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Rational design of thermoresponsive polymers in aqueous solutions:A thermodynamics mapChuanzhuang
writer:mapChuanzhuang Zhaoa, Zhiyuan Ma X.X. Zhu
keywords:UCST polymer; LCST polymer; temperature responsive; thermodynamics
source:期刊
specific source:Progress in Polymer Science
Issue time:2019年
Temperature variations may induce changes in solution properties for thermoresponsive polymers, whichhave drawn much research attention due to their potential applications in different areas. To meet thepractical requirements, rational design of the polymers is important and necessary. We reviewed litera-ture in this field and proposed a thermodynamic map to guide the design of such polymers. The map isdrawn up based on the enthalpic and entropic contributions (ΔHm and ΔSm) to the free energy changeof mixing (ΔGm). The map is divided into four zones: soluble, insoluble, upper critical solution temper-ature (UCST), and lower critical solution temperature (LCST), with two lines representing the freezingand boiling points of the solvent (water) as two boundaries for the UCST and LCST zones. With the helpof such a map, we attempt to illustrate how the UCST and LCST are affected by the various interactionsin polymer-water mixtures, such as hydrophobic and ionic interactions, and hydrogen bonding, so thatthe thermoresponsive properties of a polymer can be predicted according to their molecular structures.The critical temperatures UCST and/or LCST of a polymer can be obtained from the slope of the straightline that passes through the original point and the location of the polymer on the map. Examples inthe literature are shown to fit in different zones of this map, and we also demonstrate how the varia-tions of the chemical composition or the molecular structure of the polymers can change the intra- andinter-molecular interactions involved, which in turn change the solution properties of the polymers andinduce changes in the critical solution temperatures. This map may be used in the design and preparationof thermoresponsive polymers with UCST and LCST on demand.