Preparation Of PH-sensitive,Light-responsive And Light-catalytic Starch-based Functional Hydrogels

In view of the structure and properties of starch,the original starch was converted into starch-based macromonomer?SM?containing both carboxyl groups and unsaturated C=C bonds.Then a series of multi-responsive starch-based hydrogels were obtained through radical cross-linking reaction among SM,carboxylated poly?vinyl alcohol??PVAM?and 4-acryloyoxyazobenzene?AHAB?.Afterward,the pH-responsive,light-responsive and photo-catalytic properties of the hydrogels were analyzed.Effects of the amount of original materials were examined.Furthermore,the possibility of changing the range of responsive by adding chitosan was testified.The results are summarized below:1.Starch-based hydrogel containing azo group?SVA?was prepared through radical cross-linking reaction among starch-and PVA-based macromonomers,acrylic acid?AA?and 4-acryloyoxyazobenzene?AHAB?by using KPS as initiator.The structures of AHAB and SVA were confirmed with ¹HNMR,FTIR and TGA.The light-responsive behavior of the hydrogel was tested with UV–Visible spectroscopy after UV and visible light irradiation.The pH-responsive property of the hydrogel was verified by analyzing the swelling ratio of the hydrogel in different salines of various pH values.The dual-responsive characteristic was easily tailored via varying the initial amount of AHAB or AA.The swelling measurement of the hydrogel after exposing to UV irradiation for an hour indicated that the amount of AHAB didn't affect the swelling ratio,which meant the light irradiation didn't affect the pH-sensitive swelling behavior of the hydrogel.2.Similarly,the dual-responsive polysaccharide-based hydrogel was prepared through radical cross-linking reaction among SM,chitosan-based macromonomer?CSM?,PVAM and AHAB.The structure of the obtained interpenetrating functional hydrogel was confirmed with FTIR,TGA and UV-Vis.The light-and pH-responsive properties of the hydrogel were also analyzed with UV-Vis and swelling test.The dual-responsive characteristic could be tailored via varying the initial amount of CSM,SM and AHAB as well.The chitosan-based hydrogels were also prepared as control.The properties of starch-based hydrogel,chitosan-based one and starch-chitosan-IPN were compared and discussed.3.In order to endow the starch-based hydrogel one more function,TiO₂ particles were added during the cross-linking reaction.Dual-responsive composite gels were successfully prepared in the presence or absence of SM.The obtained composite hydrogels could be used to catalyze the degradation of methyl orange?MO?under light irradiation.The UV-Vis spectroscopy demonstrated that the light-responsive could be tailored by changing the initial amount of AHAB or TiO₂.The UV absorbance increased as the amount of AHAB was increased.Conversely,the absorbance decreased as the amount of TiO₂ was increased.In addition,the photo-catalytic property could be tuned by adjusting the amount of TiO₂.The degradation percentage increased as increasing the amount of TiO₂.In conclusion,the pH-and light-responsive starch-based hydrogels were successfully developed and analyzed.The dual-responsive characteristic was easily to be tailored via varying the initial amount of AHAB or AA.To extend the pH-responsive range,chitosan-based macromonomer was introduced to prepare the interpenetrated functional hydrogel,which offered more tunable factors.In addition,TiO₂ was added to provide the hydrogel with one more function,i.e.photo-catalytic capacity.As a result,the potential application field of starch-based hydrogel is enlarged.