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The aim of this study is to determine the characteristics of PANI/ZnO nanocomposites and its sensitivity to methanol, ethanol, and butanol at low concentrations. The synthesis process was oxidation polymerization followed by wet mixing. FTIR was used to identify the PANI/ZnO NCs phase, XRD to investigate the PANI/ZnO NCs structure, EDX to analyze the elements, and SEM to examine the sample microstructure. Sensitivity is determined using the four-point probe (FPP) method, which measures the change in resistance of PANI/ZnO NCs when exposed to alcohol vapor. The FTIR analysis results confirmed the presence of C=C stretch (Quinoid) and C-C stretch (Benzenoid) bonds from PANI, as well as ZnO's unique peaks, notably Zn-O-Zn. The PANI/ZnO nanocomposite's diffraction peak at 2θ = 21.22° showed amorphous semicrystalline PANI, whereas the peak at 31.75° suggested crystalline ZnO. Elemental analysis revealed that the sample contained N and C elements from PANI, as well as Zn elements from ZnO. Microstructure investigations revealed that the PANI/ZnO NCs had an ovoidal form with an average diameter of 293 nm. PANI/ZnO NCs have been shown to detect methanol, ethanol, and butanol vapors at low levels. When exposed to butanol vapors, the PANI/ZnO NCs exhibit a greater resistance change response than when exposed to other alcohol vapor. Although PANI/ZnO NCs have a higher sensitivity for detecting butanol vapor, they respond faster to methanol vapor than the other two alcohols. The response time was 40 seconds when PANI/ZnO NCs were subjected to methanol vapor at a concentration of 5 ppm, followed by a 20-second recovery period. Furthermore, PANI/ZnO NCs become more sensitive as alcohol vapor concentration increases. [ABSTRACT FROM AUTHOR]

In material extrusion (MEX), it is challenging to accurately predict the steady and transient feeding forces at various polymer extrusion rates when printing island and thin-walled structures involving rapid start/stop or acceleration/deceleration, especially for semi-crystalline polymers. This research presents a non-isothermal viscoelastic Computational Fluid Dynamics model to investigate the steady and transient feeding forces, as well as the phase transition process and viscoelastic behaviour of polylactic acid (PLA), a semi-crystalline polymer, during the extrusion process. The study establishes a relationship between polymer flow and viscoelastic stress, demonstrating that the elastic effect during extrusion is more significant than the viscous effect, particularly at higher feeding rates. Furthermore, the study uncovers critical aspects of PLA melt flow behaviour during the MEX process, laying the foundation for future research and optimisation of MEX printing processes. [ABSTRACT FROM AUTHOR]

Semicrystalline polymers are lightweight, multiphase materials that exhibit attractive shock dissipation characteristics and have potential applications as protective armor for people and equipment. For shocks of 10 GPa or less, we analyzed various mechanisms for the storage and dissipation of shock wave energy in a realistic, united atom (UA) model of semicrystalline polyethylene. Systems characterized by different levels of crystallinity were simulated using equilibrium molecular dynamics with a Hugoniostat to ensure that the resulting states conform to the Rankine–Hugoniot conditions. To determine the role of structural rearrangements, order parameters and configuration time series were collected during the course of the shock simulations. We conclude that the major mechanisms responsible for the storage and dissipation of shock energy in semicrystalline polyethylene are those associated with plastic deformation and melting of the crystalline domain. For this UA model, plastic deformation occurs primarily through fine crystallographic slip and the formation of kink bands, whose long period decreases with increasing shock pressure. [ABSTRACT FROM AUTHOR]

The mechanical properties and blocking resistance of films cast from latex particles can be improved by addition of a reinforcing polymer of high modulus that acts as a "hard" phase. This work demonstrates that blocking resistance, a key performance parameter for use in coatings, of such films can be understood in terms of the relative contribution of the "hard" and "soft" components to the rheological properties of the material. In order to do so, representative latexes that contain a semicrystalline core of poly(stearyl acrylate) as a reinforcing phase and a shell of amorphous poly(styrene‐co‐butyl acrylate) are synthesized. By varying the composition of the amorphous phase (glass transition temperature, molar mass) and the relative amorphous/semicrystalline fraction, it is demonstrated that the improvement in blocking resistance is strongly correlated with the increase in the modulus of the material but is also affected by the dynamics of polymer diffusion of chains in the soft phase. This work allows to establish design rules for polymer and colloidal structures that can be targeted to maximize blocking resistance. [ABSTRACT FROM AUTHOR]

Spherulites are radial distributions of acicular crystals, common in biogenic, geologic, and synthetic systems, yet exactly how spherulitic crystals nucleate and grow is still poorly understood. To investigate these processes in more detail, we chose scleractinian corals as a model system, because they are well known to form their skeletons from aragonite (CaCO3) spherulites, and because a comparative study of crystal structures across coral species has not been performed previously. We observed that all 12 diverse coral species analyzed here exhibit plumose spherulites in their skeletons, with well-defined centers of calcification (CoCs), and crystalline fibers radiating from them. In 7 of the 12 species, we observed a skeletal structural motif not observed previously: randomly oriented, equant crystals, which we termed "sprinkles". In Acropora pharaonis, these sprinkles are localized at the CoCs, while in 6 other species, sprinkles are either layered at the growth front (GF) of the spherulites, or randomly distributed. At the nano- and micro-scale, coral skeletons fill space as much as single crystals of aragonite. Based on these observations, we tentatively propose a spherulite formation mechanism in which growth front nucleation (GFN) of randomly oriented sprinkles, competition for space, and coarsening produce spherulites, rather than the previously assumed slightly misoriented nucleations termed "non-crystallographic branching". Phase-field simulations support this mechanism, and, using a minimal set of thermodynamic parameters, are able to reproduce all of the microstructural variation observed experimentally in all of the investigated coral skeletons. Beyond coral skeletons, other spherulitic systems, from aspirin to semicrystalline polymers and chocolate, may also form according to the mechanism for spherulite formation proposed here. STATEMENT OF SIGNIFICANCE: Understanding the fundamental mechanisms of spherulite nucleation and growth has broad ranging applications in the fields of metallurgy, polymers, food science, and pharmaceutical production. Using the skeletons of reef-building corals as a model system for investigating these processes, we propose a new spherulite growth mechanism that can not only explain the micro-structural diversity observed in distantly related coral species, but may point to a universal growth mechanism in a wide range of biologically and technologically relevant spherulitic materials systems.

This study aims to bio-modulate Poly (vinyl alcohol) crosslinked by silver and gold nanoparticles fabricated by one-step laser ablation. The optical, cell viability, and antibacterial characterization of the fabricated films have been studied via different techniques. FTIR and XRD were used to investigate the molecular structures of the polymer matrix of Polyvinyl Alcohol incorporating gold and silver (Ag-Au NPs) created by laser ablation. XRD data illustrate the semicrystalline structure of PVA, with two hump peaks at 2θ = 8.52° and 2θ = 20.17° that are decreased when loaded with Ag-Au nanoparticles at different laser ablation times. The FT-IR spectra demonstrated a variation in the intensity of different peaks compared to the spectrum of the Polyvinyl Alcohol. This suggests that PVA and Ag-Au nanoparticles interacted and complexed in semicrystalline areas. The optical energy gap (Eg) reduces from 5.55 eV to 5.00 eV during direct transition and from 4.79 eV to 3.10 eV during indirect transition. The cell viability value for sample S2 was 91.7 ± 5.8%, indicating that both nanocomposites are biocompatible. S2 represents the high values of the inhibition zone, which make it preferred in antibacterial applications. The results demonstrate that Polyvinyl Alcohol/metal composite materials have excellent cell viability and antibacterial properties, implying that they may be suggested in antibacterial utilizations.

A new ternary nanocomposite comprising nickel oxide (NiO) embedded into a binary polymeric network of polyaniline (PANI) and polypyrrole (PPy), i.e. PANI‐PPy‐NiO, is synthesized using an in situ chemical oxidative method. The infrared spectrum of PANI‐PPy‐NiO exhibits most of the characteristic peaks of unary nanoparticles with slight shift in the frequencies. The shift is due to the synergistic interaction of binary PANI‐PPy with the inorganic NiO nanoparticles. X‐ray diffraction pattern reveals the semicrystalline structure of the PANI‐PPy‐NiO nanocomposite with an average crystallite size of 22 nm. From Williamson–Hall plot, the micro‐strain value of as‐prepared PANI‐PPy‐NiO is found to be −0.16727. Surface morphology of PANI‐PPy‐NiO shows fine grains of NiO‐encapsulated PANI‐PPy that tend to coalesce and form an agglomeration assembly. The elements detected from energy‐dispersive X‐ray analysis indicate the purity of synthesis of the ternary material. Further, the optical constants obtained from UV–visible spectra (absorption coefficient, extinction coefficient, refractive index, optical conductivity and real and imaginary dielectric constants) are found to be higher for PANI‐PPy‐NiO than for the unary PANI, PPy and NiO nanoparticles. Tauc plot and Urbach energy studies indicate the low bandgap energy of PANI‐PPy‐NiO (2.67 eV) compared to unary nanoparticles. Further, the emission intensity peak (492 nm) observed in the photoluminescence spectrum of PANI‐PPy‐NiO corresponds to the blue region of the visible spectrum. Thus, the optical studies clearly indicate the high suitability of the synthesized PANI‐PPy‐NiO in visible‐light‐based device applications. © 2022 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

As actuated devices become smaller and more complex, there is a need for smart materials and structures that directly function as complete mechanical units without an external power supply. The strategy uses light-powered, twisted, and coiled azobenzene-functionalized semicrystalline liquid crystal elastomer (AC-LCE) springs. This twisting and coiling, which has previously been used for only thermally, electrochemically, or absorption-powered muscles, maximizes uniaxial and radial actuation. The specially designed photochemical muscles can undergo about 60% tensile stroke and provide 15 kJ m -3 of work capacity in response to light, thus providing about three times and two times higher performance, respectively, than previous azobenzene actuators. Since this actuation is photochemical, driven by ultraviolet (UV) light and reversed by visible light, isothermal actuation can occur in a range of environmental conditions, including underwater. In addition, photoisomerization of the AC-LCEs enables unique latch-like actuation, eliminating the need for continuous energy application to maintain the stroke. Also, as the light-powered muscles processed to be either homochiral or heterochiral, the direction of actuation can be reversed. The presented approach highlights the novel capabilities of photochemical actuator materials that can be manipulated in untethered, isothermal, and wet environmental conditions, thus suggesting various potential applications, including underwater soft robotics., (© 2024 Wiley‐VCH GmbH.)

Polyvinylidene fluoride (PVDF) is a common semicrystalline fluoropolymer polymer. Due to its excellent piezoelectric properties, thermal stability, and mechanical strength, it has excellent processability and chemical tolerance to a range of materials such as acids, bases, organic solvents, grease, and fat. The current research provides an overview of recent advancements and developments in the implementation and modification of PVDF membranes, with a particular emphasis on sensors, biomedical engineering and devices, nanotechnology, solar applications, energy harvesting, and drug delivery carrier. Ferroelectric polymers are interesting from an electrical perspective. Ferroelectric polymers are insulating and polar and have a non-conjugated backbone, so they are known as strongly insulating materials from an optical perspective. Insulating polymers are particularly appealing for the study of charge transportation and storage. Because of their insulating properties and high concentration, such polymers often provide the best electrets for practical use. On the other hand, PMMA is an amorphous polymer, and poly (methyl methacrylate) (PMMA) advances have opened a wide variety of uses in nanotechnology. The understanding of PMMA properties has greatly aided recent advancements in the polymer's synthesis, modification, and applications. As a result, this analysis aims to compare the physical, chemical, thermal, and mechanical properties of PVDF and PMMA. This article also gives a wise guide in the advancement of these two polymers in various fields of science and technology. [ABSTRACT FROM AUTHOR]

Reverse electrodialysis (RED) generates power directly by transforming salinity gradient into electrical energy. The ion transport properties of the ion-exchange membranes need to be investigated deeply to improve the limiting efficiencies of the RED. The interaction between “counterions” and “ionic species” in the membrane requires a fundamental understanding of the phase separation process. Here, we report on sulfonated poly(vinylidene fluoride-co-hexafluoropropylene)/graphitic carbon nitride nanocomposites for RED application. We demonstrate that the rearrangement of the hydrophilic and hydrophobic domains in the semicrystalline polymer at a nanoscale level improves ion conduction. The rearrangement of the ionic species in polymer and “the functionalized nanosheet with ionic species” enhances the proton conduction in the hybrid membrane without a change in the structural integrity of the membrane. A detailed discussion has been provided on the membrane nanostructure, chemical configuration, structural robustness, surface morphology, and ion transport properties of the prepared hybrid membrane. Furthermore, the RED device was fabricated by combining synthesized cation exchange membrane with commercially available anion exchange membrane, NEOSEPTA, and a maximum power density of 0.2 W m−2 was successfully achieved under varying flow rates at the ambient condition.

In the present work, we propose the synthesis of a new family of sugar derived 1,4:3,6-dianhydrohexitol based AA/AB-type monomers. Unprecedented diacids based on Isomannide and Isoidide were elaborated with high yields and showed interestingly high melting point ranges (240–375 °C). Optimization of reaction conditions (temperature, time of reaction, and reactant ratios) has been investigated to synthesize the key intermediate of a set of AB monomers with acid, ester, and acid chloride functionalities. Isosorbide based ether benzoic acid AB monomer was polymerized and characterized by NMR and DSC techniques. The results show a semicrystalline behavior of the obtained polymer thanks to the controlled stereoregular arrangement of the AB starting monomer.

In the present study, we report the development of poly (vinyl alcohol) (PVA) and chitosan oligosaccharide (COS)-based novel blend films. The concentration of COS was varied between 2.5–10.0 wt% within the films. The inclusion of COS added a brown hue to the films. FTIR spectroscopy revealed that the extent of intermolecular hydrogen bonding was most prominent in the film that contained 5.0 wt% of COS. The diffractograms showed that COS altered the degree of crystallinity of the films in a composition-dependent manner. As evident from the thermal analysis, COS content profoundly impacted the evaporation of water molecules from the composite films. Stress relaxation studies demonstrated that the blend films exhibited more mechanical stability as compared to the control film. The impedance profiles indicated the capacitive-dominant behavior of the prepared films. Ciprofloxacin HCl-loaded films showed excellent antimicrobial activity against Escherichia coli and Bacillus cereus. The prepared films were observed to be biocompatible. Hence, the prepared PVA/COS-based blend films may be explored for drug delivery applications.

One pot synthesis of "Schiff" base is carried out in this study. The synthesis by using microwave reaction as a modern method is realized from 4-dimehtylamino-5,5-dimethyl-1,3-cyclohexanedione, benzene 1.4-diamine and 1,3-benzodioxole-5-carbaldéhyde. The structural properties of the resulting compound were determined by NMR (1H and 13C), low-resolution mass spectrometry (ESI–MS), FTIR spectroscopy and x-ray diffraction. The product is semicrystalline material with a monoclinic unit cell. Based on the optical spectra, the compound has an optical band gap of (Eg = 2.89 eV). In addition, the dielectric spectroscopy was applied for studying the ac-electrical conductivity, dielectric constant and dielectric losses of the synthesized "Schiff" base. The results obtained from this study show that it has a promising future in the field of organic optoelectronics and their potential applications especially in photovoltaic conversion energies. [ABSTRACT FROM AUTHOR]

• Semicrystalline yellow TiO 2 nanoparticles are new synthesized. • Lattice O O bonds is firstly in-situ created within semicrystalline TiO 2. • Lattice O O bonds significantly enhance photocatalytic activity for H 2 production. • Reaction mechanism is proposed that describes the role of lattice O O bonds. Atomic defects (e.g., Ti3+, oxygen vacancies) have been intenstively investigated for modifying TiO 2 in order to reach visible light active photocatalytic H 2 production. However, the atomic defects within TiO 2 could easily act as photo-generated charge-carrier recombination centers, resulting in relatively low H 2 conversion efficiency. In this paper, semicrystalline yellow TiO 2 nanoparticles rich of superoxide ions are new synthesized by a simple aqueous solution method. Instead of introducing atomic defects, we show for the first time that catalytic performance can also be significantly improved via in-situ creating lattice O O bonds within metastable semicrystalline TiO 2. The synthesized semicrystalline yellow TiO 2 exhibits significantly enhanced photocatalytic activity for H 2 production after cycle tests. The formaldehyde in aqueous solution is used as target pollutant to simulate industrial wastewater. In-situ created elastic lattice O O bonds are proposed to improve catalytic performance through facilitating the breakage of C H bonds of HCHO. A series of internally consistent reaction equations is proposed that describes the role of in-situ created lattice O O bonds for improving the catalytic performance. This is strongly supported by that the H 2 production rate at the end of the fourth cycle test is significantly more than that of the beginning of the first cycle test. [ABSTRACT FROM AUTHOR]

Oxygen and sulfur co-doped semicrystalline graphitic carbon nitride (HGCNOS) was synthesized by a one-pot hydrothermal method and applied in visible-light photocatalytic nitrogen fixation. Remarkably, HGCNOS exhibited a higher photocatalytic activity than pristine graphitic carbon nitride (GCN). Oxygen doping caused semicrystalline structure, making exciton dissociated at the order-disorder interfaces of HGCNOS and releasing more electrons and holes. Furthermore, the conduction band position of HGCNOS was elevated by sulfur doping, promoting the reduction ability of HGCNOS. Thus, the special electronic and physicochemical structure of HGCNOS contributed to the enhanced photocatalytic activity, facilitating its application on nitrogen photofixation. [ABSTRACT FROM AUTHOR]

Solution-processable semiconducting polymers have been explored over the last decades for their potential applications in inexpensively fabricated transistors, diodes and photovoltaic cells. However, a remaining challenge in the field is to control the solid-state self-assembly of polymer chains in thin films devices, as the aspects of (semi)crystallinity, grain boundaries, and chain entanglement can drastically affect intra-and inter-molecular charge transport/transfer and thus device performance. In this short review we examine how the aspects of molecular weight and chain rigidity affect solid-state self-assembly and highlight molecular engineering strategies to tune thin film morphology. Side chain engineering, flexibly linking conjugation segments, and block co-polymer strategies are specifically discussed with respect to their effect on field effect charge carrier mobility in transistors and power conversion efficiency in solar cells. Example systems are taken from recent literature including work from our laboratories to illustrate the potential of molecular engineering semiconducting polymers.

Abstarct Small strain deformations below yielding can cause plastic deformation in semicrystalline polymers by a process similar to what is described for filled rubber-like materials known as the Mullins effect. Inter-lamellae chains contribute predominantly in deformations at this level, and the residual plastic strain can be attributed to permanent damage to the tie chains, affecting the long-term mechanical resistance of a molded part. With little detectable alteration of the polymer crystallinity at this early onset of plastic deformation, the primary characterization method applied to date is cyclic tensile loading, which provides information of stress-softening by monitoring the unloading path or relaxed stress behavior. An alternative method for monitoring the development of Mullins effect is proposed that can examine a molded part by using selected modes based on ultrasonic guided waves analysis. The technique was examined to determine if it could follow this effect induced by cyclic strain-controlled tensile deformations since it does not require sample preparation and could ultimately be applied while a part was in-service. Results for different polyethylene grades agree in trend with relaxed stress values over four cycles for tests of increasing applied tensile strain, demonstrated by an increase in the attenuation of ultrasonic guided waves. The correlation reveals a good promise in applying this method to structural health monitoring of plastic parts, while in use, to follow the initiation and progress of early service damage. [ABSTRACT FROM AUTHOR]

In the present work, we propose the synthesis of a new family of sugar derived 1,4:3,6-dianhydrohexitol based AA/AB-type monomers. Unprecedented diacids based on Isomannide and Isoidide were elaborated with high yields and showed interestingly high melting point ranges (240–375 °C). Optimization of reaction conditions (temperature, time of reaction, and reactant ratios) has been investigated to synthesize the key intermediate of a set of AB monomers with acid, ester, and acid chloride functionalities. Isosorbide based ether benzoic acid AB monomer was polymerized and characterized by NMR and DSC techniques. The results show a semicrystalline behavior of the obtained polymer thanks to the controlled stereoregular arrangement of the AB starting monomer. [ABSTRACT FROM PUBLISHER]

This study aims to bio-modulate Poly (vinyl alcohol) crosslinked by silver and gold nanoparticles fabricated by one-step laser ablation. The optical, cell viability, and antibacterial characterization of the fabricated films have been studied via different techniques. FTIR and XRD were used to investigate the molecular structures of the polymer matrix of Polyvinyl Alcohol incorporating gold and silver (Ag-Au NPs) created by laser ablation. XRD data illustrate the semicrystalline structure of PVA, with two hump peaks at 2θ = 8.52° and 2θ = 20.17° that are decreased when loaded with Ag-Au nanoparticles at different laser ablation times. The FT-IR spectra demonstrated a variation in the intensity of different peaks compared to the spectrum of the Polyvinyl Alcohol. This suggests that PVA and Ag-Au nanoparticles interacted and complexed in semicrystalline areas. The optical energy gap (Eg) reduces from 5.55 eV to 5.00 eV during direct transition and from 4.79 eV to 3.10 eV during indirect transition. The cell viability value for sample S2 was 91.7 ± 5.8%, indicating that both nanocomposites are biocompatible. S2 represents the high values of the inhibition zone, which make it preferred in antibacterial applications. The results demonstrate that Polyvinyl Alcohol/metal composite materials have excellent cell viability and antibacterial properties, implying that they may be suggested in antibacterial utilizations. [ABSTRACT FROM AUTHOR]

In this work, the effect of mold temperature variation on the short-term mechanical properties obtained from the tensile and Charpy impact tests, and the long-term mechanical properties obtained from dynamic mechanical loading and flexural creep of injection molded polybutylene terepthalate (PBT) are reported. It has been observed that the effect of changing the processing condition viz. mold temperature on the viscoelastic properties are more pronounced when their long-term behavior is tested. The tensile and impact properties showed only a negligible effect to the change in mold temperature. Further, analysis of the creep curves by applying a four-element Burger model presented a comprehensive understanding of their long-term viscoelastic behavior with respect to the change in mold temperature.

This study investigates the penetrant transport properties of water, oxygen, and carbon dioxide at 35 °C in poly(ethylene 2,5-furanoate) (PEF) isothermally crystallized at 115 and 160 °C. Dual-mode analysis of the water sorption isotherms for the semicrystalline vs. amorphous PEF samples indicates that the Henry’s law sorption parameter ( k D ) is reduced for the semicrystalline samples in direct proportion to the volume fraction crystallinity measured via both density and thermal methods. While the k D for water obeys the simple two-phase model of crystallinity, an unexpected large reduction in the Langmuir capacity constant ( C H ′) for the semicrystalline vs. amorphous samples resulted in an overall reduction in water sorption capacity greater than predicted by the two-phase model. Corroboration of this behavior for water is provided by independent oxygen and carbon dioxide permeation and sorption measurements, which also exhibit larger than expected reductions in solubility for the semicrystalline vs. amorphous samples. This study, which complements prior work, provides an initial look into the effect of crystallinity and morphology on the penetrant transport properties of PEF. [ABSTRACT FROM AUTHOR]

Vibration welding technique has been used to study the weld zone of thermoplastic polymers using ABS (amorphous), PC (amorphous), PMMA (amorphous), and PBT (semicrystalline). Polymers were welded using alike components and combinations of semicrystalline polymer with different amorphous polymers. Mechanical testing of welded polymers has proved that the tensile strength, elongation at break, and deformation was highest for PC–PC weld and least for ABS–ABS weld, when alike polymers were welded. However, welding of semicrystalline and amorphous polymer shows enormous reduction in its tensile strength as well as other tensile properties. Also, the tensile fracture of PBT with other amorphous polymers always occurred at weld zone which was not always in case of alike polymer welds. The weld strength of these polymers was observed to be dependent on the mechanical interlocking among the layers and not on interfacial bonding. This phenomenon may be due to the difference in glass transition temperatures of semicrystalline and amorphous polymers. XRD, FESEM, and AFM have been used in this study to observe the morphology of welded surfaces. [ABSTRACT FROM PUBLISHER]

Abstract: Electronic properties of organic semiconductors are often critically dependent upon their ability to order from the molecular level to the macro-scale, as is true for many other materials attributes of macromolecular matter such as mechanical characteristics. Therefore, understanding of the molecular assembly process and the resulting solid-state short- and long-range order is critical to further advance the field of organic electronics. Here, we will discuss the structure development as a function of molecular weight in thin films of a model conjugated polymer, poly(3-hexylthiophene) (P3HT), when processed from solution and the melt. While focus is on the microstructural manipulation and characterization, we also treat the influence of molecular arrangement and order on electronic processes such as charge transport and show, based on classical polymer science arguments, how accounting for the structural complexity of polymers can provide a basis for establishing relevant processing/structure/property-interrelationships to explain some of their electronic features. Such relationships can assist with the design of new materials and definition of processing protocols that account for the molecular length, chain rigidity and propensity to order of a given system. [Copyright &y& Elsevier]

Morphological and thermodynamic transitions in drugs as well as their amorphous and crystalline content in the solid state have been distinguished by thermal analytical techniques, which include dielectric analysis (DEA), differential scanning calorimetry (DSC), and macro-photomicrography. These techniques were used successfully to establish a structure versus property relationship with the United States Pharmacopeia standard set of active pharmaceutical ingredient (API) drugs. A distinguishing method is the DSC determination of the amorphous and crystalline content which is based on the fusion properties of the specific drug and its recrystallization. The DSC technique to determine the crystalline and amorphous content is based on a series of heat and cool cycles to evaluate the drugs ability to recrystallize. To enhance the amorphous portion, the API is heated above its melting temperature and cooled with liquid nitrogen to −120 °C (153 K). Alternatively a sample is program heated and cooled by DSC at a rate of 10 °C min. DEA measures the crystalline solid and amorphous liquid API electrical ionic conductivity. The DEA ionic conductivity is repeatable and differentiates the solid crystalline drug with a low conductivity level (10pS cm) and a high conductivity level associated with the amorphous liquid (10pS cm). The DSC sets the analytical transition temperature range from melting to recrystallization. However, analysis of the DEA ionic conductivity cycle establishes the quantitative amorphous and crystalline content in the solid state at frequencies of 0.10-1.00 Hz and to greater than 30 °C below the melting transition as the peak melting temperature. This describes the 'activation energy method.' An Arrhenius plot, log ionic conductivity versus reciprocal temperature (K), of the pre-melt DEA transition yields frequency dependent activation energy ( E, J mol) for the complex charging in the solid state. The amorphous content is inversely proportional to the E where the E for the crystalline form is higher and lower for the amorphous form with a standard deviation of ±2%. There was a good agreement between the DSC crystalline melting, recrystallization, and the solid state DEA conductivity method with relevant microscopic evaluation. An alternate technique to determine amorphous and crystalline content has been established for the drugs of interest based on an obvious amorphous and crystalline state identified by macro-photomicrography and compared to the conductivity variations. This second 'empirical method' correlates well with the 'activation energy' method. [ABSTRACT FROM AUTHOR]

Abstract: Nylon 13,6 was successfully synthesized and its chemical composition, thermal properties, crystal structure, and moisture absorption characterized. Melting temperature and glass transition temperature were determined to be 206 °C and 60 °C, respectively, while the equilibrium melting temperature was determined to be 248 °C. Characterization of the crystallization kinetics showed that nylon 13,6 exhibits very fast crystallization compared to the industrially important nylons, nylon 6 and nylon 6,6. In addition, the moisture absorption of nylon 13,6 was dramatically lower than nylon 6 and nylon 6,6 which is consistent with the much lower amide content of nylon 13,6. The crystal structure was determined to be different from the expected γ-form, which possess a pseudohexagonal unit cell. Instead, the x-ray scattering pattern was more similar to the α-form. A similar result has been obtained for other odd–even nylons including nylon 5,6, nylon 5,10, nylon 9,2, nylon 11,10, and nylon 11,12. [Copyright &y& Elsevier]

Abstract: We report the visualization of the electrodeposition of chitosan hydrogels and structural characterization of such materials. An electrode embedded microfluidic device is used to visualize the gel deposition process as a distinguishable sol–gel interface separating the clear electrolyte solution region and the orderly textured gel region. The crystalline structure and the nanostructure of the as-deposited gel is characterized with synchrotron X-ray scattering measurements, confirming the semicrystalline nature of the deposited chitosan gels by a neutralization process at the cathode. [Copyright &y& Elsevier]

We present results from molecular dynamics simulations for an all-atoms model of a semicrystalline polyethylene under uniaxial tensile test. Our model has a realistic semicrystalline organization of two high molecular chains which are involved in two crystalline and two amorphous phases. The tie-molecules link these phases. A high content of tie-molecules is compatible with the stability of the semicrystalline organizations in the initial state. The main objective of the study is to check the effect of some molecular parameters, poorly known from experiments, on the mechanical properties under uniaxial tensile test. It is a way to have an insight on the value of the probable molecular parameters. We show that the number of tie-molecules mainly acts on the elastic modulus and the lamellar thickness acts on the yield stress. A nearly constant stress, a plateau, results from the narrow length-distribution of tie-molecules. This plateau is not observed during mechanical experiments. This plateau is the direct result of isomolecular tie-molecules. The only way to predict the progressive increase of the stress up to the yields stress observed experimentally is to consider a large length-distribution of tie-molecules. This progressive increase of stress implies a progressive deformation of the crystalline phase. The basic mechanism of plastic deformation is the pull-out of crystalline chain segments by the tie-molecules in extended conformation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Purpose |!|#8211; The purpose of this paper is to provide a computational procedure for a novel damage-coupled material law for semicrystalline polyethylene. Using a damage mechanics approach, the model seeks to gain insight into the mechanical behaviour of polyethylene considering the microstructure and degradation processes occurring under uniaxial tension. Design/methodology/approach |!|#8211; The material morphology is modelled as a collection of inclusions. Each inclusion consists of crystalline material lying in a thin lamella attached to an amorphous layer. The interface region interconnecting the two phases is the plane through which loads are carried and transferred by the tie molecules. It is assumed that the constitutive model contains complete information about the mechanical behaviour and degradation processes of each constituent. After modelling the two phases independently, the inclusion behaviour is found by applying some compatibility and equilibrium restrictions along the interface plane. Findings |!|#8211; The model provides a rational representation of the damage process of the intermolecular bonds holding crystals and of the tie-molecules connecting neighbouring crystallites. The model is also used to analyze the degree of relationship between some of the material properties and the mechanical responses. Practical implications |!|#8211; In practice, the numerical model clearly helps to understand the influence of the different microstructure properties on the tensile mechanical behaviour of semicrystalline polyethylene |!|#8211; an issue of particular interest in improving material processability and product performance. Originality/value |!|#8211; To the authors|!|#39; knowledge, a phenomenon such as microstructural degradation of polyethylene has not received much attention in the literature. The proposed model successfully captures aspects of the material behaviour considering crystal fragmentation and tie-molecule rupture. [ABSTRACT FROM AUTHOR]

Abstract: Tin dioxide is emerging as an important material for use in copper indium gallium diselenide based solar cells. Amorphous tin dioxide may be used as a glass overlayer for covering the entire device and protecting it against water permeation. Tin dioxide is also a viable semiconductor candidate to replace the wide band gap zinc oxide window layer to improve the long-term device reliability. The film properties required by these two applications are different. Amorphous films have superior water permeation resistance while polycrystalline films generally have better charge carrier transport properties. Thus, it is important to understand how to tune the structure of tin dioxide films between amorphous and polycrystalline. Using X-ray diffraction (XRD) and Hall-effect measurements, we have studied the structure and electrical properties of tin dioxide films deposited by magnetron sputtering as a function of deposition temperature, sputtering power, feed gas composition and film thickness. Films deposited at room temperature are semicrystalline with nanometer size SnO2 crystals embedded in an amorphous matrix. Film crystallinity increases with deposition temperature. When the films are crystalline, the X-ray diffraction intensity pattern is different than that of the powder diffraction pattern indicating that the films are textured with (101) and (211) directions oriented parallel to the surface normal. This texturing is observed on a variety of substrates including soda–lime glass (SLG), Mo-coated soda–lime glass and (100) silicon. Addition of oxygen to the sputtering gas, argon, increases the crystallinity and changes the orientation of the tin dioxide grains: (110) XRD intensity increases relative to the (101) and (211) diffraction peaks and this effect is observed both on Mo-coated SLG and (100) silicon wafers. Films with resistivities ranging between 8mΩ cm and 800mΩ cm could be deposited. The films are n-type with carrier concentrations in the 3×1018 cm−3 to 3×1020 cm−3 range. Carrier concentration decreases when the oxygen concentration in the feed gas is above 5%. Electron mobilities range from 1 to 7cm2/Vs and increase with increasing film thickness, oxygen addition to the feed gas and film crystallinity. Electron mobilities in the 1–3cm2/Vs range can be obtained even in semicrystalline films. Initial deposition rates range from 4nm/min at low sputtering power to 11nm/min at higher powers. However, deposition rate decreases with deposition time by as much as 30%. [Copyright &y& Elsevier]

The low and the high molecular weight poly(perfluoro-2-methylene-1,3-dioxolane)s were prepared using perfluorobenzoyl peroxide as a free radical initiator. Both polymers obtained were semicrystalline and insoluble in organic solvents. The glass transition temperatures ( Tg) of polymers obtained were 94-106°C, and their melting points were 224-229°C. Wide-angle X-ray diffraction measurements showed that polymers as prepared are semi-crystalline (21% crystalline fraction) and the crystallinity increased to 47% after annealing at 170°C. However, the films prepared by heating (at 230-250°C) and pressing of the high molecular weight polymers are transparent and flexible. The refractive index of the film is 1.3320 and 1.3245 at 533 and 1546 nm, respectively. The transparent polymer films did not recrystallize while annealing below Tg, and they are chemically and thermally stable. This polymer may have potential applications in optoelectronic fields. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Polymerized n-octadecylsiloxane (PODS) was prepared by coating glass substrates with liquid ocatdecyltrichlorosilane (OTS) followed by dipping-in a solvent. The morphology control of PODS was investigated by the post curing temperature as well as the use of different solvents. The resulting substrates were characterized by scanning electron microscopy (SEM), contact angle measurements, and wide angle X-ray diffractometry (XRD). It is shown that both post curing temperature and extracting solvents affect the morphology of PODS. The temperature dependent morphology was investigated and is ascribed to the physiochemical properties of PODS. For the solvent-dependent morphology, it is proposed that the solvation capability of a solvent to OTS and the presence of a hydrophilic/hydrophobic interface are critical in the PODS morphology. This paper shows the controlling parameter and possible explanation in the crystallinity and wettability of PODS films, which may be useful to other silane-based systems. [Copyright &y& Elsevier]

Abstract: Dynamic mechanical analysis (DMA) was applied to investigate the correlation between dynamic mechanical behaviors of regenerated silk fibroin (RSF) and its structural transition which was characterized by near-infrared (NIR) spectroscopy. The tan δ peak split of DMA demonstrated that the apparent glass transition of amorphous RSF film (at around 177°C) was the contribution of both uncrystallizable and crystallizable segments through homogeneous amide–amide hydrogen bonds, which were gradually separated from each other and produced disordered and β-sheet domains during ethanol treatment. Furthermore, DMA was also applied as “thermal fingerprint” to investigate water effect on the disordered domains of silk fibroin. The results showed that glass transition temperature of permanently disordered domains in crystallized RSF films was increased from 155°C to 190°C after thermal dehydration, and even approached 205°C for stretched RSF films. [ABSTRACT FROM AUTHOR]

Abstract: We have previously shown that most small-angle scattering (SAS) patterns from a range of polymer fibers can be best fit using elliptical coordinates, where the minor axis of the ellipse is parallel to the fiber axis. Analysis of small-angle X-ray scattering patterns obtained during elongation of poly(ethylene-co-1-octene) films now shows that elliptical coordinates also provide a natural way to fit four-point radiating-out patterns, also called “butterfly” or “eyebrow” patterns. To fit this type of pattern the minor axis of the ellipse is tilted away from the fiber draw direction by some angle α, and as the films have rotational symmetry, the pattern is fitted with the sum of two ellipses, at +α and −α. As a result, the reflections appear to fall on a hyperbolic arc – the butterfly pattern. The Matlab code to carry out this analysis on full 2D data is available on request. The elliptical analysis is primarily an empirical fit, much strengthened by its ability to be applied to all observed types of SAS patterns and by its relevance to the mechanical behavior of polymers. [Copyright &y& Elsevier]

Abstract: The successful application of zeolite A membranes in the industrial market has thus far been restricted to the pervaporative dehydration of solvent streams in the pharmaceutical and engineering industries. Their application in gas separation processes remains elusive, largely due to the existence of uncontrollable, intercrystalline diffusion pathways in the boundary regions of neighbouring crystals. In this study the gas permeation characteristics of an unconventional, semicrystalline (70%) zeolite NaA layer, where the boundary phase is filled with amorphous aluminosilicate, was examined and compared to a traditional polycrystalline membrane. To this end, we used single gas permeation of H2, N2 and SF6 at two temperatures. In general, the permeances of all gases through the conventional layer increased in response to temperature, indicating a governing contribution of activated (gaseous) diffusion over the temperature interval tested. Typical permeances of H2 were in the order of 4.8×10−7 (23°C) to 6.5×10−7 molm−2 s−1 Pa−1 (107°C). For the semicrystalline layer, the same trends were observed for N2 and SF6, while the permeance of H2 decreased from 8.7×10−7 (23°C) to about 3.9×10−7 molm−2 s−1 Pa−1 at 107°C. This was attributed to the expansion of the crystal/amorphous interface at higher temperature. By comparing the permselectivity values with the respective Knudsen factors, it was shown that diffusion through the semicrystalline layer, at lower temperature, was predominantly based on molecular sieving (PS H2/SF6 =63.8), which yielded higher selectivities than the traditional membrane under the same conditions (PS H2/SF6 =11.4). However, at higher temperature the H2/SF6 permselectivity of the crystalline layer (5.7) was somewhat higher than that of the semicrystalline membrane (5.2). Based on theoretical considerations, it was concluded that the crystal/amorphous interface in the semicrystalline membrane constituted a denser closure of the boundary interface, which could be attributed to a lower charge barrier presented by the amorphous phase (Si/Al>1), but this integrity was lost at higher temperature due to the thermal instability of the amorphous material. The results therefore suggested that future research should focus on lowering the intercrystalline charge barrier during synthesis, which could reduce the intercrystalline porosity and improve the gas separation properties of NaA membranes in general. [Copyright &y& Elsevier]

A cis-poly(phenylene vinylene) (cis-PPV) recently synthesized by Katayama, Ozawa, and coworkers undergoes photo-isomerizatian into trans configuration. This isomerization occurred rather quickly within 45 min in solvent-cast films at room temperature. The cis-PPV chains exhibiting this quick isomerization were expected to be highly mobile in the bulk state, and this expectation was examined from thermal, structural, and viscoelastic tests for a cis-PPV sample with Mn = 4300 and Mw/Mn = 2.16. It turned out that the as-polymerized cis-PPV was partially crystalline and fully melted at Tm≅109°C. The samples quenched from a molten state to lower temperatures (≤ 70°C < Tm) as well as cast from a solution were amorphous for few hours, enabling the viscoelastic test in the fully amorphous state. The WLF-type time-temperature superposition was valid for these quenched and/or cost sample, confirming the amorphous character of the cis-PPV chains therein. The terminal viscoelastic relaxation time of these chains, equivalent to a time required for thermal changes in a large-scale conformation, was ≅10 s at room temperature. This result suggested that the conformational changes of the amorphous chains (the major component in the cast films) were sufficiently fast to allow the efficient cis-to-trans photo-isomerization. [ABSTRACT FROM AUTHOR]

The synthesis of ternary semicrystalline poly(a-methylstyrene- b -isobutylene- b -pivalolactone) poly(aMeSt- b -IB- b -PVL) linear triblock copolymers has been accomplished for the first time, taking advantage of living cationic sequential block copolymerization and site-transformation technique from living cationic to anionic ring-opening polymerization (AROP). Poly(aMeSt- b -IB) diblock copolymer with ?-methoxycarbonyl group was successfully prepared by sequential addition of IB to living PaMeSt chain ends modified with p -chloro-a-methylstyrene, followed by capping with 1,1-diphenylethylene and in-situ quenching with 1-methoxy-1-trimethylsiloxy-propene. The poly(aMeSt- b -IB) diblock macroinitiator, prepared by subsequent hydrolysis of ?-methoxycarbonyl group, initiated AROP of PVL in conjunction with 18-crown-6 in THF at 60°C. Characterization by 1 H NMR spectroscopy and DSC confirmed that poly(aMeSt- b -IB- b -PVL) copolymers consisted of three microphases, low glass transition (T g ?=?-66°C) rubbery PIB, amorphous glassy PaMeSt, and high melting (T m ?=?232~235°C) PPVL with 72~92% of crystallinity normalized for the content of PPVL. [ABSTRACT FROM AUTHOR]