Structural studies of polyethers, [(CH₂)_mO]_n. V. Polyoxacyclobutane

Abstract

Structural Studies of Polyethers, [-(CH,)m-O-]n. SUMMARY:The structure of polyoxacyclobutane has been studied by x-ray diffraction and infrared absorption methods, and three crystal modifications have been found. The molecular conformation of modification I is essentially planar zigzag, fiber period being 4.80 A. Modification I1 is trigonal, R3c-C:,, a = 14.13 A, and c (fiber axis) = 8.41 A; nine molecular chains of a T,GT,G type pass through a unit cell. Modification I11 is orthorhombic, C222,-Dz, a = 9.23 A, b = 4.82 A, and c (fiber axis) = 7.21 A; two molecular chains of a (T,G,), type pass through the center and the corner of a unit cell.The transitions among these three modifications were studied and discussed. Modification I is stable only in the presence of water. Modification I11 is the most stable form, and this is consistent with the antiparallel arrangement of the strong dipole-moments of the COC groups. Modification I1 is stable only as oriented samples. ZUSAMMENFASSUNG: Die Struktur von Polyoxacyclobutan wurde mit Rontgenstrahlbeugungs-und Ultrarotabsorptionsmethoden untersucht. Dabei wurden drei Kristallmodifikationen gefunden. Modifikation I hat im wesentlichen eine ebene Zickzackkonformation mit einer Faserperiode von 4,80 A. Modifikation I1 ist trigonal, R3c-C&, a = 14,13 A,und c (Faserachse)= 8,41 A; neun Molekiilketten vom Typ T3GT3c gehen durch eine Elementarzelle. Modifikation I11 ist orthorhombisch, C222,-D;, a = 9,23 A, b = 4,82 A,und c (Faserachse) = 7,21 A; zwei Molekiilketten vom Typ (T,G,), laufen durch das Zentrum und die Ecke einer Elementarzelle.Die Ubergange zwischen diesen drei Modfiationen werden untersucht und erortert. Modifikation I ist nur in Gegenwart von Wasser bestandig. Modfiation I11 ist die stabilste Form, was durch die antiparallele Anordnung der starken Dipolmomente der COC-Gruppen zu erklaren ist. Modifikation I1 ist nur in orientierten Proben stabil.

Complex formation between poly(oxytrimethylene) and cyclodextrins

“…X-ray crystallographic studies [6,7] and IR studies [8] also provide evidence that a (T3G) conformation is also stable in POT. According to calculation not only a planar zigzag conformation but also other conformations such as a (T3G) conformation and a (T2G2) conformation are also stable in the case of POT.…”

Effect of molecular weight and temperature on the isothermal crystallization of poly(oxetane)

“…The relationship between the specific volume of the amorphous material, ~Ta, and temperature, t (~ was determined dilatometrically in the melted state and it is given by: The corresponding relationship for the specific volume of the crystal, Fc, for the orthorhombic modification, was given by: #c= 0.833 +5.1 x 10 -4 (t-25) taking 0.833 as the specific volume of this form [2] at 25 ~ Dilatometric measurements were carried out in the range from -12 to 19 ~ depending on molecular weight. Crystallization kinetics at higher undercoolings were studied in a Perkin-Elmer DSC-1B.…”

“…The first term of this series is polyoxacyclobutane, polyoxetane or poly(trimethylene oxide), PTO, which is a semicrystalline polymer. Structural studies on this polymer have been carried out by Tadokoro et al [2][3][4] and four crystal modifications, one of which is an hydrate, have been found. The molecule assumes, depending on crystallization conditions, a planar zig-zag conformation in the hydrate (Modification I) and in Modification IV, a T3GT3G conformation in Modification II and a (T2G2)2 conformation in Modification III.…”

Conformational Characteristics of Poly(trimethylene sulfide) and Structure−Property Relationships of Representative Polysulfides and Polyethers

“…37 In modifications I, II, and III, the PTMO chain adopts tttt, tgtt, and tggt conformations, respectively. The tgtt sequence of modification II repeats in such a manner as (tg + tt)(tg -tt)....…”