X-ray methods have been used to analyze the supramolecular tubular structures in the hexagonal solid state and columnar hexagonal liquid crystalline ( &, ) phases of a polymethacrylate with tapered side groups: specific~y,poly(2-(2-[2-(2-(methacryloyloxy)ethoxy)ethoxylethoxy)ethyl3,4,5-tris(@-(dodecyloxy)-benzyl)oxy)benzoate), abbreviated as 12-ABG-4EO-PMA. Oriented fibers were drawn from the liquid crystalline phase at -60 O C and annealed for several days at 4 "C. The X-ray pattern for these fibers recorded at room temperature (25 "C) contained eight equatorial reflections that are orders predicted for a hexagonal unit cell with a = b = 60.4 A. The similarity of the data to those for unoriented specimens in the & phase suggests that both phases contain the same type of supramolecular cylindrical moieties. In addition, wideangle maxima are observed on the equator and two layer lines that suggest formation of a three-dimensionallyordered structure at room temperature. These data give the first available information on the supramolecular structure within the columns. The layer line spacings define a repeat of c = 5.03 A along the column axis, containing eight monomeric units based on the observed density. Strong off-meridional maxima at d = 4.30 and 3.84 A on the first layer line suggest that the "planes" of the aromatic moieties are tilted rather than perpendicular to the cylinder axis. Possible "pine tree" models are discussed in which the tapered side groups are stacked in 8-fold layers or form &fold helices within the columns. Increasing the temperature to 60 O C leads to a reduction in the cylinder diameter to 58.0 A. Stacking correlations remain along the fiber axis direction, but otherwise the internal structure of the cylinder is muchmore disordered than at room temperature. On cooling, the three-dimensional order is restored.

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This paper describes further X-ray diffraction work on the structure of the copolyamide prepared from terephthaloyl chloride (TPA), phenylenediamine (PDA), and 3,4'-diaminodiphenyl ether (DPE). X-ray fiber diagrams of this material consist of a series of nonperiodic layer lines, and we have shown previously that these are consistent with a structure consisting of parallel chains of completely random comonomer sequence. The meridional peak positions are predicted accurately for a fully extended chain conformation, and the peak intensities are also in reasonably good agreement. However, there is a less than adequate match between the observed and calculated peak profiles, most notably that for the peak at d % 2.15 A, which is predicted to be very much sharper than that observed. The latter peak has been shown to be a measure of the correlation or persistence length for the stiff chain conformation in the solid state and is predicted to be extremely sharp when the chain is modeled by a linear infinite chain of random monomer sequence. A better fit to the broader observed peak is achieved by using a model that incorporates nonlinearity of the chain conformation due to the presence of the ether and 1,3-phenylene linkages, as well as torsional variations. This has been done by defining the nonlinearity in terms of histograms of the axial advance per monomer for each monomer type, based on a survey of models of a large number of chains with sequences selected by Monte Carlo methods. It is clear that the requirements of chain packing imply highly extended conformations, and this probably involves some distortion of the bond and torsion angles in order to align the random sequences.

X-ray diffraction and computer molecular modeling Methods are being used to investigate the ordering of random sequence copolyesters when cooled for the nematic Melt. Data will be presented for the copolymers prepared from p-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid. The non-periodic diffraction patterns arising from the random monomer sequences are also indicative of the presence of limited three dimensional order. For both polymer systems, we can generate the qualitative feature of the x-ray data using models in which short non-identical segments of 10–12 Monomers on adjacent chains are approximately in register at their center. Molecular Mechanics calculations show that mese non-identical sequences can be packed on the observed hexagonal lattice with only small energy differences when compared to analogous homopolymer structures. Data will also be presented showing how x-ray diffraction can be used to follow transesterification of copoly (HBA/HNA) in the nematic MelL

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