Homo-and Block Copolymerization Of ε-Deca-Lactone With L-Lactide Catalyzed By Lanthan-um Compounds

Bio-based and environment-friendly polylactones provide a solution to the increasing crisis of fossil-sourced products. Ring-opening polymerization (ROP) of ε-decalactone (DL) catalyzed by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate)[La(OAr)3] and lanthanum tris(borohydride)[La(BH4)3(THF)3] is reported for the first time. Both of them exhibit good activities under mild condition (e.g.30℃within2h) producing poly(ε-decalactone)(PDL) with molecular weight (MW) up to26.4Kg/mol and polydispersity index (PDI) as low as1.10. The La(BH4)3(THF)3-mediated homo-PDL is an a,ω-dihydroxyltelechelic polymer which can be employed as a macroinitiator and used for further functionalization.Well-defined PLLA--PDL-b-PEG-b-PDL-b-PLLA pentablock copolymers with predictable MWs and relatively narrow PDIs (1.19-1.28) are synthesized by sequential ROP of DL and L-lactide (LLA) catalyzed by La(OAr)3in the presence of poly(ethylene glycol)(PEG) due to the fact that lactones cannot insert into rare earth-PLLA chain ends. Chain extension reactions of the pentablock copolymers are carried out using L-lysine diisocyanate (LDI) to produce multiblock copolymers with relatively high MW. The thermal behaviors studied by DMA and DSC measurements indicate that PDL is completely amorphous under ambient temperature and the copolymers with two Tgs suggest microphase separation of hard and soft domains. We employ tensile tests to assess mechanical properties and find excellent elongation up to723%of the chain-extended samples. Based on the bio-renewable resource of DL and LLA, the multiblock copolymers are a novel, bio-based, biodegradable and biocompatible elastomer applicable as bio-materials.Polymerization kinetics of hexamethylcyclotrisiloxane (D3) is carried out using n-butyllithium (n-BuLi) as catalyst and tetrahydrofuran (THF) as promoter. A first-order kinetics indicates the polymerization performs in a controlled/living fashion giving predicted MWs and relatively narrow PDIs. Thus, trivinyltrimethylcyclotrisiloxane, an analogue to D3monomer, is polymerized using n-BuLi/THF system so as to obtain the standard polysiloxanes with MWs ranging from5400to16100and PDIs as low as1.06. The rich vinyl groups can be used for further modification.Scandium metal triflate (Sc(OTf)3) and Sc(OTf)3/propylene oxide are efficient catalysts for ROP of D3under relatively mild condition (e.g.60℃for22.5h) in comparison with other rare earth catalysts (e.g.120℃for400h). Hence Sc(OTf)3is a promising rare earth catalyst and worthy of further study.