Synthesis And Properties Of Pvp / Chitosan Graft Copolymer Hydrogels

The article research the graft-copolymer reaction between polyvinylpyrrolidone and chitosan . Hydrogels, which have good performances of swelling ,have been synthesised. On the base of some single-elements'test, processing parmeters have been optimized with orthogonal test. The best technological conditions are obtained while hydrogels have the best performances of swelling. Through the DSC test, the phase transition temperature of PVP/CHI hydrogel and different kinds of water contents have been determinated. The datas of FITR also give the great support about the graft- copolymer reaction between polyvinylpyrrolidone and chitosan. In addition, experiments have studied the swelling and deswelling kinetics about the PVP/CHI hydrogel and confirmated the basic rules and characters of hydrogel' swelling and deswelling kinetics. The main contents and results as follows:1, On the base of single elements'test,five factors four levers orthogonal experiments have been done. The best technological conditions are mole-ratio:8:l, reaction temperature:60 C,reaction time :10hours, the dose of initiator:3ml(0.05mol/l), the dose of cross-linker:3ml(l%,v/v).2, Through DSC test of seven samples in different mole-ratio, the polyvinylpyrrolidone' phase transition temperature is 155 C. It belower 20 C than the powder of polyvinylpyrrolidone. In term of different mole-ratio, the temperature of hydrogel is between 155 C and 203 C. According to the direct proportion of endothermic peak's area with water content at the 8#sample, the percentage of free water , bonding water , crystalline water are respectively 42.72%, 43.26%and 14.02%. Through the 12# sample DSC test from -123 C to 300 C, the sample have occurred three crystalline phase transition and one dehydration process during the warm-up temperature controlling. The necessary heat of three crystalline phase transition are respectively 64.70J/g, 164.5J/g and 124.8J/g. The total dehydration weight is 4.4400mg.3 , Through FITR test, the sample occure the characteristic peak of -NH2 near 1640cm-1 before reaction, but after reaction it change to 1660cm-1. the sample also occure the characteristic peak of dibasicolefin R1CH=CHR2 near 660cm-1 before reaction, but after reaction it have disappeared. This evidences give the great support to graft-copolymerization between olefinic link and -NH2.4, Experiments research the hydrogel's swelling changes with time , temperature , PH, the donsistency of salt and different mole-ratio compared to the single element PVP hydrogel. In term of comparing test, the graft-copolymeried hydrogel have better characters of swelling than the single element PVP hydrogel. The PVP/CHI hydrogel's Lnt-LnF relative map have been made. Its characteristic exponent greater than 0.5. According to the characters of FICK swelling mode, the swelling of PVP/CHI hydrogel suit to FICK mode.5 , Emperiments select four kinds of hydrogels which have different mole-ratio and synthetic conditions. The hydrogels originally swollen up to equilibrium in the buffered solutions at PH7.0 then transferred into the PH2.0buffered solutions and from PH10.0 to PH4.0 at 37掳C. After making its swelling characteristic graph we find that the speed of dehydration have reciprocal relation with the data of swelling. Its results suit to theoretical value.