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Synthesis and swelling-deswelling kinetics of poly(N-isopropylacrylamide) hydrogels grafted with LCST modulated polymers.

Abstract

Two types of thermo-responsive hydrogels are synthesized to obtain comb-type grafted gels with different lower critical solution temperatures (LCSTs) between graft chains and cross-linked backbone networks: these are poly(N-isopropylacrylamide) (PIPAAm) cross-linked hydrogels grafted with poly(N-isopropylacryl amide-co-N,N-dimethylacrylamide) (poly(IPAAm-co-DMAAm)) maintaining a freely mobile end and poly(IPAAm-co-DMAAm) cross-linked hydrogels grafted with PIPAAm chains. The effect of graft chain hydrophilic/hydrophobic balance as well as its mobility on deswelling kinetics of these grafted gels are investigated through the polymer LCST modulation and external temperature changes. The deswelling rate of poly(IPAAm-co-DMAAm)-grafted PIPAAm gel increases with increasing in temperature. This gel shows a discontinuous increase of the deswelling rate when the temperature is applied from below to above the graft chain LCST (37 degrees C). The deswelling rate of PIPAAm-grafted poly(IPAAm-co-DMAAm) gel increases continuously when the temperature is applied from below to above the graft chain LCST (31 degrees C). Due to the strong hydrophilicity of backbone network, the hydrophobic aggregation force weak. In contrast to the graft-type gels, normal-type poly(IPAAm-co-DMAAm) cross-linked gel without graft chains demonstrates the discontinuous decrease for the deswelling rate when the temperature is applied from below to above the polymer LCST (36 degrees C), entrapping water inside the gel due to the formation of an impermeable dense skin layer at the gel surface. These gel deswelling mechanisms are discussed in terms of gel structures.

Authors+Show Affiliations

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Department of Chemical Engineering, Waseda University, Tokyo, Japan.

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Source

MeSH

Absorption
Acrylic Resins
Biocompatible Materials
Hydrogel
Kinetics
Materials Testing
Particle Size
Polymers
Temperature
Water

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

10606027