ε-Caprolactone-Tetrahydrofuran High-Molar-Mass Copolymers: Polymerization in Bulk above <i>T</i> _c of THF and Ordered Copolymers with Two-Dimensional NMR and DFT Analysis

Copolymers of ε-caprolactone (CL) and tetrahydrofuran (THF) with high molar masses (Mn ∼ 105 g/mol) were synthesized in bulk at ∼80 °C, i.e., above the ceiling temperature (Tc) of THF. This thermodynamic limitation reduced the length of units to monads and dyads, allowing the synthesis of ordered (alternating) copolymers, [(thf-thf)-cl]n, at a sufficiently high [THF]0/[CL]0 feed ratio. The presence of the -thf-thf-dyads (apparently against thermodynamic predictions) results from the antepenultimate influence of the -cl- fragment. A combination of COSY, TOCSY, and ROESY spectra enabled the identification of all chemical shifts in the most detailed copolymer spectrum. Thus, whenever copolymers with -cl- and/or -thf- units are to be analyzed, the present analysis provides the corresponding reference points. According to the kinetic data, both comonomers polymerize at an identical rate at the chosen feed ratio. The particular rates of the four major reactions in the copolymerization scheme were analyzed using the DFT method.