The crystal structure and drawing-induced polymorphism in poly(aryl ether ketone)s .1. Poly(oxybiphenyl-4-4'-diyloxy-1,4-phenylenecarbonyl-1,3-phenylenecarbonyl-1,4-phenylene)

Crystal structure and polymorphism induced by uniaxial drawing of a poly(aryl ether ketone) [PEDEKmK] prepared from 1,3-bis(4-fluorobenzoyl)benzene and biphenyl-4,4'-diol have been investigated by means of transmission electron microscopy (TEM), electron diffraction (ED), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) techniques. The melting and recrystallization process in the temperature range of 250-260 degrees C, far below the next melting temperature (306 degrees C), was identified and found to be responsible for the remarkable changes in lamellar morphology. Based on WAXD and ED patterns, it was found that crystal structure of isotropic-crystalline PEDEKmK obtained under different crystallization conditions (melt-crystallization, cold-crystallization, solvent-induced crystallization, melting-recrystallization, and crystallization from solution) keeps the same mode of packing, i.e., a two-chain orthorhombic unit cell with the dimensions a = 0.784 nm, b = 0.600 nm, and c = 4.745 nm (form I). A second crystal modification (form II) can be induced by uniaxial drawing above the glass transition temperature, and always coexists with form I. This form also possesses an orthorhombic unit cell but with different dimensions, i.e., a = 0.470 nm, b = 1.054 nm, c = 5.064 nm. The 0.32 nm longer c-axis of form II as compared with form I is attributed to an overextended chain conformation due to the expansion of ether and ketone bridge bond angles during uniaxial drawing. The temperature dependence of WAXD patterns for the drawn PEDEKmK suggests that form II can be transformed into the more stable form I by relaxation of overextended chains and relief of internal stress at elevated temperature in absence of external tension.

Interaction of La3+ and cholesterol with dipalmitoylphosphatidylglycerol bilayers by FT-Raman spectroscopy

The interaction of La3+ and cholesterol with the negatively charged phospholipid dipalmitoylphosphatidylglycerol bilayers was studied by Fourier transform-Raman spectroscopy. La3+ was shown to increase interchain order and intermolecular ordering of the lipid lattice, cholesterol exhibited less of an effect, the La3+-DPPG-cholesterol complex was more ordered than cholesterol=DPPG nd less ordered than La3+-DPPG complexes, cholesterol modulates the order/disorder parameters of DPPG bilayers.

Laser light scattering studies of soluble high-performance polyimides: Solution properties and molar mass distributions

Two soluble high-performance polyimides, poly(BCPOBDA/DMMDA) and poly(ODPA/DMMDA), in CHCl3 at 25 degrees C have been studied using laser light scattering. We found that the z-average radius of gyration ([R(g)]) can be scaled to the weight-average molecular weight (M(w)) as [R(g)] (nm) = 4.95 x 10(-2)M(w)(0.52) and [R(g)] (nm) = 1.25 x 10(-2)M(w)(0.66) respectively for poly(BCPOBDA/DMMDA) and poly(ODPA/DMMDA), indicating that poly(ODPA/DMMDA) in CHCl3 at 25 degrees C has a more extended chain conformation than poly(BCPOBDA/DMMDA). Using the wormlike chain model approach, we found that the Flory characteristic ratios (C*) of poly(BCPOBDA/DMMDA) and poly(ODPA/DMMDA) are similar to 20 and similar to 31, respectively, indicating that both of them have a slightly extended chain conformation in comparison with typical flexible polymer chains, such as polystyrene, whose C-infinity is similar to 10. A combination of the weight-average molar mass (M(w)) with the translational diffusion coefficient distributions (G(D)) has led to D (cm(2)/s) = 3.53 x 10(-4)M(-0.579) and D (cm(2)/s) = 4.30 x 10(-4)M(-0.613) respectively for two soluble high-performance polyimides, poly(BCPOBDA/DMMDA) and poly(ODPA/DMMTA), in CHCl3 at 25 degrees C. Using these two calibrations, we have successfully characterized the molar mass distributions of the two polyimides from their corresponding G(D)s. The exponents of these two calibrations further confirm that both of the polyimides have a slightly extended coil chain conformation in CHCl3. The chain flexibility difference between these two polyimides has also been discussed.

2D NMR and FT-Raman spectroscopic studies on the interaction of lanthanide ions and Ln-DTPA with phospholipid bilayers

The interactions of lanthanide ions and the Ln-DTPA (DTPA = diethylenetriaminepentaacetate) complex with di palmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPE) bilayers are studied by 2D NOESY and FT-Raman spectroscopy. Proton NMR spectroscopic results show that lanthanide ions combine with phosphate groups in the polar region of the outer layer of DPPC liposomes, leading to the separation in chemical shift of the proton signal of N(CH3)(3) The conformational change of the O-C-C-N+ backbone from the gauche conformer to the trans one is not found; i.e., the orientation of the polar headgroup is still parallel to the surface of the bilayers. The Ln-DTPA complex at low concentration in a pH 7.4 solution localizes far away from bilayers and thereby has little effect on the structure of bilayers. The FT-Raman spectroscopic results indicate that lanthanide ions affect strongly the fluidity of acyl chains of DPPE bilayers while the Ln-DTPA complex affects it slightly.

Crystal packing of poly(ether ketone ketone)

The crystal structure of poly(ether ketone ketone) (PEKK) is predicted by using Cerius2 software according to the wide angle X-ray diffraction (WAXD) experiment result. The predicted structure has a planar zigzag chain conformation between ether oxygen and ketone carbons in an orthorhombic lattice. Average zigzag angle is 126 degrees and average torsion angle is 30.32 degrees. The WAXD powder pattern calculated from the crystal packing model is in good agreement with the experiment result.

NMR and FT-Raman studies on the interaction of lanthanide ions with sphingomyelin bilayers

The interactions of lanthanide ions with sphingomyelin bilayers have been studied by using 2D NOESY spectroscopy and FT-Raman spectroscopy methods. The results indicate that lanthanide ions, as well as divalent calcium, combine mainly to the phosphate group in the polar headgroup and do not change the conformation of O-C-C-N+ backbone in the choline group of sphingomyelin bilayers. The polar headgroup is still extending parallel to the bilayer surface and O-C-C-N+ group is still in its gauche conformer.

A NMR investigation on the interaction of lanthanide complexes with phospholipid bilayers

One and two dimentional NMR methods were used to investigate the interactions of lanthanide complexes (Lncit(2) and Ln-DTPA) with phospholipid bilayers, The results showed that in the phospholipid bilayers dispersion containing citrate ligand at pH 7.4, lanthanide ions would initially combine with citrate ligand and form Lncit, complexes which have little effect on the structure of phospholipid bilayers. Ln-DTPA complex does not affect the bilayers structure either. These results provided important experimental data for evaluating scientifically the toxicities of lanthanide ions when they were introduced into the biological body.

Synthesis and crystal structure of (eta(8)-C8H8)Gd(eta(5)-C6H5CH2C5H4)center dot DME

LnCl(3) reacted with C6H5CH2C5H4Na in THF (tetrahydrofuran) in the ratio 1.1 at room temperature for 1 h giving C(6)H(5)CH(2)C(6)H(4)LnCl(2) . nTHF, which reacted with C8H8K2/THF and the crystals obtained were recrystallized in DME to yield the title complex. The crystal structure of (C8H8) Ln (C6H5CH2C5H4). DME was determined revealing that the Gd complex has one conformation. One benzylcyclopentadienyl (eta(5)), one cyclooctatetraenyl (eta(8)) and the two oxygen atoms of DME (dimethoxyethane) are coordinated to Gd with the effective coordination number of 10.

FT-RAMAN SPECTROSCOPIC STUDIES ON THE INTERACTION OF METAL-IONS WITH SPHINGOMYELIN BILAYER

The interaction of trivalent lanthanide ions and divalent calcium ions with sphingomyelin bilayer has been studied by FT-Raman spectroscopy. The results showed that the bonding of metal ions to the phosphate group of sphingomyelin bilayer, either La3+ or Ca2+, did not change the conformation of the choline group, that is, O-C-C-N+ is still in its gauche conformation. The presence of metal ions changed the states of the interfacial region from liquid-like to amorphous state and even to crystalline. They increased the fluidity of acyl chains of sphingomyelin bilayer and made them packed disorderly.

VOLTAMMETRY OF CYTOCHROME-C ENTRAPPED IN HYDROGEL MEMBRANE ON GRAPHITE ELECTRODE

The voltammetric behavior of cytochrome c entrapped in hydrogel membranes at paraffin wax-impregnated spectroscopic graphite electrodes (WISGE) was studied in this paper. A pair of well-defined peaks appeared at +70 mV (vs. Ag/AgCl). Beside these two peaks, another pair of peaks emerged at around +225 mV. Further investigations suggested that at least three states of cytochrome c existed in the membranes due to the special structure of the hydrogel. The native conformation of cytochrome c molecules was stabilized by the hydrophilic environment that was formed by the hydroxyl structure of the membranes and facilitated the cytochrome c electron transfer reaction at +70 mV. The molecules directly adsorbed on the surface of the graphite electrode were responsible for the redox peaks at around +225 mV. Whether the adsorption peaks were detectable or not was related to the thickness of membranes and the pre-retaining time before the formation of membranes.

A NMR-STUDY OF THE INTERACTION OF SILICA WITH DIPALMITOYLPHOSPHATIDYLCHOLINE LIPOSOMES

The interaction of silica with dipalmitoylphosphatidylcholine (DPPC) liposomes has been studied by detecting H-1 and 2D NOESY NMR spectra and measuring proton spin-lattice relaxation time (T-1). The antagonistic effect of aluminium citrate on silica has also been studied by measuring the proton T-1 values, The results show that silica particles mainly bind to the phosphate moiety of the polar headgroup of DPPC bilayers through hydrogen bonds between Si-OH and O-P groups, but they have no significant effect on the conformation of the choline group of the polar headgroup, The addition of silica particles decreases the mobilities of the hydrocarbon chains slightly, Proton T-1 data also indicate that aluminium citrate reduces the effect of silica, A possible mechanism for the toxicity of silica and the antagonistic effect of aluminium titrate on silica is suggested. (C) 1995 Academic Press Inc.

LOCAL MAIN-CHAIN DYNAMICS OF PHENOLPHTHALEIN POLYETHERSULFONE

Local main chain dynamics of dissolved phenolphthalein polyethersulfone (PES-C) in solution with chloroform-d(1) were examined through C-13 NMR relaxation measurements. Spin-lattice relaxation times and NOE (nuclear Overhauser effects) factors were measured as a function of temperature. The relaxation data were interpreted in terms of main chain segmental motion by using the damped orientational diffusion model (DAMP) and the conformation jump model (VJGM) derived by Valeur, Jarry, Geny, and Monnerie. The simulation method used is N-SIMPLEX, which gives, in this study, a result of the object function less than 10(-4). Correlation times were obtained for the main chain motion of PES-C with these models and the results indicate that the main chain of PES-C are flexible. The comparison between PES-C and 1,2-polybutadiene is proposed. The distribution of the correlation time for the main chain motion by using VJGM model is discussed. The temperature dependence of correlation times for PES-C indicating the dynamical rigidity of its chains is obtained.

Study of FT-Raman Spectroscopy on the Effects of Lanthanide Ions and Their Complexes on the Fluidity of Dipalmitoylphosphatidylethanolamine Bilayer

The effects of lanthanide ions and their complexes of citrate and DTPA ligands on the fluidity of dipalmitoylphosphatidylethanolamine (DPPE) bilayers have been studied by FT-Raman spectroscopy. the results show that lanthanide ions of lower concentrationn decrease the fluidity of acyl chains of DPPE bilayers and change the conformation of C C-C backbone from gauche to the trans lanthanide ions of higher concentration, however, increase the fluidity of acyl chains and increase the gauche population of C-C-C backbone. Lanthanide complex of citrate have no effect on the fluidity of acyl chains of DPPE bilayers in the region of experimental concentration, but La-DTPA complex increase slightly the fluidity of acyl chains. the results also indicated that lanthanide ion of lower concentration changed the lattice packing of hydrocarbon chains from hexagonal form to orthorhombic form, but it is still in hexagonal or distorted hexagonal lattice cell in the gel state in the presence of metal ions and lanthanide complexes of higher concentration

RAMAN-SPECTROSCOPIC STUDY OF CRYSTAL PHASE-TRANSITION IN BIS(N-UNDECYLAMMONIUM) TETRACHLOROZINCATE

The solid-solid phase transition of [n-C11H23NH3]2ZnCl4 Complex have been studied by Raman spectroscopy. The results show that the occurence of the structural phase transitions mainly related to the change of packing structure and molecular conformation o

EFFECT OF LANTHANIDE IONS ON THE PHASE-BEHAVIOR OF DIPALMITOYLPHOSPHATIDYLCHOLINE MULTILAMELLAR LIPOSOMES

The effect of lanthanide ions (Ln(3+)) and their coordination compounds of diethylenetriamine pentaacetic acid (DTPA) on the phase behavior of dipalmitoylphosphatidycholine (DPPC) multilamellar liposomes has been studied by differential scanning calorimet