coupling time, decreases with the increasing arm molecular weight. The FT IR and1H-NMRresults proves that, the SC-(SI)n are block copolymers and have no random segment. SC-(SI)n have two glass transition temperatures (Tg) determined by DSC, proves the existence of microphase separation structure. The intrinsic viscosity of SC-(SI)n is lower than that of linear SIS with the same molecular weight, and it decreases with the increasing branching degree, increases with the increasing molecular weight. The theology test showed that, the melting viscosity at the same shear rate of SC-(SI)n is lower than that of linear SIS. And the sensitivity to the shear rate of SC-(SI)n is higher than SIS. With the molecular weight of SC-(SI)n increasing, the melt viscosity increased, the sensitivity to the shear rate decreased. The theology showed that SC-(SI)n and SIS polymer melt have totally different dynamic viscoelastic behavior, the elastic modulus G’of SC-(SI)n melt is much higher than the loss modulus G".