Effect of Methoxy Side Groups on the Crystal Structures of a Series of Syndiotactic Polymethoxystyrenes as Studied by the X-ray Diffraction Data Analysis

Abstract

The crystal structures have been elucidated for a series of novel syndiotactic polymethoxystyrenes (OMe-SPSs) having −OCH3 groups at the ortho-, meta-, or para-positions of phenyl rings on the basis of the detailed analyses of the two-dimensional X-ray diffraction patterns of the highly oriented and highly crystalline samples. The ortho-OMe-SPS has a monoclinic-type unit cell of a = 11.60 Å, b = 17.90 Å, c (fiber axis) = 7.72 Å, and β = 99°, in which the two 21 helical chains of TTGG conformation are packed with the space group P1211. The unit cell of the meta-OMe-SPS is of the monoclinic type with a = 16.20 Å, b = 14.39 Å, c (f. a.) = 10.12 Å, and β = 90°. The four all-trans zigzag chains are packed in the cell with the space group P1121. The para-OMe-SPS takes a large monoclinic unit cell of a = 16.80 Å, b = 29.00 Å, c (f. a.) = 10.12 Å, and β = 80°, in which the eight chains of trans-zigzag conformation (TTTT) are packed with P121/c1 space group symmetry. For both of meta- and para-OMe-SPS, the crystal structure is disordered in the chain packing mode and chain conformation. The existence of the OCH3 side groups and their positions have been found to play an important role in the determination of the chain conformation and chain packing mode in comparison with the crystal structures of SPS.

Crystal Structures of Syndiotactic Polymethoxystyrene–Solvent Complexes Derived by X-ray Diffraction Data Analysis and Computer Simulation

“…The integrated intensities I of individual diffraction peaks were evaluated by analyzing the observed diffraction profiles using a GRAMS software (Thermo Fisher Scientific, Inc.). The structure factors | F obs | of the diffraction peaks were estimated by using the following equation: where K is a scale factor, A is an absorption factor, L is a Lorentz factor, p is a polarization factor, and m is a multiplicity. , The initial structure models were built up by the energy minimization with the commercial softwares Cerius (version 4.10, Biovia) and Materials Studio (Biovia), where the COMPASS force field was used as a set of potential functions …”

“…1 As the basically important information, the crystal structures of the ortho-, meta-and para-OMe-SPSs were reported in our previous paper. 2 The ortho-OMe-SPS has a monoclinic unit cell of a = 11.60 Å, b = 17.90 Å, c (chain axis, c.a.) = 7.72 Å, and β = 99°.…”

“…A detailed structure analysis of the meta-OMe-SPS β form was presented in our previously published paper. 2 The mother polymer of OMe-SPS, or SPS itself is known to exhibit the various kinds of crystalline modifications, the α, 3,4 β, 5,6 γ, 7 δ, 8,9 and δ e , 10 and they show the complicated phase transitions among them. 11 SPS α and β form are obtained from melt crystallization.…”

“…The OMe-SPS are synthesized using custom-designed rare-earth catalysts, which exhibit the extremely high syndio -selectivity and high degree of polymer conversion . As the basically important information, the crystal structures of the ortho-, meta- and para-OMe-SPSs were reported in our previous paper . The ortho-OMe-SPS has a monoclinic unit cell of a = 11.60 Å, b = 17.90 Å, c (chain axis, c.a.)…”

“…These crystal forms having the all-trans-conformations are now called the β form by imitating the name used in the SPS case. A detailed structure analysis of the meta-OMe-SPS β form was presented in our previously published paper …”