Phosphorus-containing oligoamides obtained by a novel one-pot degradation of polyamide-6

This paper describes a novel strategy for the recycling of polyamide materials and their transformation into functional reactive oligomers with new properties. The method is illustrated by the heating of polyamide-6 (20,000 Da) in the presence of diesters of the phosphonic acid, (RO)₂P(O)H, where R could be -CH₃, -C₂H₅ or -C₆H₅. It is found that the reaction proceeds in several parallel processes: (i) phosphorylation of the amide group by the alkyl esters of the phosphonic acids and (ii) degradation of the main chain through an exchange reaction between the amide and phosphonic acid ester groups. Alternatively the depolymerization could be induced via a radical reaction with the participation of the polyamide moieties and the P-H group. The proceeding of the abovementioned reactions and the structure of the phosphorus-containing oligoamides are confirmed by ³¹P, ¹H and ¹³C NMR spectroscopy. Their molecular weights are determined by size exclusion chromatography.     

Structure and morphology of nylon 2 4 lamellar crystals: Comparison with polypeptides and relationship with other nylons

Chain-folded lamellar crystals of nylon 2 4 have been prepared from dilute solution by addition of poor solvent. Two crystal structures are observed at room temperature: a monoclinic form I, precipitated at elevated temperature, and a less-defined, orthorhombic form II, precipitated at room temperature. The unit cell parameters for both forms are similar to those reported for its isomer, nylon 3. Nylon 2 4 form II is a liquid–crystal-like or disordered phase, consisting of hydrogen-bonded sheets in poor register in the hydrogen bond direction. Form I crystals have two characteristic interchain spacings of 0.41 nm and 0.39 nm at room temperature and on heating, exhibit a structural transformation and a Brill temperature (250°C) characteristic of many other even–even nylons. Nylon 2 4 is a member of the nylon 2 Y and nylon 2N 2(N+1) families, and the form I crystals show behavior commensurate with both. We propose they contain a proportion of intersheet hydrogen bonds at room temperature, similar to that for the nylon 2 Y family, and the short dimethylene alkane segments mean that the structure consists of hydrogen-bonded a-sheets, with an amide unit in each fold, similar to that of nylon 4 6. The fold geometry and sheet structure is compared with chain-folded apβ-sheet polypeptides and nylon 3. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2401–2412, 1998     

Morphology of nylon 6/polypropylene blends compatibilized with maleated polypropylene

Transmission electron microscopy (TEM) was used to examine the morphology of blends of nylon 6 and polypropylene (PP) containing various maleated polypropylenes (PP-g-MA). The size of the dispersed polypropylene particles decreases as the content of maleic anhydride in the PP-g-MA increases for binary blends of nylon 6 and the maleated polypropylenes. Ternary blends of nylon 6, PP, and PP-g-MA show morphologies that depend on the content of maleic anhydride of the PP-g-MA and on the miscibility of PP and PP-g-MA. Blends where PP and PP-g-MA are immiscible show a bimodal distribution of particle sizes. Miscibility of the PP and PP-g-MA was determined by TEM using a special staining technique. Experimental observations of miscibility were further corroborated by thermodynamic calculations. The morphology of the ternary blends was also found to be dependent on the ratio of PP/PP-g-MA. By changing this ratio it was possible to induce drastic changes of morphology, going from a continuous nylon 6 phase to a continuous PP phase at a fixed composition. The mechanical properties of these blends were found to be dependent on their morphology. ©1995 John Wiley & Sons, Inc.     

尼龙6/蒙脱土纳米复合材料非等温结晶动力学和透明性研究

将有机化的蒙脱土与尼龙6(PA6)在Haake共混机中共混,制备出尼龙6/蒙脱土纳米复合材料(PA6N);对尼龙6/蒙脱土纳米复合材料和纯尼龙6分别进行差示扫描量热法非等温结晶试验,以了解蒙脱土在尼龙6/蒙脱土纳米复合材料中的成核作用、扩大尼龙6在包装领域的应用范围.与此同时,采用偏光显微镜测定了样品的结晶形态;采用紫...     

Study of the structure development during the melt spinning of nylon 6 fiber by on‐line wide‐angle synchrotron X‐ray scattering techniques

The melt spinning of nylon 6 has been studied with on‐line wide‐angle synchrotron X‐ray scattering techniques. The apparatus consisted of a single screw extruder and a metering pump mounted on a horizontal platform that could be translated in the vertical direction allowing a range of distances to be sampled with the X‐ray beam. The structure development, equatorial crystallinity index, and crystalline orientation were studied as a function of take‐up speed and position along the spinline. For low‐speed (50 mpm) situations, the nylon chains crystallize into independent hydrogen bonded sheets that start to interact with each other as their concentration starts to increase. For higher speed situations, the nylon chains crystallize directly into the interacting hydrogen‐bonded sheet structure. Upon conditioning at room temperature for 24 h, this interacting hydrogen‐bonded sheet structure transforms into the well‐known three‐dimensional alpha and gamma phases of nylon 6, probably existing in a shish‐kabob structure. The equatorial crystallinity index increases as distance from the spinneret increases and as take‐up speed decreases. The crystalline orientation function is constant along the spinline for a constant take‐up speed, and increases as take‐up speed is increased. Conditioning further increases both the crystallinity and crystalline orientation of the fibers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1277–1287, 1999     

Effect of EVM/EVA‐g‐MAH ratio on the structure and properties of nylon 1010 blends

The nylon 1010/ethylene‐vinyl acetate rubber (EVM)/maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) ternary blends were prepared. The effect of EVM/EVA‐g‐MAH ratio on the toughness of blends was examined. A super tough nylon 1010 blends were obtained by the incorporation of both EVM and EVA‐g‐MAH. Impact essential work of fracture (EWF) model was used to characterize the fracture behavior of the blends. The nylon/EVM/EVA‐g‐MAH (80/15/5) blend had the highest total fracture energy at a given ligament length (5 mm) and the highest dissipative energy density among all the studied blends. Scanning electron microscopy images showed the EVM and EVA‐g‐MAH existed as spherical particles in nylon 1010 matrix and their size decreased gradually with increasing EVA‐g‐MAH content. Large plastic deformation was observed on the impact fracture surface of the nylon/EVM/EVA‐g‐MAH (80/15/5) blend and related to its high impact strength. Then with increasing EVA‐g‐MAH proportion, the matrix shear yielding of nylon/EVM/EVA‐g‐MAH blends became less obvious. EVM and EVA‐g‐MAH greatly increased the apparent viscosity of nylon 1010, especially at low shear rates. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 877–887, 2009     

Crystalline structure and thermal behavior of nylon‐10,14

The structure and morphology of a novel polyamide, nylon‐10,14, and its lamellar crystals from dilute solution were examined by transmission electron microscopy and wide‐angle X‐ray diffraction (WAXD). Both the electron‐diffraction pattern and WAXD data demonstrated that nylon‐10,14 adopts the structure of a triclinic lattice similar to that of the traditional nylon‐66 but with a corresponding increase of the c parameter to 3.23 nm. In addition, the thermal behavior of melt‐crystallized nylon‐10,14 was investigated by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The glass‐transition temperature of nylon‐10,14 determined by the DMA data was 46.6°C. DSC indicated that the multiple melting behavior of isothermally crystallized nylon‐10,14 probably results from the melt and recrystallization mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1422–1427, 2003     

Toughening of nylon 6 with a maleated core-shell impact modifier

Super-tough nylon 6 was prepared by using maleic anhydride grafted polyethylene-octene rubber/semicrystalline polyolefin blend (TPEg) as an impact modifier. The morphology, dynamic mechanical behavior, mechanical properties, and toughening mechanism were studied. Results indicate that TPEg with a semicrystalline polyolefin core and a polyethylene-octane rubber shell, possesses not only a better processability of extruding and pelletizing with a lower cost, but also an improved toughening effect in comparison with the maleated pure polyethylene-octene rubber. The shear yielding is the main mechanism of the impact energy dissipation. In addition, the influence of melt viscosity of nylon 6 on toughening effectiveness was also investigated. High melt viscosity of matrix is advantageous to the improvement of notched Izod impact strength. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1987–1994, 1998     

Syntheses and Molecular Structures of Liquid Pyrophoric Hydridosilanes

Trisilane, isotetrasilane, neopentasilane, and cyclohexasilane have been prepared in gram scale. In-situ cryo crystallization of these pyrophoric liquids in sealed capillaries on the diffractometer allows access to the single crystal structures of these compounds. Structural parameters are discussed and compared to gas-phase electron diffraction structures from literature and with the results from quantum chemical calculations. Significantly higher packing indices are found for the silanes compared to the corresponding alkanes. Radiation with ultraviolet light (365 nm) and parallel ESR (EPR) measurement shows that cyclohexasilane is easily split into radicals, which subsequently leads to the formation of branched and chain-like oligomers. The other compounds form no radicals under these conditions. NMR spectra of all four compounds have been recorded.     

Structures of X 34‐nylons in chain‐folded lamellae and gel‐spun fibers

Structural studies and morphological features of a new family of linear, aliphatic even–even, X 34‐nylons, with X = 2, 4, 6, 8, 10, and 12, are investigated with X‐ray diffraction and electron microscopy. Solution‐grown crystals were obtained by isothermal crystallization from N,N‐dimethylformamide solutions. The thickness of lamellar‐like crystals was orders of magnitude less than the chain lengths of the polymer samples used, implying that the chains fold to form chain‐folded lamellae. The results bear a close resemblance, with the noticeable exception of 2 34‐nylon, to those reported for nylon 6 6 and other even–even nylon chain‐folded lamellar crystals. The basic structure of the straight‐stem lamellar core is similar to that of the classic nylon 6 6 triclinic α structure, and the chains tilt ≈42° relative to the lamellar normal. In the case of 2 34‐nylon, the structure resembles the 2 Y nylon series, and the chain tilt angle reduces to 36.6°. These combined results suggest that, even with a relatively low frequency of amide units along the backbone of these molecules, hydrogen bonding is still the dominant element in controlling the behavior, structure, and properties of these polymers. In addition, gels were prepared in concentrated sulfuric acid, and gel‐spun fibers were studied using X‐ray diffraction. The data are interpreted in terms of a modified nylon triclinic α structure that bears a resemblance to the structure of even–even nylons at elevated temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2685–2692, 2002     

Synthesis and Crystal and Band Structures of YbCu_6In_6 with 3D Framework

A new intermetallic compound,YbCu6In6,has been synthesized by solid-state reaction of the corresponding pure elements in a welded tantalum tube at high temperature.Its crystal structure was established by single-crystal X-ray diffraction.YbCu6In6 crystallizes in tetragonal space group I4/mmm with a = 9.2283(5),c = 5.4015(4),V = 460.00(5) 3,Z = 2,Mr = 1243.20,Dc = 8.976 g/cm3,μ = 38.243 mm-1,F(000) = 1076,and the final R = 0.0258 and wR = 0.0602 for 173 observed reflections with I > 2σ(I).The structure of YbCu6In6 belongs to the ThMn12 type.It is isostructural with RECu6In6(RE = Y,Ce,Pr,Nd,Gd,Tb,Dy),containing one-dimensional(1D) [Cu10In6] cluster chain along the c axis,which is interconnected via sharing the Cu(1) atoms to form a three-dimensional(3D) [Cu6In6] framework with Yb atoms encapsulated in the 1D tunnels along the c axis.Band structure calculations based on Density Functional Theory(DFT) method indicate that YbCu6In6 is metallic.     

A novel method for encapsulation of a liquid crystal in monodisperse micron-sized polymer particles

Liquid crystals (LCs) encapsulated in monodisperse micron-sized polymer particles were prepared to control the size and size distribution of LC droplets in polymer-dispersed LCs. The poly(methyl methacrylate) (PMMA) seed particles were swollen with the mixture of liquid crystal, monomers (methyl methacrylate and styrene) and initiator by using a diffusion-controlled swelling method. A single LC domain was produced by the phase separation between PMMA and LC through polymerization. The optical microscopy and scanning electron microscopy showed that the particles are highly monodisperse with core–shell structure. Moreover, monodisperse LC core domains were confirmed from polarized optical microscope observations. The final particle morphology was influenced by the cross-linking of the seed particle. When linear PMMA particles, which are not cross-linked, were used as a seed, the microcapsules were distorted after annealing for a few days; however, in the case of cross-linked PMMA particles, the core–shell structure was sustained stably after annealing. Received: 22 November 2000 Accepted: 12 March 2001     

Hydrothermal synthesis,crystal structure,and properties of a novel magnesium phosphonate with a 1D chain structure

A novel 1D chain magnesium phosphonate with a 1D channel system along the c-axis, [Mg(H₄L)(H₂O)₃]_n (1) (H₄L^2-=HN(CH₂PO₃H)₃)^2-, has been synthesized under hydrothermal condition using triphosphonate ligand. The MgO₆ polyhedra and NC₃ planes are connected by phosphonate groups to form a 1D chain. The chains are interlinked by hydrogen bonds into 2D layers. Adjacent layers are further linked via hydrogen bonds to build a 3D network structure. The luminescent property of complex 1 has been also studied. For the complex 1, a blue fluorescent emission band with a maximum peak at 460 nm was observed.     

Isothermal and nonisothermal crystallization kinetics of nylon 6/functionalized multi‐walled carbon nanotube composites

The well dispersion of functionalized multi‐walled carbon nanotube (f‐MWCNT) in nylon 6 matrix was prepared by solution mixing techniques. The isothermal and nonisothermal crystallization kinetics of nylon 6 and nylon 6/f‐MWCNT nanocomposites were studied by differential scanning calorimetry (DSC), X‐ray diffraction and polarized optical microscopy analysis. DSC isothermal results revealed that the activation energy of nylon 6 extensively decreased by adding 1 wt % f‐MWCNT into nylon 6, suggesting that the addition of small amount of f‐MWCNT probably induces the heterogeneous nucleation. Nevertheless, the addition of more f‐MWCNT into nylon 6 matrix reduced the transportation ability of polymer chains during crystallization process and thus increased the activation energy. The nonisothermal crystallization of nylon 6/f‐MWCNT nanocomposites was also discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 158–169, 2008     

Structural and mechanical behavior of nylon 6 films part I. Identification and stability of the crystalline phases

The crystalline phase of polyamide 6 (otherwise nylon 6) films produced following various physical treatments is investigated by means of thermal analysis, X‐ray diffraction, and infrared spectroscopy. A recently published procedure for treating infrared spectra of multicomponent compounds without a priori knowledge of the individual component spectra allowed us to perform a semiquantitative analysis of the structural changes upon annealing, including data from drawn samples. Melt‐cast films display a mesomorphic state that is thermally stable up to about 120 °C. This structure partly reorganizes into the stable monoclinic α form above 120 °C. Films in major γ form produced by iodine treatment are thermally stable up to 200 °C. Films in major α form are also prepared by superheated water treatment. No evidence is given for a Brill transition about 170 °C. This is an important fact for further understanding of the drawing behavior of PA6 at temperatures above and below this domain. The mesomorphic phase can hardly be separated from the amorphous component both from X‐ray and infrared analysis. However, scanning calorimetry, which is often criticized due to possible reorganization of unstable species during the heating scan, turned out to be a very useful technique. Indeed, recrystallization from the amorphous phase or improvement of ordering from the mesomorphic state both result in exothermic effects in quite different temperature domains that allow to discriminate the two phenomena. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 484–495, 2001     

Synthesis and crystal structure of a novel chiral compound prepared from (-)-borneol as a natural chiral auxiliary

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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     

In‐situ microfibrillar PET/iPP blend via slit die extrusion,hot stretching,and quenching: Influence of hot stretch ratio on morphology,crystallization, and crystal structure of iPP at a fixed PET concentration

The in situ microfibrillar blend of poly(ethylene terephthalate) (PET)/isotactic polypropylene (iPP) was fabricated through a slit die extrusion, hot stretch, and quenching process. The morphological observation indicates that while the unstretched blend appears to be a common incompatible morphology, the hot stretched blends present PET in situ fibers whose characteristics, such as diameter and aspect ratio, are dependent on the hot stretching ratio (HSR). When the HSR is low, the elongated dispersed phase particles are not uniform at all. As the HSR is increased to 16.1, well‐defined PET microfibers were generated in situ, whose diameter is rather uniform and is around 0.6 ～ 0.9 μm. The presence of the PET phase shows significant nucleation ability for crystallization of iPP. Higher HSR corresponds to faster crystallization of the iPP matrix, while as HSR is high up to a certain level, its variation has little influence on the onset and maximum crystallization temperatures of the iPP matrix during cooling from melt. Optical microscopy observation reveals that transcrystalline layers form in the microfibrillar blend, in which the PET microfibers play as the center row nuclei. In the as‐stretched microfibrillar blends, small‐angle X‐ray scattering measurements show that matrix iPP lamellar crystals have the same orientation as PET lamella. The long period of lamellar crystals of iPP is not affected by the presence of PET micofibers. Wide‐angle X‐ray scattering reveals that the β phase of iPP is obtained in the as‐stretched blends, whose concentration increases with the increase of the HSR. This suggests that finer PET microfibers can promote the occurrence of the β phase. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4095–4106, 2004     

General analysis of the measurements of the lateral crystal lattice moduli of semicrystalline polymers by x-ray diffraction and the application to nylon 6

A mathematical representation based on a linear elastic theory is proposed by which one may investigate the dependences of molecular orientation and crystallinity on the crystal lattice moduli and linear thermal expansion coefficients in the direction perpendicular to the chain axis as commonly measured by x-ray diffraction. In the theoretical calculation, a previously introduced model was employed in which oriented crystalline phase is surrounded by oriented amorphous phase and the strains of the two phases at the boundary are identical. The mathematical analysis indicated that the lateral crystal lattice moduli and linear thermal coefficients as measured by x-ray diffraction may be different from the intrinsic crystal moduli and linear thermal coefficients of a crystal unit cell, depending on the structure of the polymer solid. The numerical calculation was applied to nylon 6. As a result, it may be confirmed that the lateral crystal lattice moduli measured by x-ray diffraction are sensitive to the morphology of the bulk speciments and close to the intrinsic crystal moduli if the morphology of the test specimen can be represented by a parallel model with respect to the original stretching longitudinal direction.     

A novel crystalline structure - poly(tetrafluoroethylene) spherulitic crystal and its crystallization kinetics

Spherulitic crystals of Poly(tetrafluoroethylene) (PTFE), for the first time, are observed in a kind of PTFE composite, and are verified by polarized optic microscopy (POM). Differential scanning calorimetry (DSC) is used to study the isothermal crystallization kinetics of PTFE matrix at different temperatures. The result shows that Avrami parameter is near 3, which may be elucidated that PTFE crystallizes three-dimensionally from preexisting nuclei. The result is in accordance with scanning electric microscopy (SEM) and POM observation of the crystalline morphology of PTFE. Compared with the rate of one-dimension crystallization, the rate of three-dimension crystallization is lower. So the three-dimension crystallization is easier to control than the one-dimension crystallization of PTFE.