3 years ago

A Twisting Ring Polymer: Synthesis and Thermally Induced Chiroptical Responses of a Cyclic Poly(tetrahydrofuran) Having Axially Chiral Units

A Twisting Ring Polymer: Synthesis and Thermally Induced Chiroptical Responses of a Cyclic Poly(tetrahydrofuran) Having Axially Chiral Units
Satoshi Honda, Yasuyuki Tezuka, Takuya Yamamoto, Kaoru Adachi
A series of cyclic poly(tetrahydrofuran)s, poly(THF)s, having a pair of stereoisomeric forms of axially chiral, 2,2′-disubstituted-1,1′-binaphthyl (BiNap) unit at the opposite positions, CR-R, CR-S, and CR-R/S, have been newly synthesized through an electrostatic self-assembly and covalent fixation (ESA-CF) process by using a center-functionalized (kentro-telechelic) poly(THF) having an axially chiral BiNap unit and N-phenylpyrrolidinium salt end groups, carrying a dicarboxylate counteranion having a BiNap unit. The relevant cyclic and linear analogues, having one axially chiral unit, CR (CR-1 and CR-2) and LR, respectively, have also been prepared according to the ESA-CF protocol. The subsequent CD measurements of these cyclic and linear polymers having axially chiral units by lowering the temperature toward −10 °C in hexane revealed the noticeable reduction of the dihedral angle of the binaphthyl units exclusively for the cyclic CR-R as well as for the CR-1 and CR-R/S. The observed thermally induced cyclic topology effect on this chiroptical response is reasoned by the solvophobic interaction promoted for the topologically constrained, looped poly(THF) segments in the vicinity of the BiNap units.

Publisher URL: http://dx.doi.org/10.1021/acs.macromol.7b00839

DOI: 10.1021/acs.macromol.7b00839

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