Poly(thioether)s from Closed-System One-Pot Reaction of Carbonyl Sulfide and Epoxides by Organic Bases

The synthesis of poly­(thioether), a highly desired sulfur-containing polymer, is still a key challenge. Herein, we report a simple and facile approach to poly­(thioether)­s by closed-system one-pot reaction of carbonyl sulfide (COS) and epoxides. This route underwent the coupling reaction of COS with epoxides, followed by decarboxylative ring-opening polymerization (ROP) of the generated mixed cyclic thiocarbonates with releasing of CO2 and a little bit of COS. Organic base was used as catalyst and initiator in the two steps, respectively. The oxygen/sulfur exchange reaction was driven by successive regioselective elementary reactions and spontaneous releasing of CO2 (COS), leading to the sulfur atom of COS transferring to poly­(thioether)­s, which was well demonstrated by DFT studies. This work provides an easy-to-handle, metal-free route to poly­(thioether)­s bearing diverse structures by using readily available chemicals

Closed-Loop Phase Behavior of Block Copolymers in the Presence of Competitive Hydrogen-Bonding and Coulombic Interaction

The closed-loop phase behavior, where a lower disorder-to-order transition (LDOT) takes place first, followed by an upper order-to-disorder transition (UODT) upon heating, is seldom observed in block copolymers (BCPs). In this work, we prepared a model BCP, LiClO₄-doped poly­(ethylene oxide)-<i>b</i>-poly­(<i>tert</i>-butyl acrylate-<i>co</i>-acrylic acid) (PEO-<i>b</i>-P­(<i>t</i>BA-<i>co</i>-AA)), in which the hydrogen (H)-bonding between the PEO and AA units and the Coulombic interaction in salt-doped PEO block have opposite effects on the miscibility of BCPs. The relative strength of the H-bonding and Coulombic interaction can be easily tuned by the hydrolysis degree (<i>D</i>_H) of the P<i>t</i>BA block and the amount of doped salt. Various phase behaviors are observed by changing relative strength of different forces. Especially, the closed-loop phase behavior can be achieved when H-bonding, Coulombic interaction, and mixing entropy reach a delicate balance

Design and Regulation of Lower Disorder-to-Order Transition Behavior in the Strongly Interacting Block Copolymers

Lower disorder-to-order transition (LDOT) phase behavior is seldom observed in block copolymers (BCPs). Design of LDOT BCPs is important for broadening the applications and improving the high temperature properties of BCPs. In this work, the LDOT phase behavior was first achieved in the strongly interacting BCPs consisting of poly­(ethylene oxide) (PEO) and poly­(ionic liquid) (PIL) blocks (EO_<i>m</i>-<i>b</i>-(IL-X)_<i>n</i>, X: counterion) by introducing two extra strong forces (hydrogen-bonding and Coulombic interaction) with different temperature dependences. It is also found that the LDOT phase behavior of the EO_<i>m</i>-<i>b</i>-(IL-X)_<i>n</i> BCPs can be regulated by molecular weight (related to mixing entropy), counterion, and salt doping. Increasing counterion size and salt content shifts the disorder-to-order transition temperature (<i>T</i>_DOT) to higher temperature, whereas a higher molecular weight leads to a lower <i>T</i>_DOT. Based on our findings, some general rules for design of LDOT phase behavior in the strongly interacting BCPs were proposed. Moreover, the conductivity of the EO_<i>m</i>-<i>b</i>-(IL-X)_<i>n</i> BCPs was correlated with the LDOT phase behavior. A remarkable increase in conductivity after LDOT, i.e., a thermo-activated transition, is observed for the EO_<i>m</i>-<i>b</i>-(IL-X)_<i>n</i> BCPs, which can be attributed to the cooperative effects of temperature rising and LDOT