Issue 23, 2023

Thermoresponsive “irreversible” property change of POSS-crosslinked PNIPAAm hydrogels

Abstract

Control over the reversibility of property changes of a stimuli-responsive polymer hydrogel such as transient fixation and on-demand recovery is a key challenge in realizing a sophisticated function as observed in natural soft tissues. Inspired by the denaturation process of proteins, we focused on incorporation of a highly hydrophobic component into a thermoresponsive hydrogel to induce internal structural fixation by hydrophobic aggregation upon thermoresponsive macroscopic shrinking of a gel network. A polyhedral oligomeric silsesquioxane (POSS) compound with 8 ammonium cation groups was employed as a crosslinker for gel synthesis through end-crosslinking of telechelic poly(N-isopropylacrylamide) (PNIPAAm) with an activated ester terminus, which was prepared by reversible addition–fragmentation chain-transfer (RAFT) polymerization. POSS-crosslinked PNIPAAm gels were obtained with good reproducibility under the reaction conditions in the presence of a large amount of a base. The product gels exhibited reversible swelling/deswelling in water against temperature change; however, their appearance did not return to the original transparency once the gel was heated in water. This behavior contrasts sharply with the reversible change in appearance with a normal PNIPAAm gel. The “irreversible” change in turbidity was likely to result from the aggregation of the POSS moieties induced by macroscopic volume shrinking of the POSS-containing PNIPAAm gels. This internal structural change also led to an appreciable change in mechanical properties: an increase in Young's modulus and elongation. In addition, the turbid POSS-crosslinked gels after a heating/cooling cycle returned to almost transparent ones by immersion in a highly polar solvent such as dimethylsulfoxide.

Graphical abstract: Thermoresponsive “irreversible” property change of POSS-crosslinked PNIPAAm hydrogels

Supplementary files

Article information

Article type
Paper
Submitted
30 jan 2023
Accepted
13 apr 2023
First published
14 apr 2023

Polym. Chem., 2023,14, 2771-2778

Thermoresponsive “irreversible” property change of POSS-crosslinked PNIPAAm hydrogels

S. Ida, T. Hikida, A. Kawai, T. Matsuda, S. Suzuki, H. Imoto, K. Naka and S. Kanaoka, Polym. Chem., 2023, 14, 2771 DOI: 10.1039/D3PY00097D

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements