Preparation and salt-resistivity of poly(vinyl alcohol)-4-hydroxyl phthalate hydrogels

• Published in: Macromolecular Research Vol. 19; no. 5; pp. 468 - 475
• Main Authors: Wang, Jianquan, Satoh, Mitsuru
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Science and Business Media LLC 01.05.2011; The Polymer Society of Korea; 한국고분자학회
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Complex Fluids and Microfluidics; Nanochemistry; Nanotechnology; Physical Chemistry; Polymer Sciences; Soft and Granular Matter; 고분자공학; salt-resistivity; hydrogel; Hofmeister series; poly(vinyl alcohol); thermo-swelling
• ISSN: 1598-5032; 2092-7673
• DOI: 10.1007/s13233-011-0511-y

A series of poly(vinyl alcohol)-4-hydroxyl phthalate (PVA-HP) polymers with different esterification degrees (ED: 98, 50, and 26 mol% for PVA-HP1.0, PVA-HP0.5, and PVA-HP0.25, respectively) were synthesized, and their structures were confirmed by FTIR and 1 H NMR. Using ethylene glycol diglycidyl ether (EGDGE) as a crosslinker, the PVA-HP hydrogels were prepared to examine their swelling properties and temperature dependence in a variety of salt solutions. As a typical kosmotrope, the sulfate anion showed a significant salting-in effect to PVAHP1.0, whereas thiocyanate and chloride showed no obvious effect, demonstrating the anti-Hofmeister-Series (anti-HS) property of PVA-HP1.0. This extraordinary behavior was attributed to the scission of hydrogen bonds (HBs) involving -COOH and -OH groups linked to benzene rings under the effect of a sulfate anion. The scission of HBs became enhanced at elevated temperature, leading to thermo-swelling of the PVA-HP1.0 gels in Li 2 SO 4 solutions. Regarding PVA-HP0.5 and HP0.25, the nature of the unesterified PVA part, which is subject to ordinary HS and thermo-deswelling properties, more or less counteracted the anti-HS by the substituting side groups, resulting in the performance of PVA gels.