Preparation And Properties Of Light And Temperature Responsive Polypeptides

Stimulus-responsive polymers are a class of polymers whose physical or chemical properties occur under external stimuli.Changing polymers.Stimulus-responsive polymers can be divided into temperature-responsive,pH-responsive,light-responsive and so on according to different external environments.When the polymer contains two or more functional groups,a polymer with multiple stimulus response properties will be formed.Polymers with multiple stimulus response properties have important theoretical research value and application prospects in the fields of drug controlled release systems,biosensors,intelligent surfaces,etc.Polymer materials constructed by combining temperature and photoresponse have important application prospects in regulating the activity of biological macromolecules,surface hydrophilicity and aggregation behavior of nanomaterials.However,the traditional construction method is mainly to graft temperature and photoresponsive groups onto the polymer backbone,which will inevitably lead to a lower density of side groups of single type of responsive groups,which is not conducive to the performance of material response.In this paper,it is proposed to introduce two kinds of reactive groups into one-side chain at the same time,focusing on the effects of side group structure and external conditions on the response properties of polymers.In this paper,two light and temperature responsive polypeptides were synthesized,their structures were characterized by ¹H NMR,FTIR and other testing methods,and their stimulus responses were studied by UV-vis or DLS.The specific content of this article is as follows:The first part of the work is that in the second chapter of this paper,we synthesized poly-polypeptide?P?Azo-S-OEG₇??with azobenzene and thioether bonds in the side chain through a series of reactions such as diazo coupling,hydroxyl dehydrogenation coupling,carboxylic acid acylation,acyl chloride and alcohol esterification,mercapto and olefin addition,and obtained P(Azo-S^OX-OEG₇)through hydrogen peroxide oxidation.The chemical structure,solubility,interaction with solvent molecules,and structural changes before and after oxidation and illumination of the polymer were characterized by ¹H NMR,FTIR,UV-Vis and other methods,and its photoresponse,temperature sensitivity and oxidation properties were studied.P?Azo-S-OEG₇?and P(Azo-S^OX-OEG₇)show reversible UCST transition in ethanol/water mixed solvent.We found that the influence of light response on UCST cloud point before and after oxidation is opposite,that is,the cloud point decreases after ultraviolet irradiation before oxidation and increases after visible light irradiation.After oxidation,the cloud point increases after UV irradiation and decreases after visible light irradiation.P(Azo-S^OX-OEG₇)also showed an unusual light-regulated LCST solution phase behavior in water.The cloud point decreased after UV irradiation and increased after visible light irradiation.The second part of work is that in the third chapter of this paper,we synthesized a butyl imidazole-containing ionic polypeptide P?Azo-OEG₃-ImCl?containing azobenzene and oligoethylene glycol?OEG?on the basis of the known polymer PAPLG through acyl chloride and alcohol esterification,quaternization,click chemistry and other reactions,and obtained P?Azo-OEG₃-ImI?and P?Azo-OEG₃-ImBF₄?through ion exchange.The molecular structure was confirmed by FTIR and ¹H NMR.P?Azo-OEG₃-ImI?shows reversible UCST transition in ethanol solution,while P?Azo-OEG₃-ImI/BF₄?shows reversible UCST transition in ethanol/water mixed solvent.We tested the effect of light response on UCST cloud point transition.Cloud point decreases after ultraviolet irradiation and increases after visible light irradiation.P?Azo-OEG₃-ImCl/I?exhibits UCST-type temperature and light dual response properties in aqueous solution under the condition of salt?NaI?induction.At the same time,we also tested the potential application of polymer in drug release.P?Azo-OEG₃-ImCl?was added into PVA hydrogel to study its potential application as an additive in drug release.