Synthesis And Properties Of Novel Multi-stimuli Responsive Polymers Based On Dynamic Covalent Bond

Multi-stimuli responsive polymer refers to a class of polymers that could change their chemical or physical properties when the environment changes or some external stimuli.With the development of science and technology,multi-stimulation responsive polymers have been gradually become multi-functional,controllable,sensitivity and reversible.At present,most of multi-responsive polymers were synthesized by random polymerization,block polymerization and graft polymerization.However,all those methods have limitations.In this work,we mainly synthesized two kinds of reactive dendronized aldehyde monomer and a polymer with amino side chain,then the multi-responsive copolymers were obtained by the self-assembly of the polymer and the dendronized monomers,when the pH of the solution changes,the assembly action can reverse.The properties of those copolymers were investigate.Due to the unique molecular structure,the copolymers were exhibits unique multi-responsive characters during the test.At the same time,the synthesis of multi-responsive based on the self-assembly provides a new way to synthesis multi-responsive copolymer and enriches the theoretical studies of the responsive polymer,and we believed that all those work will deepened the industrial application of the responsive polymers.1.According to the successful synthesis of the dendrimer aldehyde with different OEG tail G1-MTEO3-CHO and G1-MTEO2-CHO.Before the assembly,both monomer and the amino polymer were show nothing responsive properties.With the added of the amino polymer the dual-responsive copolymers were synthesized,after assembly with the amino polymer,the copolymers with thermo-and pH-responsive were obtained.The LCST?lower critical solution temperature?of the copolymer increased with length of the OEG tail chain increased.In addition,when the pH of the solution were in acidic condition,the dendrimer monomer G1-MTEO₃-CHO could undergo hydrogen bonding self-assembly with the amino polymer;when the pH of the solution were adjusted to alkaline conditions,both dendrimers could assembly with the amino polymer through dynamic covalent bonding.In the final part of this work,we have found that the LCST of the copolymer can be easier control by adjusting the number of aldehyde,when the number of the dendrimer aldehyde increased the LCST increased.2.Through reasonable molecular design,the photosensitive groups were introduced into the previous dendronized aldehyde,then we have synthesized a copolymers with temperature,light and pH response.The responsive characters of the copolymer were investigated by adjusting the pH of the solution or the molar ratio of aldehyde group to amino.The results of UV-Vis test showed that all the copolymers have sensitivity thermo-and light-response,and its littler affect by the concentration,but mainly rely on the number of the aldehyde in copolymer.At the same time,the LCST of the copolymers can affected by the salt and the degree of the salt influence was basically consistent with the Hofmeister sequence.The relationship of photosensitivity and temperature sensitivity of the copolymer were investigated.After UV irradiation for 1 h,the LCST of the copolymers were decreased,followed by the visible irradiation for 1 h the LCST recovered to the initial state.Therefore,the LCST of the copolymer can be control by change all the factors above.3.By control the molar ratio of the initiator of the polymerization,another amino polymer with lower molecular weight was synthesized.The responsive properties of those copolymer were compared with the previous copolymers.However,with the increased of the molecular weight of the amino polymer,the LCST of the assembled copolymer decreased.Subsequently,we also investigated how the increase of the molecular weight and the concentration of the solution affected the morphology of the copolymer aggregates and the response behaviors.The results showed that the assembled copolymers at a high concentration have a different assembly ways and morphology with the copolymers assembled at low concentration,the LCST of the copolymers formed at high concentration do not change with the dilution of the solution.