Living Anionic Polymerization (LAP) In The Synthesis Of New Structural Polymers

With the rapid progresses of"living"/controlledradical polymerization in recent years,a variety of polymers with special polymers structures can be synthesized.However,due to the limitation of termination reaction and transfer reaction on the radicals in the“starved”state of monomers,the sequence structure prepared in a“living”controlled radical polymerization often deviates from the ideal design.In contrast,the living anionic polymerization?LAP?has a very fast initiation rate and polymerization rate,and the living species can remain active without any side reactions in the“starved”state of the monomer.These characters allow various model polymers can be accurately synthesized by LAP polymerizaion.In this work,the LAP polymerization was innovatively used tosynthesize a series of periodic structures and polydisperse polymers,and the LAP was further introduced into the polymerization induced self-assembly?PISA?technique.The main results obtained are as follows:?1?Application of LAP in the synthesis of periodic polymer.Using n-butyl Lithium?nBu^-Li⁺?as initiator,the LAP polymerization was performed by adopting a programmed continuous feeding process of a mixture of styrene?St?and isobutene?Is?.The polymerization system was controlled under a monomer“starved”state,and a series of periodic Poly?St-per-Is?were collected.Meanwhile,a series of random copolymer Poly?St-ran-Is?,homopolymer PS,homopolymer PI and block copolymer PS-b-PI were also synthesized by LAP polymerization.The structures of Poly?St-per-Is?and Poly?St-ran-Is?polymers were characterized by ¹H NMR and 2D HSQC NMR.The results demonstrate that both polymers have the same composition but different 1,4-addition and 1,2-addition isoprene units.The thermal properties of the polymers were monitored and compared by DSC.The glass transition temperature?T_g?of Poly?St-per-Is?and Poly?St-ran-Is?increases regularly with the increase of[St]/[Is]increases.The T_g of the polymers follow a regular tendency of T_g,_{Poly?St-per-Is?}>T_g,_PS-b-PI>T_g,_{Poly?St-ran-Is?}.These results comprehensively demonstrate that the sequence of polymers exert an important influence on the physical properties of the polymers.?2?The application of LAP in the synthesis of polydisperse polymer.Using nBu^-Li⁺as initiator,a series of polydisperse PS with different molecular weight distributions were obtained by LAP polymerization assisted by a programmed monomer addition process.Also,a series of homopolymer PS with different molecular weight and narrow distribution were obtained LAP polymerization.The results of ¹H NMR and SEC demonstrate that the polydisperse PS and the narrowly distributed PS were successfully synthesized.The T_g of polymers was monitored and compared by DSC.The results show that the T_g of the narrowly distributed homopolymer PS was regularly increased with the increasing of molecular weight.However,the T_gs of polydisperse PS was significantly lower than that of the narrowly distributed PS with similar molecular weight These results actually confirmed that the polydispersity can exert an important influence on the properties of polymers.?3?The application of LAP in PISA technique.Using nBu^-Li⁺as initiator and n-heptane/tetrahydrofuran?THF?as co-solvent,the monomer of Is was first polymerized.After the monomer of Is was completely consumed,the monomer of St was continuously added to realize a LAP based PISA system.The ¹H NMR and SEC results demonstrated that both PI and PI-b-PS were successfully synthesized.The characterization of DLS shows that the assembled nanoparticles have an average size of 10¹00 nm in n-heptane,while an average size of 1¹0 nm in THF.The TEM measurement further confirmed that the nanoparticles were successfully prepared.These results show that the LAP can be actually introduced into the PISA system,and self-assembled particles with PI as shell and PS as core were prepared.