Synthesis of Thermoresponsive Copolymers with Tunable UCST-Type Phase Transition Using Aqueous Photo-RAFT Polymerization
Lertturongchai P.a,Ibrahim M.I.A.b,Durand A.b,Sunintaboon P.a,Ferji K.b
a Department of Chemistry, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
b Université de Lorraine, CNRS, LCPM, Nancy, F-54000, France
Currently, the phase transition of aqueous binary systems containing thermoresponsive (co)polymers, and exhibiting upper critical solution temperature (UCST), is exclusively investigated in dilute solutions, which can limit the knowledge of their UCST-type phase transition. Herein, a photo-RAFT polymerization approach, using acrylamide (AAm) and acrylonitrile (AN) as monomer models, is used to prepare well-controlled poly(AAm-co-AN) copolymers “in situ” in highly concentrated dispersions (60 wt%). The impact of the copolymer concentration and the chemical composition (as a variation of AN fraction in the copolymers) on the cloud point temperature (TCP) are investigated using turbidity measurements. Importantly, the results show that upon increasing the polymer concentration, a sharp increase of TCP up to a maximum point is observed, representing the UCST, before the decrease of TCP at higher polymer concentrations. Finally, a model equation is developed to fit the UCST values of poly(AAm-co-AN), which can be useful to design new poly(AAm-co-AN) copolymers with a desired UCST for a specific application.
Keywords: cloud point temperature; lower critical solution temperature; phase diagrams; thermoresponsive copolymers; turbidity; upper critical solution temperature
For more details: Macromolecular Rapid Communications Volume 41, Issue 91 May 2020 Article number 2000058.