Ring-opening Polymerization Catalyzed By Phosphazene And Amidine Organic Base

Polycaprolactone（PCL）and polylactide（PLA）biodegradable polymers have been widely used in packaging,medical treatment,agriculture and other fields.However,with the prominent problems of environmental resources,the development prospect of biodegradable polymers is very broad.Traditional metal-based catalysts have the disadvantages of storage trouble,complex synthesis steps,and difficult to remove metal residues,which greatly limits the application of biodegradable polymers.Organic nonmetallic catalysts have become a research hotspot for the synthesis of biodegradable polymers due to their advantages of simple synthesis,convenient storage,high reactivity and strong substrate tolerance.It is of great significance to develop new organic catalysts and new polymerization methods.In this thesis,the ring-opening polymerization（ROP）of cyclomonomers,such as caprolactone and lactide with metal free catalysts amidine and phosphazene was studied.We also studied the kinetics and polymerization mechanism of the polymerization.The results are as follows:1)Ring-opening polymerization（ROP）of caprolactone（CL）with 1,8-diazabicyclo[5.4.0]undec-7-ene（DBU）as the catalyst and benzyl alcohol（Bn OH）as the initiator in bulk at 80°C to obtain relative molecules PCL with controlled mass and narrow dispersion（D<1.10）.¹H NMR,GPC and MALDI-TOF MS measurements clearly indicate the presence of the initiator residue at the chain end of the obtained PCL homopolymers.The study on polymerization kinetics confirm the controlled/living nature of the ROP of CL.It is speculated that the ring-opening polymerization of CL catalyzed by DBU is based on the activation initiator/chain end mechanism,and verified by ¹H NMR and theoretical simulation calculations.In addition,terminal functional PCL was successfully prepared with ethyl methacrylate（HEMA）,propargyl alcohol（PGA）,azide hexanol（AHA）,methoxypolyethylene glycol（m PEG）and 1-pyrene methanol as initiators.Three-arm and four-arm PCL star polymers were prepared successfully with propanediol and pentaerythritol as initiators.Finally,PCL-b-PVL and PCL-b-TMC block copolymers were synthesized.2)Firstly,Fe₃O₄@PZS nanocomplex was prepared by the cross-linking reaction of HCCP and 4,4’-dihydroxydiphenol（BPS）on the outside of Fe₃O₄ magnetic nanoparticles.Then,Fe₃O₄@PZS@HMP₁ was successfully prepared by the reaction of active phosphochloric bond with iminotrimethylamino-phosphine（HMP₁）.The introduction of magnetic nanoparticles gives the catalyst cyclic properties,while the phosphine nitrogen moiety in HMP₁ could catalyze the ring-opening polymerization of cyclomonomers.Fe₃O₄@PZS@HMP₁ could efficiently catalyze CL active ring-opening polymerization at room temperature and can be recycled.