Dual thermoresponsive homopolypeptide with LCST-type linkages and UCST-type pendants: Synthesis, characterization, and thermoresponsive properties. (6th December 2017)

• Record Type: Journal Article
• Authors: Li, Minjie; He, Xiongliang; Ling, Ying; Tang, Haoyu
• Is Part Of: Polymer. Volume 132(2017)
• Page Start: 264
• Page End: 272
• Publication Date: 2017-12-06
• Subjects: Thermoresponsive polymer -- Polypeptide -- Ionic liquid; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2017.11.016
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Water-soluble homopolypeptides bearing di(ethylene glycol) (DEG) linkages and various ionic liquid (IL) pendants with both lower and upper critical solution temperature (LCST and UCST) or a UCST were prepared and systematically investigated. Poly ( γ -2-(2-chloroethoxy)ethyll -glutamate) (PCEELG) with DEG linkage and reactive chloro groups can be readily prepared from ring-opening polymerization of γ -2-(2-chloroethoxy)ethyll -glutamic acid based N -carboxyanhydride. Homopolypeptides were conjugated with various IL pendants and counteranions by nucleophilic substitutions and subsequent ion-exchange reactions. Homopolypeptide with DEG linkages and tributylphosphonium iodide (PEELG-TBP-I) showed interesting LCST < UCST (i.e., soluble-insoluble-soluble) dual thermoresponsive behavior in DI-H2 O and NaI aqueous solutions. The LCST-type and UCST-type phase transition temperatures ( T pt s) were tunable by polymer concentration, molar mass, and NaI concentration. Homopolypeptide with DEG linkages and tributylphosphonium tetrafluoroborate showed a UCST both in DI-H2 O and PBS buffer while homopolypeptide with DEG linkages and triphenylphosphonium iodide (or tetrafluoroborate) or with alkyl linkages and tributylphosphonium iodide (or tetrafluoroborate) showed a UCST in PBS buffer. The UCST-type T pt in PBS buffer was in a broad temperature range of 20–90 °C which was tunable by adjusting the polymer concentration, molar mass, IL moieties, and counteranions. Graphical abstract: Highlights: We prepared homopolypeptides with di(ethylene glycol) (DEG) linkages and ionic liquid pendants. Homopolypeptide bearing DEG and tributylphosphonium iodide groups showed LCST < UCST dual thermoresponsiveness. Some homopolypeptides showed UCST-type phase behaviors in DI water and/or PBS buffer.