Issue 35, 2020

Stereocomplexed and homocrystalline thermo-responsive physical hydrogels with a tunable network structure and thermo-responsiveness

Abstract

The widespread application of thermo-responsive hydrogels requires materials with robust mechanical properties and tunable responsiveness. Herein, we report robust thermo-responsive physical hydrogels with a tunable network structure and responsiveness by controlling the manner of crystallization of hydrophobic blocks. Biocompatible, stereocomplexable poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) were introduced into thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) to obtain the enantiomeric grafted copolymers PNIPAM-g-PLLA and PNIPAM-g-PDLA and their corresponding hydrogels. The hydrophobic PLLA/PDLA domains served as physical crosslinking junctions in the hydrogels. The crystalline structure of the hydrogels can be facilely tuned by varying the ratio of PLLA/PDLA enantiomeric blocks. Stereocomplex (SC) crystallization between PLLA and PDLA facilitates the formation of H-bonded hydrophobic domains with denser chain packing, which endows the racemic hydrogels with a stronger network structure, higher mechanical strength, and better solvent resistance compared to enantiopure examples. The hydrogels exhibit good thermo-sensitivity in water; the stronger racemic hydrogel network restricts volume shrinkage and water desorption at high temperatures, enabling the facile control of thermo-responsiveness. The crystallization-tuned thermo-responsiveness of racemic and enantiopure hydrogels also allows for the design of assembled bilayer hydrogels capable of thermally triggered reversible shape morphing.

Graphical abstract: Stereocomplexed and homocrystalline thermo-responsive physical hydrogels with a tunable network structure and thermo-responsiveness

Supplementary files

Article information

Article type
Paper
Submitted
13 Jun 2020
Accepted
21 Jul 2020
First published
22 Jul 2020

J. Mater. Chem. B, 2020,8, 7947-7955

Stereocomplexed and homocrystalline thermo-responsive physical hydrogels with a tunable network structure and thermo-responsiveness

K. Liu, H. Cao, W. Yuan, Y. Bao, G. Shan, Z. L. Wu and P. Pan, J. Mater. Chem. B, 2020, 8, 7947 DOI: 10.1039/D0TB01484B

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