Poly(1,3-dioxolane) (PDO) is widely used as a pH-and temperaturesensitive water-soluble polymer applied in functional hydrogels and nanoparticles. In this contribution, we report a series of highly efficient rare-earth triflate catalysts for a Brønsted-acid-free ring-opening polymerization of DO. The repeat unit of PDO comprises perfectly alternating hydrophilic ethylene glycol and hydrophobic methyl aldehyde units leading to hydrogen-bonding-controlled self-assembly in aqueous solution. Spherical aggregates are observed in transmission electron microscopy images whose sizes can be tuned by concentration and temperature, further confirming that the hydrate is derived from "blocked" water molecules through hydrogen bonding. The size and morphology of the aggregates can be modulated not only by the annealing process owing to the realignment of semicrystalline regions but also by metal salts generating rodlike, wormlike, or spherical structures. In this case, PDO is able to act as both a surfactant and as a reductant on account of the acidolysis of acetal moieties, which form a core−shell Cudecorated hybrid material in situ in one step, thus providing a promising future template for the generation of metal nanoparticles.
Zwitterionic copolymerization of γ-butyrolactone with 3,3-bis(chloromethyl) oxacyclobutane is catalyzed by scandium triflates generating random linear and cyclic copolymer.
Janus polymerization consists of anionic and cationic ring opening polymerizations (AROP and CROP) at the two ends of a single propagating polymer chain, followed by a self-triggered chain extension generating multiblock copolymers (MBCPs) in one step. In the contribution, Janus polymerization by Tm(OTf) 3 or Er(OTf) 3 catalyst with an epoxy initiator is applied to synthesize MBCPs of semi-crystalline poly(ε-caprolactone) (PCL) blocks from coordinated AROP and poly(1,3-dioxolane-co-ε-caprolactone) (P(DO-co-CL)) blocks from CROP of DO with CL. Meanwhile, amorphous random copolymers [P(DO-r-CL)] are synthesized as control by employing other rare earth triflates [RE(OTf) 3 , RE = Y, Nd, Gd and Lu] as catalysts or in the absence of an initiator via CROP. On account of the distinguishable chemical structures and thermal properties between Janus MBCPs and cationic random copolymers, Janus features are confirmed including the CROP and AROP at a single propagating chain. The resultant amphiphilic copolymers self-assemble to nanoparticles in aqueous solution with designable diameters with the corresponding ratios of hydrophilic and hydrophobic segments. MBCPs exhibit good shape memory properties with appropriate deformation temperature close to human body's, providing a prospect on the applications in biomedical devices.
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