Abstract
A pentablock copolymer was prepared via the atom transfer radical polymerization of 2-hydroxyethyl methacrylate (HEMA) initiated by 2-bromoisobutyryl end-capped PPO-PEO-PPO as a macroinitiator in DMF. Attaching PHEMA blocks altered the self-assembly process of the pentablock copolymer with γ-CDs in aqueous solution. Before attaching the PHEMA, the macroinitiator was preferentially bent to pass through the inner cavity of γ-CDs to give rise to tight-fit double-chain stranded polypseudorotaxanes (PPRs). After attaching the PHEMA, the resulting pentablock copolymer was single-chain stranded into the interior of γ-CDs to form more stable, loose-fit PPRs. The results of 1H NMR, WXRD, DSC, TGA, 13C CP/MAS NMR and FTIR analyses indicated that γ-CDs can accommodate and slip over PHEMA blocks to randomly distribute along the entire pentablock copolymer chain. This results in unique, single-chain stranded PPRs showing no characteristic channel-type crystal structure.
Highlights
Cyclodextrins (CDs) are a family of cyclic oligosaccharides composed of 6, 7 or 8 glucose units linked via α-1,4-glycosidic bonds
A distal 2-bromoisobutyryl end-capped PEG was preferably bent to fit into the cavity of γ-CDs to form stable and unconventionally conformational PPRs. γ-CDs can accommodate the bulkier poly(N-isopropylacrylamide) (PNIPAAm) blocks to give single-chain stranded, loose-fit PPRs or PRs [14,15,16]
To extend the scope of self-assembly of γ-CDs with polymers having bulkier cross-sectional areas, poly(2hydroxyethyl methacrylate) (PHEMA) is attached to both ends of PPO-PEO-PPO by atom transfer radical polymerization (ATRP) to yield a pentablock PHEMA-PPO-PEO-PPO-PHEMA copolymer
Summary
Cyclodextrins (CDs) are a family of cyclic oligosaccharides composed of 6, 7 or 8 glucose units linked via α-1,4-glycosidic bonds. A pentablock copolymer PHEMA-PPO-PEO-PPO-PHEMA is prepared via atom transfer radical polymerization (ATRP) in DMF, and allowed to self-assemble with γ-CDs in aqueous solution to form PPRs. The results of 1H NMR, WXRD, DSC, TGA, 13C CP/MAS NMR and FTIR analyses indicate that the attachment
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