Study On The Living Polymerization Of Several Polar Diene And Lactone Monomers

Since Staudinger proposed the concept of polymer in the 1920s,polymer chemistry has made considerable progress.Polymer materials have been used in all aspects of human life,but to obtain the desired polymer in a controllable manner,people have never stopped the research on synthetic polymer catalysts.There are still many difficult problems in polymer synthesis,such as,1)for polar vinyl monomers containing multiple double bonds,it is difficult to achieve selective and living/controlled polymerization at the same time;2)For the ring-opening polymerization of lactones,it is difficult for the catalyst to selectively catalyze the ring-opening polymerization of monomers,and avoid transesterification.Thus,it is difficult to realize the controllable synthesis of block polyester and super tough aliphatic polyester elastomers.Faced with these challenges,we have developed Lewis pairs catalytic systems and alkyl metal-based catalysts in this paper.In chapter?,the living and controlled polymerization of conjugated polar alkenens including methyl methacrylate(MMA)and polar divinyl monomers such as allyl methacrylate(AMA)and vinyl methacrylate(VMA),has been achieved at room temperature(RT)by Lewis pairs(LPs)using the strong nucleophilic N-heterocyclic olefins(NHOs)as Lewis base(LB)and sterically encumbered,but modestly strong(4-Me-2,6-~tBu2-C6H2O)2Al Me((BHT)2Al Me)as Lewis acid(LA).Both the classical Lewis adducts(CLAs)and frustrated Lewis pairs(FLPs)exhibited not only the comparable polymerization activity and a high degree of control over the molecular weight(MW)and molecular weight distribution(MWD)of the yielded polymer,but also high chemoselectivity towards the polymerization of the conjugated acrylic double bond in the polar divinyl monomers without the involvement of the non-conjugated allylic C=C bonds.By strictly control the time for the addition of co-monomers,well-defined diblock copolymer(PMMA-b-PAMA,PAMA-b-PMMA and PAMA-b-PVMA)and triblock copolymer(PMMA-b-PAMA-b-PMMA,PAMA-b-PMMA-b-PAMAand PAMA-b-PVMA-b-PAMA)could be successfully synthesized through the sequential block copolymerization method.In chapter?,LPs composed of NHO with different steric hindrance and nucleophilicity as Lewis bases and Al-based LAs with comparable acidity but different steric hindrance as Lewis acid were applied for 1,4-selective Lewis pairs polymerization of(E,E)-alkyl sorbates,including(E,E)-methyl sorbate(MS)and(E,E)-ethyl sorbate(ES).The effects of steric hindrance,electron donating ability and acidity of LPs on MS and ES were systematic investigated under different temperature.Low to high molecular weight PMS(Mn up to 287 kg/mol)coupled with narrow MWD and 100%1,4-selective addition were prepared catalyzed by optimal LP.Through simple chemical reactions,PMS could be further quantitatively converted into different polymers,such as poly(sorbic acid)and three polymers poly(propylene-alt-methyl acrylate),poly(propylene-alt-acrylic acid),and poly(propylene-alt-ethylene)with strict(AB)n sequence structures,their hydrophilic ability,thermal properties and peel adhesion strength are fully studied and characterized.In chapter?,five dimethylaluminum complexes with different sidearms were prepared for living ring-opening polymerization(ROP)of lactones such as?-caprolactone(?-CL),?-valerolactone(?-VL)and pentadecanolide(PDL)in the presence of Bn OH at RT,affording medium to high MW linear polyesters with Mw up to 303 kg/mol and narrow MWD((?)as low as 1.12).It should be noted that sidearm plays a significant important role in reactivity of these Al-based catalyst system.More specifically,Al2 system with a butyl substituent on sidearm exhibited the highest polymerization activity and Al5 system with the bulkiest sidearm showed the lowest one among the investigated catalysts.Moreover,Al4 system with a pyridine group on the sidearm could effectively inhibit transesterification and maintain well-defined block copolymer structure even after heating at 50°C for 10 h.Furthermore,we successfully realized the ROP of PDL by using the characteristics of the Al3 catalyst that can activate the polymer chain.And block copolymers and random copolymers of PDL with?-CL or?-VL were also prepared with customized Tm.In chapter?,we presented a rapid,one-pot strategy for preparation of triblock ABA TPEs from the butylmagnesium 2,4-di-tert-butyl-6-((methyl(2-(methylamino)ethyl)amino)methyl)phenolate(Mg(?))and 1,4-benzenedimethanol(BDM)system promoted living/controlled ROP of renewable and degradable cyclic lactones,including?-CL,?-VL and L-lactide(LLA).The living/controlled nature of Mg(?)/BDM system enabled us to prepare the renewable polyester-based TPEs with higher enough molecular weight and easily adjust the composition and microstructure of the polymers by simply changing the monomers feed ratios as well.Without requirement of specific functionalized groups,these sustainable polyester TPEs consisting of PLLA hard end block and random copolymer PCL-co-PVL(PCVL)soft midblock exhibited high stretchability(up to 2100%)and strong tensile strength(up to 71.5 MPa),thus giving rise to TPEs with super toughness(445 MJ/m~3).Through systematic investigation towards the intrinsic toughening mechanism,we disclosed that the key to the successful enhancement of both elongation at break and tensile strength lies in the block-like,gradient microstructure of the copolymer PCVL,which not only provides flexible elastic network to enhance the ductility of PCVL,but also brings about strain induced crystallization effect to enhance the tensile strength at the same time.Furthermore,the practicability of this strategy could be demonstrated by the lifting over 30000 times of the sample bar's weight and the easy scale-up experiments.