Ring-Opening Copolymerization Catalyzed By Porphyrins

Polymer materials play a very important role in social production and life.Among them,aliphatic polyester is called a“green material”,due to many reasons,in the aspect of health and medicine,owing to its good biocompatibility,bioabsorbability,and safety,non-toxicity,it can be used as medical materials and drugs substrate,etc.;it is used for slow-release pesticides and fertilizers in agriculture,not only can achieve the purpose of low toxicity and long-lasting,but also does not pollute the environment;As a result of aliphatic polyesters have biodegradability,adjustable mechanical and physical properties.It is also well used in the field of engineering materials.Aliphatic polycarbonate is prepared by the carbon dioxide?CO₂?copolymerization with epoxide.This synthetic method not only taken full advantage of the CO₂ as a C1 source,but also reduce greenhouse effect.As a substitute for non-degradable traditional petroleum-based plastics and relieve the environmental problem of“white pollution”.However,efficient catalysts are required for the synthesis of aliphatic polyesters and aliphatic polycarbonates.At present,various metal complex catalysts have been studied as highly active catalysts,owing to metal catalysts have metal residues that cause environmental pollution,we should turning attention to the development and application of metal-free catalysts,so we catalyze the synthesis of aliphatic polyesters and aliphatic polycarbonates by using porphyrins as metal-free catalysts.The contents of this thesis mainly incloude the following three parts:First,using?tetrabromophenylporphyrin?TBPP as a metal-free catalyst to catalyze the copolymerization of different epoxides and cyclic acid anhydrides,and investigate the mechanism;The second,?quaternized tetraimidazolyl porphyrin?IL-TImp was used as a metal-free catalyst to catalyze the terpolymerization of CO₂,propylene oxide?PO?,and phthalic anhydride?PA?to prepared aliphatic polycarbonates.Furthermore,exploring the chemical selectivity of mixed monomers,conditions and the catalytic activities of different catalysts TBPP,tetraphenylporphyrin?TPP?,and tetraimidazolyl porphyrin?TImp?;Finally,TBPP was used to catalyze the terpolymerization of epichlorohydrin?ECH?,succinic anhydride?SA?and?-caprolactone??-CL?/L-lactide?L-LA?.The chemical selectivity of bulk mixing and the control of catalysts for polymerization were explored.1.The copolymerization of different epoxides and cyclic anhydrides catalyzed by TBPP as a metal-free,and investigate the polymerization mechanism.The experimental results show that TBPP as a metal-free catalyst catalyzes the copolymerization of SA and ECH.Under the polymerization conditions of 100?,10 h and a molar ratio of SA to ECH of 1,the conversion rate of SA is as high as 98.70%,and PDI of 1.28 and high H-T content of 72%are obtained,the Mn of 2.2 KDa.The better one is TBPP in the activity of four phthaloline compounds TBPP,TPP,TImp and IL-TImp to catalyze the synthesis of polyester,the halogen atoms in the structure increase acidity and promote ring opening.We supposed mechanism that the hydrogen atom on pyrrole nitrogen in the TBPP structure combines with the oxygen in the epoxide to form hydrogen bond,which activates the epoxide ring opening to form active intermediates,and then the cyclic anhydride is continuously inserted to form an alternating polyester chain segment.2.Using IL-TImp as a metal-free catalyst to catalyze the terpolymerization of CO₂,PO and PA,a terpolymer with a relative molecular weight of 2.6 KDa was successfully prepared,a TON value of 39.58,and a narrower PDI of 1.03 and polyether content of 4.13%.Explore the optimal conditions for polymerization at 60?for 12 h,a molar ratio of PO to PA of 50:1,and a CO₂ pressure of 2³ MPa.Invesitgated the catalytic activities of different catalysts TBPP,TPP,TImp and IL-TImp,the experimental results show that IL-TImp has higher activity for the terpolymerization of CO₂,PO and PA.IL-TImp introduces ionic liquid?anion is Br??on the basis of containing hydrogen on pyrrole nitrogen as hydrogen bond,which improve catalytic activity.The mechanism indicates that the hydrogen on the pyrrole nitrogen in the IL-TImp structure combines with the oxygen atom on the PO to form hydrogen bonds.At the same time,Br?attacks the carbon atom with a small steric hindrance in the PO,which catalyzes the PO ring opening.There is a synergistic catalysis effect mechanism.3.The terpolymerization of ECH,SA and?-CL/L-LA was catalyzed by TBPP.The chemical selectivity of the three monomers was investigated,and the controllability of the catalyst for polymerization was discussed.The experimental results show that the optimal molar ratio of ECH,SA and?-CL/L-LA is 1:1:1,and the terpolymer synthesized by ECH,SA and?-CL are obtained at 100?for 12 h with a PDI of 1.23 and SA conversion up to99.05%;The Mn of ECH,SA and L-LA terpolymer was 2.4 KDa and PDI of 1.34.The conversion rates of SA and L-LA were 97.67%and 97.19%,respectively.The experimental results indicated that TBPP cannot catalyze the cyclic ester ROP.Under the condition of the active intermediate formed by ECH and TBPP,cyclic ester ROP occurs.