Structure and morphology of poly(methacrylic acid) poly(N -isopropyl acrylamide) interpenetrating polymeric networks with pH and temperature sensitivity
Abstract
In this work, interpenetrating polymeric networks (IPNs) composed of pH sensitive poly(methacrylic acid) and temperature sensitive poly(N-isopropyl acrylamide) were synthesized. These IPNs exhibit combined pH and temperature sensitivity due to the contribution of each individual network. The effects of polymerization sequence and monomer concentration of each individual network were discussed to yield the maximum pH and temperature sensitivity. The swelling behavior was investigated under various pH and temperature conditions. The observed pH and temperature transitions in swelling studies of the IPNs are approximately the same as each individual network. A possible hydrogen-bonding structure is proposed between the carboxylic acid groups in poly(methacrylic acid) and the amide groups in poly(N-isopropyl acrylamide). ATRFTIR studies show small shifts in the wavenumbers of the characteristic peaks of the IPNs versus the non-IPN polymers, an indication of intermolecular hydrogen-bonding interactions within the system. Diffusion behavior of the IPN hydrogels was investigated using solute permeation and controlled release studies. The IPNs exhibit a significant size exclusion behavior on solutes with various sizes. The pH and temperature effects on the solute permeation and release are discussed. An ideal property of the IPN can be tailored by manipulating the pH and temperature inputs. Additionally, the IPN morphology was studied using SEM and AFM. A cryogenic technique was used in the SEM studies to visualize the effects of pH and temperature on the IPN morphology. Finally, a single-phase IPN model was developed to predict the swelling behavior of this dual-responsive IPN. The pH and temperature influence on the secondary network mesh size was calculated, which will help significantly in the understanding of the swelling and diffusion behavior of the IPNs.
Degree
Ph.D.
Advisors
Peppas, Purdue University.
Subject Area
Chemical engineering
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