Synthesis and Single-Chain Folding of Amphiphilic Random Copolymers in Water
journal contributionposted on 2014-01-28, 00:00 authored by Takaya Terashima, Takanori Sugita, Kaoru Fukae, Mitsuo Sawamoto
Amphiphilic random methacrylate copolymers, consisting of poly(ethylene glycol) (PEG) and alkyl pendent groups, undergo reversible single-chain self-folding in water via intramolecular hydrophobic interaction, to generate a dynamic unimolecular hydrophobic nanospace, similar in shape but structurally different relative to micelles and microgel star polymers. These copolymers were prepared by the ruthenium-catalyzed living radical copolymerization of a PEG methacrylate (PEGMA) and an alkyl methacrylate (RMA; R, −CnH2n+1, n = 1–18), where copolymer composition, degree of polymerization, and hydrophobic R moiety were varied. Detailed structural and chain-folding characterization has revealed: single-chain folding is favored with the RMA content 20–40 mol % per chain; the hydrophobic inner compartment (or the self-folded structure) is stable even at a high polymer concentration (up to ∼6 wt %); and folded–unfolded transition occurs on addition of methanol or by elevating solution temperature, finally to phase-separation above a lower critical solution temperature.