Study On Preparation And Phase Transition Properties Of Chitosan-g-fatty Acid Polymer

This paper reported on the preparation of solid to solid phase change comb-like functional polymer via an N-acyl reaction with chitosan as the macromolecular backbone and nanometer TiO₂ as a phase change promoter,oleic acid、lauric acid as the grafting reaction monomer.By means of discussed the grafting reaction solvent system,the grafting reaction temperature,the cleaning temperature and the time of ultrasonic cleaning etc.to select the best preparation process route.Analysis by grafting weight gain rate,fourier transform infrared spectroscopy（FTIR）,Xray scattering（XRD）,polarizing thermal microscope,scanning electron microscope（SEM）,differential scanning calorimetry（DSC）and thermogravimetric analysis（TG）.In addition,study on the dissolve performance of the chitosan-g-fatty acid polymer.The results showed that,pretreatment of chitosan,grafting temperature around 95 ℃,through the solvent-free system^atmospheric perssure^vacuum grafting reaction which can make the grafting weight gain rate of chitosan-g-oleic acid polymer raised to 355.4%,the grafting weight gain rate of chitosan-g-lauric acid polymer raised to 357.0%,added a phase change promoter（TiO₂）could make the average grafting weight gain rate of the polymer raised to 318.5%;On the FTIR picture,chitosan-g-oleic acid polymer appeared absorption peak at 1540 cm^-1,chitosan-g-lauric acid polymer appeared absorption peak respectively at 1540 cm^-1 and 1640 cm^-1,this implies that the fatty acids molecules have been grafted onto chitosan molecules by amide and ester bond;XRD curve of the pure chitosan only shows diffused peak while that of the chitosan-g-lauric acid polymer shows sharp diffraction peak at 6.5°and 9.7°of the 2 theta angle,for the chitosan-g-lauric acid polymer,the polymer which added TiO₂ shows sharp diffraction peak strength respectively reached up to 1.4,1.5 multiples.It is observed that the useing of TiO₂ could help for improving the part crystallinity of the polymer;The DSC curve of the chitosan-g-lauric acid polymer which added TiO₂ shows endothermic peak in 44.0℃ to 54.4℃,the melting peak temperature（Tm）was 46.9 ℃,and during the heating process with 74.0J/g heat enthalpy value,and exothermic peak in 40.3℃to 29.5℃,the crystallization peak temperature（Tc）was 38.1℃,during thecooling process with 61.4J/g heat enthalpy value,obviously it has a good heat storage performance.Under similar conditions,for the chitosan-g-lauric acid polymer,the polymer which added TiO₂ has heat enthalpy value during the heating process reached up to7.6 multiples.This data can prove that during the experiment through the application of TiO₂ usually could play a very important role in the cooling process significantly promote the side chain fast crystallization,therefore it was able to effectively improve the polymer which without TiO₂ concomitanting supercooling phenomenon during the cooling process;The thermal weightlessness inflection point temperature of the chitosan-g-lauric acid polymer which added TiO₂ was 256.1℃,the thermal weightlessness inflection point temperature of the chitosan-g-fatty acids polymer mainly depends on the side chain of polymer structure;The polarizing thermal microscope observation results shows that,from 30℃ to250 ℃ heating process,the pure chitosan has no obvious changed,but the chitosan-g-fatty acid polymers shows varying degrees of melting phase change process and parts of the side chain thermal decomposition phenomenon;The Scanning electron microscopy（SEM）observation results shows that the chitosan-g-lauric acid polymer revealed loose and more small hole structure,and the pore size was about 1³microns;In this article,those chitosan-g-fatty acid polymers insoluble in 3% acetic acid aqueous solution,anhydrous ethanol,dimethyl sulfoxide,but the quality of the grafted polymers would be losed in a certain degree when dealing with above 60 ℃ of ethanol solution.This research will provided beneficial reference data for the study on the solid to solid phase change materials which phase transition temperature close to the human body comfortable temperature and prepared by the grafting copolymerization process.