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Solid polymer electrolytes (SPEs) have gained remarkable development within the realm of new energy resources. With its improved electrochemical stability and environmental‐friendly sustainability, bacterial cellulose (BC) has emerged as a promising candidate for applications in SPEs. Herein, bacterial cellulose was chemically cyanoethylated and integrated with lithium bis(trifluoromethanesulphonyl)imide/polyethylene oxide (PEO) based SPE. Some vertical channels are formed when trace amounts (0.5 wt%) of cyanoethylated bacterial cellulose (BC‐CN) are added to PEO‐based SPE, as revealed by SEM. This formula's corresponding PEO‐based SPE presents the highest ion conductivity of 5.7 × 10−4 S cm−1 at 60°C. The ion migration activation (Ea) deduced from the Arrhenius equation is 0.48 eV, lower than the value of 0.82 eV for the pristine PEO SPE. Besides, the Li+ migration number of this modified PEO‐based solid electrolyte is calculated to be a relatively high value of 0.33, while that of its counterpart, the pristine PEO SPE, is as low as 0.06. The all‐solid‐state lithium battery with PEO/0.5%BC‐CN SPE can operate stably for 115 cycles, which is longer than the 80 cycles achieved with the pristine PEO SPE. This study introduces a novel strategy for creating modified BC composites PEO‐based SPE. Highlights: Bacterial cellulose was chemically cyanoethylated.Cyanoethylated bacterial cellulose composite polyethylene oxide (PEO)‐based solid polymer electrolytes (SPEs) are prepared in DMF.Opening pores penetrate the surface of the PEO/0.5% cyanoethylated bacterial cellulose (BC‐CN) SPE membrane.PEO/0.5% BC‐CN shows ionic conductivity of 5.7 × 10−4 S cm−1 at 60°C.Full cell with PEO/0.5% BC‐CN performs stably for 115 cycles. [ABSTRACT FROM AUTHOR]

It is still a challenge to synthesize high-performance adsorbents for uranium extraction from seawater. The stable uranyl tricarbonate complex in seawater seems to preclude coordination of uranyl ions by adsorbents. This study reports 3D networked colloidal particles consisting of polyamidoxime (PAO) and sodium polyacrylate (PAA-Na) segments via competitive conversion between amidoximation and hydrolysis in NaOH aqueous solutions. PAA-Na can promote the dissociation of uranyl ions via ion exchange for high-efficiency coordination by PAO. As a result, the colloidal particles, with high selectivity for uranyl ions, reach an outstanding uranium uptake capacity of 17.8 mg U per g in real seawater after 20-day adsorption. [ABSTRACT FROM AUTHOR]

In this work, we designed and synthesized two novel bi-heteroatom functionalized hyper-crosslinked porous polymers (HCP-CT and HCP-CF) through a simple one-step Friedel–Crafts alkylation reaction. The resulted polymers N/S bi-heteroatom functionalized polymer HCP-CT and N/O bi-heteroatom functionalized polymer HCP-CF both have good adsorption property for organic dyes such as methyl orange (MO) and methylene blue (MB) in aqueous solution due to its rich pore structure, high specific surface area and rich-heteroatoms of pore surface. It is worth mentioned that the maximum adsorption capacity (qmax) of cationic dye MB by the porous polymer HCP-CT at room temperature was reached up to 1571.46 mg/g, which is much higher than that of most reported porous materials. Furthermore, the adsorption capacity of HCP-CT for the cationic dye MB was more than seven times that of the anionic dye MO (qmax = 212.77 mg/g). Also, the polymer HCP-CF for the MB adsorption capacity (qmax = 352.11 mg/g) was more than twice higher than that of anionic dye MO (qmax = 131.75 mg/g). The above trends may be because of the stronger electrostatic interaction between the negatively charged N-S/O bi-heteroatom of HCP-CT and HCP-CF with the cationic dye MB than that of MO. In addition, the removal percentage of polymers HCP-CT and HCP-CF still remained above 80% after five adsorption–desorption cycles. Hence, this work may provide a convenient synthetic route to develop a novel hyper-crosslinked polymer with high capacity for the entrapment of dyes from aqueous solution. [ABSTRACT FROM AUTHOR]

The confinement and high utilization of sulfur in the cathodes is critical for improved cycling performance of lithium‐sulfur batteries. In this case one‐pot hydrothermal strategy is developed to produce rGO/MXene/sulfur composite aerogels where sulfur is in situ trapped in the 3D rGO/MXene conductive skeleton. The optimized composite aerogels as free‐standing cathodes delivery a specific capacity of 951 mAhg−1 after 100 cycles at 0.2 C with a low fading rate of 0.062 % per cycle. The excellent cycling performance is correlated with highly oxidized MXene and in situ formed sulfate/thiosulfate complex layer in the long‐term cycles. [ABSTRACT FROM AUTHOR]

A heterostructure composed of ZIF-67-derived nitrogen and cobalt-doped carbon enfolded silicon (C@Si) nanoparticles anchored on 2D MXene layers was constructed for boosting the performance of lithium-ion batteries (LIBs). The heterostructure anode demonstrated a high initial discharge capacity of 3021 mA h g−1 at 0.2 A g−1, retaining outstanding cycling stability with a reversible capacity of 520 mA h g−1 at 2000 mA g−1, and the coulombic efficiency remained above 97% after 500 cycles. The introduced Ti3C2 nanosheets and the cobalt-doped carbon can not only contribute to the interfacial transfer of Li+ and electrons but also buffer the volume expansion of Si. [ABSTRACT FROM AUTHOR]

In lithium batteries, composite solid electrolytes gain their reputation owing to their great safety, excellent mechanical properties, and remarkably improved electrochemical performance. Herein, composite polyethylene oxide (PEO)‐based solid electrolytes with well‐dispersed in situ polydopamine‐coated lithium montmorillonite (PDA@LiMMT) nanofillers are successfully fabricated. The involvement of PDA@LiMMT retards significantly the crystallization of PEO, addressing a manifest enhancement in the ionic conductivity of the modified composite solid electrolyte. A conducive ionic conductivity value of 3.06 × 10−4 S cm−1 at 60 °C is reached, while the electrochemical window widens to 4.7 V. The assembled Li/solid polymer electrolytes/LiFePO4 battery exhibits a 158.2 mA h g−1 high discharge specific capacity at a current density of 0.5C; besides, the capacity retention rate keeps 86% after 200 cycles. The enhancement of the cycle stability of the solid‐state batteries highlights the excellent interfacial stability between the modified solid electrolytes and the lithium electrode, which originates from lithiophilicity of PDA. [ABSTRACT FROM AUTHOR]

Adsorption‐photocatalysis technology based on covalent organic frameworks (COFs) offers an alternative method for advancing the field of uranium extraction from seawater. When determining the photocatalytic activity of COFs, the binding energy of excitons (Eb) functions is the decisive factor. Nevertheless, the majority of reported COFs have a large Eb, which seriously restricts their application in the field of photocatalysis. Using a practical π‐skeleton engineering strategy, the current study synthesizes three donor‐acceptor olefin‐linked COFs containing amidoxime units in an effort to minimize Eb. Theoretical and experimental results reveal that the construction of planar and continuous π‐electron delocalization channels can significantly reduce Eb and promote the separation of electron‐hole pairs, thereby enhancing the photocatalytic activities. Moreover, the Eb of the TTh‐COF‐AO with a planar π‐skeleton donor is significantly reduced, and exhibits a substantially smaller Eb (38.4 meV). Under visible light irradiation, a high photo‐enhanced uranium extraction capacity of 10.24 mg g−1 is achieved from natural seawater without the addition of sacrificial reagents, which is superior to the majority of olefin‐linked COFs that have been reported to date. This study, therefore, paves the way for the development of tailored, efficient COFs photocatalysts for the extraction of uranium from seawater. [ABSTRACT FROM AUTHOR]

This study reports Zn2+-mediated supramolecular composite hydrogels from the mixtures of sodium alginate and polyethyleneimine in the aqueous solutions. The composite hydrogels, consisting of both carboxylate and amino groups, show enhanced uptake capacity of 718 mg-U/g in a 20 mg/L uranium-spiked water at pH = 6. Furthermore, uranium uptake by the composite hydrogels, an endothermic and spontaneous process, follows pseudo-second-order kinetic model and Langmuir model. Importantly, the composite hydrogels can reach a high uranium uptake capacity of 692 mg-U/g in a simulated uranium wastewater with other metal ions. [ABSTRACT FROM AUTHOR]

In this paper, a new type of carbazole-based hyper-crosslinked porous polymer (HCP-CP) was prepared through a very simple "knitted" method. The obtained novel polymer HCP-CP has a good adsorption property of methyl orange (MO) and methylene blue (MB) organic dyes in aqueous solution due to its high surface area and rich nitrogen atoms. The effect of pH, adsorption time, different initial concentration of dyes and adsorption reusability were investigated in detailed. The optimum pH is 8 for the adsorption of MB and 6 for the adsorption of MO, respectively. Under the best condition, the Langmuir model fitted the adsorption isotherm well and the adsorption behavior follow pseudo-second-order kinetics. The maximum adsorption capacity of HCP-CP for cationic dye MB (qmax=751.88 mg/g) is more than twice higher than that of anionic dye MO (qmax=274.73 mg/g). These capacity differences may be owing to the stronger electrostatic interaction between the negatively charged nitrogen atoms of HCP-CP with the cationic dye MB than that of MO. Moreover, the used polymer HCP-CP still retain a removal percentage above 92% after 5 times adsorption-desorption recycle. Therefore, this work provided a convenient synthetic route to develop a novel hyper-crosslinked polymer with high adsorption capacity for the entrapment of dyes from aqueous solution. [ABSTRACT FROM AUTHOR]

With the rapid development of the nuclear resource industry, the development of high-efficiency adsorbents is the key to the separation and removal of uranium from aqueous solutions. In this paper, phenyl phosphonic acid was designed as a functional monomer, the aromatic building blocks such as benzene and triptycene as an external crosslinker. Through the "knitting" strategy, a novel phosphonic acid-based functionalized triptycene-based hyper-crosslinked porous polymer (TPP-BPP) and benzene-based hyper-crosslinked porous polymer (B-BPP) were prepared by the above monomer and crosslinker. The resulting polymer B-BPP has a much higher surface area (SBET = 836.21 m2/g) than that of polymer TPP-BPP (SBET = 30.60 m2/g) due to the large skeleton triptycene confines the void. Owing to a large number of phosphonic acid functional groups, the polymer TPP-BPP and B-BPP both have a good ability to remove uranium. The optimal adsorption pH is 7 and the adsorption time is 90 min. Under the best experimental conditions, the maximum adsorption capacity of TPP-BPP for uranium is 119.05 mg/g, and the maximum adsorption capacity of B-BPP for uranium is 222.72 mg/g. Furthermore, in the presence of coexisting ions Na+, Mg2+, Al3+, Co2+, Ni2+, NO3−, CO32−etc., they still have good selectivity to uranium ascribed to the strong complexation between UO22+ and P=O groups anchored on the polymer, which was evidenced by experimental results. Also, it has good reusability and can still maintain a very high removal percentage after at least being recycled five times. Therefore, the convenient synthesis route for the novel phosphonic acid-based functionalized hyper-crosslinked porous polymer has a promising application prospect for uranium adsorption. [ABSTRACT FROM AUTHOR]

High conductivity, facilitating rapid electron transport and ion diffusion, is necessary for high‐performance lithium‐ion battery cathodes. At a given electrode formula, it is critical to tailor the distribution of conductive agents in the cathodes to achieve a highly conductive network.Herein, free‐standing LiFePO4‐based composite membranes with a high conductivity of 2.55 S cm−1 are obtained by adding alcohol in the aqueous slurry. The composite membranes have superior rate capability and a specific capacity of about 116 and 105 mAhg−1 is achieved at 5 C for a LiFePO4 mass loading of about 6 and 10 mg cm−2, respectively. Furthermore, a specific capacity is retained as 137.2 mAhg−1 after 300 cycles at 1 C, corresponding to excellent long‐term cyclic stability of the composite membranes. [ABSTRACT FROM AUTHOR]

In order to construct nanofiltration membrane with anti-"trade-off" effect, polyamide nanofiltration membranes are modified by metal-organic framework UiO-66-NH2 and UiO-66-(COOH)2, respectively. The results indicate that the introduction of UiO-66-X can enhance the hydrophicity and anti-protein adsorption performance of the membrane. Different from the expectation, compared with polyamide nanofiltration membrane without MOFs, the MgCl2 removal rate of the membrane with UiO-66-(COOH)2 can nearly remain sta¬ble when the content of UiO-66-(COOH)2 changes from 0.01 g to 0.03 g, but that of Na2SO4 decreases obviously. However, salts rejection rate of the polyamide nanofiltration membrane for MgCl2 and MgSO4 can both keep nearly stable by introduction of UiO-66-NH2 when the loading ranged from 0.01g to 0.04 g. Meanwhile, the flux improves with increasing the dosage of UiO-66-NH2. Moreover, the flux of the membrane with UiO-66-NH2 is higher than that of the membrane containing UiO-66-COOH) 2. When the dosage of UiO-66-NH2 is 0.03 g (NF-NH2-3), the removal rates of MgCl2 and MgSO2 are 83% and 95% respectively, and the flux is a¬bout 40.7 L/(m² • h), which is 2.6 times of the membrane without MOFs. When NF-NH2-3 is used to remove bssphenol A from water, the removal rate is about 93%. It shows potential applications in water softening and treatment of wastewater containing endocrine disrupting chemicals. [ABSTRACT FROM AUTHOR]

The development of high-efficiency absorbents is an ongoing demand to purify uranium-containing wastewater. This study reports a poly(acrylic acid) (PAA) supramolecular hydrogel with hydrogen bonding interactions via physical cross-linking in acidic solutions. The protons in the carboxyl groups of the PAA hydrogel can exchange with uranyl ions in aqueous solution during adsorption, and vice versa upon desorption/regeneration. It enables easy uranyl coordination with the PAA hydrogel, responsible for an ultrahigh uranium uptake of 1362 mg g−1 in 20 mg L−1 uranium-spiked water (pH = 7). In addition, the PAA hydrogel can tolerate high-concentration metal cations to a large extent, beneficial for high-efficiency uranium removal under realistic conditions. The findings give deep insights into the development of high-efficiency adsorbents for uranium removal from wastewater via supramolecular tailoring. [ABSTRACT FROM AUTHOR]

A highly conductive interlayer, as the dual current collector, is necessary to reutilize lithium polysulfide for better performance of lithium–sulfur batteries. Slurry coating usually results in poor conductivity owing to the insulating binders. Herein, a metal coordinated compound (Mn‐BDC) serves as the sacrificed template to induce a highly conductive polypyrrole (PPy) skeleton via in situ polymerization. Simultaneously, the decomposition of Mn‐BDC produces fine particles that are highly absorptive in the PPy skeleton. The resultant PPy hybrid interlayer, about 5 μm in thickness, can remarkably inhibit the shuttle effect and reuse the adsorbed lithium polysulfide. As a result, a high specific capacity of 517.3 mAh g−1 is achieved after 500 cycles at 0.5 C with a fading rate of 0.093% per cycle. [ABSTRACT FROM AUTHOR]

Dissolution and nucleation are the two indispensable processes to be investigated in order to understand crystallization behavior of a compound. In this study, the crystalline valnemulin hydrochloride water–ethanol solvate (VHWES) was successfully prepared by the solution crystallization method. The solubility of VHWES in ethanol + water binary solvents was measured at eight different temperatures from 278.15 to 313.15 K using a static analytical method, and these solubility data was correlated by several different thermodynamic models. The model parameters were calculated and analyzed based on the difference between calculated results and measured solubility data. It was found that the results correlated by thermodynamic models are in good agreement with the measured solubilities. Furthermore, the nucleation process of VHWES in the ethanol + water (molar ratio of 1:1) system was investigated in detail. The induction times of nucleation and metastable zone width were measured at various temperatures under different supersaturations, and interfacial energies were calculated using classical nucleation theory. The results reveal that homogeneous nucleation predominates under high supersaturation while heterogeneous nucleation predominates under low supersaturation. [ABSTRACT FROM AUTHOR]

Polymer film capacitors with high stability and reliability at elevated temperatures are promising for next‐generation power electronic systems and hybrid electric vehicles. In this work, sandwich‐structured composite films with good dielectric thermal stability were fabricated based on hybrid membranes of poly(vinylidene fluoride)/polyacrylonitrile blend nanofibrous skeleton highly filled with BaTiO3 nanoparticles. Composite films with 64.7 vol% BaTiO3 nanoparticles in the core layer exhibited high permittivity (38.1) and low loss (0.046) at 1 kHz and room temperature, and the dielectric permittivity and loss were only slightly increased to 41.5 and 0.08, respectively, at 120°C. Good dispersion and high loading of BaTiO3 nanoparticles in the composites films contributed to enhanced dielectric thermal stability and permittivity. Moreover, the composite films showed good flexibility, which could be ascribed to its sandwich‐structure. Our work paves a generic way to fabricate flexible composite films with excellent dielectric thermal stability via high loadings of ceramic nanoparticles. POLYM. COMPOS., 39:E1841–E1848, 2018. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Two novel solvates of valnemulin hydrochloride (VH), one is valnemulin hydrochloride water–ethanol solvate (VHWES) and the other is valnemulin hydrochloride water–methanol solvate (VHWMS), were first crystallized successfully. The structural and spectral characteristics of VHWES and VHWMS were studied by single crystal X-ray diffraction (SCXRD), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. It was found that both solvates crystallized in the monoclinic system with a P2 space group, and comprised protonated ammonium moieties, hydrochloride anions, water molecules and solvent molecules (ethanol or methanol) which are held together by a number of hydrogen bonds. The thermal characterization of VHWES and VHWMS was conducted through DSC/TG analysis. The results indicated that both of them would undergo a solvent loss over a certain temperature range, and then return to their original amorphous form. The solution-mediated phase transformation from VH to VHWES was in situ investigated by using PVM and Raman spectroscopy, and the kinetic parameters of the transformation process were also determined. It was found that the nucleation of VHWES was the limiting step of the transformation process, and the transformation rate accelerated with increasing temperature. [ABSTRACT FROM AUTHOR]

ABSTRACT Ideal membranes toward separation of stable oil/water emulsions should have surface hydrophilicity and submicron pores in the separating layer. However, electrospun membranes made from poly(vinylidene fluoride) (PVDF) cannot meet these requirements, failing to remove oil droplets from a stable oil/water emulsion. By doping with a certain polyamide 6 solution, surface hydrophilicity, and interconnected pores with submicron size are successfully achieved. As a result, separation of a stable emulsion with an efficiency above 99% is exhibited by the modified PVDF membranes. Moreover, underwater oleophobicity of the modified PVDF membranes imparts them with good antifouling performance. The modified PVDF membranes could have great potentials in practical stable oil/water emulsion separation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44980. [ABSTRACT FROM AUTHOR]

Cellulose, abundant in nature, is very attractive for application in energy storage devices. Herein, cellulose nanofibers (CNF), detached from natural cellulose, are employed to fabricate flexible electrodes with polyaniline (PANI) as the active material for high performance supercapacitors. The presence of CNF in conductive composite substrates can tailor the morphology and doping of grown PANI worm-like nanorods during in situ polymerization, resulting in the improvement of specific capacitance. A maximum specific capacitance of 421.5 F g−1 is achieved for hybrid PANI electrodes based on composite substrates with 20 wt% CNF loading at a current density of 1 A g−1. Moreover, good rate capability and energy/power density balance are exhibited by the hybrid PANI electrodes. All-solid-state supercapacitors assembled from the hybrid PANI electrodes show excellent electrochemical performance and capacitance retention under repeated bending over 1000 cycles due to the mechanical flexibility of composite substrates with CNF as binders. This research provides a facile route to fabricate high performance flexible supercapacitors from bio-sourced CNF and low-cost PANI. [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, we report the effects of the molecular weight on the electrospinnability of polylactide (PLA) solutions under identical conditions. Only above the entanglement concentration could uniform fibers be generated for PLA with a low molecular weight. However, electrospinning from a solution below its entanglement concentration produced uniform nanofibers when a high-molecular-weight PLA was adopted. The slow relaxation of high-molecular-weight PLA was expected to preserve chain interconnectivity in the highly stretched liquid jets during electrospinning. Correspondingly, rapid cold crystallization and a high modulus were exhibited by the resulting PLA nanofibers because of their remarkable molecular alignment.© 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44853. [ABSTRACT FROM AUTHOR]

Incorporation of an ionic liquid, nonvolatile and thermally stable, promoted formation of ring-banded spherulites in poly (l-lactide) (PLLA) during its sol–gel transition. Their formation is correlated with low viscosity and insignificant chain entanglements in the mixtures induced by the ionic liquid. In addition to a driving force for lamellar twisting that depended on the crystallization temperatures, it is believed that reduced lamellar twisting resistance caused by the ionic liquid plays a vital role in the formation of the ring-banded spherulites of PLLA from the mixtures. This study gives further insights into the structural formation of PLLA during a sol–gel transition, which could open new opportunities to tailor the properties of ion gels based on PLLA. [ABSTRACT FROM PUBLISHER]

ABSTRACT Fibrous membranes are promising as high-performance lithium ion battery separators because of high porosity and superior electrolyte uptake. Electrospinning is a popular approach to produce fibrous membranes, but its production rate is very low. As a comparison, mass production of fibrous membranes can be achieved by centrifugal spinning. This study reports fibrous membranes based on poly(vinylidene fluoride)/poly(acrylonitrile) blends by centrifugal spinning and their application as lithium ion battery separators. The blend fibrous membranes have high electrolyte uptake of about 300%, excellent dimensional stability at 180 °C and good mechanical strength over 18 MPa. The coin cells with the blend fibrous membranes as separators show high discharge capacity of 147.7 mAh/g at 0.2 C and superior C-rate performance. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44515. [ABSTRACT FROM AUTHOR]

ABSTRACT Effect of immiscible polyamide 6 (PA6) on the melt rheology and stretch-induced crystal transformation of poly (vinylidene fluoride) (PVDF) matrix is reported. PA6 is dispersed as submicron droplets in the PVDF matrix, responsible for significant enhancement in the melt elasticity. Nevertheless, crystallization habits of PVDF matrix from melt are little affected by submicron PA6 droplets, and the α-form of PVDF prevails in the blends. Upon mechanical stretching, the α-form is converted to the β-form, which is remarkably reduced with the increasing of PA6 content in the blends. It could be correlated with the decreased tensile stress in the presence of submicron PA6 droplets that act as stress concentrators. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43499. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(vinylidene fluoride) (PVDF) membranes with exclusive β-form have been directly obtained by immersion precipitation from the mixed solvents containing an ionic liquid (IL). In contrast, without the IL only the α-form is generated. The ion-dipole interactions between the IL and PVDF chains should account for the formation of the β-form with TTTT conformation. In addition, the presence of the IL accelerates the crystallization and gelation of PVDF, responsible for the particulate morphology and high water flux in the membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40505. [ABSTRACT FROM AUTHOR]

It is still a challenge to achieve a high degree of stereocomplexation in enantiomeric polylactides with high molecular weight. This study demonstrates that gelation of enantiomeric polylactides in an ionic liquid, a non-volatile solvent, is a facile route to overcome this problem. The presence of the ionic liquid enhances the molecular mobility and mutual diffusion and thus to a large extent eliminates the kinetic barrier for stereocomplex formation. The gelation and stereocomplex formation in the ionic liquid may provide a new opportunity for the application of polylactides as scaffolds with high thermal stability in tissue engineering. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT Stretching of amorphous polylactide above glass transition temperature can lead to strain-induced crystallization, which is mainly determined by stretching rate and temperature. This study demonstrates that thermal annealing prior to stretching is alternative to enhance strain-induced crystallization of a given polylactide at the identical stretching conditions. The local order generated during thermal annealing acts as physical crosslinks to effectively alleviate molecular relaxation and thus facilitates the advent of strain-induced crystallization. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39993. [ABSTRACT FROM AUTHOR]

Cold crystallization of poly (l-lactide)/poly (d-lactide) blends at low temperatures results in the formation of a stereocomplex with loose intermolecular packing. Upon heating, it undergoes significant reorganization into a compact one with an extremely high melting point via a solid–solid transition. In contrast, the stereocomplex crystallized at high temperatures exhibits little reorganization and thus a relatively low melting point. [ABSTRACT FROM AUTHOR]

The mesophase in the as-stretched poly( L-lactide) (PLLA) exhibits low thermal stability and undergoes melting around Tg. As a consequence, without constraints as-stretched PLLA can recover to its original (unstretched) length while being held above Tg. Upon constrained annealing at 70°C mesophase is transformed into highly oriented crystals, responsible for little free shrinkage and superior dimensional stability. At the same time, molecular orientation in the amorphous phase first decreases significantly due to thermodynamic relaxation, and then increases moderately with the advent of cold crystallization. It correlates well with the change of yield strength with respect to annealing time. POLYM. ENG. SCI., 53:2568-2572, 2013. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This study reports the high impact toughness of polyamide 6 (PA6)/poly (vinylidene fluoride) (PVDF) blends achieved via adding an ionic liquid. The presence of the ionic liquid in the blends promotes the transformation of sea-island structure into co-continuous morphology, which to a large extent accounts for the improvement in toughness. In addition, it is believed that the enhanced mobility of the PA6 matrix by the ionic liquid also contributes to the high impact toughness. [ABSTRACT FROM AUTHOR]

The effect of amorphous poly( D, L-lactide) (PDLLA) on the molecular orientation and crystallization of crystalline poly( L-lactide) (PLLA) on stretching is reported in this study. It is indicated that the presence of PDLLA in its miscible blends with PLLA is not favorable for either cohesive mesophase formation below Tg or strain-induced crystallization above Tg at strains beyond the segmental extensibility limit. Because of lack of constraints imposed by cohesive mesophase or crystals, oriented segments are liable to slide each other or recoil, responsible for low-molecular orientation in the stretched blends. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This study explores the interactions of the environmental barriers, coping behaviors, and personal characteristics of persons living with hepatitis B in China within the framework of Bandura's social cognitive theory. An analysis of 1,607 messages from an online support group revealed multiple barriers including institutional discrimination, relationship difficulty, alcohol-drinking social norm, limitations of the health care system and pharmaceutical market, and financial constraints. Major coping behaviors were identified as seeking health and reproductive advice, avoiding disclosure and discrimination, protecting legal rights, preventing transmission, and outreaching support behaviors. At the intrapersonal level, a combatant identity was constructed in the online community. The combatant identity was significantly associated with high self-efficacy, positive emotions, and outreaching support behaviors, but it was not significantly associated with environmental barriers. The constructed online combatant identity appeared to be support-focused instead of politically oriented. [ABSTRACT FROM AUTHOR]

It is still a challenge to obtain polar phase of poly(vinylidene fluoride) from melt crystallization at normal conditions. This study demonstrates that polar β- and γ phases can be produced through melting re-crystallization of α phase, provided that moderate memory effects in the melt is achieved by annealing. Otherwise, it is inevitable to re-crystallize into α phase without any trace of polar phase. Small fragments, generated from the disintegration of long TGTG′ sequences, most likely adopt trans conformation in the melt before approaching random coils, thus responsible for the formation of polar phase upon cooling. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]

Shape-memory polymers (SMPs) are stimuli-responsive materials whose shape recovery is usually stimulated by directly heating above the switching temperature. However, combination of SMPs with conductive fillers enables shape recovery by applying a voltage instead of using external heating, which may permit fabrication of smart electroactive actuators. Herein, we demonstrate that, by controlling drawing temperature and related morphology, rapid electroactive shape recovery has been realized in a ternary composite consisting of multiwalled carbon nanotubes (MWCNTs) and two biodegradable polyesters, a property that was not available in composites using only one of the polyesters. [ABSTRACT FROM AUTHOR]

The toughness of conventional injection-molded isotactic polypropylene bars has been investigated with respect to the notch location and β-nucleating agent. Superior toughness is achieved in the β-nucleated bars with notches near the gate, but is absent in the near-gate bars without β-nucleating agent or in the β-nucleated ones far from the gate. With detailed structural analysis across the sample thickness, it is indicated that in these tough bars, extensive flow close to the surface suppresses the formation of β-form to a large extent but favors the generation of oriented α-form, whereas toward inner region, an opposite tendency is presented with the decay of flow strength and the activation of β-nucleating agent. Allowing that this peculiar hierarchical structure is absent in other two kinds of bars, it is deduced that the cooperative effect of molecular orientation of α-form in the skin layer and rich β-form in the inner region is responsible for the significant toughness enhancement in the β-nucleated bars near the gate. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Toughening of poly (L-lactide) (PLLA) by flexible poly (ε-caprolactone) (PCL) is very attractive for biomedical applications. However, PLLA/PCL blends usually behave brittle fracture, which is ascribed to the immiscibility between two components. This study demonstrates that without physical aging dispersed PCL particles can induce significant ductile deformation of PLLA matrix, accompanied by remarkable decreasing of yield strength, opposite to what is observed in the aged blends. It is deduced that segmental mobility of PLLA matrix and crystalline order of PCL domains, rather than immiscibility, play vital role in determining the ductility of PLLA/PCL blends. [ABSTRACT FROM AUTHOR]

To improve the toughness of isotactic polypropylene (iPP), by blending modification or special processing techniques, is an ongoing pursuit in the polymer community. In this study, the toughness of injection-molded iPP bars has been enhanced by about four times upon annealing at 140°C, in parallel with slight increasing of stiffness. Through various structural characterizations it has been confirmed that the remarkable toughening effect in the annealed iPP bars mostly results from the enhanced molecular mobility in the amorphous phase due to lamellar perfection, rather than from the change of molecular orientation, crystal modification, crystallinity, and so on. Moreover, it is deduced that the gain of mobile amorphous fraction in the hierarchical iPP bars upon annealing follows the order of skin > intermediate > core, same to that contributing to the toughness enhancement. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A plasticizer, polyethylene glycol (PEG), was used to disperse multiwalled carbon nanotubes (MWCNTs) in biodegradable poly( L-lactide) during one-step melt mixing. Incorporation of PEG significantly promotes the formation of a percolating MWCNT network in the plasticized composites, as revealed by rheological measurements and morphological observations. It, in turn, results in the retarded glass transition and cold crystallization behaviors in these plasticized composites as a result of constrained chain relaxation. It is believed that noncovalent wrapping of MWCNTs by PEG is responsible for the improved affinity between MWCNTs and the poly( L-lactide) matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Achieving high molecular orientation, by increasing spinning velocity and/or postdrawing, is critical to improve the mechanical properties of isotactic polypropylene (iPP) fibers. In this study, we have demonstrated that upon annealing around melting point the molecular orientation of both amorphous and crystalline phases in melt-spun iPP monofilaments is significantly enhanced, in parallel with the improved stability of crystals, because of partial melting and oriented recrystallization. As a result, high level stress and remarkable strain hardening are generated during stretching of annealed monofilaments. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Poly(L-lactic acid) (PLA) samples prepared by hot pressing were treated by two different processes: process a—quenching of the molten specimens in water, then annealing at high temperatures; process b—direct crystallization at high temperatures from the molten specimens. The crystal modification and morphology of PLA were investigated by differential scanning calorimetry, dynamic mechanical analysis, polarized light microscopy, and wide-angle X-ray diffraction. In the case of process a, the α′ (disordered α) crystal modification was formed at relatively low annealing temperature (T a < 100°C), while the ordered α phase was formed in the case of process a at high T a (> 100°C) and process b. Furthermore, in process a, the nucleation density of spherulites was higher and the radius of the spherulites was much smaller compared with that of the spherulites formed by process b. The effects of crystal modification and morphology on the impact behaviors of PLA were investigated by notched Izod impact testing. The macroscopic fracture toughness was discussed in terms of the microscopic structures. Finally, we suggest an alternative approach for the preparation of high-performance PLA. [ABSTRACT FROM PUBLISHER]

Different from other semi-crystalline polymers, the crystallization of syndiotactic polypropylene (sPP) into helical sequences under flow is largely inhibited due to favorable formation of trans-planar conformations. The results presented in this study, using micro-FTIR, 2D-WAXS, and 2D-SAXS characterization, indicate that molecular orientation and crystallization in melt-spun sPP monofilaments can be dramatically enhanced by a sorbitol-based nucleator. It is suggested that, similar to the oriented crystallization in the nucleated isotactic polypropylene (iPP), the phase-separated nanofibrils, aligned under flow prior to sPP crystallization, act as shish structure (primary nuclei) to mediate the molecular orientation and crystallization of sPP. [ABSTRACT FROM PUBLISHER]

In this study, a facile route to realize the superior toughness of injection molded polypropylene random copolymer (PPR) is reported. The toughness of PPR is increased about twofold when the processing melt temperature increases from 180 to 250 °C. Systematic and detailed structural characterizations have been carried out to establish the structure-property relationships by using polarized light microscopy, scanning electron microscopy, infrared microscopy and dynamic mechanical analysis. It is found that increasing the melt temperature is beneficial for the coalescence of rubbery domains and enhanced molecular mobility which are mainly responsible for the improvement in toughness. Other factors, such as molecular orientation, crystallinity and so on, seem to have little effect. The vital role of enhanced molecular mobility in improving toughness is further demonstrated by the annealing of injection molded samples at elevated temperature, i.e. 110 °C. Copyright © 2011 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A promising method for toughening isotactic polypropylene (iPP) without loss of stiffness is to enhance molecular orientation during processing. However, conventional injection molding cannot impart remarkable molecular orientation to the molded bars as a result of retarded lamellar growth upon rapid solidification and thus has little contribution to the toughness enhancement. Herein, we demonstrated that molecular orientation in the conventional injection molded iPP bars has been notably enhanced through oriented re-crystallization after partial melting at 175 °C. As a result, about 3.5 times increase in the toughness, in parallel with apparent strength enhancement, has been gained in these re-crystallized bars. Our findings offer a simple and economic approach to produce tough iPP and maybe other semi-crystalline polymers in practice. [ABSTRACT FROM AUTHOR]

The oriented crystallization in stretched rubbery poly(L-lactide) has been studied with the aid of in-situ rheo-Fourier transform infrared spectroscopy (FTIR) measurements and morphological observations. The oriented segments that survived after stretching are first transformed into shish structure composed of helical sequences via intra-chain conformational ordering and propagation, followed by the transverse growth of kebabs from the coiled chains in the surrounding matrix. Moreover, the formation of shish structure and kebabs shows different dependences on the stretching temperature as a result of different controlling molecular processes. [ABSTRACT FROM AUTHOR]

Special crystallization event of isotactic polypropylene (iPP) in a constrained environment, a layered clay network, was followed by in situ Fourier transform infrared (FTIR) spectroscopy during the cooling process. Before occurrence of nucleation/crystallization, a conformationally ordered phase, which consists of significant amounts of long 31 helices with 14 monomeric units, has been identified for the first time. More importantly, it was found that the long-ordering helices could play a more important role than short ones for the confined crystallization. It could be tentatively explained as due to the existence of constrained regions in the proximity of the nanoclay platelets or tactoids and the heterogeneous nucleation capability of the surface of nanoclay. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]