Study On The Synthesis Of POSS Double-end Functionalized SSBR

Living anionic polymerization is a particularly suitable way for the preparation of chain-end functionalized polymers,given that it generates stable polymer chain ends and no termination no transfer,once all the monomer is consumed.From now on,all electrophiles are organic compounds.However,many reported chain-end functionali-zation reactions produce a complex mixture of functionalized and unfunctionalized polymer products,including dimers and trimers.We choose polyhedral oligomeric silsesquioxane(POSS)as electrophilic reagent(terminator)to synthesize end functionalized polymers.This can prevent undesired products produced.Heptaisobutyl polyhedral oligomeric silsesquioxane double-end functionalized polystyrene(PS-POSS-POSS)has been synthesized by reaction of Poly(styryl)dilithium with chloropropyl heptalsobutyl POSS(Cl-POSS)using styrene as monomers,dilithium as initiator,chloropropyl heptalsobutyl POSS as terminator,cyclohexane as solvent via anionic living polymerization.The functionalized polystyrene was characterized by 1H-NMR,13C-NMR and GPC.The results of 1H-NMR and 13C-NMR clearly proved that the reaction of poly(styryl)dilithium with Cl-POSS has been carried out and POSS functionalized PS was successful obtained.GPC chromatograms showed that POSS incorporation into both end of PS obviously increased the molecular weight and the molecular weight distribution of POSS-PS-POSS compared to the increase of the molecular weight distribution of PS-POSS.It was noteworthy that no dimeric side-products are observed,which was similiar to the result of PS-POSS.The result of XRD indicates that the aggregation of POSS in the functionalized PS is not formed.And the thermal stability of POSS-PS-POSS is improved.Then the effects of the content of structure modifier,the molar ratio of POSS/dilithium,PS molecular weight,terminating reactive temperature,terminating reactive time and different treatment methods of terminator were investigated to optimize the yield of functionalized PS.The results show that the terminating efficiency reached the highest values when the molar ratio of THF/di lithium was 5,POSS/dilithium was 1.1,the terminating temperature reached 60 ℃,the terminating time reached 50 min and POSS powder was added directly in the polymerization system without dilution.However,the functionalized efficiency decreased with the increase of PS molecular weight.In addition,according to the optimum terminating condition,we use the terminator to end-functionalize polybutadiene and the styrene-butadiene copolymer and investigate the terminating efficiency in order to lay theoretical foundation for end-functionalizing SSBR by POSS.The terminating efficiency of POSS-PB-POSS and POSS-SSBR-POSS can be increased when DPE or PS was added to change the structure of molecular chain-end before terminating,and can prevent undesired products produced.