Polymorphic forms of nylon 3

The crystal structure of nylon 3 was studied, and four crystalline modifications were observed. Modification I, as determined from the x-ray diffraction pattern of drawn fibers, is similar to the α crystal structure of nylon 6. The unit cell is monoclinic; a = 9.33 Å, b = 4.78 Å, (fiber identity period), c = 8.73 Å, and β = 60°. The theoretical density for nylon 3 with four monomeric units in the unit cell is 1.39 g/cm³, and the observed density is 1.33 g/cm³. The space group is P2₁. The nylon 3 chains are in the extended planar zigzag conformation. Although other odd-numbered nylon form triclinic or pseudohexagonal crystals when oriented, drawn nylon 3 crystals are monoclinic. In addition to modification I, modifications II, III, and IV were studied. Lattice spacings of modifications II and III are equal to those of modification I. However x-ray diffraction intensities are different. Infrared spectra of those forms indicate an extended planar zigzag conformation of the chains. Modification IV is thought to correspond to the so-called smectic hexagonal form. No γ crystals were found, and it appears that polyamide chains with short sequences of methylene groups cannot form crystals of this type.     

Structural analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepared by drawing and annealing processes

Structure of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepared by drawing and annealing processes has been analyzed through wide-angle X-ray diffraction (WAXD), density, infrared dichroism, and birefringence measurements. There are three different types of crystalline structure in these fibers: two of these are the two types of orthorhombic with different orientation modes (the ordinary c-axis orientation (c//Z), and the preferential orientation of c-axis to the direction perpendicular to the fiber axis (c⟂Z)); and the third is pseudohexagonal. The weight fractions of the three types of crystals and amorphous phase were analyzed combining the WAXD integrated intensity and density data. The relation between crystalline orientation factors obtained separately from the WAXD measurement and the infrared dichroic ratio is also discussed. The birefringence of these fibers shows negative and positive values, depending on drawing and annealing temperatures. Considering the intrinsic birefringence and weight fraction of the c//Z, c⟂Z, and pseudohexagonal crystals, birefringence of the amorphous phase was evaluated. The amorphous birefringence shows positive values and decreases with an increase in the annealing temperature. From the analyzed fiber structure, it was speculated that the c⟂Z and pseudohexagonal crystals are preferentially formed in the drawing process irrespective of the drawing temperature.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2471–2482, 1998     

Electron diffraction and computer modeling of poly(naphthalic anhydride) crystal structure

Single crystals of poly(naphthalic anhydride) (PNA) have been grown using our confined thin film melt polymerization technique. Lamellae, 70–100 Å thick, are found for the crystals polymerized at 180°C with thinner lamellae for a 200°C polymerization temperature. In addition, irregular lath-shaped crystals are found for both polymerization temperatures, apparently formed by a solid-state polymerization process within the original needle-like monomer crystals. The crystal structure of PNA has been studied by electron diffraction (ED) and computer modeling based on seven different zonal ED patterns. It is found that, in most cases, two or three different zonal patterns are superimposed with a common plane, suggesting variable chain tilting even in individual lamellae. Shearing of the material shortly after the initiation of polymerization, permitted obtaining an additional [010] zone ED pattern. A monoclinic unit cell with one chain, two repeat units is proposed based on measurements of 21 independent reflections; the space group is Pc11; a = 6.26 Å, b = 4.33 Å, c = 18.60 Å, and α = 122.5°. The computer-simulated (Cerius²) molecular conformation and chain packing are described with the corresponding simulated electron diffraction patterns being in good agreement with the observed ones. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1575–1588, 1997     

The thermal expansion of the monoclinic unit cell of isotactic polypropylene

The lattice parameters of a highly stereoregular metallocene polypropylene crystallized at 145°C were obtained after cooling and heating cycles in a temperature interval between 25°C and 165°C. The b dimension undergoes a large thermal expansion with temperature (0.6 Å) while the change of the a axis is relatively small (0.1 Å). The unit cell dimension along the molecular (c) axis appears less sensitive to temperature than are the intermolecular distances. The difference in dimensions between the a and c axis at low and high crystallization temperatures is small, varying from 2.3 to 3.5%. This small difference allows the formation of daughter, crosshatched lamellae in the complete interval of crystallization temperatures. The thermal expansion coefficient of the unit cell specific volume is also reported. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2945–2949, 1997     

Structure of a poly(2,5‐benzimidazole)/phosphoric acid complex

As‐cast films of poly(2,5‐benzimidazole) exhibit uniplanar orientation in which the planes of the aromatic rings lie parallel to the film surface. Upon doping with phosphoric acid, the original crystalline order is lost, but the doped film can be stretched to produce films with uniaxial orientation. After thermal annealing at 540 °C, nine Bragg reflections are resolved in the fiber diagram, and these are indexed by an orthorhombic unit cell with the dimensions a = 18.1 Å, b = 3.5 Å, and c = 11.4 Å, containing four monomer units of two chains. The absence of odd‐order 00l reflections points to a 2₁ chain conformation, which is probably planar so that the aromatic units can be stacked along the b axis. The water and phosphoric acid contents of the crystalline structure cannot be determined exactly because of the presence of extensive amorphous regions that probably have different solvation. The best agreement between the observed and calculated intensities is for an idealized structure containing two phosphoric acids and two water molecules per unit cell. However, the phosphoric acid is probably present mainly in the form of pyrophosphoric acid and its higher oligomers. In addition, the X‐ray data are consistent with a more disordered structure containing chains with random (up and down) polarity and a lack of c‐axis registry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2576–2585, 2004     

Crystalline structure and morphology of biaxially oriented polyamide‐11 films

The effect of the uniaxial and biaxial stretching and subsequent solution annealing of extrusion‐cast polyamide‐11 films on the crystalline structure and morphology was investigated with differential scanning calorimetry, wide‐angle X‐ray diffraction (WAXD), Fourier transform infrared spectroscopy, and small‐angle X‐ray scattering (SAXS). The extrusion‐cast polyamide‐11 films exhibited elevations in the glass‐transition and cold‐crystallization temperatures with a constant crystallinity and a constant melting point during aging under room conditions (20–26 °C and 20–31% relative humidity). WAXD and SAXS suggested that chain‐folded lamellae of coexisting α‐ and β‐crystals existed in all the stretched polyamide‐11 films. WAXD pole figures indicated that hydrogen bonds in the hydrogen‐bonded sheets of these two crystalline forms apparently formed between antiparallel chain molecules. The unit cell parameters [a = 9.52 Å, b = 5.35 Å, c = 14.90 Å (chain axis), α = 48.5°, β = 90°, and γ = 74.7° for a triclinic α form and a = 9.52 Å, b = 14.90 Å (chain axis), c = 4.00 Å, α = 90°, β = 67.5°, and γ = 90° for a monoclinic β form] for polyamide‐11 crystals were proposed according to the results of this study and the results of previous investigators. The unit cell parameters of the stretched extrusion‐cast polyamide‐11 films varied, depending on the stretching conditions (the stretch temperature and stretch ratio). As the stretch temperature and stretch ratio were increased, the crystal became more similar to the form described previously and was accompanied by an increase in the long spacing of crystalline lamellae. Annealing the stretched films in a boiling 20% formic acid solution made slightly more perfected crystals. The hydrogen‐bonding α(010) + β(002) planes, which are nearly parallel to both amide group planes and zigzag methylene sequence planes of the biaxially stretched films were found to be parallel to the film surface. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2624–2640, 2002     

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.     

Structural data on the packing of poly(ester amide)s derived from glycine,hexanediol, and odd‐numbered dicarboxylic acids

The crystalline structure of a series of Poly(ester amide)s derived from glycine, hexanediol, and odd‐numbered dicarboxylic acids has been studied using transmission electron microscopy and X‐ray diffraction. Polymers crystallize in an orthorhombic lattice with parameters a = 4.80 Å, b = 22.68 Å, and c in the 45–55 Å interval, depending on the number of methylenes of the chemical repeat unit. The structure of the glutaric derivative can be interpreted as a singular packing of six hydrogen‐bonded sheets. Amide and ester interactions between neighboring layers favor two different sheet arrangements that give rise to the observed superstructure. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2521–2533, 1999     

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     

Cs2[PdCl4] — neue Ergebnisse zu einer „altbekannten”︁ Verbindung

Hochtemperatur‐Cs₂[PdCl₄] — New Results on a “wellknown” Compound Two modifications of Cs₂[PdCl₄] have been characterized by X‐ray powder and single crystal diffraction, respectively. The crystal structures are described and the group‐subgroup‐relations between these structures are discussed. In addition to the tetragonal (P4/mmm (No. 123), a = 7.4158(8) Å, c = 4.6792(6) Å) and the orthorhombic (Cmcm (No. 63), a = 10.529(1) Å, b = 10.310(1) Å, c = 9.460(1) Å) modification DSC investigations and high‐temperature X‐ray diffraction experiments with synchrotron radiation show the existence of another modification or of yet unknown decomposition products. The phase transformation from the orthorhombic to the tetragonal polymorph is completely finished at 100 °C. The second effect is detected at 319 °C.     

Metallic Conductivity in Metal Tetraaza [14]Annulene Iodides: The Crystal Structures of Dihydrodibenzo-[b,i]-1, 4, 8, 11-tetraazacyclotetradecinenickel and -palladium Iodides

Single crystals of dihydrodibenzo[b, i]-1, 4, 8, 11-tetraazacyclotetradecinenickel iodide show metallic conductivity between room temperature and approx. 110 K. The crystals are orthorhombic, space group I_bam with four formula units per cell of the following dimensions: a = 20.245, b = 13.416, c = 6.418 Å. The analogous palladium complex is isomorphous, the cell constants being a = 20.452, b = 13.430 and c = 6.499 Å. A number of other partially oxidized metal tetraaza [14]annulenes also show electrical conductivity.     

Moisture sorption mechanism of aromatic polyamide fibers. V: Growth of crystallites in as-spun wet poly(p-phenylene terephthalamide) fiber during dehydration

Wide-angle x-ray diffraction studies were performed for as-spun wet poly(p-phenylene terephthalamide) fiber. The effects of sorbed water on the equatorial diffractions from the (110) and (200) crystal planes and on the meridional diffractions from the (002), (004), and (006) crystal planes were analyzed during desorption and absorption. There was no significant change in the d-spacing from the respective crystal plane irrespective of the moisture (water) regain. The ratio of the diffracted intensity from the (110) diffraction to that from the (200) diffraction remarkably increased by removing the sorbed water. The crystallite size estimated from the (110) diffraction, L₁₁₀, also increased as the moisture regain decreased, while the L₂₀₀ did not increase. The longitudinal size of paracrystallite, D₀₀₁, also remarkably increased with the decrease in moisture regain with the lattice distortion factor, g_II, kept unchanged. These results strongly suggested the growth of the crystallite via hydrogen bonds in the lateral (b-axis) direction. The growth of the lateral size of crystallite also accompanied the longitudinal growth of crystallite during desorption. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1423–1432, 1997     

Epitaxial growth of long-chain molecules on potassium hydrogen phthalate and potassium chloride substrates from the vapor phase

Pentacontane, hexacontane, 15-ketohentriacontane (palmitone), and solid solutions of the two n-paraffins were deposited from the vapor phase onto surfaces of potassium hydrogen phthalate (PHP) crystals and cleavage faces of potassium chloride (KCl) crystals in vacuo. Epitaxial growth, with molecular chains parallel to the substrates, occurs within a temperature range (e.g., 25–50°C for palmitone), and the epitaxial relationship between molecules and substrates was broken at higher temperatures. The electron diffraction patterns, similar to that of polyethylene, were obtained from all samples prepared at room temperature. The [100] or [130] directions of palmitone crystals are parallel to the substrate surface of PHP, and the [110] direction is parallel to that of KCl; the crystals in both cases are the orthorhombic form with lattice parameters a = 7.56 Å, b = 4.93 Å, c = 82.8 Å and a space group of Pna2₁. The (100) planes of n-paraffin crystals are parallel to the surface of PHP, and the crystals are again orthorhombic. Also, solid solutions of n-paraffins can be formed from the vapor phase, with the nucleation process on the two substrates being the same as for pure paraffins.     

Isotactic poly(pentene-1): Form III

A new crystalline form of isotactic poly(pentene-1) was obtained from dilute solution in amyl acetate. We have designated it as form III. The morphology and structure of isothermally crystallized samples were investigated by electron microscopy and electron and x-ray diffraction. This crystalline modification can be indexed on an orthorhombic unit cell (cell dimensions: a = 21.20 ± 0.05 Å, b = 11.48 ± 0.05 Å, c = 14.39 ± 0.05 Å (fiber axis) and probable space group P2₁2₁2₁).     

Polymorphic structure and physical properties of the polyester/ether poly(ethylene-1,2-diphenoxyethane-p,p′ -dicarboxylate)

X-ray diffraction studies of fibers of the polyester/ether poly(ethylene-1,2-diphenoxyethane-p,p′ -dicarboxylate) (PEET) produced by high-speed melt spinning show the existence of two polymorphic forms, designated α and β, in the solid state. The α form is obtained by annealing filaments melt spun at takeup speeds below 3000 m/min and is also found in samples crystallized from the melt and from dilute solutions. The α form has a monoclinic unit cell with dimensions a = 7.83, b = 10.33, c = 18.68 Å, and β = 83.1°. The equilibrium melting temperature and heat of fusion of the α form are 288.3°C and 19.1 cal/g, respectively. The β form predominates in highly oriented filaments obtained at takeup velocities above 6000 m/min. The unit cell is orthorhombic with dimensions a = 7.28, b = 5.65, and c = 18.64 Å. The β form does not transform to the α form on annealing.     

Synthesis,structure and antimicrobial study of two new copper(II) complexes derived from N-(3-aminopropyl) benzylamine ligand (apba) and N-salicylidene-apba

Two new copper(II) complexes were synthesized by reaction of N-(3-aminopropyl)benzylamine (L1: apba, for complex 1) and N-salicylidene-apba (L2: for complex 2) with Cu²⁺. Crystals of complex 1 were orthorhombic, space group pccn, with a?=?15.2149(10), b?=?25.0071(16), c?=?7.6280(5)?Å and α?=?β?=?γ?=?90°. Complex 2 crystals were monoclinic, space group P2₁/c, with a?=?8.688(6), b?=?12.812(9), c?=?16.022(11)?Å and β?=?99.241(10)°. Structures of the two complexes were centro-symmetric and both Cu(II) atoms were four coordinate with a distorted square-planar geometry. The toxicity of the complexes was evaluated by testing antimicrobial activity against bacterial strands.     

Crystal structure of an alternating copolymer of ethylene and tetrafluoroethylene

The unit cell of an alternating copolymer of ethylene and tetrafluoroethylene was determined by x-ray diffraction. In spite of uncertainties due to irregularities in the chain structure and a low level of crystallinity, a reasonable unit cell and structure was derived which gives a calculated crystalline density of 1.9 g/cm³. The unit cell is believed to be either orthorhombic or monoclinic with the following parameters: a = 9.6 Å, b = 9.25 Å, c = 5.0 Å, (γ = 96°). The molecular conformation is that of the extended zigzag, and the molecular packing appears to be orthorhombic, each molecule having four nearest neighbors with the CH₂ groups of one chain adjacent to the CF₂ groups of the next.     

Structures of poly(p-hydroxybenzoic acid) (PHBA) at ambient temperature

The molecular structure of poly (p-hydroxybenzoic acid) (C₆H₄COO)_x at ambient temperature was determined by x-ray powder diffraction analysis. The diffraction pattern is explained as a mixture of two orthorhombic phases having the same space group Pbc2₁ with four C₆H₄COO chemical repeats in the unit cell and the following cell parameters: a = 7.42 Å, b = 5.70 Å, and c = 12.45 Å for phase I (ρ_calc = 1.51 g cm^?3); and a = 3.83 Å, b = 11.16 Å, and c = 12.56 Å for phase II (ρ_calc = 1.48 g cm^?3). The chain conformation is the same in both phases, involving two benzoyl rings staggered by ca. 120° along the chain. Disorder has been considered in the packing of phase I by giving equal occupancy to the two molecules oriented up or down along the c chain axis. ©1995 John Wiley & Sons, Inc.     

Single Crystal Growth and Crystal Structure of Mercurous Diarsenate(V), (Hg2)2(As2O7)

Polycrystalline mercurous diarsenate(V), (Hg₂)₂(As₂O₇), was prepared by a redox‐reaction between stoichiometric amounts of HgO and As₂O₃. Canary yellow single crystals were obtained by subsequent chemical transport reactions using HgCl₂ as transport agent [550 → 500 °C, 5 d, sealed and evacuated silica ampoules]. The crystal structure (orthorhombic, Pnma, Z = 4, a = 9.9803(8), b = 12.2039(10), c = 7.2374(6)Å) is composed of two crystallographically independent Hgequation/tex2gif-stack-1.gif dumbbells (d¯(Hg—Hg) = 2.5133Å) with a symmetric oxygen coordination sphere, and a diarsenate group with a staggered conformation and a bent bridging angle As—O—As = 121.0(7)°. The building units are arranged in a layer‐like assembly parallel to (010) and are connected via common oxygen atoms to form a three‐dimensional network.     

Synthesis,structure and spectroscopic characterization of 1,2-bis-(2,4,6-trimethylbenzylideneamino)ethanedichloropalladium(II)

The structure of 1,2-bis(2,4,6-trimethylbenzylideneamino)ethanedichloropalladium(II) was determined by X-ray diffraction methods. The structure derived from NMR and IR spectra and elemental analysis is consistent with it. The complex is orthorhombic, space group Pcab, with a?=?14.8662(12), b?=?15.0861(13), c?=?20.6255(14)?Å, V?=?4625.7(6)?ų and Z?=?8. In the lattice, there exists a weak C–H?···?Cl hydrogen bond.