Study On Preparation Of Hydroxyethyl Chitin And Its Hydrogels,and On Its Physical And Chemical Properties And Drug Release Properties

Chitin is the second most abundant natural polymer in the world . Hydroxyethyl chitin (HECH) is a water soluble chitin derivative which was prepared by etherification of chitin. Ethylene chlorohydrin was used as etherification reagent . Series of experiments were carried out on different amount of alkali and amount of chlorethyl alcohol, and different reaction time respectively. Monofactorial experiment and orthogonal design were used to acquire optimal values of experimental factors.The optimal combination of the reaction is as follows : alkalinity content (15%), reaction time (10 hours) , ethylene chlorohydrin: chitin (w/w)=39:5, the ratio of solid and liquid is 5g:250ml, room temperature . The structure of product was analyzed by infrared spectrum and elementary analysis. The IR spectra of chitin and HECH showed that there were marked difference between them: association hydroxyl peaks (3200cm~ 3500 cm ) were appeared in HECH which manifested strengthen of hydroxyl group .Amino-group (3450 cm) of chitin were disappeared in HECH ; The elemental analysis results showed that substituting degree increased with the increase of amount of ethylene chlorohydrin, which show linear relation .Hygroscopicity and humidity-retaining ability of chitin and HECH were studied by comparing to glycerine and propylene glycol . The results showed that hygroscopicity and humidity-retaining ability of HECH was better than chitin ,but not as good as glycerine and propylene glycol.The factors of influence on rheological property of HECH water solution were studied at different mass percentage (1%-2.8%) and different temperature (25 -45). The results show it was a pseudoplastic fluid. The flowing behaviour was coincided with power-law. As far as the experimental data were concerned, they were processed with regression method. Thus, the semi-experimental data fitting formulaunder certain temperature were gotten. The result of thixotropic experiment of series different HECH solution shows they are positive thixotropic liquid. Three novel hydrogels based on HECH was obtained by using glutaraldehyde(GA) epichlorohydrin (ECH) and PTGE as crosslinking reagents respectively. The swelling behaviour, swelling kinetics of HECH hydrogels and the effects of temperature , pH value on the swelling ratio of hydrogels were studied . The results showed that : (1) the swelling ratio of hydrogels decreased with the increase of dosage of crosslink reagents. (2) amount of liber amino-group of hydrogels was decreased with the increase of dosage of crosslink reagents. (3) The hydrogels exhibited a typical pH-sensitivity property .ECH-HECH hydrogel was activated by epoxy chloropropane on which ethanediamine and hexamethylendiamine were bonded as spacers. Orthogonal design was used to acquire optimal reaction conditions of activation. The amount of amino-group , swelling behaviour , swelling kinetics of hydrogels and the effects of temperature , pH value on the swelling ratio of hydrogel were studied . The results showed that ammates hydrogels had better pH sensitivity than former hydrogels .A series of interpenetrating polymer network hydrogels composed of different amount of PAA and HECH was prepared. The IR spectra and scanning electron microscope of HECH, PAA and IPN hydrogels confirmed that PAA and HECH was formed through chemical bond interaction. The IPN hydrogel exhibited a typical pH-sensitivity. The swelling ratio of hydrogels increased with the increase of temperature in artificial intestinal juice.The sustained-release drug systems of dichlofenac potassium and ibuprofen based on PAA/HECH IPN were prepared . The release experiments showed perfect release behaviors in artificial intestinal juice, especially for dichlofenac potassium sustained-release drug systems . This IPN system was expected to be used as a good drug delivery system for enteric medicine .