ISOMORPHISM IN THE POLY(3,3-BIS-HYDROXYMETHYLOXETANE) FAMILY AND COPOLYMERS - POLY YMETHYLOXETANE-CO-3-METHYL-3-HYDROXYMETHYLOXETANE)

Copolymers of 3,3-bis-hydroxymethyloxetane, BHMO, 3-methyl-3-hydroxyme thyloxetane, MHMO, or with 3-ethyl-3-hydroxymethyloxetane, EHMO, monom er units were characterized by x-ray fiber diffraction, differential s canning calorimetry and C-13 solid-state nuclear magnetic resonance (N MR). The copolymers are statistically random and crystalline throughou t the range of compositions. Both P (BHMO) and P(MHMO) appear to cryst allize in the same crystal form. The fiber repeat indicates a planar z igzag backbone conformation, c(fiber axis) = 4.77 +/- 0.03 angstrom. S imilarities in the x-ray fiber diagrams as well as a linear dependence of T(m) with composition of copolymer with no change in fiber diagram s indicates isomorphism, a phenomenon in which the random substitution of MHMO monomeric units into the crystalline lattice of P(BHMO) occur s without hindering crystallization of the resulting copolymer. (C) 19 94 John Wiley & Sons, Inc.