Crystal structure and morphology of poly(16-hexadecalactone) chain-folded lamellar crystals

Solution-grown, chain-folded lamellar crystals of poly(16-hexadecalactone) (PHDL) were crystallized isothermally from 1-hexanol at 70 degrees C. The morphology of lozenge-shaped crystals was studied by TEM and AFM. The lamellae are ca. 10 nm thick and the chains run orthogonal to the lamellar surface with folding along (110) and (110) planes. The crystal structure of PHDL was determined by XRD and election diffraction of single crystals. The chains are in the 2(1) helix conformation close to all-trans and the structure consists of an orthorhombic unit cell with a P2(1)2(1)2(1) space group with the lattice constants a = 0.746 +/- 0.001 nm, b = 0.504 +/- 0.001 nm, and c (chain axis) = 4.116 +/- 0.003 nm. There are two chains per unit cell, which exist in an antiparallel arrangement. Molecular packing structure has been studied in detail, taking into account both diffraction data and energy calculations. The setting angles, with respect to a axis, were +/-40 degrees for the corner and center chains, respectively. By using the electron and XRD data, the best molecular packing model was refined to R-factors of 0.168 and 0.196, respectively. A brief comparison of chain-packing structure is also made with related polymer structures.     

Crystal structure and morphology of phenyl‐capped tetraaniline in the leucoemeraldine oxidation state

A series of crystals of phenyl‐capped tetraaniline in the leucoemeraldine oxidation state were obtained at different isothermal temperatures and were observed directly under transmission electron microscope. The crystals obtained at higher temperatures exhibit more perfect structures than those obtained at lower temperatures. Both the lamella thickness and the crystal size increase with crystallization temperature. The tetraaniline is apt to form larger scale crystals under lower degree of supercooling. However, their crystal structures keep steady with the crystallization temperature. The tetramer was found to adopt a monoclinic lattice with unit cell parameter of a = 13.93 Å, b = 8.82 Å, c = 23.20 Å, and β = 95.03°, as determined using electron diffraction tilting method combined with wide‐angle X‐ray diffraction experiment. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 764–769, 2006     

Synthesis and Crystal Structure of 1,4-Bis(2-hydroxymethylphenyl)-1,4-dioxabutane

1 INTRODUCTION Macrocyclic ligands and their metal complexes have received much attention due to their applications in ion transport, ion separation and as models in biomimic researches[1~7]. The synthetic methods of macrocyclic ligands and their metal complexes are mainly divided into three kinds[8]. The first one is synthesizing free ligand, then forming the metal complexes; the second is template synthesis; and the third is synthesizing the end-off or side-off precursor ligand, then c…     

Synthesis,phase transitions and birefringence of novel liquid crystalline 1,4-phenylene bis(4-alkylthio benzoates) and insights into the cybotactic nematic behaviour

We synthesised a novel family of liquid crystalline 1,4-phenylene bis(4-alkylthio benzoates), of which homologues with different alkyl chain lengths of 1–8 were designed, to investigate the structure–property relationship. The mesogenic incidence and tendency were found to be strongly dependent on the carbon numbers in the terminal alkyl chains. Even members formed widely monotropic or enantiotropic nematic (N) phases compared to odd members that showed either none or monotropic-narrower ones. The temperature dependence of birefringence (Δn) for the hexylthio homologue was evaluated and compared to that for a hexyloxy counterpart. It was found that the hexylthio homologue exhibited higher Δn values than the hexyloxy counterpart over the entire range of near T_IN–T. In addition, wide-angle X-ray diffraction measurements, using magnetically aligned specimens, found enhanced cybotactic nematic tendency with smectic (Sm) A-like temperature dependence for the hexylthio analogue, due to the intermolecular attractive S···S interaction, in comparison with the hexyloxy analogue exhibiting N phase with clear Sm C-type clusters. We revealed the actual benefits of alkylthio groups in the fluid N phase.     

聚对甲基苯胺的合成及其晶体结构

在水相中,FeCl3催化对甲基苯胺聚合合成了对甲基苯胺三分子聚合物——(N,N′E,N,N′E)-N,N′-(2-氨基-5-甲基-2,5-环己二烯-1,4-二亚基)二(4-甲基苯胺)(1),其结构经X-射线单晶衍射仪表征。1属六方晶系,R3空间群,晶胞参数:a=21.116(2),b=21.116(2),c=10.364(2),α=90°,β=90°,γ=120°,Mr=315.41,Z=9,V=4002.1(10)3,Dc=1.178 g.cm-3,μ=0.070 mm-1,λ=0.710 73,F(000)=1 512,R=0.067 8,wR=0.112 6。     

Crystallization, glass transition and morphology of (R)-3-hydroxybutyrate oligomers

The study focuses on the effect of the molecular length of isotactic hydroxybutyrate oligomers on the crystal morphology, crystallinity, and spherulitic superstructure. Furthermore, the process of solidification of the quiescent melt is evaluated by the analysis of the crystallization kinetics and of the glass transition. Melt-crystallization is strongly controlled by the chain length, and the regime of cooling. Crystallization can completely be avoided by rapid cooling. Slow cooling allows at best incomplete crystallization, with the crystallinity increasing with chain length. Typically, the maximum crystallinity is between 50% and 80% for OHB of molecular weights of 500 and 5000 g mol⁻¹, respectively. The temperatures of the glass transition and of crystallization/melting increase with molecular length, and are discussed in terms of the Fox-Flory and Gibbs-Thomson equations, respectively. For all samples, regardless of the chain length, spherulitic crystallization is observed, with the perfection of spherulites increasing with decreasing crystallization temperature. The transition of formation of extended-chain crystals to formation of folded-chain crystals occurs at a molecular weight of about 2000 g mol⁻¹, which corresponds to chain length of about 7 nm. Analysis of the heat-capacity increment at the glass transition temperature reveals the existence of a rigid amorphous fraction.     

Crystal structure and morphology of biaxially oriented polyamide 12 films

The structural and morphological characteristics of biaxially oriented polyamide 12 films are described on the basis of the results from differential scanning calorimetry, wide‐angle X‐ray diffraction (WAXD), polarized FT‐IR spectroscopy, and small angle X‐ray scattering (SAXS). The WAXD patterns of the oriented polyamide 12 films indicated only the monoclinic γ crystal with little dimensional changes of its unit cell depending on the stretching conditions. The crystallographic angles (α = γ = 90°, β = 121°) that were determined via the WAXD patterns confirmed the monoclinic symmetry of the γ crystal. Annealing the films stretched at 115 °C in boiling 20% formic acid solution did not result in structural changes of the crystalline unit cell. The chain‐axis repeat distance of 31.9 Å for the γ crystal was experimentally obtained with (0 26 0) planes. It was shortened as compared with that of all‐trans conformation. For films having primary orientation to MD, normals to the basal plane of folded‐chain lamellae were parallel to MD (primary stretch direction) resulting in two‐point SAXS patterns. Growth in long spacing with an increase of stretch temperature was discovered. Annealing the films induced further elongation in long spacing. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1189–1200, 2002     

Poly(terephthalic anhydride) single crystals: Morphology and crystal structure

Single crystals of poly(terephthalic anhydride) (PTA) have been grown using the confined thin film melt polymerization technique. Thin lamellae (ca. 50 Å) are found for low polymerization temperatures, with thick crystals forming for polymerization at 200°C. Shearing of the material shortly after the initiation of polymerization at 200°C yielded single crystal domains composed of fibrillar texture material; these samples gave [010] zone ED patterns complementing the [001] zone patterns from the unsheared CTFMP samples. A monoclinic, single chain, two repeat unit, unit cell (Pc11) is proposed based on four different electron diffraction zone patterns: a = 6.01 Å, b = 3.94₅ Å, c = 14.11 Å, α = 106.9°. Simulations, using the Cerius² program, of the corresponding molecular conformation, packing and electron diffraction (ED) patterns were performed; the ED simulations are in good agreement with the observed patterns. An R-factor of 0.23 is obtained based on a comparison of calculated and observed structure factors for the 39 independent ED reflections observed on the different zone patterns. © 1996 John Wiley & Sons, Inc.     

The crystal structures and thermal shrinkage properties of aromatic polyimide fibers

Three aromatic polyimides based on 3,3,4,4-biphenyl-tetracarboxylic dianhydride (BPDA) and three different diamines 2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl (PFMB), 2,2-dimethyl-4, 4-diaminophenyl (DMB) or 3,3-dimethylbenzidine (OTOL) have been synthesized. These polyimides are soluble in hotp-chlorophenol,m-cresol or other phenolic solvents. Fibers have been spun from isotropic solutions using a dry-jet wet spinning method. The as-spun fibers generally exhibit low tensile properties, and can be drawn at elevated temperatures (>380° C) up to a draw ratio of 10 times. Remarkable increases in tensile strength and modulus are achieved after drawing and annealing. The crystal structures of highly drawn fibers were determinedvia wide angle X-ray diffraction (WAXD). The crystal unit cell lattices have been determined to be monoclinic for BPDA-PFMB and triclinic for both BPDA-DMB and BPDA-OTOL. Thermomechanical analysis (TMA) was used to measure thermal shrinkage stress and strain. A selfelongation has been found in the temperature region around 450°C. This phenomenon can be explained as resulting from the structural development in the fibers as evidencedvia WAXD observations.Dedicated to Profeseor Bernhard Wunderlich on the occasion of his 65th birthdayThis work was supported by SZDC's Presidential Young Investigator Award from the National Science Foundation (DMR-9175538) and NSA/EPIC/Ohio Industry Center of Molecular and Microstructure Composites at Case Westen Reserve University and The University of Akron.     

poly(4,4′-oxybibenzoate): Polymerization,morphology, transitions,and crystal structures

4-Acetoxy 4′-carboxy biphenyl has been polymerized from solution, the bulk melt, and in constrained thin films, all below the melting point of the monomer as measured by differential scanning calorimetry (DSC). An isothermal sublimation–recrystallization–melting (and chemical change)–polymerization–crystallization process is proposed. From solution and in the thin films, single crystals consisting of ca. 100 Å thick lamellae are observed, with evidence for monomer addition–reaction on the end (top and bottom) surfaces. The bulk samples are fibrous, the “fibers” consisting of whisker-like single crystals. The polymer is highly heat and radiation (electron beam) resistant, with numerous successive electron diffraction (ED) patterns from the same crystal or sheared sample permitting comparison of the changes in ED patterns with transitions seen by DSC at ca. 350, 530, and 590°C. Phase I (a = 7.8, b = 5.5, c = 10.8 Å), a possible phase II (a = 15.6, b = 3.6 Å c = unknown), and a phase III (a = 9.0, b = 5.2 = √3a, c = 10.8 Å). Phases I and II are seen in samples polymerized at temperatures at and below 310°C; phase III is observed in samples polymerized at and above 350°C and in sheared samples. © 1993 John Wiley & Sons, Inc.     

Crystal and molecular structure of organosilicon titanium(iv) derivatives: (Me3Si)3SiTi(NEt2)3 and ClTi[N(SiMe3)2]3

An X-ray structural study of two titanium-containing organosilicon compounds, (Me₃Si)₃SiTi(NEt₂)₃ (1) and ClTi[N(SiMe₃)₂]₃ (2), has been performed. The conformation of molecule1 in a crystal is staggered (approximate inherentC ₃ symmetry), the Ti-Si and Ti-N bond lengths are 2.671(2) and 1.874–1.890(5) Å, respectively. A crystal of1 consists of one type of enantiomers (the space group is P4₁2₁2; the absolute configuration has been determined). The structure of2 studied previously has been refined to the value of R=0.029 on the basis of 3442 reflections (the absolute structure has been determined), the Ti-Cl and Ti-N bond lengths are 2.260(1) and 1.926(1) Å, respectively. The strong distortions in the symmetry of the valence environment of the N atoms in the molecules of1, 2, and related structures are caused by electronic effects, in which the conformation of the relevant molecular fragments plays a determining role.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1473–1476, August, 1993.     

Synthesis and Crystal Structure of （E）-4-（3-oxo-3-（（4- （N-（pyrimidin-2-yl）-sulfamoyl）phenyl）amino）prop- 1-en-l-yl）-l,2-phenylene diacetate Dimethanol

The title compound, (E)-4-(3-oxo-3-((4-(N-(pyrimidin-2-yl)sulfamoyl)-phenyl)ami- no)prop- 1-en- 1-yl)- 1,2-phenylene diacetate dimethanol, was synthesized by the reaction of caffeic acid with sulfadiaz...     

Crystal Structure of (3S, 6S, 7R, 8R)-3,6-Bis-diphenylphosphino-1,4-dioxabicyclo〔3.3.0〕octane

1INTRoDUCTIONThetitlecompoundhasbeenfoundtobeaveryefficientchiralligandusedtoco-ordinatewithpalladiumformingcatalystsystemsforasymmetrichydroesterificationofnorborneneandstyrene.Intheseasymmetriccatalyticreactions,thechiralinduc-tionofthetitlecompoundisratherstronggivingveryhighoptica1yields(>9o%)ofproductstl3.Inordertostudytherelationshipoftheperformanceandthestructureofthisligand,itisimportanttodeterminethemolecularstructureofthechiraldiphos-phinecompound,whichwaspreparedbytheliteraturem…     

Synthesis and Crystal Structure of[Cu（dppb）（NO_3）]_2（dppb=1,4-Bis（diphenylphosphino）butane）

The synthesis and molecular structure of a new dinuclear copper(Ⅰ) complex [Cu(dppb)(NO 3)] 2 are reported.The compound crystallizes in the monoclinic system,space group P2 1 /n with a=12.830(3),b=10.899(2),c=19.666 (4),β=104.69(3)°,V=2660.1(9)3,Z=4,D c=1.378 g/cm 3,F(000)=1144,the final R=0.0600 and wR=0.0668 for 2951 observed reflections with I > 2σ(Ⅰ).The complex contains a folded Cu 2 P 4 core structure,with two Cu(Ⅰ) atoms being bridged by a pair of dppb ligands to form a 14-membered Cu 2 P 4 C 8 zigzag ring.The ligand sphere of each metal center is completed by a nitrate anion in a chelating fashion.     

O－（3，4－二甲苯基）－苯基－硫代膦酰基氨基异马来酰胺的合成和晶体结构

标题化合物Ｃ_（１８）Ｈ_（１７）Ｎ_２Ｏ_３ＰＳ是Ｏ－芳基苯基硫代膦酰肼与马来酸酐加成后的关环产物，其晶体属于单斜晶系，空间群Ｐ２_１／ｃ，α＝１０．７２６（３），ｂ＝１０．２４８（２），ｃ＝１７．４５４（５）Ａ，　β＝１０４．０１（２）°，Ｍｒ＝３７２．３７，Ｖ＝１８６１．４Ａ３，Ｄｃ＝１．３３ｇ／ｃｍ￣３，Ｚ＝４，μ（ＣｕＫα）＝２４．６８ｃｍ￣（－１），Ｆ（０００）＝７７６，Ｒ＝０．０７０，Ｒｗ＝０．０６７。结构由直接法解出，分子中Ｐ原子与其相邻的Ｓ，Ｏ，Ｎ，Ｃ原子形成变形四面体构型。     

O－（3，4－二甲苯基）－苯基－硫代膦酰基氨基异马来酰胺的合成和晶体结构

标题化合物Ｃ_（１８）Ｈ_（１７）Ｎ_２Ｏ_３ＰＳ是Ｏ－芳基苯基硫代膦酰肼与马来酸酐加成后的关环产物，其晶体属于单斜晶系，空间群Ｐ２_１／ｃ，α＝１０．７２６（３），ｂ＝１０．２４８（２），ｃ＝１７．４５４（５）Ａ，　β＝１０４．０１（２）°，Ｍｒ＝３７２．３７，Ｖ＝１８６１．４Ａ３，Ｄｃ＝１．３３ｇ／ｃｍ￣３，Ｚ＝４，μ（ＣｕＫα）＝２４．６８ｃｍ￣（－１），Ｆ（０００）＝７７６，Ｒ＝０．０７０，Ｒｗ＝０．０６７。结构由直接法解出，分子中Ｐ原子与其相邻的Ｓ，Ｏ，Ｎ，Ｃ原子形成变形四面体构型。     

Crystal Structure of Chlorinate （N,N-1,3-Dibenzyl-benzimidazole） Hydrate

1 INTRODUCTION Benzimidazole is an interesting heterocyclic ring because it is present in various naturally occurring drugs, such as omeprazole, astemizole and emedastine difumarate[1]. The efficacy of substituted benzimidazoles in the treatment of parasitic infections is well known[2～4], and the pharmacophores in parasitic chemotherapy are established by benzimidazole-substituted moieties. Bis(2-benzimidazoles) and some substituted bis- (benzimi-dazol-2-yl) alkanes have attracted much…     

Crystal structure refinement for trans-[Pd(NO3)2(H2O)2]

Single crystals of trans-[Pd(NO₃)₂(H₂O)₂] were obtained, and the crystal structure of this complex, previously obtained for polycrystals, was refined. Crystal data (BRUKER X8APEX diffractometer): a = 4.9973(7) Å, b = 10.5982(14) Å, c = 11.7008(17) Å, V = 619.70(15) ų, space group Pbca, Z = 4, d _calc = 2.856 g/cm³. The structure is composed of neutral complexes with a trans configuration. The square plane environment of the Pd atom is formed by four oxygen atoms (Pd-O(NO₃) 1.999(5) Å, Pd-O(H₂O) 2.030(5) Å) and completed to a distorted bipyramid by two intramolecular contacts (Pd…O(NO₃) 2.926 Å). The shortest hydrogen bonds are O…H 2.72 Å.     

Poly(vinyltriethoxysilane) modified MWCNT/polyimide nanocomposites—Preparation,morphological, mechanical,and electrical properties

Multi‐walled carbon nanotube (MWCNT) modified by vinyltriethoxysilane (VTES) via free radical reaction has been prepared (poly (vinyltriethoxysilane) modified MWCNTs, PVTES‐MWCNT). Precursor of polyimide, polyamic acid has been synthesized by reacting 4,4′‐oxydianiline with 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride. PVTES‐MWCNT were then mixed with polyamic acid and heated to 300 °C to form CNT/polyimide composite. During the imidization processes, the silanes on CNT surface reacted with each other and may be connected together by covalent bond (Si? O? Si). The PVTES‐MWCNT was analyzed by Fourier transform infrared and X‐ray photoelectron spectroscopy. The PVTES‐MWCNT/polyimide composites were analyzed by CP/MAS solid state ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. Morphological properties of the PVTES‐MWCNT/polyimide composites were investigated by scanning electron microscope and transmission electron microscope. Electrical conductivity increased dramatically comparing to the unmodified MWCNT/polyimide composites. Mechanical properties of nanocomposite were enhanced significantly by PVTES‐MWCNT. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 803–816, 2008