Swelling characteristics of a blend hydrogel made of poly(allylbiguanido- co-allylamine) and poly(vinyl alcohol)

• Published in: Polymer Vol. 36; no. 13; pp. 2579 - 2583
• Main Authors: Lio, Kokoro, Minoura, Norihiko, Nagura, Masanobu
• Format: Journal Article
• Language: English; Japanese
• Published: Oxford Elsevier Ltd 1995; Elsevier BV; Elsevier
• Subjects: Applied sciences; cationic PAB/PVA hydrogel; Exact sciences and technology; Organic polymers; pH response; Physicochemistry of polymers; Properties and characterization; Solution and gel properties; swelling characteristics; pH response; swelling characteristics; cationic PAB/PVA hydrogel; Polyelectrolyte; Polyvinylalcohol; Biguanides; Swelling; Ionic strength; Quaternary ammonium copolymer; Physical gel; pH; Allylic derivative copolymer; Experimental study; Lateral group; Mixture
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/0032-3861(95)91204-K

A hydrogel was prepared by mixing poly(allylbiguanido- co-allylamine) hydrochloride (PAB) with poly(vinyl alcohol) (PVA) and by repeatedly freezing and thawing the blend. The swelling behaviour of the gel was studied as a function of the pH and ionic strength of the medium. The performance of the gel was compared to that of a blend hydrogel made from poly(allylamine) hydrochloride (PAA) and PVA. In a salt-free aqueous medium, the PAB/PVA hydrogel displayed a remarkable pH response: a drastic reduction in size was observed above pH 9 and below pH 3, but the size was little affected in the pH range 3–9. In a medium of constant ionic strength (μ = 0.1), the hydrogel's pH response was much different: it was significantly reduced in size above pH 10, but the size was affected only moderately below pH 10. When the ionic strength of the medium was varied at a fixed pH, the size change of the hydrogel was gradual. For instance, in sodium chloride solutions (at a pH of 6.0), the hydrogel shrank by about 30% as the electrolyte concentration was raised from 10 −6 to 2 mol l −1. All these phenomena could be understood by observing that: (i) PAB is subject to multiple acid-base equilibria (with widely spaced p K a values); and (ii) the electrostatic interactions among the charges on the polymer backbone are shielded by the added electrolyte as the ionic strength of the medium is raised.