Synthesis And Properties Of Starch-Acrylate-Pullulan Semi-IPN

In this study,a novel Starch-Acrylate-Pullulan semi-interpenetrating network polymer material（St-AA-PULL）was prepared by two-step aqueous microwave polymerization IPN technology.The influence of raw material ratio and microwave radiation intensity to swelling performance were studied.The optimal synthesis conditions:Pullulan is added in an amount of 20%of the starch quality,the mass ratio of acrylic acid to starch is 5:1,acrylic neutralization is 80%,the amount of initiator and crosslinker is 0.2%and 0.15%of acrylic acid mass fraction,respectively.The microwave power is 420 W,and 3.5 min of radiation reaction time.The equilibrium swelling ratio of the best synthesized product in deionized water is 1333 g/g,and the equilibrium swelling ratio in physiological saline is 126 g/g.St-AA-PULL was synthesized under the optimized conditions of the above screening,and under the same conditions,the Starch-grafted acrylic hydrogel（St-AA）without the addition of Pullulan was used as a control to analyze the structure of these two samples,and test its hydration properties.From the results of SEM,there are a lot of wrinkles and gullies as well as many pore-like structures on the surface of St-AA-PULL,which are completely different from the smooth and flat surface of St-AA.The IR shows that the peak width of O—H vibration peak in St-AA-PULL is wider than that of St-AA;the C—O—C anti-symmetric stretching peak appears in St-AA-PULL and PULL near 1025 cm^-1,indicating PULL has been interspersed into the grafted starch network.The results of BET further confirmed that St-AA-PULL has a large specific surface area.TGA analysis showed that the thermal stability of St-AA-PULL was higher than that of St-AA.At 800℃,the residual mass of St-AA was42.3%,while the residual mass of St-AA-PULL was 47.3%.The St-AA-PULL synthesized in this study has excellent liquid absorption and swelling properties.Due to the introduction of PULL,the Semi-interpenetrating network structure of St-AA-PULL has been greatly improved in salt tolerance as well as acid and alkali resistance.Repeated operation has also been greatly improved.After 90 minutes of high temperature,it retains nearly 30%of water.After repeated water absorption for 5 times,the water absorption and swelling rate only decreased by 43%.The highest adsorption rate of St-AA-PULL for Cu²⁺is 85.9%.The product has good salt and acid resistance.The adsorption capacity is still 27.9 mg/g at pH 2.0,and the adsorption rate is 55.7%.The adsorption amount remained at 20.4 mg/g,when the sodium chloride salt concentration reached to 0.10 mol/L,and the adsorption rate was 40.7%.Compared with the heavy metal ion Cu²⁺,St-AA-PULL has better adsorption to MB and wide applicability.The maximum adsorption rate of St-AA-PULL to methylene blue（MB）was 95.5%.In the range of pH 2.0¹2.0,St-AA-PULL has higher adsorption capacity and adsorption rate for MB.At pH 2.0,the lowest adsorption amount still retains the adsorption amount of 160 mg/g,and the adsorption rate is 90.9%,showing good acid and alkali resistance;at the same time,the product also has excellent salt tolerance.The adsorption amount is still 152 mg/g and the adsorption rate is 85.4%in the environment where the salt concentration reaches 0.10 mol/L.The kinetic analysis showed that the adsorption behavior of St-AA-PULL on Cu²⁺and MB was more consistent with the quasi-secondary kinetic model,this adsorption involves all processes of adsorption and is dominated by chemisorption processes.The isothermal adsorption model analysis showed that the adsorption of Cu²⁺and MB by St-AA-PULL accorded with the Freundlich isotherm adsorption model,this adsorption is a multi-molecular layer adsorption.