Study On Synthesis Of Ionic Liquid And Its Catalytic Copolymerization

In recent years,polymer-based materials have undergone tremendous development.Because of its numerous renewable resources,hydrolysis and degradation into benign products,and high biocompatibility,polyester is considered a potential sustainable alternative to petroleum-based polymers and has become an indispensable important material in life.At present,the preparation of polyesters by ring-opening polymerization of epoxides and cyclic anhydrides has become the most promising method for synthetic polyesters.The main advantages include:mild polymerization conditions,a wide range of polyesters that can be prepared,Using two different groups of monomers can easily adjust performance and modification after polymerization.Recently,the advent of polymer nanotechnology has opened up new possibilities for designing functional materials with custom shapes.However,in these nanoscale materials,the most basic component is still the homopolymer long chain in most cases,which means that the development of synthetic polymers containing controlled monomer sequences is an important area of research.At present,the catalysts used in ring-opening polymerization are mainly metal catalysts.For the ring-opening alternating copolymerization of cyclic anhydride and epoxide,it has been successfully obtained alternating polyester with controlled molar mass,chemoselectivity,regioselectivity or stereoselectivity,and block copolymers with alternating polyester.However,the development of metal catalysts is hindered by their high price,corresponding pollution problems and their inability to be applied in biological and medical fields.Although several metal-free catalysts have been reported for ring-opening polymerization,additional initiators need to be added during the reaction,which undoubtedly increases the process cost.Therefore,it is important to develop new metal-free catalysts for ring-opening polymerization of epoxides and cyclic anhydrides.Ionic liquids,as a material composed entirely of anions and cations,have many special properties,which provides a certain basis for the application of ionic liquids in various aspects.In this thesis,by preparing different types of ionic liquids and applying them to the ring-opening polymerization of epoxides and cyclic anhydrides,a metal-free catalyst for one-pot mixed monomer sequence controlled polymerization was developed.By studying the reaction process of ring-opening polymerization,the possible reaction mechanism of ionic liquid in this process was proposed,and the influence of catalyst structure on ring-opening polymerization was studied using ionic liquids with different structures.The main research contents and results are as follows:1.A simple one-step neutralization reaction was used to prepare protonic ionic liquids with different structures from 1,8-Diazabicyclo[5.4.0]undec-7-ene?DBU?and organic carboxylic acids.The ring-opening polymerization of epoxides and cyclic anhydrides was studied using different ionic liquids.The obtained polymer was characterized by ¹H NMR,¹³C NMR and GPC.By comparing the experimental results of ionic liquids with different structures,it is shown that the ring-opening polymerization catalyzed by ionic liquids needs appropriate acidity and alkalinity.Then,we selected the best performing ionic liquid[DBU][Pac].At 100?,10 h,and the monomer ratio is 1:1,the polyester yield up to 97.6%,and the polyester content in the polymer is 97%.Finally,based on the above experimental results,We have studied the reaction process of ring-opening polymerization catalyzed by[DBU][Pac]and proposed the possible reaction mechanism.2.Through a simple one-step quaternization reaction,1-methylimidazole and bromoethane were used to synthesize the imidazole ionic liquid 1-ethyl-3-methylimidazole bromide?EMIMB?.AB-type block polymers were prepared from the copolymerization of mixed monomers of phthalic anhydride,epoxide,and lactide catalyzed by EMIMB via a one-pot method within 15 h.The block polymers were characterized by ¹H NMR,¹³C NMR,GPC and DOSY NMR.By studying the reaction process of ternary copolymerization,We proposed the possible catalytic mechanism of EMIMB in this reaction,and proposed the possible properties of ionic liquids for the copolymerization of phthalic anhydride,epoxide and lactide mixed monomers.3.Through a simple quaternization reaction,a hydroxyl-functionalized ionic liquid,1-?2-hydroxyethyl?-3-methylimidazole bromide?HEMIMB?,was synthesized from 1-methylimidazole and 2-bromoethanol.AB-type block polymers were prepared from the copolymerization of mixed monomers of phthalic anhydride,epoxide,and lactide catalyzed by HEMIMB via a one-pot method within 13 h.The block polymers were characterized by ¹H NMR,¹³C NMR,GPC and DOSY NMR.By studying the reaction process of ternary copolymerization,we proposed the possible catalytic mechanism of HEMIMB in this reaction.