Synthesis and swelling behavior of super-absorbent soluble starch-g-poly(AM-co-NaAMC14S) through graft copolymerization and hydrolysis

Abstract

By introducing sodium 2-acrylamido-tetradecanesulfonate (NaAMC14S) to graft copolymerization of soluble starch and acrylamide (AM), a novel super absorbent resin (SAR) of soluble starch-g-poly(AM-co-NaAMC14S) (SR-14) was synthesized. Polymer gels were hydrolyzed with sodium hydroxide (NaOH) to convert the function group -CONH2 to -COO-. The structures and qualitative changes of the polymer gels were characterized through Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Elemental analysis and Rheometer. Results showed the polymer gels through the hydrolysis by NaOH increased the water absorbency of the final SR-14 resin from 31.71 g/g to 1183.43 g/g as the degree of hydrolysis (DH) increased from 0 % to 80 %. Drastic increases in the storage and loss modulus of SR-14 reflected the intensive molecular structural changes induced by the addition of NaAMC14S. The changes in the molecular structures of SR-14 could be attributed to hydrophobic associations among long-chain alkane. Soluble starch-g-poly(AM-co-NaAMC14S) exhibited the maximum water absorbency of 2536.77 g/g in distilled water and 92.98 g/g in 0.9 wt.% NaCl solution. In the absence of NaAMC14S, however, the water absorbency of soluble starch-g-poly(AM) decreased to 1222.27 g/g in distilled water and to 62.29 g/g in 0.9 wt.% NaCl solution. Results indicated that NaAMC14S has potential applications as a material that could enhance the water absorbency of SAR.

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ORCID for Yongqiang Liu: orcid.org/0000-0001-9688-1786

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