Issue 10, 2015

Double thermo-responsive hydrogels from poly(vinylcaprolactam) containing diblock and triblock copolymers

Abstract

The thermally-induced gelation and gel properties of concentrated aqueous solutions of double thermoresponsive poly(N-vinylamide)-based di- and triblock copolymers are studied by rheology. The copolymers under investigation, prepared by cobalt-mediated radical polymerization and coupling reactions, are composed of poly(vinylcaprolactam) (PNVCL) blocks and of a statistical poly(vinylcaprolactam-stat-vinylpyrrolidone) segment with a cloud point temperature (TCP) higher than that of PNVCL. Heating the di- and triblock solutions beyond the first phase transition temperature favors gel formation while heating above the second TCP leads to opaque gels without macroscopic demixing. Moduli of the triblock hydrogels are systematically higher than those of the corresponding diblocks, even above the second transition. Rheological data suggest distinct micellar structures for each copolymer architecture: densely packed micelles of diblocks and 3-D networks of bridged micelles for triblocks. Strain sweep experiments also emphasize the positive effect of the micelle bridging on the elasticity and stability of the hydrogels. The formation and properties of the obtained gels are also shown to depend on the copolymer concentration, block length, and composition. Addition of salt also allows us to tune the phase transition temperatures of these double thermoresponsive hydrogels.

Graphical abstract: Double thermo-responsive hydrogels from poly(vinylcaprolactam) containing diblock and triblock copolymers

Supplementary files

Article information

Article type
Paper
Submitted
20 Nov 2014
Accepted
17 Dec 2014
First published
19 Dec 2014

Polym. Chem., 2015,6, 1856-1864

Author version available

Double thermo-responsive hydrogels from poly(vinylcaprolactam) containing diblock and triblock copolymers

J. Thomassin, K. Mathieu, A. Kermagoret, C. Fustin, C. Jérôme and A. Debuigne, Polym. Chem., 2015, 6, 1856 DOI: 10.1039/C4PY01606H

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