in Wiley InterScience (www.interscience.wiley.com).The ring opening polymerizations of p-substituted phenol-based benzoxazines are self-terminated as soon as dimers form. The polymerization of benzoxazine monomers does not proceed according to the theoretical mechanism even though the conditions, temperature, molar ratio, solvent polarity, and reactant ratio are varied. The speculated mechanism, involving the unique structure of a dimer with interand intramolecular hydrogen bonds, is applied to explain an obstructive effect on ring opening polymerization. In this article, we clarify an important case which the stereo structure of the compound controls the reaction and prevents the polymerization expected from the theoretical mechanism.

The crystal structure of poly­(3-hydroxybutyrare) β crystal form has been analyzed on the basis of two-dimensional X-ray diffraction data. The all-trans zigzag chains are packed in the hexagonal unit cell of a = b = 9.22 Å, c (chain axis) = 4.66 Å, and γ = 120° with the space group P3221. The upward and downward chains are statistically located at one lattice site at 50% probability. By combining the thus-analyzed structure information of the β-form with the previously reported structure information of the α-form, the geometrical relation between these two crystalline phases has been clarified in detail. The tension-induced α-to-β phase transition affects the higher-order structural change, as known from the small-angle X-ray scattering (SAXS) data collected in the tensile deformation process. By analyzing all experimentally obtained wide-angle X-ray diffraction and SAXS data, the following transition model has been proposed: the high tension to the oriented sample causes the increase of the long period of the α-form lamellae. As the tensile force is increased, the local stress concentration starts to occur at the short tie chain segmental parts in the amorphous region sandwiched between the stacked lamellae. These highly tensioned tie chains induce the α-to-β structural change in both amorphous and directly connected crystalline regions and generate the 40 Å-wide bundles of zigzag chain segments passing through several neighboring lamellae along the draw direction. These bundles are repeated with the averaged period of about 90 Å in the lateral direction perpendicular to the draw axis. Further stretching causes the cut of the highly tensioned extended chain parts, resulting in the formation of voids and finally the breakage of the whole sample before the completion of the phase transition from the α- to β-form.

No abstract

INTRODUCTIONEthylene-tetrafluoroethylene (ETFE) alternating copolymer with molar content of E/TFE 50/50 mol % is used in the various application fields due to its excellent chemical stability, thermal stability, electric properties, and so on. 1 As reported by several researchers, 2-10 this copolymer exhibits the reversible phase transition at around 100°C between the low-temperature and hightemperature phases, reflecting on the physical properties sensitively. Crystal structure and phase transition behavior are basically important for understanding the characteristic properties of the polymer. The whole scheme of the phase transition behavior of this ETFE copolymer is clarified relatively well. But, we have still one serious and not-yet-perfectly solved problem, which is needed to solve correctly for understanding the structural transition behavior in a concrete manner. The problem is to analyze the accurate crystal structure of this copolymer. The molecular chain conformation and the crystal structure of both the low-and high-temperature phases must be clarified with enough accuracy, in particular, the structure of the low-temperature phase as a starting point of discussion.So far, several researchers reported the crystal structure of the lowtemperature phase, but the correct answer is still ambiguous. 10-12 For example, Wilson and Starkweather proposed the monoclinic structure with space group C2/m-C 2h 3 and a = 9.6 Å, b = 9.2 Å, c (fiber axis) = 5.0 Å and γ = 96°, and also the structure of orthorhombic cell with space group Cmca-D 2h 18 . 11 But they did not determine the structure through the quantitative comparison of X-ray diffraction intensities between the observed and calculated values. Tanigami et al. proposed the orthorhombic unit cell of a = 8.57 Å, b = 11.20 Å, and c (fiber axis) = 5.04 Å, in which four planar-zigzag chains were packed in a herringbone mode. 12 The setting angle of planar-zigzag chains was determined by comparing the observed and calculated intensity ratio of the two innermost equatorial X-ray reflections (120 and 200). But, their model does not give a good agreement between the observed and calculated intensities of many other reflections, as will be checked in a later section of the present paper. Besides, judging from the source, their sample is speculated to contain small amount of the third monomer content and it is not a purely two-component ETFE copolymer. Existence of the third component might affect the unit cell parameters as well as the X-ray diffraction pattern itself. 13 Phongtamrug et al. determined the unit cell parameters for a series of ETFE copolymers with various E/TFE contents. 10 Since the innermost reflection was found to be an overlap of two reflections of slightly different lattice spacings, their proposal of monoclinic unit cell might be reasonable. But they did not give any plausible crystal structure model in their paper.In this way, the crystal structure of ETFE alternating copolymer has not yet been established enough satisfactorily. In the present pape...

N,N-Bis(2-hydroxybenzyl)alkylamine derivatives form a cage-like assembly consisting of two molecules via inter- and intramolecular hydrogen bonds. The derivatives exhibit themselves as host to accept copper-ion guests under the double-oxygen-bridged dimeric system. Quantum chemical calculation suggested that the host-guest interaction is based on a charge-transfer coordination. Comparison of the crystal structures before and after complexation clarifies a rare example of a host-guest compound where the hosts maintain their cage framework through the change of hydrogen bonds to coordination bonds.