| Poly (γ-glutamic acid)(γ-PGA) hydrogel which can absorb several hundred times their dry weight of water is a biodegradable and non-toxic polymer which is three dimensional structures. Therefore, potential applications of γ-PGA hydrogel and its derivatives have been of interest in a broad field of agriculture, medicine, environment protection and food technology. The preparation, properties and modification of γ-PGA hydrogel are studied.Diethylene glycol diglycidyl ether has been prepared from diethylene glycol with epichlorohydrin, using boron trifluoride etherate as catalyst. Its structure of the production has been confirmed by IR and epoxy value. The optimal conditions are as follows: the dose of diethylene glycol is 0.05mol, the dose of boron trifluoride etherate is 3ml, the ratio between epichlorohydrin and diethylene glycol is 4:1, the ratio between NaOH and diethylene glycol is 2:1 and the reactive temperature is 40°C. The yield of diethylene glycol diglycidyl ether is 81%. Polyethylene glycol bisglycidyl ether has been synthesized by the reaction of polyethylene glycol(average mol weight is 1000, PEG-1000) with epichlorohydrin and KOH, under the catalysis of tetrabutylammonium bromide(Bu4NBr). The conditions of the reaction, such as the temperature of reaction, reaction time, the mol ratio of the raw materials and amount of catalyst were studied. The results showed the optimal yield and epoxy value could be obtained when 0.05mol PEG-1000, 0.3mol epichlorohydrin reacted with 5.8g KOH for 8h, under 55°C, 0.8g Bu4NBr. The yield of polyethylene glycol bisglycidyl ether is 62.5%. Its structure has been characterized by IR and epoxy value.γ-PGA hydrogel has been prepared from γ-PGA and different crosslinking agent. The conditions of the reaction, such as PGA concentration, crosslinking agent, pH, temperature, time were studied. γ-PGA hydrogel which was synthesized by the reaction of γ-PGA and polyethylene glycol(average mol weight is 1000, PEG-1000) bisglycidyl ether can absorb 2200 times their dry weight of water, 88 times their dryweight of 0.9%NaCl. The optimal conditions are as follow: the concentration of y-PGA is 18%, the dose of crosslinking agent is 8% of the monomer mol dose of y-PGA, the temperature is 60°C, pH is 4.8 and time is 40h. Its structure has been characterized by IR, !HNMR, TG and SEM. y-PGA hydrogel has heat stability and upper hygroscopility.Sodium hydrogen epoxysuccinate was prepared by reaction of H2O2 and maleic anhydride. The product was characterized by elemental analysis, IR and !HNMR measurement. The crystal structure was determined by single-crystal diffraction analysis. The crystal belongs to the monoclinic system with space group C2/c, a = 21.132(3), b = 8.646(2), c = 6.196(3) A, ￡ =90.67(1) ° .In order to increase the capacity of water-absorption for y-PGA hydrogel, side structure of y-PGA hydrogel is added by carboxyl or sulfonic. y-PGA hydrogel that is modified can absorb more water.The agriculture applications of y-PGA hydrogel were studied. The capacity of water-absorption for y-PGA hydrogel is affected by pH of the solution and electrolyte. When the pH of solution was either higher or lower than 7, the water absorption capacity of y-PGA hydrogel declined comparing to the neutral. Because the hygroscopility of y-PGA hydrogel is affected by the concentration of the solute in edaphic water, y-PGA hydrogel is added early, and then fertilizer is added. y-PGA hydrogel that was fertilized in the channel can greatly improve plant growth rate. y-PGA hydrogel could effectively reduce soil water evaporation. The moisture-preserved capacity of y-PGA hydrogel increased with the increasing concentration of y-PGA hydrogel in soil.In a word, y-PGA hydrogel that was synthesized has high capacity of water-absorption, and has definite effect in the agriculture applications. But fhe capacity of saltwater-absorption for y-PGA hydrogel is not optimistic. So y-PGA hydrogel should be more improved.
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