Effect of degree of substitution on structural properties of hydroxypropyl starch-based polymers
Highly water-absorbent polymers of hydroxypropyl starch grafted with acrylic monomer were rapidly prepared by solution copolymerization using six hydroxypropyl starch with different degrees of substitution as the backbone,acrylic acid as the monomer,ammonium persulfate as the initiator,and N,N'-methylenebisacrylamide as the cross-linking agent to investigate the effect of the degree of substitution on the structure and properties of the polymers after hydroxypropylation.The infrared spectra,X-ray diffraction,thermogravimetry,water absorption and methylene blue adsorption of the polymers show that the starch-based poly-mers are prepared by polymerization,which is not a simple physical blending process.After the starch is involved in the preparation of the polymers,the diffraction peaks disappear from the X-ray diffraction spectra,and the crystalline structure is damaged,the thermal stability of the polymers is improved after the hydroxypropylation,the hydroxypropylated polymers has a good thermal stability,and the hydroxypropylated polymers has the same decomposition temperature.The thermal stability of the polymers is improved after hydroxypropylation,and the mass of hydroxypropyl starch-based polymers is higher than that of the original starch-based polymers at the same decomposition temperature,the water absorption and methylene blue adsorption properties of the origi-nal starch and the high substitution polymers are better than those of the polymers prepared in the range of low substitution,and all the polymers have water absorption capacity of more than 40 g/g.The water absorption capacity is still maintained at more than 30%,and the removal rate of methylene blue is also more than 17.6%after three times of repetitive absorption and desorption.In addition,with the increase of cation valence in the salt solution,the liquid-absorbing ability of all the polymers is weakened,and the salt sensitivity factor become larger,indicating that the polymers are more sensitive to ions.After hydroxypropylation,the structure and properties of starch-based polymers are changed to different degrees.The water absorption and methylene blue adsorption of the polymers are superior at high substitution,which provides the possibility of preparing functional and environmentally friendly poly-mers with better properties.
degree of substitutionhydroxypropyl starchpolymerswater absorptionabsorption capacity
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