Kinetic study of the copolymerization of tetrahydrofuran‐3,3‐dimethyloxetane: Microstructure of the copolymers

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Abstract
The cationic copolymerization of tetrahydrofuran‐(A)‐3,3‐dimethyloxetane (B) was studied at 0°C with BF3·OEt2‐epichlorhydrin and acetylhexafluoroantimonate as initiators. The values of the reactivity ratios, calculated by the Fineman–Ross and Kelen–Tüdos methods, were rA = 0.13, rB = 8.1 and rA = 0.13, rB = 7.9, respectively. These values are in satisfactory agreement with those obtained with a kinetic scheme in which depropagation reactions were considered. The product rArB was approximately equal to unity, which indicated an ideal random copolymerization. The copolymers were also analyzed by 1H‐NMR spectroscopy. Their spectra presented a doublet at 3.1 and 3.15 ppm that corresponded to the methylene protons of the dimethyloxetane units and allowed the determination of the probabilities P(AA), P(AB), and P(BB). Good agreement was found between the values calculated by spectroscopic methods and those obtained by using the classical probability theory of copolymerization.