Post-polymerization Modification For Construction Of Cyclic Brush Polymers And Cyclic Polymers Based Gels

Due to their unique endless molecular topology, cyclic polymers have markedly different characteristics from their linear counterparts, including density, melt viscosity, glasstransition temperature, hydrodynamic volume and crystallization property. Preparation of functional polymer materials with cyclic and other topologies(star polymers based on cyclic derivatives, cyclic brush polymers, cyclic dendronized polymers and polymer network based on cyclic polymers) has been paid much attention by polymer material scientists in recent years. However, the study on the synthesis and performance about this kind of cyclic and nonlinear complex topological structure functional polymer materials is a complex and challenging job.Post-polymerization modification is one of effective strategies for preparing various polymer materials based on one polymer precursor, which has been widely used to prepare those functional polymer materials difficult or impossible to be produced by direct polymerization routes. It greatly promotes the development of the cyclic polymer field when post-polymerization modification technique is employed to prepare the functional polymer materials with nonlinear complex topological structure and cyclic molecular topology. The postpolymerization modification method mainly depends on highly efficient chemical reactions. Therefore it has been one of the main research direction to synthesize a variety of cyclic polymers with more diversified chemical components, more complex structures and more novel functions by post-polymerization modification technique and investigate their properties.In this thesis, we carried out the research on functional polymer materials with cyclic molecular topologies from two main aspects. In the first part, the universal cyclic polymer precursor was prepared by ATRP and Cu AAC techniques, and then the cyclic functional polymer and cyclic polymer brush were achieved by using efficient Suzuki coupling reaction. In the second part, gel materials based on cyclic polymers and linear counterparts were prepared by chemically cross-linking cyclic precursor using the coupling agents. The effect of topological structure on gel performance was studied. The detailed studies were summarized as the following.(1) Synthesis of the cyclic functional polymer and cyclic polymer brush(A) Activators Generated by Electron Transfer(AGET) ATRP was used to synthesize lPBr S-Br using prop-2-ynyl 2-bromo-2-methylpropanoate(PBMP) as the initiator. Subsequently, the terminal bromide(Br) of l-PBr S(l-PBr S-Br) was transferred to azidoterminated l-PBr S(l-PBr S-N3) by Na N3. Finally, the c-PBr S was successfully obtained via Cu AAC ring closuring reaction of α-alkynyl-ω-azide l-PBr S-N3. NMR, SEC, FT-IR and MALDI-FOT MS have been employed to verify the ring topological structure of the cyclic polymers.(B) Prior to prepare the corresponding cyclic brush polymers, 4-bromotoluene and 4-methoxyphenylboronic acid pinacol ester were employed as model compounds to model reaction of Suzuki coupling reaction. The reaction conversion was monitored by GC and using Pd(PPh3)4 as the catalyst, K2CO3 as the base, H2 O and THF as the solvent. The result showed that the conversion of 4-bromotoluene increased with reaction time and the reaction completed within 7 hours with ~100% conversion.(C) First of all, the small molecule functionalized cyclic polymer was prepared via Suzuki coupling reaction between 4-methoxyphenylboronic acid pinacol and c-PBr S synthesized above. The complete transformation of c-PBr S was evidenced by SEC, NMR and MALDIFOT MS. Similarly, under the similar experimental conditions, cyclic-brush polymer with arylboronic pinacol ester-end captured PS as grafting chains were successfully constructed via Suzuki coupling reaction endowing excellent modification efficiency(~100%). The obtained polymer structures were carefully characterized by(1H and 13C) NMR and GPC.(D) The DSC results demonstrated a significant change of thermal property among c-PBr S, c-PMOPS, PBAPE-PS-N3 and c-PS-g-PS. The Tg value of resultant cyclic-brush polymer is between those of c-PBr S and PBAPE-PS-N3, due to the change of free volume by introducing many PS branch chains.(2) Synthesis of gels based on cyclic polymers(A)With two ends for benzene boric acid pinacol ester of polyethylene glycol(PBAPEPEG-PBAPE) as coupling agent, polystyrene gels(l-Gel and c-Gel) were prepared respectively by chemically cross-linking l-PBr S-Br and c-PBr S.(B) To compare the storage shear modulus and loss modulus of l-Gel and c-Gel, rheology measurements were performed on a HAAKE rheometer. Meanwhile swelling ratios(Q) were tested and compared.The above studies can provide a highly efficient method for construction of functional cyclic polymers, cyclic-brush polymers and gels based on cyclic polymers.