Study On A Novel Block Polymer Comprising Styrene, Butadiene And Isoprene

Styrenic block copolymer (SBC) is a type of widely used polymer material with the characteristics of both rubber and thermoplastics. One of the most important of its applications is hot-melt type pressure sensitive adhesive. However, SIS type block copolymer undergoes heat deterioration upon its melt processing, and so its melt viscosity rapidly decreases. On the other hand, SBS type block copolymer undergoes crosslink upon its melt processing, and so its melt viscosity rapidly increases. A novel block polymer comprising a polymer block of styrene (S), a polymer block of butadiene (B) and a polymer block of isoprene (I) has specific physical properties and adhesive properties.At the first part of the article, butadiene-isoprene copolymer is synthesized with cyclohexane as solvent and n-butyllithium (n-BuLi) as initiator. Effects of different initiation temperature, different additives and their dosage and different monomers proportion on the polymerization kinetics, copolymeriation composing distribution, and reactivity ratios are investigated through gas chromatography. Potassium p-methlyphenoxide (ROK) is firstly used as modifier in the coplyomerization of butadiene and isoprene. Results show that the copolymer becomes random when adding ROK. Microstructures, number average molecular weight and distribution, and T_g of the copolymers are obtained by NMR, IR, GPC and DSC.S-B/I-S is synthesized with THF and TMEDA as additives. Microstructures, number average molecular weight and distribution, T_g, and morphology are studied by NMR, DSC, GPC, TGA, DMA and TEM. It is showed that with increasing the amount of additives, T_g1 is increased. The block polymer has sharp phase separation with increasing the content of isoprene.A novel block polymer of S-B/I-S is successfully synthesized with ROK as modifier for the first time. GPC and DMA analysis shows that the molecular weight distrubution is broadend and T_g1 is increased with the increasing of ROK. NMR and TEM results suggest that the block polymer has phase separation. However, heat deterioration temperature is decreased because of some small polyomers.The mechanical expriment shows that the polymers have good conbination properties of SBS and SIS.