Preparation And Application Of Polyaspartic Hydrogel

Polyaspartic acid(PASP)hydrogel is formed by cross-linking of polyhydroaspartate molecular chains,and its microstructure is spatial network.Because the main chain of PASP is soft and easy to extend in space,and there are a lot of hydrophilic groups such as amide,carboxyl,hydroxyl,ether bond in the molecule,PASP is easy to combine with water molecules,and has excellent water absorption and retention.In addition,as an amino acid polymer,its main chain is similar to protein structure and has excellent biocompatibility and biodegradability.These characteristics make PASP hydrogel widely used water retaining agent in agriculture,daily chemical products,biomedicine and other fields.At present,our team has achieved pilot production of PASP hydrogel and applied to windbreak,sand fixation,agriculture and forestry cultivation,drug carriers and sanitary products,but the higher cost restricts the promotion of products.Therefore,the preparation of low-cost PASP hydrogels,the formulation of large-scale and mechanized application procedures,and the development of specific structural materials will help to promote the industrialization of PASP hydrogels.The research work of this article mainly includes the following four parts.First of all,glycerol polyglycidyl ether(GPE)was used as crosslinking agent to prepare PASP hydrogel by hydrolysis and crosslinking.Through the optimization of technological conditions,the optimum conditions for preparation of hydrogels can be obtained:liquid solid ratio 6:1,pH value 4.5,reaction temperature 50 centigrade.GPE:PSI unit ring 1.0?1.4:10,and the pH value and the amount of crosslinking agent were the significant factors affecting the water absorption of the product.At this time,the crosslinking degree of the hydrogel was about 42%,and the maximum water absorption of the product can reach 600 g/g.Furthermore,the prepared hydrogel has better thermal stability.The plate culture and fermentation broth prove that the PASP hydrogel has good biodegradability.Compared with ethylene glycol diglycidyl ether crosslinker,the water absorption did not decrease significantly,but the cost decreased by about 6.5%.Secondly,PASP hydrogel was used as water retaining agent to grow cotton and jujube in southern Xinjiang.During the whole growth period of cotton planting,it can reduced dripping water 3 times,reduced water by 18.6%,and increased cotton yield by 3.6%.During the whole growth period of jujube planting,irrigation can be reduced once,water saving was about 23%,and production can be increased by 2.6?4.9%.The quality has also been significantly improved,the average weight of a single jujube increased by 16.2%,and the commercial jujube rate increased by 6.3?30%.In addition,the water retaining agent also has good effects of salt inhibition,heat preservation,slow release of fertilizer and pest control.The application rules of water retaining agent were also formulated.On this basis,the planting technology of non film cotton with water retaining agent instead of plastic film was explored.The results of soil temperature and humidity show that in the early and midterm of cotton growth,the heat preservation effect of water-retaining agent was better than that of mulching film.The physiological indexes of growth period also proved that SAP could promote the growth of cotton with higher plant height and more bolls.The estimated yield of cotton field is slightly higher than the average value in this region.Thirdly,take Pickering high internal phase emulsion(HIPE)as a template to prepared polyaspartic acid porous material and applied it to drug loading.O/W type Pickering HIPE was prepared by using cyclohexane as internal phase and Tween80 and nano SiO2 as composite stabilizers.The PASP porous material can be obtained by polymerizing the outer phase with the prepared high phase emulsion as template.The water absorption experiment proved that the material has a faster water absorption rate.SEM images showed that the prepared material shows a good open-hole skeleton structure with many windows.The pore size and distribution of this material are controllable.The average pore diameter d(0.5)of sample 5 is 33.8 nm and the porosity is 82.5%.The PASP porous material was applied to drug loading.The results showed that the macroporous gel with good pore structure showed superior drug loading and drug loading rate.Drug release rate was controlled by pore structure and environmental pH value.The drug was easily released in the simulated intestinal fluid,and the released drug contained almost no impurities.Finally,Using PASP hydrogel as the precursor,the microporous/mesoporous carbon material(C-CroPASP)was prepared by in-situ one-step carbonization method and applied to gas adsorption.The porosity and gas adsorption ability of C-CroPASP porous carbon materials were investigated.Using KOH provides alkaline environment,and PASP hydrogel(CroPASP)is prepared by aqueous phase method.EDS confirms that the K element can be evenly distributed in CroPASP,which improves the etching effect of K.C-CroPASP was prepared by one-step carbonization without adding activator.SEM observation revealed that C-CroPASP has a uniform pore size distribution.BET proved that there were both microporous structure(0.60 nm)and mesoporous structure(3.97 nm)on the surface,with obvious secondary pore structure.C-CroPASP also has good gas adsorption performance,in which the adsorption capacity of H2 is 4.43 wt%,which is better than most porous carbon materials.The preparation of C-CroPASP by in-situ one-step carbonization does not need additional activator,which avoided the use of a large amount of water and acid in the washing process and was more environmentally friendly.Moreover,the in-situ one-step carbonization method combines carbonization and activation steps,the energy requirement of the preparation process is lower,and complicated temperature adjustments are avoided.The above work not only provides a research foundation for improving the economic value of polyaspartic acid hydrogels and broadening the application fields,but also lays a foundation for the industrial application of polyaspartic acid hydrogel.