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Phenylalanine‐Tethered pH‐Responsive Poly(2‐Hydroxyethyl Methacrylate)
Author(s) -
Choudhury Neha,
Das Somnath,
Samadder Satyajit,
De Priyadarsi
Publication year - 2021
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.202100136
Subject(s) - copolymer , polymer chemistry , chemistry , methacrylate , reactivity (psychology) , chain transfer , monomer , polymerization , aqueous solution , glass transition , radical polymerization , polymer , organic chemistry , medicine , alternative medicine , pathology
A series of pH‐responsive random copolymers comprised of 2‐hydroxyethyl methacrylate (HEMA) and tert ‐butyl carbamate (Boc)‐protected phenylalanine methacryloyloxyethyl ester (Boc‐Phe‐EMA) were synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization in N , N ′‐dimethylformamide (DMF) at 70 °C. The synthesized copolymers were comprehensively characterized using a combination of techniques, including 1 H NMR, FT‐IR spectroscopy and size exclusion chromatography (SEC). Reactivity of each monomers towards controlled radical polymerization was evaluated by determining the reactivity ratios by virtue of extended Kelen‐Tüdös method at high conversions revealed the higher reactivity of non‐modified HEMA ( r HEMA =1.03) in contrast to Boc‐Phe‐EMA ( r Boc‐Phe‐EMA =0.48). Furthermore, the expulsion of the Boc‐groups resulted copolymers with ionizable pendant primary ammonium and hydroxyl groups. To understand the glass transition behaviours of homo‐ and co‐polymers, differential scanning calorimetric (DSC) measurements were carried out. The effect of HEMA content on the pH‐sensitivity of the copolymers in aqueous medium was investigated through turbidity measurements. Finally, the counteranion exchange from trifluoroacetate to chloride provided copolymers with enhanced water solubility and unaltered phase transition pH.