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The bidentate ligand, 1,4-bis(diphenlyphosphoryl)butane (dppbO2), was used to prepare a 1D polymeric Pr(III) complex which was characterised by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Rudolph A. Marcus (b. 1923) Canadian-born American theoretical chemist has had a distinguished career. The period of 1956 to 1965 stands out when at Brooklyn Polytechnic he created his theory of electron transfer reactions in chemical systems. At the time, Brooklyn Polytechnic had a concentration of pioneers in polymer science and in crystallography. Marcus then moved to the University of Illinois at Urbana, and finally to the California Institute of Technology in 1978 where he has stayed ever since. His theoretical contribution was awarded the Nobel Prize in Chemistry in 1992. [ABSTRACT FROM AUTHOR]

In this study, we aim to improve our understanding of the doping mechanism involved in the polymer poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b′)dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno [3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-c) doped with tris[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] [Mo(tfd-COCF3)3]. We follow the evolution of the hole density with dopant concentration to highlight the limits of organic semiconductor doping. To enable the use of doping to enhance the performance of organic electronic devices, doping efficiency must be understood and improved. We report here a study using complementary optical and electrical characterization techniques, which sheds some light on the origin of this limited doping efficiency at a high dopant concentration. Two doping mechanisms are considered, the direct charge transfer and the charge transfer complex. We discuss the validity of the model involved as well as its impact on the doping efficiency. [ABSTRACT FROM AUTHOR]

Particle size polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased polydispersity fractionate on the basis of particle size and a bimodal subpopulation favors the formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms. [ABSTRACT FROM AUTHOR]

The phase-field method has been developed to simulate the shish-kebab crystal growth in polymer crystallization by introducing the oriented nucleus. With the help of this developed phase-field model, the role of oriented nucleus in polymer shish-kebab crystal growth has been investigated. It appears that the growth mechanisms of shish-kebab crystal on a preformed oriented nucleus may be attributed to epitaxial growth and lattice match. First the oriented nucleus (early shish) further grows into stable shish entity through epitaxial growth, and then lattice match supplies the sites for kebabs and epitaxial lateral growth from these sites forms the kebabs. It also has been verified that kebabs can be grown on oriented nucleus in the total absence of any flow. Therefore, with regard to flow induced shish-kebab crystal, the oriented nucleus plays a major role in the growth of shish-kebab morphology and the flow mainly helps to generate the oriented nucleus. Besides, when the nucleus possesses a rod-like profile, the kebabs are generally parallel and equidistantly distributed, and the well-defined interval between adjacent kebabs is strongly influenced by the orientation angle of the rod-like nucleus. On the other hand, when the nucleus is slightly curved and presents a thread-like profile, the distribution of kebabs on the shish is no longer equidistant and the influence of orientation angle on the kebab density becomes weak. [ABSTRACT FROM AUTHOR]

Abstract A novel potassium complex, [K 2 L 2 (H 2 O)MeOH] n (1), was prepared by reacting KOH and a substituted tetrazolyl ligand L H ( L H = 1-[5-(2-hydroxyphenyl)-2H-tetrazol-2-yl]-2-methyl-2-propanol). The prepared complex was characterized by infrared spectroscopy and mass analysis and its solid-state structure was determined to be a high dimensional coordination polymer by X-ray crystallography. The synthesized potassium coordination polymer 1 was used as a catalyst for the cycloaddition of CO 2 to propylene oxide and is the first potassium coordination polymer to be used for this purpose. The prepared catalyst provided high selectivity toward cyclic propylene carbonate (>99%) and showed considerable activity despite the heterogeneous reaction condition. Highlights • The new potassium coordination polymer containing substituted tetrazolyl ligand. • The formation of two dimensional coordination polymer consisted of a tetra-potassium rhombus-shape basic unit. • Usage of potassium coordination polymer as a catalyst in cycloaddition of carbon dioxide. [ABSTRACT FROM AUTHOR]

The 1H–29Si multiple‐contact cross polarization (MC‐CP) MAS NMR experiment is evaluated for the class of silicate‐siloxane copolymers called POSiSils, that is, polyoligosiloxysilicones. It proves a reasonably good solution to tackle the challenge of recording quantitative 29Si NMR data in experimental time much reduced compared with single pulse acquisition. In a second time, we report 29Si–29Si MC‐CP double‐quantum single‐quantum (MC‐CP‐DQ‐SQ) NMR experiment, which provides information about the through‐space proximities between all silicon species despite the high degree of heterogeneity of this material. This work furthers the NMR tools for NMR crystallography for inorganic polymers, as it covers flexible polymers with different dimensionalities and long or heterogeneous relaxation characteristics at low 29Si natural abundance. [ABSTRACT FROM AUTHOR]

Blend based polymer nanocomposites, comprising Janus nanoparticles at their polymer/polymer interface, were analytically/experimentally evaluated. The modeling procedure was performed in two stages: first, modeling of polymer/polymer interface region comprising Janus nanoparticles and second, modeling of the entire systems as a function of the variation of the blend morphology. In the first stage, the modeling procedure was performed based on the development of the model proposed by Ji et al. and in the second stage, the fundamental of Kolarik's model was used in order to propose a developed and more practical model. It was shown that Janus nanoparticles may form dual polymer/particle interphase at polymer/polymer interface which can drastically affect the final mechanical properties of the system. Comparing the results of tensile tests imposed on different prepared samples with the predictions of the model proved its accuracy and reliability (error < 9%). [ABSTRACT FROM AUTHOR]

The 2 D assembly of polymers to form free‐standing and large crystalline films is quite appealing but very challenging. Although there have been some works using interface templates, reports of in situ assembly in solution are still rare. Herein, a simple strategy is developed for the creation of a free‐standing and centimeter‐sized 2 D crystalline polymer film through crystallization of an amphiphilic brush polydiacetylene (PDA) in solution. The film exhibits good shape memory, a low dielectric constant, and good carrier mobility. This strategy may be applied extensively to produce a variety of other macroscopic 2 D crystalline polymer films for applications in electronics, catalysis, and so on. Crystallizing polymers: An amphiphilic brush polydiacetylene is crystallized in solution, yielding a free‐standing and centimeter‐sized 2 D crystalline polymer film (see figure), which exhibits good flexibility, shape‐memory properties, an ultra‐low dielectric constant, and good carrier mobility. [ABSTRACT FROM AUTHOR]

Recently ternary polymer solar cells (PSCs) have shown big potential to enhance the photovoltaic performance, however, the relevant systematic studies based on thick-film active layers are extremely scarce and have not been well elucidated. Herein, as-cast 1D/2A thick-film ternary active layers based on highly crystalline polymer PBODT as the donor and PC 71 BM plus non-fullerene ITIC as the acceptors were investigated, with full comparison to PBODT:PC 71 BM and PBODT:ITIC blends, the two binary systems. It was found that PBODT:ITIC binary PSCs showed very poor thickness tolerance, whose power conversion efficiencies (PCEs) dropped sharply from 6.45% for 100 nm thick active layer to 4.44% and 2.58% for 200 and 300 nm thick active layers, respectively. Relatively, PBODT:PC 71 BM binary PSCs could display much better thick-film performances, with a 5.14% PCE at 110 nm and a maximum PCE of 7.55% at 300 nm. For the as-cast PBODT:PC 71 BM:ITIC (1:1.2:0.3 by weight) ternary PSCs, the PCE for 300 nm thick active layer could be further elevated to 8.42%. Interestingly, notable thickness tolerance was also achieved for the ternary PSCs, whose PCEs ≥7.22% could be maintained for thickness range from 110 to 520 nm. Based on AFM and TEM analyses, the PBODT:PC 71 BM:ITIC ternary blend film could show good surface and bulk-heterojunction morphologies. Relative to the two binary active layers, the ternary active layer could contribute higher short-circuit current due to improved photo-response and suppressed carrier recombination. Furthermore, the thermal stability of the as-cast ternary solar cells was quite better than those of binary solar cells. The simultaneous improvements of efficiency, thickness tolerance, and thermal stability via ternary blends in this work suggest that ternary polymer solar cells would be very promising in future. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study is to investigate the possibility of enhancing mechanical properties of poly(lactic acid) (PLA) samples processed by a rapid manufacturing (RM) technique by increasing PLA crystallinity degree via thermal annealing. The samples are manufactured by fused deposition modeling (FDM) at different temperatures and subsequently evaluated by three‐point bending flexural and tensile tests. The polymer processed at 215 °C is thermally annealed over its glass transition temperature in order to increase the degree of crystallinity to the maximum attainable level as measured by the differential scanning calorimetry and confirmed by X‐ray diffraction. The increase in the degree of crystallinity of FDM‐PLA enhances flexural stress of the samples by 11–17%. The study also demonstrates applicability of radiation sterilization for FDM‐PLA parts. Therefore, thermal annealing might be introduced into a standard RM technology of PLA, particularly for sterilizable customized implants, to efficiently improve their mechanical properties. [ABSTRACT FROM AUTHOR]

Ease of heat sealing and oligomer/additive migration are two important and often interrelated phenomena that affect the engineering performance of high clarity polypropylene random copolymer (RCP) films. From a fundamental standpoint, this work investigates the non‐standard microstructural aspects that play a critical role in the heat sealing process of semicrystalline polymer films. Two different propylene–ethylene copolymers having widely different seal initiation temperatures (SITs) but similar melting points were chosen for this study. The contribution of both the amorphous phase and the crystalline phase to heat sealing was investigated utilizing dynamic mechanical analysis and thermal fractionation differential scanning calorimetry, respectively. Results indicate that the melting distribution of the thermally fractionated material plays a critical role in determining SIT while the effect of the mobility of the amorphous phase was found to be insignificant. In order to deeply understand the molecular origin of this difference in melting distribution or lamellar thickness distribution, the composition distribution of the co‐monomer was measured using Gel Permeation Chromatography‐Infra‐Red (GPC‐IR) and found to be fundamentally different. In addition, this work systematically studies the effect of oligomer/additive migration on optics, co‐efficient of friction (CoF), and most importantly heat sealing behavior. Migration is found to dramatically increase the SIT and haze while decrease the CoF of PP RCP films. POLYM. ENG. SCI., 58:1479–1484, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A novel comb-like copolymer with carboxyl group as an anchoring group and polycaprolactone as a solvent chain was first used as the dispersant of CaCO3 particles in polypropylene (PP). The dispersion of CaCO3 particles in PP matrix was significantly improved in the presence of comb-like copolymer dispersant because of the strong repulsive force caused by steric hindrance effect. The influences of the coating amount of comb-like copolymer dispersant on crystallization behaviors, mechanical properties, and thermal stabilities were systematically investigated. The crystallization temperature, crystallinity, and crystallization rate of PP/CaCO3 composites prepared with monolayer-coated CaCO3 were all improved, where the monolayer comb-like copolymer coating remained as a rigid layer and provided a noticeable nucleating effect. The PP/CaCO3 composites coated with monolayer SP comb-like copolymer also had the best mechanical properties, including tensile strength, Young’s modulus, flexural modulus, and impact strength because of the good dispersion of CaCO3 particles in PP matrix. The thermal stability of PP/CaCO3 composites were measured by thermogravimetric analysis. The results showed that SP comb-like copolymer dispersant treated CaCO3 filled composites had excellent thermal stability than untreated and neat PP, especially for the composite prepared with monolayer-coated CaCO3. [ABSTRACT FROM AUTHOR]

Abstract: Processing solvent additives in polymer:fullerene bulk heterojunction systems are known as a promising method to enhance photovoltaic performance. It is generally agreed that solvent additives enable polymers to have a high degree of molecular order which increases the device performance. However, the understanding of the efficiency enhancement is not complete. There is a lack of insight regarding the quantitative determination of the molecular miscibility between polymer and fullerene as well as the inner morphology changes induced by the additives. In this work, understanding of the influence of the solvent additive 1,8‐octanedithiol (ODT) is provided on the classic system poly(3‐hexylthiophene‐2,5‐diyl):[6,6]‐phenyl‐C61 butyric acid methyl ester (P3HT:PCBM) films. The impact on polymer crystallinity, surface structure, inner morphology, and quantitative molecular miscibility of P3HT and PCBM is studied as a function of ODT volume concentration. The crystallinity is probed with absorption spectroscopy and grazing incidence wide‐angle X‐ray scattering. The morphology and miscibility are characterized via atomic force microscopy and time‐of‐flight grazing incidence small angle neutron scattering. Besides an increased crystallinity and prominent phase separation, ODT increases the solubility of PCBM in P3HT and reduces the size of amorphous P3HT domains. Moreover, solvent processing with a high ODT concentration alters the vertical material composition of the active layer. [ABSTRACT FROM AUTHOR]

Polymer-urea inclusion compounds (P-U-ICs) were formed using a series of linear aliphatic polyesters with varying crystallizabilities: from highly crystalline to wholly amorphous. The traditional hexagonal P-U-ICs were obtained irrespective of the crystallinities of the neat guest polyesters. Two distinct co-crystallization mechanisms were evident based on the observation of the change in thermal stabilities of the ICs using DSC and the crystal morphologies by SEM; one involves polymer chain folding back and forth in a lamella-like crystal structure and the other grows much like short chain molecule U-ICs absent of chain reentering different channels. For polymers with sufficient chain length, their inherent flexibility is the key factor determining the co-crystallization mechanism while their crystallizability affects the kinetics, the consequences of which are more pronounced during recrystallization from melt. The amorphicity induced by random ester group placement is an interchain property, which does not play a role in affecting IC thermal stability. Rather, increasing the average ester group content can be understood as introducing more defects in the IC crystal and therefore reduces its thermal stability. The understanding gleaned in this study provides a new avenue for designing P-U-ICs to be used in both theoretical modeling and engineering of high-performance materials. [ABSTRACT FROM AUTHOR]

The linear stability analysis is carried out for the straight jet of a polymer melt in an electrospinning process. The stability of axisymmetric disturbances is examined in order to comprehend the onset of fiber morphology with diametric variations or bead formation along the fiber under non-isothermal electrospinning conditions. As the polymeric fluid (polylactic acid melt) is a low conductivity fluid with unentangled polymer molecules, the viscoelasticity is described using the non-linear rheological Giesekus constitutive model assuming very small axial conduction current. The non-periodic axisymmetric disturbances are imposed on the non-uniform radius jet, obtained as the solution of the 1-D slender filament governing equations and the eigenspectrum for the disturbance growth rate is constructed under the realistic melt electrospinning conditions. The growth rate corresponding to the leading mode in the eigenspectrum is found to increase with increasing surface tension forces and decrease with the enhanced external electric field. Thus, the leading growth rate behavior suggests that the classical Rayleigh–Plateau instability dominates over the conducting mode of instability for melt electrospinning. Further, the role of non-isothermal conditions in the stability behavior is examined. The convective heat transfer from electrified jet to the cooling ambiance leads to thicker fibers with greater stability to axisymmetric disturbances. The stabilizing effect of heat transfer is attributed mainly to the temperature sensitive fluid rheology. In particular, the enhancement in polymer viscosity in the jet propagation direction is responsible for the build up of stabilizing viscoelastic stress. The fluid elasticity, denoted by the flow Deborah number, also tends to stabilize the electrified jet as temperature drop along the flow increases the relaxation time of the polymer chains leading to high polymeric stress associated with the stretched chains. As crystallization of polymeric chains under non-isothermal condition is not considered, the analysis holds for either amorphous polymers or polymers with slow crystallization kinetics compared to the short residence time during the spinning flow. [ABSTRACT FROM AUTHOR]

In order to modify the brittleness of poly(lactic acid) (PLA), a series of PLA/poly(ethylene glycol) (PEG) blends were prepared by the solution‐cast technique using PEG as a plasticizer. The thermal, crystallization, mechanical, and hydrophilic properties of the PLA/PEG blends were compared with those of neat PLA. It is concluded that the PLA/PEG blends change from miscible to partially miscible at the critical PEG content of 10 wt%. Above 10 wt% PEG content, the miscible PLA/PEG blends occur the phase separation, and the PEG component does not co‐crystallize with PLA component with PLA and PEG crystallizing separately. The introduction of PEG reduces the intermolecular force and enhances the mobility of PLA chains, thus improving the crystallization capacity and flexibility of PLA. The PLA/PEG blends show plastic fracture behavior, yielding higher elongation and lower modulus values compared with neat PLA. Below 30 wt% PEG content, blending with PEG significantly decreases the modulus and yield stress and increases the fracture strain of PLA with an increase in the PEG content. Whereas above 30 wt% PEG content, the crystallization of PEG component results in an increase in modulus and a corresponding decrease in elongation at break of the blends. The thermal degradation temperature is in the range of 320–330°C for PLA/PEG blends, in comparison with 375°C for neat PLA. At ambient temperature, the desired mechanical properties are achieved by blending PLA with 30 wt% PEG. The PEG plasticizer is compatible with the PLA matrix and has a relatively low migration rate toward the blend surfaces with a low PEG content (≤30 wt%). J. VINYL ADDIT. TECHNOL., 24:E154–E163, 2018. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

It was the aim of this study to elucidate the impact of the injection mold temperature upon the polymer crystallinity, its microstructure and the resulting drug release from immediate and sustained release tablets containing semi-crystalline polymers. The immediate release formulation contained 20% (w/w) ketoprofen (KETO) in poly (ethylene oxide) (PEO) and the sustained release formulation contained 20–40% (w/w) metoprolol tartrate (MPT) in polycaprolactone (PCL). Physical mixtures of drug-polymer were characterized via isothermal crystallization experiments using DSC and rheological measurements to elucidate the impact of the drug solid-state upon the crystallization kinetics. Tablets were prepared using various thermal histories (extrusion barrel temperature and injection mold temperatures). Polymer crystallinity and microstructure in the tablets was characterized via DSC and polarized optical microscopy. The polymer microstructure was altered by the various applied thermal histories. The differences in PEO crystallinity induced by the various mold temperatures did not affect the KETO dissolution from the tablets. On the other hand, MPT (20–40% w/w) dissolution from the PCL matrix when extruded at 80 °C and injection molded at 25 and 35 °C was significantly different due to the changes in the polymer microstructure. More perfect polymer crystals are obtained with higher mold temperatures, decreasing the drug diffusion rate through the PCL matrix. The results presented in this study imply that the injection mold temperature should be carefully controlled for sustained release formulations containing hydrophobic semi-crystalline polymers. [ABSTRACT FROM AUTHOR]

Position-resolved microstructure in a single spherulite of iPP is quantitatively studied by synchrotron microfocus wide angle X-ray scattering. The results show that the normal of mother lamellae in a spherulite is aligned mainly perpendicular to the radius, and the subsidiary daughter lamellae are inclined 80.75° with respect to that of the dominant mother lamellae. The crystallinity in the spherulite is in the range of 46%–56%, which is rarely influenced by the crystallization temperature. The ratio between the daughter lamellae and the mother lamellae is 0.18 when iPP crystallizes at 138 °C and it decreases to 0.11 as the crystallization temperature is decreased to 130 °C. The b- axis and c - axis in the mother lamellae tend to orient perpendicular to the radius direction, and the a -axis prefers to align in the radius direction. [ABSTRACT FROM AUTHOR]

Flow-induced crystallization (FIC) is a dominant mechanism of polymer self-assembly, but the process is poorly understood at high supercooling and under fast cooling conditions because of structural rearrangements that occur during slow heating and cooling conditions typically used for investigation. Incorporating fast-scanning chip calorimetry techniques, the influence that specific amounts of shear flow have on the subsequent crystallization of polyamide 66 over a wide range of temperatures, 85-240 °C, is determined. At high temperatures, heterogeneous nucleation dominates and crystallization rate increases with increasing shear. Low-temperature crystallization, driven by homogeneous nucleation, is not influenced by previous shear flow, but sheared samples are able to crystallize via the heterogeneous nucleation route at temperatures 15 K lower than unsheared materials. The magnitude of previous shear flow also dictates α-/γ-crystalline phase development and crystallization during cooling at rates below 200 K/s. This approach provides a route to develop important thermodynamic and kinetic insights that describe the crystallization behavior of many important polymers to enable the advanced engineering of polymer processing and injection molding applications, where practical cooling rates typically range between 10 K/s and 1000 K/s. [ABSTRACT FROM AUTHOR]

This article reviews the application of the "Food Polymer Science" approach to the practice of industrial R&D, leading to patent estates based on fundamental starch science and technology. The areas of patents and patented technologies reviewed here include: (a) soft-from-the-freezer ice creams and freezer-storage-stable frozen bread dough products, based on "cryostabilization technology" of frozen foods, utilizing commercial starch hydrolysis products (SHPs); (b) glassy-matrix encapsulation technology for flavors and other volatiles, based on structure-function relationships for commercial SHPs; [ABSTRACT FROM AUTHOR]

This study investigates the polymorphous transformation of microcrystalline cellulose at different NaOH concentrations and the nonisothermal crystallization kinetics of polypropylene/microcrystalline cellulose (II) composites by differential scanning calorimetric technique (DSC) with various cooling rates. The synchrotron X‐ray diffraction reveals that the polymorphous transition from cellulose (I) to cellulose (II) begins at NaOH concentration of 10 (wt%) and the complete transformation is obtained at the NaOH concentration of 15–20 (wt%) during the mercerization process. The Avrami equation was applied to depict the nonisothermal crystallization process and to analyze the experimental data of the composites. The DSC results show that the values of t1/2 for iPP/MCC (II) composites are lower than that for pure iPP. The polarized optical microscopy images reveal that the peculiar hybrid shish–calabash structure (HSC) with MCC (II) fibers serving as shish and iPP spherulites as calabash finally be formed. POLYM. COMPOS., 39:1064–1075, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Short ramie/poly(lactic acid) (PLA) composites were prepared by using extrusion and injection moulding method. The water absorption and hygrothermal aging behaviors of ramie/PLA composites at 60°C was analyzed. The water absorption and mechanical properties of the ramie/PLA composites with immersion time were reported and compared to those of neat PLA. Crystallinity and molecular weight of neat PLA and ramie/PLA composites were determined by differential scanning calorimetry and gel permeation chromatography, respectively. The results showed that the water absorption and mechanical properties was affected by the short ramie fiber. Ramie/PLA composites showed higher saturation weight gains and diffusion coefficients than that of neat PLA, which indicated that the addition of short ramie fiber induced higher water absorption caused by the hydrophilic nature of the fibers. Tensile strength and flexural strength severely decreased after aging. Moreover, it was found that PLA was severely degraded in hygrothermal environment, and ramie accelerated the degradation of PLA. The morphologies of fractured surfaces of neat PLA and ramie/PLA composites with different immersion time were observed by scanning electronic microscopy. The micro‐cracks and voids were found which was due to the degradation of PLA and debonding of ramie and PLA. POLYM. COMPOS., 39:1098–1104, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Galactomannan, a water-soluble heteropolysaccharide was isolated and purified from seed of fenugreek locally called as Kasuri Methi. Polysaccharide was chemically characterized and its functional attributes were studied in detail. FTIR analysis divulges representative peaks of polysaccharide in region of 3324, 2914 & 1653 cm −1 . Galactomannan depicted lower water holding capacity compared to guar gum. Emulsifying activity and emulsion stability of biopolymer was on higher side as compare to reference material. Oil-holding capacity, foaming capacity, swelling index and foaming stability of galactomannan were 626.46%, 25.5%, 86%, 18.55 respectively which were higher than reference gums. Thermal analysis revealed a melting range of 66–139 °C and degradation temperature of 296.45 °C. XRD depicted a large degree of crystallinity in galactomannan. SEM imaging depicted a glittering surface which is suitable for film making. EDS spectroscopy depicted that element was not uniformly distributed in biopolymer. [ABSTRACT FROM AUTHOR]

In this study, as cast (AC, at 30 °C) and annealed (AN, at 130 °C, 3 h) samples of polyvinylidene fluoride (PVDF) and PVDF/hyperbranched polyester (HBP) (90/10) blend ultrathin films were subjected to heating-cooling (30 → 210 → 30 °C) cycle, and studied for their changes in crystalline phase transition behavior using in-situ Fourier transform infrared-transmission spectroscopy (FTIR-TS) and grazing incident reflection absorption spectroscopy (FTIR-GIRAS) techniques. Factor analysis was employed to extract the pure crystalline and amorphous spectra as well as the percentage content of ferroelectric crystallinity for both the samples. Irrespective of the thermal treatment (AC or AN) and spectral measurement (FTIR-TS or GIRAS) techniques, neat PVDF sample exhibited irreversible phase transitions during heating-cooling cycle associated with the transformation from ordered β -crystalline (1276 cm −1 ) into disordered amorphous (1234 cm −1 ) form. Interestingly, annealed PVDF/HBP blend sample measured using FTIR-GIRAS exhibited reversible crystalline phase transition behavior similar to a ‘dipole memory effect’ even after heating to 210 °C (> T m ) and then cooled to 30 °C. Compared to neat PVDF, higher ferroelectric crystallinity and reversible phase transition in PVDF/HBP blend may be attributed to (i) the existence of H-bonding between HBP (C O and OH groups) and PVDF ( CH 2 and CF 2 ) and/or (ii) HBP acting as a nanoparticle in PVDF matrix. [ABSTRACT FROM AUTHOR]

This article describes ccCluster, a software providing an intuitive graphical user interface (GUI) and multiple functions to perform hierarchical cluster analysis on multiple crystallographic datasets. The program makes it easier for users to choose, in the case of multi-crystal data collection, those datasets that will be merged together to give good final statistics. It provides a simple GUI to analyse the dendrogram and various options for automated clustering and data merging. [ABSTRACT FROM AUTHOR]

One new 3D Zn(II) coordination polymer based on H 2 L (H 2 L = 4-[(8-hydroxy-5-quinolinyl)azo]-benzenesulfonic acid), [ZnL(H 2 O)]n ( 1 ), has been synthesized. This compound displays an amazing (3, 6)-connected topological net. Compound 1 is the first example of azo coordination compound co-sensitized TiO 2 photoanode with N719. In the tandem structure of compound 1 /N719/TiO 2 , compound 1 forms a re-organization of energy level due to its single-crystal structure, which is advantageous the improving of photoelectric conversion efficiency. The result demonstrates the compound 1 /N719/TiO 2 solar cell exhibited excellent photovoltaic performance with the photoelectric conversion efficiency of 8.2% under standard global AM 1.5 solar irradiation conditions. Fluorescent property and electrochemical property of compound 1 were performed. [ABSTRACT FROM AUTHOR]

Growth by oriented assembly of nanoparticles is a widely reported phenomenon for many crystal systems. While often deduced through morphological analyses, direct evidence for this assembly behavior is limited and, in the calcium carbonate (CaCO3) system, has recently been disputed. However, in the absence of a particle-based pathway, the mechanism responsible for the creation of the striking morphologies that appear to consist of subparticles is unclear. Therefore, in situ atomic force microscopy is used to investigate the growth of calcite crystals in solutions containing a polymer additive known for its ability to generate crystal morphologies associated with mesocrystal formation. It is shown that classical growth processes that begin with impurity pinning of atomic steps, leading to stabilization of new step directions, creation of pseudo-facets, and extreme surface roughening, can produce a microscale morphology previously attributed to nonclassical processes of crystal growth by particle assembly. [ABSTRACT FROM AUTHOR]

In natural gas sweetening, gas dehydration with glycols is typically carried out upstream of membrane separation of carbon dioxide. This means that when process upsets occur, these glycols can reach the membrane unit. In this work, we study the impact of two common glycols (monoethylene glycol and triethylene glycol) on the gas transport performance of cellulose triacetate membranes. We find that the glycol absorbed into the membrane initially obstructs the permeation of CH 4 and CO 2, due to pore filling or antiplasticisation effects, but the permeability then increases again, indicative of polymer relaxation and a loss of crystallinity in the polymer. The smaller helium molecule is significantly less affected by the presence of the glycols, possibly because its lower solubility within glycol limits its movement through the swollen structure. However, after removing the glycols with a methanol wash, the membrane performance recovers with only a slight residual plasticisation observed. In addition, the permeation of H 2 S, a common contaminant within natural gas streams, was studied across a range of temperatures. At the partial pressures studied (up to 0.75 kPa), H 2 S had very little effect on the membrane performance even in long-term exposure for up to 300 days. [ABSTRACT FROM AUTHOR]

Here, the fabrication of unimolecular micelles functionalized with helical polymeric chains as a chiral nucleating agent in enantioselective crystallization is reported. Starting from a fractionated hyperbranched polyester (Boltorn H30), the ring-opening polymerization of l-lactic acid (LLA) and subsequent terminal-group modification affords the alkyne-Pd(II)-anchored hyperbranched macroinitiator (H30-PLLA-Pd). By taking advantage of a Pd(II)-catalyzed living polymerization of chiral pendant modified l- or d-phenyl isocyanide (PI) monomers, well-defined chiral unimolecular micelles (H30-PLLA-PPI) grafted with radiating helical PPI coronas of one predominant screw sense are obtained. The resultant chiral materials demonstrate excellent application in the enantioselective crystallization of racemic threonine in water, and a 92% enantiomeric excess value of the residual solution is obtained. It is believed this present proof of concept and methodology are facile and powerful for preparing novel and versatile chiral materials with different topological structures, not only applicable to PPI but also to other types of polymers. [ABSTRACT FROM AUTHOR]

Mixtures of ultrahigh-molecular-weight polyethylene with 95 wt % oxides of different elements were subjected to plastic deformation under the pressure of 1 GPa at a high pressure device of the Bridgman anvil type and thermal effects were studied using the DSC technique. Thermograms contained exothermic peaks with a maximum at 50-90°C related to cold crystallization of the polymer. The process of polymer fusion was described by two peaks with the maximums at T = 125-128°C and T = 136-139°C. The low-temperature peak was related to fusion of a structure with high amounts of defects formed on the oxide surface. [ABSTRACT FROM AUTHOR]

Utilizing glycerol as a plasticizer, an accelerated physical stability testing method of amorphous solid dispersions (ASDs) was developed. The influence of glycerol concentration on the glass transition temperature and α-relaxation time (a measure of molecular mobility) of amorphous ketoconazole, celecoxib, and the solid dispersions of each prepared with polyvinylpyrrolidone was investigated. By temperature scaling (Tg/T), the effects of glycerol concentration and temperature on the relaxation time were simultaneously evaluated. Glycerol, in a concentration dependent manner, accelerated crystallization in all of the systems without affecting the fragility. In celecoxib-PVP ASDs, the drug crystallization was well coupled to molecular mobility and was essentially unaltered at glycerol concentrations up to 2% w/w. The acceleration in crystallization brought about by glycerol expedited the determination of the coupling between molecular mobility and crystallization. As a result, we were able to predict the physical stability of the unplasticized ASD. This approach is especially useful for ASDs with high polymer content where drug crystallization is extremely slow at the relevant storage temperature. [ABSTRACT FROM AUTHOR]

Polymer-induced heteronucleation can dramatically increase the nucleation rate of pharmaceuticals. However, directly comparing the heteronucleation rates of different polymer functionalities is often convoluted with changing physical or structural aspects of heteronuclei. Here, we report a methodology for comparing nucleation efficiencies of different functionalities on polymer heteronuclei of uniform topology with the goal of identifying those functionalities that best accelerate nucleation of a model pharmaceutical. It was found that the previously employed design for additives to speed acetaminophen crystallization underperforms a modified framework that accounts for the effect of competitive solvent binding. These findings are informed by a survey of interactions from the CSD and not only serve to aid in the controlled crystallization of pharmaceuticals, but also provide insight into the mechanism of heteronucleation. [ABSTRACT FROM AUTHOR]

The dipyridamole is emissive in the solution state; however, the emission is weakened in the solid state due to the aggregation-caused quenching. The aggregation of dipyridamole can be prevented by synthesizing star-shaped poly(l-lactide) (SSPLLA) using dipyridamole core. During crystallization of the polymer, chromophore molecules were expelled out of crystalline lamellae and reside at the interface of crystalline and amorphous phase. The helical chains of poly(l-lactide) (PLLA) can induce the helicity to chromophore moieties during the crystallization of PLLA. The photoluminescence (PL) quantum yield measured for the semicrystalline polymer is 46%. When the polymer is melt-quenched to amorphous, PLLA chains remain in the random conformation, and no induced circular dichroism of dipyridamole was found. In the amorphous polymer, the dipyridamole molecules are scattered and show higher PL quantum yield ~55%. Transparency of the polymer and the disruption of π-stacking of chromophore resulted in the higher quantum yield in the amorphous star-shaped PLLA. These results suggest that the morphology and the polymer chain packing could play an important role in determining the solid-state optical properties of chromophores. In addition, a detailed investigation is carried out to understand the relationship between chain conformation, the growth of crystal lamellae, and superstructure of star-shaped PLLA. [ABSTRACT FROM AUTHOR]

ABSTRACT The attempts to predict the swelling of semicrystalline polyolefins using equations of state have not been successful so far and the few conducted experimental investigations have been limited to a narrow range of samples and conditions. This article presents a systematic video-microscopic study of the swelling induced in various grades of PE particles by the sorption of ethylene and co-monomers (propylene, 1-hexene) at condition relevant to gas-phase polymerization. Based on experimental data for various PE densities, the swelling factor H was evaluated, which enables the prediction of PE swelling by ethylene. The swelling data were compared with the corresponding gravimetrically measured sorption isotherms. In the case of ethylene and propylene sorption, the swelling significantly influences the evaluation of sorption isotherms. Conversely, the effect of swelling was negligible for higher hydrocarbons. The observed impact of swelling on the sorption is discussed based on the evaluated partial molar volumes of penetrants. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45035. [ABSTRACT FROM AUTHOR]

ABSTRACT Facile microscale patterning of ferroelectric P(VDF-TrFE) thin films are presented. Simple spin-coating of the polymer solution on a patterned stamp has led to a variety of features due to the topographic dewetting. The effects of important experimental parameters, such as polymer solution concentration, spin speed, and stamp geometry, are systematically examined and the results are presented as morphological phase diagrams. Further, the dewetted cylindrical lines on the stamp protrusions are found to undergo Rayleigh-Plateau instability, which leads to the break-up of lines into dots in a row. The various pattern features formed on structured stamp has then been successfully transfer-printed onto various substrates such as Si, glass, polymers. The P(VDF-TrFE) micropatterns have shown more uniform ferroelectric performances than those of unpatterned film, due likely to confinement effect. The proposed simple patterning and transfer-printing of ferroelectric polymer thin films can be found very useful in various emerging applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45028. [ABSTRACT FROM AUTHOR]

The effect of gelatinization on the in vitro glycemic index (GI) of starch obtained from jicama tubers was investigated, and the relationships between the starch crystallinity, granule morphology, and the GI were measured. Samples were prepared by heating an aqueous dispersion of starch (1:3 w/v) at different baking process temperatures (60, 65, 70, 75, or 80°C). Native starch granules showed spherical and polyhedral shapes, with a morphometric aspect ratio (AR) of 0.89-1.0 and sizes ranging from 3 to 21mm. During the thermal process a change in the AR (0.21-0.88) and size (3.0-46mm) was observed, as well as the formation of agglomerates. Native jicama starch exhibited a CA-type X-ray diffraction pattern, while those thermally treated showed a transition from the CA-type to CB-type, decreasing their crystallinity (20.8-11.5%) at higher temperatures. The gelatinization degree of the starch samples and the glycemic index showed the largest values (97.4% and 98.6% respectively) at the highest temperature (80°C), while the crystallinity percentage followed an inverse correlation to temperature (11.5%, 80°C), indicating that the thermal history affected the behavior of the starch enzymatic digestion. The in vitro glycemic index correlated positively with the gelatinization degree based on aspect ratio (R²=0.977), DSC gelatinization enthalpy (R²=0.969), and crystallinity (R²=-0.988). Based on these results a mathematical model is proposed to determine the glycemic index as a function of the aspect ratio. However, more studies are required to validate this information. [ABSTRACT FROM AUTHOR]

Degradation has a significant impact on the crystallinity of biodegradable polymers. This work was undertaken to investigate the degradation of a poly(vinyl alcohol) (PVA)/starch blend and its nanocomposites with graphene under natural weathering conditions in Dhahran, Saudi Arabia. Changes in crystallinity, mechanical properties, molecular structure, and morphology of the nanocomposites during the aging period have been observed and inferred. The thermal and spectroscopic results demonstrated the dissolution of the amorphous phase during early stages of exposure followed by the deterioration of the crystalline phase in later stages. Morphological micrographs showed that the surface of the nanocomposites had fewer defects compared to the PVA/starch blend. PVA/starch/graphene nanocomposites showed a remarkable retention in total crystallinity compared to the PVA/starch blend during the aging period. The incorporation of graphene into the PVA/starch blend made both the polymers less vulnerable to environmental degradation, and these nanocomposites could therefore be suitable as packaging films for use in outdoor applications. [ABSTRACT FROM AUTHOR]

Recently, crystallization engineering has become a novel processing technique for various materials, including ceramics, polymers, and composites. Herein, a novel processing technology of polymers based on controlled directional crystallization was developed for biomimetic surfaces and interfaces. Solvent was allowed to come into contact with a polymer surface for a limited time, followed by controlled crystallization of the solvent along a temperature gradient perpendicular to the surface. As a result, perpendicular pores of well-defined patterns were successfully prepared, as well as adhesive-free strong interfaces mimicking neuromuscular junctions. By increasing the temperature of the polymer or solvent contact time, the pore depth and contact angle increased. Highly hydrophobic surfaces of polycarbonate were efficiently prepared, and interfacial adhesion with polydimethylsiloxane was improved by more than 4-fold. This novel processing technique based on crystal engineering could open completely new application possibilities, particularly for biomedical devices, soft lithography, microfabrication, soft sensors, and flexible and stretchable electronics. [ABSTRACT FROM AUTHOR]

The entrapment of quantum dots (QDs) in the inner part of micelles formed by surfactant polymers is a powerful methodology to prepare stable and photoluminescent core nanoparticles with enhanced optical properties. These features are crucial for the application of QDs in the design of hybrid assemblies for light harvesting applications, where energy transfer processes are required. The present work was focused on the synthesis of a surfactant homopolymer, poly (acrylic acid) (PAA) macroRAFT, to be used as a stabilizer of hydrophobic cadmium telluride (CdTe) QDs in aqueous solution. PAA macroRAFT was synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization in a single chemical reaction. Its micelles were used to entangle and entrap hydrophobic CdTe QDs, with different molar ratio of polymer and QDs. The morphology and optical properties of the entrapped QDs were determined. The results showed that PAA macroRAFT is able to form micelles with a critical micelle concentration of 2.08 mg/mL. It was also noticed that the molar ratio of polymer and QDs have high influence on the QDs' morphology and their optical properties. The QDs' photoluminescence quantum yield was enhanced approximately 23% upon their entrapment in PAA macroRAFT micelles, using 60 equivalents of polymer. Moreover, while in solution, QDs are well-dispersed, having a 3.5 nm diameter, upon being entrapped in the micelles, tend to form clusters with a size around 100 nm. [ABSTRACT FROM AUTHOR]

Poly(4-methyl-1-pentene) (PMP) nanocomposites were prepared by solution mixing of poly(ethylene- co -vinyl alcohol) (EVOH)-coated TiO 2 ( c -TiO 2 ) nanoparticles. The effects of c -TiO 2 addition on the microstructure, thermal, mechanical and electrical insulation properties of prepared nanocomposites were evaluated. The tensile-fracture morphology observed by SEM showed that there was obvious cavitation structures in the nanocomposites. Introduction of small amounts of c -TiO 2 has been significantly improve the tensile strength of PMP matrix but elongation at break was gradually reduced with the increase of the c -TiO 2 content. The insulation resistance is higher for all of the nanocomposites, as compared to the pristine PMP, indicating improved electrical insulation property. XRD patterns confirm that pristine PMP and PMP/ c -TiO 2 nanocomposites have the same crystal structure, Form I. This indicated that only one crystalline modification was developed in the nanocomposites and the multiple melting behaviors seen in the DSC heating run may reflect the melting of crystalline regions of various sizes and perfection. [ABSTRACT FROM AUTHOR]

ABSTRACT Stereodefect distribution is very important in determining the morphology and properties of isotactic polypropylene (iPP). In this study, two iPPs (PP-A and PP-B) with different uniformities of stereodefect distribution were prepared. The tensile behavior and morphology evolution of their cast films were studied. The morphology study of the cast films showed that compared with PP-B, PP-A with less uniform distribution of stereodefects has smaller spherulites and spheruilitic boundaries and higher degree of crystallinity. In uniaxial tensile measurements, PP-A exhibited higher yield strength and lower elongation at break. When strain was 500%, PP-A exhibits totally transparent appearance and highly oriented structures without cavities, whereas PP-B shows opaque appearance and mass of both nanometer- and micrometer-sized cavities. Moreover, calculation of rigid amorphous fraction (RAF) indicated that PP-B cast film has a higher amount of RAF, which might be the reason for the different morphology evolutions and tensile behaviors of the samples. [ABSTRACT FROM AUTHOR]

Understanding the role of water in waterborne polyurethane synthesis and properties is a central issue. Water may bring some unique and interesting properties and phenomenon for waterborne polyurethane. This paper focus on the impact of the novel water addition procedure on the properties of waterborne polyurethane. The novel poly(neopentyl glycol adipate) (PNA)-based waterborne polyurethane was prepared using the designed in situ water reaction process. As a comparison, waterborne polyurethane was synthesized through the conventional water addition process through prepolymer method. The thermal and crystalline properties of the obtained polyurethanes were detected by XRD, DSC, DMA, POM, TG and SEM. The results indicated that the novel polyurethane dispersion presents unique performance. Furthermore, to explore the application area of the novel polyurethane dispersion, mold resistance experiments were performed. The result suggested that polyurethane dispersion from the novel process is safer and more environmentally friendly than that from conventional water addition process. [ABSTRACT FROM AUTHOR]

On the basis of sufficiently realistic chain models and simulations, it is concluded that the commonly used models of the lamellar structure of melt-crystallized semicrystalline polymers unintentionally but inevitably contain layers with a higher density than in the crystallites (density anomalies). The density excess would be particularly pronounced in polymers with planar zigzag conformations in the crystallites, such as polyethylene (PE). To avoid density anomalies, the structural models must be modified, with chain ends at the crystal surface and/or chain tilt in the crystallites. NMR and X-ray evidence for these structural features in PE is presented. Termination of chains at the crystal surface keeps dangling chain ends out of the crowded interfacial layer, reducing the density at the interface by about 17% for Mn = 15 kg/mol, a common value in commercial high-density polyethylenes. NMR of PEs shows that most CH3 end groups are indeed in all-trans chains in a nearly solid-like environment. When the ends of polydisperse polymers are trapped at the crystal surface, many chain folds cannot be tight, in agreement with NMR showing fast trans-gauche isomerization even for solution crystals of PE. We propose that for polydisperse PE, interfacial chain ends are required for the formation of regular stacks of flat melt-crystallized lamellae without extreme chain tilt or density anomalies. Chain tilt in the crystallites, which decreases the area density of chains emerging from the crystal surface, is another indispensable structural adjustment in PE that reduces excess noncrystalline density; it has occasionally been reported but was usually considered as incidental. For instance, in X-ray analyses of PEs, chain tilt was ignored, and differential broadening of the (hk0) Bragg peaks was mistakenly attributed to mosaicity, in extreme cases resulting in the assumption of overly thick, rod-shaped rather than lamellar crystallites. For various oriented PE samples, including blown films and annealed fibers, published scattering patterns exhibit clear evidence of macroscopically aligned lamellar stacks with pronounced chain tilt. Literature data for PE also show examples of the increasing importance of chain tilt at high molecular weights, where the density reduction by chain ends is minor and evidence of extreme chain tilts of up to 60° has been shown. Alternatively, when chain-end concentrations are very low, the assumption of wide regularly stacked lamellae may have to be given up in favor of ribbon-shaped crystallites. The interplay of the density effects of chain ends and chain tilt can explain many molecular-weight-dependent structural features in polyethylene. On the basis of the combined effects of chain ends at the crystal surface, chain tilt in the crystallites, and adjacent reentry of ∼1/3 of chains, we can construct a lamellar model of PE without density anomalies. Chain tilt and chain ends at the crystal surface are required to "make space" for short loops, in conjunction with noncrystalline chain segments emerging from the crystal roughly along the surface normal. These four effects together enable a structure without density anomalies. In solution crystals, the absence of tie molecules and long loops, which produce a more extensive density increase than short loops, reduces the crowding problem and allows for lamellar crystals (with strongly tilted chains) even without chain ends, e.g., at ultrahigh molecular weights. In poly(ethylene oxide) and other polymers with helical conformations in the crystallites, the higher density along the chain axis associated with greater bond tilt angles in the crystal reduces the problem of amorphous excess density relative to Flory's prediction and thus the need for chain tilt in the crystallites. [ABSTRACT FROM AUTHOR]

Hybrid materials of inorganic-organic phases in which each phase provides different functionality are attractive candidates for achieving multifunctionality. Using a layer-by-layer approach, we fabricated sheets of piezoelectric polymer P(VDF-TrFE) reinforced by aligned sub-micron thick sapphire platelets. The films were transparent and piezoelectric, exhibited ductility up to ≈330%, and tensile toughness of up to 26 J g-1. We investigated the effect of thermal annealing on the crystallinity of the polymer phase and its effect on the mechanical and piezoelectric properties of the films. Thermal annealing resulted in improvement of the elastic modulus and piezoelectric properties of the films. in situ SEM tensile experiments were conducted for observation of the deformation mechanism of the films. [ABSTRACT FROM AUTHOR]

The objective of this study was to prepare linear low density polyethylene (LLDPE)/chitosan/closite nanocomposites by using various concentrations of LLDPE, chitosan, and closite clay mineral. The nanocomposites were then characterized for their thermal, mechanical, and rheological properties by using different analytical techniques including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), rheological characterization, tensile strength study, and scanning electron microscopy. The TGA demonstrated that crosslinked composites are thermally more stable than non-crosslinked composites. The DSC stated that the percentage crystallinity of crosslinked composites is lower than the non-crosslinked composites. It is also observed that the increasing quantity of chitosan and closite also reduces the percentage crystallinity of the prepared nanocomposites. Rheological characterization revealed that, crosslinked composites are viscoelastic in nature and have high complex viscosities (η*) and high dynamic shear storage modulus (G′), while non-crosslinked composites showed high dynamic shear loss modulus (G″). Tensile strength of crosslinked composites was much higher than non-crosslinked composites, however elongation at break (Eb) values of non-crosslinked composites are higher than crosslinked composites. The scanning electron microscopy displayed strong adhesion between matrix-filler-interphase in crosslinked composites, while some gaps were also observed in non-crosslinked composites. As a conclusion, chitosan, closite clay, and the LLDPE based nanocomposites with improved thermal, mechanical, and rheological properties can be successfully prepared by employing a peroxide-initiated melt compounding technique. [ABSTRACT FROM AUTHOR]

Effect of low-pressure radiofrequency capacitively-coupled plasma parameters on the separation of model 'oil-in-water' emulsions using UPM-20 polysulfonamide membranes with a pore size of 0.01 μm has been studied. Atmospheric air has been used as a plasma gas. The plasma treatment time is 1, 5, 4, and 7 min at a plasma torch anode voltage of U = 1.5-7.5 kV. The separated medium is a 3% emulsion based on the industrial oil I-20A; the stabilizer is the surfactant Kosintol-242. The highest performance is observed in the case of membranes treated with plasma for 7 min. It is found that plasma treatment leads to an increase in the emulsion separation efficiency from 90 to 99%. It has been shown that the plasma treatment contributes to the surface hydrophilization of the membranes owing to the formation of oxygen-containing functional groups. The membrane exhibits a contact angle of water of α = 59.6° before treatment and α = 19.5° after a 4-min plasma treatment at U = 7.5 kV. Atomic force microscopy reveals that the plasma treatment leads to a change in the surface structure of the membranes, namely, to a decrease in their roughness. The internal structure of the membranes also undergoes changes which result in an increase in their crystallinity. [ABSTRACT FROM AUTHOR]

Subsequent crystallization behavior during cooling for two random propylene-ethylene copolymers with 6 mol % ethylene co-units but different molecular weights initially in a pure α-form or pure γ-form processed at different melt temperatures was investigated using differential scanning calorimetry and wide-angle X-ray diffraction techniques. The onset crystallization temperature (Tonset) and fraction of the two polymorphs after crystallization depended on the molecular weight, initial polymorph, and melt temperature (Tmelt). At high Tmelt (120-160 °C), Tonset and the fraction of the γ-form (fγ) increased with decreasing Tmelt. For the high molecular weight sample initially in α-form, a higher Tonset and fγ than the one in the γ-form was observed because a higher Tmelt was needed to fully homogenize the melt for samples initially in the α-form due to the different morphology between the samples of different polymorphs. For the low molecular weight sample, the initial polymorph did not affect this process. [ABSTRACT FROM AUTHOR]

Inorganic montmorillonite (MMT)/poly(vinylidene fluoride) nanocomposites were prepared by two methods: co-precipitation and solution casting. The effect of preparation methods and thermal treatment on crystalline phase was investigated by Fourier transform infrared spectroscopy and differential scanning calorimetry tests. The isothermal crystallization process was observed with polarized optical microscopy. It was found that the solution-casting method was more effective than the co-precipitation method in inducing the polar phase in the melt-isothermal crystallization process. The addition of inorganic MMT by the solution-casting method without further thermal treatment promoted the β-phase crystallization. The inorganic MMT significantly improved the γ phase of the solution-cast samples in the melt-recrystallization process. The degree of dispersion of inorganic MMT influenced the relative content of the polar phase and the crystallinity of the samples in the same crystallization conditions, i.e. the preparation method and the thermal treatment. The effect of dispersion on crystallization kinetics was also studied to verify the enhancement of finely dispersed nanolayer clusters on the γ phase. [ABSTRACT FROM AUTHOR]

ABSTRACT Two semicrystalline low band gap polymers based on highly electron-deficient 2,1,3-benzothiadiazole-5,6-dicarboxylicimide (BTI) were synthesized by considering the chain planarity via intrachain noncovalent coulombic interactions. The thiophene-BTI and thienothiophene-BTI based PPDTBTI and PPDTTBTI have a low band gap (∼1.5 eV) via strong intramolecular charge transfer interaction, showing a broad light absorption covering 300∼850 nm. Semicrystalline film morphology was observed for both polymers in the grazing incidence wide angle X-ray scattering measurements. Interestingly, PPDTBTI showed a pronounced edge on packing structure but PPDTTBTI showed predominantly a face on orientation in both pristine and blend films. Different packing patterns influenced significantly the charge carrier transport, recombination and resulting photovoltaic characteristics. The best power conversion efficiency was measured to be 5.47% for PPDTBTI and 6.78% for PPDTTBTI, by blending with the fullerene derivative, PC71BM. Compared to the PPDTBTI blend, PPDTTBTI: PC71BM suffered from the lower open-circuit voltage but showed the substantially higher hole mobility and short-circuit current density with smaller charge recombination, showing very good agreements with molecular structures and morphological characteristics. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3826-3834 [ABSTRACT FROM AUTHOR]