A series of size‐controlled, cyclic poly(tetrahydrofuran)s ($\overline M _{{\rm n,NMR}}$ of 4 400–8 600) that consist exclusively of the monomer, i.e., oxytetramethylene, unit (I) have been prepared in high yield through the metathesis polymer cyclization of a telechelic precursor having allyl groups, 1, in the presence of a Grubbs catalyst, and the subsequent hydrogenation of the linking, i.e., 2‐butenoxy, unit in the presence of an Adams' catalyst (PtO2). A remarkable topology effect has subsequently been observed upon the isothermal crystallization of these two model polymers, showing distinctive spherulite growth rates and spherulite morphologies in comparison with the relevant linear poly(tetrahydrofuran) counterpart that has ethoxy end groups (II).magnified image

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A metathesis condensation process was applied for the synthesis of double cyclic, 8-shaped poly(THF)s. Thus, first, a cyclic poly(THF) having an allyl group, 1, was subjected to the intermolecular metathesis condensation. The bimolecular condensation reaction was found to proceed in the presence of a Grubbs catalyst, while with noticeable concurrent reactions. Alternatively, a twin-tailed tadpole, i.e., "a ring with two branches" structure, poly(THF) having tail-end allyl groups, 2, and a kyklo-telechelic poly(THF) having two allyl groups at opposite positions, 3, were prepared for the intramolecular metathesis condensation. The unimolecular reactions proceeded effectively even under dilution of the polymer concentration at 0.2 g/L to produce the corresponding 8-shaped poly(THF)s. These products were unequivocally characterized by means of 1 H NMR, SEC, and MALDI-TOF MASS techniques.

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