Journal
JOURNAL OF MOLECULAR LIQUIDS
Volume 346, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.molliq.2021.117906
Keywords
MEO(2)MA; PEG; RAFT polymerization; Graft copolymers; Block copolymers
Funding
- CAPES (CoordenacAo de Aperfeicoamento de Pessoal de Nivel Superior/Coordination for the Improvement of Higher Education of Brazil) [88881.361580/2019-01-PDSE]
- CNPq (Conselho Nacio-nal de Desenvolvimento Cientifico e Tecnologico do Brasil/The Brazilian National Council for Scientific and Technological Development) [307695/2020-4]
- EPSRC [EP/T00813X/1]
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This article investigates graft copolymers with brush-like architectures containing thermoresponsive monomers. The study explores the chemical structure of the thermoresponsive polymer and its impact on phase behavior and rheological properties. The materials show potential for temperature-responsive applications in the field of medical materials.
Graft copolymers with brush-type architectures are explored containing poly(ethylene glycol) methacrylates copolymerized with thermoresponsive monomers which impart lower critical solution temperatures to the polymer. Initially, the chemical structure of the thermoresponsive polymer is explored, synthesizing materials containing N-isopropyl acrylamide, N,N-diethyl acrylamide and diethylene glycol methyl ether methacrylate. Thermoresponsive graft-copolymers containing di(ethylene glycol) methyl ether methacrylate (DEGMA) exhibited phase transition temperature close to physiological conditions (ca 30 degrees C). The effect of polymer composition was explored, including molecular weight, PEG-methacrylate (PEGMA) terminal functionality and PEGMA/DEGMA ratios. Molecular weight exhibited complex relationships with phase behavior, where lower molecular weight systems appeared more stable above lower critical solution temperatures (LCST), but a lower limit was identified. PEGMA/DEGMA feed was able to control transition temperature, with higher PEGMA ratios elevating thermal transition. It was found that PEGMA terminated with methoxy functionality formed stable colloidal structures above LCST, whereas those the hydroxy termini generally formed two-phase sedimented systems when heated. Two thermoresponsive DEGMA-based graft polymers, poly(PEGMA(7)-ran-DEGMA(170)) and poly(PEGMA(1)-ran-DEGMA(38)), gave interesting temperature-dependent rheology, transitioning to a viscous state upon heating. These materials may find application in forming thermothickening systems which modify rheology upon exposure to the body's heat. (C) 2021 The Authors. Published by Elsevier B.V.
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