Polypeptide‐based nanocomposite: Structure and properties of poly(L‐lysine)/Na+‐montmorillonite

The feasibility of constructing polymer/clay nanocomposites with polypeptides as the matrix material is shown. Cationic poly‐L‐lysine · HBr (PLL) was reinforced by sodium montmorillonite clay. The PLL/clay nanocomposites were made via the solution‐intercalation film‐casting technique. X‐ray diffraction and transmission electron microscopy data indicated that montmorillonite layers intercalated with PLL chains coexist with exfoliated layers over a wide range of relative PLL/clay compositions. Differential scanning calorimetry suggests that the presence of clay suppresses crystal formation in PLL relative to the neat polypeptide and slightly decreases the PLL melting temperature. Despite lower crystallinity, dynamic mechanical analysis revealed a significant increase in the storage modulus of PLL with an increase in clay loading producing storage modulus magnitudes on par with traditional engineering thermoplastics. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2579–2586, 2002     

Elaboration of open‐cell microcellular nanocomposites

Stable water‐in‐oil high internal phase emulsions, containing styrene and divinylbenzene monomers and exfoliated montmorillonite, were prepared and polymerized to obtain nanocomposite microcellular materials. The porous structure was investigated by scanning electron microscopy, mercury intrusion porosimetry, and nitrogen adsorption/desorption analyses. The exfoliation of clay was investigated by X‐ray diffraction and transmission electron microscopy analyses. The presence of inorganic filler did not modify the microcellular structure of the composite, while the use of modified clay significantly enhanced its mechanical properties. No influence on the thermal degradation was noted, except for materials with high clay content that tended to deteriorate at lower temperature than the other materials. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4193–4203, 2007     

Structural transformation from shish‐kebab crystals to micro‐fibrils through hot stretching process of gel‐spun ultra‐high molecular weight polyethylene fibers with high concentration solution

Structural evolution of gel‐spun ultra‐high molecular weight polyethylene fibers with high concentration solution via hot stretching process was investigated by in situ small‐angle X‐ray scattering, in situ wide‐angle X‐ray diffraction measurements, scanning electron microscopy, and differential scanning calorimetry. With the increase of stretching strain, the long period continuously increases at relative lower stretching temperature, while it first increases and then decreases rapidly at relative higher stretching temperature. The kebab thickness almost keeps constant during the whole hot‐stretching process and the kebab diameter continually decreases for all stretching temperatures. Moreover, the length of shish decreases slightly and the shish quantity increases although there is almost no change in the diameter of shish crystals during the hot stretching process. The degree of crystal orientation at different temperatures is as high as above 0.9 during the whole stretching process. These results indicate that the shish‐kebab crystals in ultra‐high molecular weight polyethylene fibers can transform continuously into the micro‐fibril structure composed mostly of shish crystals through the hot stretching process. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 225–238     

Thermotropic liquid crystal behavior on PBLG‐PDMS‐PBLG triblock copolymers

In this contribution, the preparation of rod‐coil‐rod triblock copolymers based on polydimethylsiloxane and polypeptide [poly(γ‐benzyl‐L ‐glutamate)] is reported. Firstly, self‐assembly in rod‐like structures was demonstrated via polarized optical microscopy and small‐angle light scattering. Further structuration details were obtained using X‐ray scattering and AFM imaging to establish the formation of a double‐hexagonal structure and to accurately define the morphological dimensions of the rodlike structures. The thermal behavior of these structures was investigated using dynamic mechanical analysis and differential scanning calorimetry. We conclude by addressing an unexpected reversible thermal transition within the 130–150 °C temperature range and the ensuing associated organizational modifications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4668–4679, 2006     

Effects of clay‐modifying agents on the morphology and properties of poly(methyl methacrylate)/clay nanocomposites synthesized via γ‐ray irradiation polymerization

Via γ‐ray irradiation polymerization, poly(methyl methacrylate) (PMMA)/clay nanocomposites were successfully prepared with reactive modified clay and nonreactive clay. With reactive modified clay, exfoliated PMMA/clay nanocomposites were obtained, and with nonreactive clay, intercalated PMMA/clay nanocomposites were obtained. Both results were confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. PMMA extracted from PMMA/clay nanocomposites synthesized by γ‐ray irradiation had higher molecular weights and narrow molecular weight distributions. The enhanced thermal properties of the PMMA/clay nanocomposites were characterized by thermogravimetric analysis and differential scanning calorimetry. The improved mechanical properties of PMMA/clay were characterized by dynamic mechanical analysis. In particular, the enhancement of the thermal properties of the PMMA/clay nanocomposites with reactive modified clay was much more obvious than that of the PMMA/clay nanocomposites with nonreactive clay. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3218–3226, 2003     

Effects of spacing between the exfoliated clay platelets on the crystallization behavior of polyamide‐6 in polyamide‐6/clay nanocomposites

Exfoliated polyamide‐6 (PA6)/organoclay nanocomposite films with planar‐oriented clay platelets were prepared by the simple hot pressing of melt‐extruded nanocomposite pellets. The average distance between the neighboring clay platelets was controlled by changes in the clay loading content in the nanocomposites. The effects of the clay platelet spacing on the crystallization behavior of PA6 were investigated with transmission electron microscopy and wide‐angle X‐ray diffraction. The crystal lamellae were found to be mainly perpendicular to the clay surface for the nanocomposites with large spacing between the clay sheets at low clay loading contents. This perpendicular orientation morphology was attributed to the strong interactions between the PA6 molecular chain and the clay surface. In contrast, the crystal lamellae were found to be parallel to the clay surface when the spacing between the neighboring clay platelets was less than 30 nm. It was concluded that the confinement crystallization of PA6 within the nanoscale channels formed by clay sheets resulted in this parallel orientation texture. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 284–290, 2006     

Synthesis,rheology, and morphology of nylon‐11/layered silicate nanocomposite

Exfoliated nylon‐11/layered silicate nanocomposites were prepared via in situ polymerization by dispersing organoclay in 11‐aminoundecanoic acid monomer. The original clay was modified by a novel method with 11‐aminoundecanoic acid. In situ Fourier transform infrared spectroscopy results show that stronger hydrogen bonds exist between nylon‐11 and organoclay than that of between nylon‐11 and original clay. The linear dynamic viscoelasticity of organoclay nanocomposites was investigated. Before taking rheological measurements, the exfoliated and intercalating structures and the thermal properties were characterized using X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis. The results show that the clay was uniformly distributed in nylon‐11 matrix during in situ polymerization of clay with 4 wt % or less. The presence of clay in nylon‐11 matrix increased the crystallization temperature and the thermal stability of nanocomposites prepared. Rheological properties such as storage modulus, loss modulus, and relative viscosity have close relationship with the dispersion favorably compatible with the organically modified clay. Comparing with neat nylon‐11, the nanocomposites show much higher dynamic modulus and stronger shear thinning behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2161–2172, 2006     

Pinecone‐like Cu(II) crystal growth on the surface of amine‐group‐immobilized polymers

Field‐emission scanning electron microscopy (FESEM) was used to monitor pinecone‐like Cu(II) crystal growth on polymeric fibers for various growth times. In FESEM images, Cu(II) complexes and Cu(OH)₂ crystal growth on poly(acryloamidino ethylene amine) and poly(acryloamidino diethylenediamine) were observed. Up to an elapsed time of 16 min, crystal growth was observed in only one direction. However, after an elapsed time of 20 h, pinecone‐like crystals covered the entire surfaces of the synthesized polymers. Fourier transform infrared spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy were used for analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1238–1247, 2005     

Isothermal crystallization kinetics of polypropylene latex–based nanocomposites with organo‐modified clay

The effect of organo‐modified clay (Cloisite 93A) on the crystal structure and isothermal crystallization behavior of isotactic polypropylene (iPP) in iPP/clay nanocomposites prepared by latex technology was investigated by wide angle X‐ray diffraction, differential scanning calorimetry and polarized optical microscopy. The X‐ray diffraction results indicated that the higher clay loading promotes the formation of the β‐phase crystallites, as evidenced by the appearance of a new peak corresponding to the (300) reflection of β‐iPP. Analysis of the isothermal crystallization showed that the PP nanocomposite (1% C93A) exhibited higher crystallization rates than the neat PP. The unfilled iPP matrix and nanocomposites clearly shows double melting behavior; the shape of the melting transition progressively changes toward single melting with increasing crystallization temperature. The fold surface free energy (σ_e) of polymer chains in the nanocomposites was lower than that in the PP latex (PPL). It should be reasonable to treat C93A as a good nucleating agent for the crystallization of PPL, which plays a determinant effect on the reduction in σ_e during the isothermal crystallization of the nanocomposites. The activation energy, ΔE_a, decreased with the incorporation of clay nanoparticles into the matrix, which in turn indicates that the nucleation process is facilitated by the presence of clay. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1927–1938, 2010     

Layer structure estimation of three‐dimensional crystal and two‐dimensional molecular film for fluorinated comb copolymers

Comb copolymers containing both hydrogenated and fluorinated side‐chains were prepared by copolymerization using acrylic or methacrylic monomers in several ratios. The crystal structures of these copolymers and layer structures of their organized molecular films were investigated by wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and out‐of plane X‐ray diffraction. Further, to selectively estimate the regularity of shorter fluorocarbon side‐chains, organized molecular films of copolymers were investigated by polarized near‐edge X‐ray adsorption fine structure (NEXAFS) spectroscopy. From the results of these measurements, it was inferred that these copolymers formed highly ordered layer structures, and a long spacing was predominantly determined by the arrangement of hydrogenated side‐chains, except in copolymers having extremely high fluorocarbon contents. In the case of the organized molecular films, the fluorinated side‐chains of methacrylate copolymers cannot form a highly ordered arrangement, whereas those of acrylate copolymers were oriented on monolayers. However, in both cases, the hydrogenated side‐chains predominantly formed layer structures in the organized films, and the fluorinated side‐chains did not contribute to the formation of the layer structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 534–546, 2008     

Strain‐induced crystallization and mechanical properties of functionalized graphene sheet‐filled natural rubber

The effects of functionalized graphene sheets (FGSs) on the mechanical properties and strain‐induced crystallization of natural rubber (NR) are investigated. FGSs are predominantly single sheets of graphene with a lateral size of several hundreds of nanometers and a thickness of 1.5 nm. The effect of FGS and that of carbon black (CB) on the strain‐induced crystallization of NR is compared by coupled tensile tests and X‐ray diffraction experiments. Synchrotron X‐ray scattering enables simultaneous measurements of stress and crystallization of NR in real time during sample stretching. The onset of crystallization occurs at significantly lower strains for FGS‐filled NR samples compared with CB‐filled NR, even at low loadings. Neat‐NR exhibits strain‐induced crystallization around a strain of 2.25, while incorporation of 1 and 4 wt % FGS shifts the crystallization to strains of 1.25 and 0.75, respectively. In contrast, loadings of 16 wt % CB do not significantly shift the critical strain for crystallization. Two‐dimensional (2D) wide angle X‐ray scattering patterns show minor polymer chain alignment during stretching, in accord with previous results for NR. Small angle X‐ray scattering shows that FGS is aligned in the stretching direction, whereas CB does not show alignment or anisotropy. The mechanical properties of filled NR samples are investigated using cyclic tensile and dynamic mechanical measurements above and below the glass transition of NR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Ethylene/vinyl acetate copolymer/clay nanocomposites

This article highlights the history, synthetic routes, material properties, and scope of ethylene/vinyl acetate copolymer (EVA)/clay nanocomposites. These nanocomposites of EVAs are achieved with either unmodified or organomodified layered silicates with different methods. The structures of the resulting polymer/inorganic nanocomposites have been characterized with X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The addition of a small amount of clay, typically less than 8 wt %, to the polymer matrix unusually promotes the material properties, such as the mechanical, thermal, and swelling properties, and increases the flame retardancy of these hybrids. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 471–480, 2006     

Effect of postcasting heat‐treatment on the structure and properties of semicrystalline phase‐inversion poly(vinylidene fluoride) membranes

Microporous PVDF membranes were prepared by immersion‐precipitation in 1‐octanol of casting dopes dissolved at different temperatures, with dissolution temperature affecting strongly the membrane microstructure. The effect of postcoagulation thermal annealing, which is an additional thermal parameter, on membrane microstructure and properties is probed herein. Membranes obtained were annealed at temperatures up to 160 °C, which is close to the melting point of PVDF polymer. Annealing leads to a substantial modification of the nano‐scale fine structure of the membranes, while the overall‐microporous structure is preserved. At elevated annealing temperatures, nano‐grains, fibrils, and stick‐like crystalline entities gradually eclipse, while globules develop more robust connections based on wide bands of crystal elements. Probing by X‐ray diffraction and dynamic scanning calorimetry shows that crystallinity increases when annealing temperature and time are increased. As regards mechanical properties, the tensile strength of the membranes can be enhanced substantially, up to about 10 times, upon appropriate high temperature prolonged annealing. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1880–1893, 2009     

Differential scanning calorimetry,small‐angle X‐ray scattering,and wide‐angle X‐ray scattering on homogeneous and heterogeneous ethylene‐α‐copolymers

The objective of this work was to use both X‐ray and differential scanning calorimetry techniques in a comparative study of the lamellar and crystalline structures of heterogeneous and homogeneous ethylene‐α‐copolymers. The samples differed in the comonomer type (1‐butene, 1‐hexene, 1‐octene, and hexadecene), comonomer content, and catalyst used in the polymerizations. Step crystallizations were performed with differential scanning calorimetry, and the crystallinity and lamellar thicknesses of the different crystal populations were determined. Wide‐angle X‐ray scattering was used to determine crystallinities, average sizes of the crystallites, and dimensions of the orthorhombic unit cell. The average thickness, separation of the lamellae, and volume fractions of the crystalline phase were determined by small‐angle X‐ray scattering (SAXS). The results revealed that at densities below 900 kg/m³, polymers were organized as poorly organized crystal bundles. The lamellar distances were smaller and the lamellar thickness distributions were narrower for the homogeneous ethylene copolymers than for the heterogeneous ones. Step‐crystallization experiments by SAXS demonstrated that the long period increased after annealing. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1860–1875, 2001     

Preparation and characterization of PP/clay nanocomposites based on modified polypropylene and clay

X‐ray diffraction and differential scanning calorimeter (DSC) methods have been used to investigate the crystallization behavior and crystalline structure of hexamethylenediamine (HMDA)‐modified maleic‐anhydride‐grafted polypropylene/clay (PP‐g‐MA/clay) nanocomposites. These nanocomposites have been prepared by using HMDA to graft the PP‐g‐MA (designated as PP‐g‐HMA) and then mixing the PP‐g‐HMA polymer in hot xylene solution, with the organically modified montmorillonite. Both X‐ray diffraction data and transmission electron microscopy images of PP‐g‐HMA/clay nanocomposites indicate that most of the swellable silicate layers are exfoliated and randomly dispersed into PP‐g‐HMA matrix. DSC isothermal results revealed that introducing 5 wt % of clay into the PP‐g‐HMA structure causes strongly heterogeneous nucleation, which induced a change of the crystal growth process from a three‐dimensional crystal growth to a two‐dimensional spherulitic growth. Mechanical properties of PP‐g‐HMA/clay nanocomposites performed by dynamic mechanical analysis show significant improvements in the storage modulus when compared to neat PP‐g‐HMA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3242–3254, 2005     

Facile green strategy for micro/nano structured conducting polyaniline‐clay nanocomposite via template polymerization using amphiphilic dopant, 3‐pentadecyl phenol 4‐sulphonic acid

Novel self‐assembled nano/microstructured conducting PANICN was prepared by in situ intercalative emulsion polymerization of aniline in aqueous dispersion of clay using bifunctional amphiphilic dopant, 3‐pentadecyl phenol‐4‐sulphonic acid (PDPSA) derivable from renewable resource. X‐ray diffraction and scanning electron microscopy (SEM) studies revealed the formation of monolayer of protonated PANI intercalated nanoclays with template polymerized self‐assembled micro/nanostructured protonated PANI. Nano/micro structured PANIs were formed by the supra molecular self‐assembling of the inter‐chain hydrogen bonding, inter‐plane phenyl stacking and electrostatic layer by layer self‐assembling (ELBS) between polarized alkyl chains present dopant anions and were manifested using fourier transform infra red spectroscopy and differential scanning calorimetry. On the basis of the results, structure‐directing effect of ‘anilinium salt micelle’ was schematically illustrated in this article. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2664–2673, 2007     

Structure and properties of polyethylene prepared via low‐frequency vibration‐assisted injection molding

A self‐made low‐frequency vibration‐assisted injection‐molding (VAIM) device was adopted to explore the relationship between mechanical property and morphology for high‐density polyethylene injected moldings. The main processing variables for the VAIM are vibration frequency and vibration pressure amplitude, and tensile properties and morphology were investigated under different VAIM processing conditions with conventional injection molding for comparison. The moldings prepared by VAIM exhibit a very well defined laminated morphology composed of a layered structure with enhanced crystallinity. Increased with vibration frequency at constant vibration pressure amplitude, the shish‐kebab structure is exhibited in the shear layer of the specimen prepared by VAIM, whereas row nucleation lamella exists in the same layer produced by enhanced vibration pressure amplitude at a constant vibration frequency. These oriented structures and enhanced crystallinity, confirmed by scanning electron microscopy, wide‐angle X‐ray diffraction, and differential scanning calorimetry, serve to obtain stronger injection moldings. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 13–21, 2005     

Effects of comonomer sequential structure on thermal and crystallization behaviors of biodegradable poly(butylene succinate‐co‐butylene terephthalate)s

In this work, new investigations on the effect of comonomer sequential structure on the thermal and crystallization behaviors and biodegradability have been implemented for the biodegradable poly(butylene succinate‐co‐butylene terephthalate) (PBST) as well as aliphatic poly(butylene succinate) (PBS). At first, these copolyesters were efficiently synthesized from dimethyl succinate and/or dimethyl terephthalate and 1,4‐butanediol via condensation polymerization in bulk. Subsequently, their molecular weights and macromolecular chain structures were analyzed by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. By means of differential scanning calorimeter (DSC) and wide‐angle X‐ray diffractometer (WAXD), thermal and crystallization behaviors of these synthesized aromatic–aliphatic copolyesters were further explored. It was demonstrated that the synthesized copolyesters were revealed to have random comonomer sequential structures with thermal and crystallization properties strongly depending on their comonomer molar compositions, and that crystal lattice structures of the new crystallizable copolyesters shifted from the monoclinic crystal of semicrystalline PBS to triclinic lattice of the poly(butylene terephthalate) (PBT) with increasing the terephthalate comonomer composition, and the minor comonomer components were suggested to be trapped in the crystallizable component domains as defects. In addition, the enzymatic degradability was also characterized for the copolyesters film samples. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1635–1644, 2006     

Poly(vinylidene fluoride)/clay nanocomposites prepared by melt intercalation: Crystallization and dynamic mechanical behavior studies

The preparation and properties of poly(vinylidene fluoride) (PVDF)/clay nanocomposites are reported for the first time. PVDF/clay nanocomposites were prepared by melt intercalation with organophilic clay. The composites were characterized with X‐ray diffraction, differential scanning calorimetry, and dynamic mechanical analysis. X‐ray diffraction results indicated intercalation of the polymer into the interlayer spacing. PVDF in the nanocomposites crystallized in the β form. Differential scanning calorimetry nonisothermal curves showed an increase in the melting and crystallization temperatures along with a decrease in crystallinity, as evidenced by the melting and crystallization peaks. Isothermal crystallization studies showed an enhanced rate of crystallization with the addition of clay, as evidenced by a reduction in the crystallization time. Dynamic mechanical analysis indicated significant improvements in the storage modulus over a temperature range of ?100 to 150 °C. The tan δ peak signifying the glass‐transition temperature of PVDF shifted to higher temperatures. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1682–1689, 2002     

Effect of the premelting temperature and sample thickness on the polymorphic behavior of syndiotactic polystyrene/clay nanocomposites

X‐ray diffraction methods and differential scanning calorimetry thermal analysis have been used to investigate the structural changes of syndiotactic polystyrene (sPS)/clay nanocomposites. sPS/clay nanocomposites have been prepared by the mixing of sPS polymer solutions with organically modified montmorillonite. X‐ray diffraction data and differential scanning calorimetry results indicate that the dominating crystal forms and their relative fractions in sPS and sPS/clay nanocomposites are different for various premelting temperatures (T_max's). Higher T_max's favor the formation of the thermodynamically more stable β‐crystalline form, and its relative fraction has been obtained from the X‐ray diffraction data in the range of 11.5–13°. The intensity of the X‐ray diffraction data in the range of 11.5–13° decreases as the thickness of sPS/clay nanocomposites decreases from 150 to 20 μm. At the same time, the intensity of the X‐ray data in the range of 6–7° becomes sharper as the thickness of sPS/clay nanocomposites decreases. The calculation ratio based on the peak intensities at 6.2 and 6.8° for sPS/clay nanocomposites of equal thickness and crystallinity in the pure β and α forms has also been determined in this study. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1730–1738, 2003