Polymerization Of Polar Monomers Catalyzed By Rare Earth Metals And Its Application In The Preparation Of Brush-like Polymers

Rare earth metal-mediated group transfer polymerization(REM-GTP)combines the advantages of living ionic and coordination polymerizations,making it a promising and versatile tool for the synthesis of designed functional materials.Since Yasuda et al.first applied rare earth metal catalysts to group transfer polymerization in 1992,the application of rare earth metal-mediated group transfer polymerization has obtained rapid development on the field of polymer chemistry.In recent years,the development and application of new catalysts and monomers have become the focus of rare earth metal-mediated group transfer polymerization.Now,researchers have developed a series of highly efficient and controllable catalyst systems for the preparation of polymers with high molecular weight and narrow molecular weight distribution,and the stereoscopic regularity of polymers can be regulated by tuning the ligands which was bond to the center metal.A series of Michael-type heteroatom-functionalized(e.g.N,P,etc.)polar monomers have been developed,so that their scope of application is no longer limited to the traditional acrylate monomers.In addition,REM-GTP has not only been applied to the preparation of polymers with different topological structures,but also successfully to the preparation of functional polymer materials with biocompatibility,halogen-free flame retardancy,thermal responsiveness and so on.Except for the preparation of bulk polymers,REM-GTP was also applied to the surface-initiated group transfer polymerization(SI-GTP),which opens up its application in the field of surface modification.On the basis of previous work,we designed a convenient and efficient method to the preparation of bottle-brush brushes which was based on REM-GTP.Secondly,REM-GTP was used for ring-opening polymerization of cyclic phosphoesters at the first time,which broadened the traditional application of this method.Then,REM-GTP was applied to the preparation of functional molecular brushes,further enriching its applications in a wider range of fields.Based on the above research background,this thesis mainly explores REM-GTP from the following three aspects:1.Based on the design of new surface initiator systems,a new method of modifying bottle-brush brushes on the surface of substrate was developed by combining REM-GTP with SI-PGP.In this method,backbone brushes containing pyridine side chains were prepared on the surface of the self-assembled monolayers by UV grafting polymerization,and the surface grafted macromolecular initiator system was formed by the coordination of the side chains with the metallocene complex.The polymerization of difterent monomers in the side chains is then initiated to form bottle-brush brushes.The composition and morphology of the polymer surface were characterized by infrared spectroscopy,X-ray photoelectron spectroscopy(XPS),atomic force microscopy(AFM)and water contact angle,and the feasibility of the method was confirmed.2.Using Cp2 YbMe as catalyst,rare earth metal catalyst was used for ring-opening polymerization of cyclic phosphoesters for the first time,which broadened the application range of its monomer.GPC and NMR were used to monitor the polymerization behavior of two kinds of four different cyclic phosphoesters,and it was found that the polymerization had the characteristics of living polymerization,and then it was successfully applied to the preparation of block polymers.In addition,the end groups of oligomers were analysed by MALDI-TOF-MS,and the possible mechanism of ring-opening polymerization of cyclic phosphoesters catalyzed by rare earth metals was proposed.3.REM-GTP was used to the preparation of functional molecular brushes.First,REM-GTP was combined with living cation ring-opening polymerization(LCROP)for the preparation of polyoxazoline molecular brush,and then P(IPOx-g-EI)was obtained by hydrolysis under acidic conditions.Nuclear magnetic resonance(NMR)and gel permeation chromatography(GPC)was used for the characterization of these polymers.Based on this,we studied the pH of P(IPOx-g-EI)in aqueous solution.The results show that the aqueous solution of P(IPOx-g-EI)prepared by this method is alkaline and pH is mainly affected by the percentage of side chains.Next,we will conduct further research on the properties of AIE group-modified PEI molecular brushs in luminescence,gene transmission and other related aspects.