Enhancement of Energy Density in the BOPP-Based Sandwich-Structured Film by the Synergistic Effect of BaTiO₃@Polyaniline Hybrid Dielectric Fillers

A series of polyaniline-coated BaTiO3 (BaTiO3@PANI) hybrid dielectric fillers were prepared through the in situ oxidative polymerization of aniline. The morphology of the hybrid fillers can be controlled by the ratio of aniline and BaTiO3 particles. Mulberry-like and core–shell BaTiO3@PANI composite particles are prepared successfully. The two kinds of dielectric fillers were introduced into the poly(vinylidene fluoride) (PVDF) matrix separately or simultaneously. The dielectric loss can be suppressed by the synergetic effect of these two hybrid fillers while enhancing the dielectric constant at the same time. The finite element simulation results showed that the surface morphology of adjacent hybrid fillers played an important role in the dielectric performance. The fillers were introduced in the biaxially oriented polypropylene (BOPP)-based sandwich-structured film; specifically, the outer layer was BOPP and the middle layer was the composites consisting of chlorinated polypropylene (CPP)/PVDF blends and the hybrid fillers. The energy storage density of the sandwich-structured film was improved significantly compared to that of the BOPP film. The highest discharge energy density was 7.31 J/cm3 at 450 MV/m, and the charge–discharge efficiency was 77.3% with 30 wt % hybrid fillers in the middle layer

Nonisothermal Crystallization Behavior and Enhanced Heat Resistance and Impact Toughness of Poly(l‑lactic acid) with Bimodal Molecular Weight Distribution

Poor heat resistance and toughness put some limitations on the applications of poly­(lactic acid), one of the most promising eco-friendly polymers. Herein, bimodal poly­(l-lactic acid) (PLLA) was prepared by melt-blending high- and low- molecular-weight PLLAs, and the nonisothermal crystallization behavior, heat resistance, and mechanical properties of bimodal PLLA were investigated. Low-molecular-weight PLLA (L-PLLA) improves the crystallization capability of bimodal PLLA. The double melting behavior is reasonably explained by the melting–recrystallization mechanism. Octamethylenedicarboxylic dibenzoylhydrazide, a typical heterogeneous nucleating agent, significantly enhances the crystallization rate and crystallinity of PLLA. The maximum crystallinity of 100% L-PLLA is as high as 54.4%, and the heat deflection temperature (HDT) of the bimodal PLLA containing 95% L-PLLA is up to 151 °C, while the impact strength drops sharply to 17.2 kJ/m2 due to the large crystallite size. d-Sorbitol (DS) exhibits a completely different mechanism from heterogeneous nucleation, that is, a lower crystallization rate but elevated crystallinity and crystallization temperature. The DS-modified sample realizes an excellent balance between heat resistance (HDT up to 136 °C) and impact strength (47.9 kJ/m2) via a self-toughening effect by increasing the crystallinity and reducing the crystallite size

Separated Immobilization of Incompatible Enzymes on Polymer Substrate via Visible Light Induced Living Photografting Polymerization

The use of the mixed catalytic system with several enzymes can provide multiple benefits in terms of the cost, simplification of a multistep reaction, and effectiveness of complex chemical reactions. Although study of different enzyme coimmobilization systems has attracted increasing attention in recent years, separately immobilizing enzymes which can not coexist on one support is still one of the great challenges. In this paper, a simple and effective strategy was introduced to separately encapsulate incompatible trypsin and transglutaminase (TGase) into different poly­(ethylene glycol) (PEG) network layer grafted on low-density polyethylene (LDPE) film via visible light induced living photografting polymerization. As a proof of concept, this dual-enzyme separately loaded film was used to catalyze the synthesis of a new target antitumor drug LTV-azacytidine. The final results demonstrated that this strategy could maintain higher activities of both enzymes than the mixed coimmobilization method. And the mass spectra analysis results demonstrated that LTV-azacytidine was successfully synthesized. We believe that this facile and mild separately immobilizing incompatible enzyme strategy has great application potential in the field of biocatalysis

Direct One-Pot Synthesis of Chemically Anisotropic Particles with Tunable Morphology, Dimensions, and Surface Roughness

Previously, synthesis of anisotropic particles by seeded polymerizations has involved multiple process steps. In conventional one-pot dispersion polymerization (Dis.P) with a cross-linker added, only spherical particles are produced due to rapid and high cross-linking. In this Article, a straightforward one-pot preparation of monodisperse anisotropic particles with tunable morphology, dimensions, surface roughness, and asymmetrically distributed functional groups is described. With a cross-linker of divinylbenzene (DVB, 8%), ethylene glycol dimethacrylate (EGDMA, 6%), or dimethacryloyloxybenzophenone (DMABP, 5%) added at 40 min, shortly after the end of nucleation stage in Dis.P of styrene (St) in methanol and water (6/4, vol), the swollen growing particles are inhomogeneously cross-linked at first. Then, at low gel contents of 59%, 49%, and 69%, corresponding to the cases using DVB, EGDMA, and DMABP, respectively, the growing particle phase separates and snowman- or dumbbell-like particles are generated. Thermodynamic and kinetic analyses reveal that moderate cross-linking and sufficient swelling of growing particles determine the formation and growth of anisotropic particles during polymerization. Morphology, surface roughness, sizes, and cross-linking degrees of each domain of final particles are tuned continuously by varying start addition time and contents of cross-linkers. The snowman-like particles fabricated with DVB have a gradient cross-linking and asymmetrical distribution of pendant vinyl groups from their body to head. The dumbbell-like particles prepared using DMABP have only one domain cross-linked; i.e., only one domain contains photosensitive benzophenone (BP) groups. With addition of glycidyl methacrylate (GMA) or propargyl methacrylate (PMA) together with DVB or EGDMA, epoxy or alkynyl groups are asymmetrically incorporated. With the aid of these functional groups, carboxyl, amino, or thiol groups and PEG (200) are attached by thiol–ene (yne) click and photocoupling reactions

Entrapment of Xylanase within a Polyethylene Glycol Net-Cloth Grafted on Polypropylene Nonwoven Fabrics with Exceptional Operational Stability and Its Application for Hydrolysis of Corncob Hemicelluloses

Enzyme immobilization is a core technique of enzymatic biochemical engineering because it can remarkably reduce the cost of enzymes and improve the enzyme recovery procedure. The most crucial issues for enzyme immobilization include (1) maintaining its activity, both in the immobilization process and in the batchwise catalyst course; (2) separating the immobilized enzyme from the reaction mixture; and (3) the readiness and cost of the immobilization process. Herein, we report a new strategy to immobilize xylanase within a hydrophilic and nonswelling polyethylene glycol (PEG) net-cloth grafted on a polypropylene nonwoven fabric (PP_NWF) membrane by a visible light-induced surface graft cross-linking polymerization. The xylanase was in situ entrapped within the PEG net-cloth. The nonswelling PEG net-cloth can effectively maintain the xylanase without leakage in long-term operation. As for the hydrolysis of corncob hemicelluloses, the experimental results showed that the as-formed immobilized xylanase retained 80% of its original activity after being reused for 25 cycles and 60% after 50 cycles, which is far better than that of other immobilization methods by entrapment. Notably, this simple in situ entrapment of enzymes on routine polymeric matrix would lead to an easy industrial production at low cost, while the form of end-products as a sheet can be readily separated from the reaction mixture and reused for batchwise production. After immobilization, the xylanase showed no significant shift in pH or temperature optima as compared with its free form. These results suggest that the immobilization of xylanase within the PEG net-cloth grafted on PP_NWF is promising for industrial applications because of its long-term operation stability and convenient recovery for reuse

Ammonium-Functionalized Hollow Polymer Particles As a pH-Responsive Adsorbent for Selective Removal of Acid Dye

In this work, a novel type of ammonium-functionalized hollow polymer particles (HPP-NH₃⁺) with a high density of ammonium groups in the shell has been specially designed and synthesized. Benefiting from both the high surface area and from the high density of positively charged ammonium groups, the as-prepared HPP-NH₃⁺ can serve as a selective adsorbent for the removal of negatively charged acid dye (e.g., methyl blue <i>a</i>-MB). The equilibrium adsorption data of <i>a</i>-MB on the HPP-NH₃⁺ were evaluated using Freundlich and Langmuir isotherm models, and Langmuir isotherm exhibited a better fit with a maximum adsorption capacity of 406 mg/g. Most importantly, because of the presence of dual functional groups (ammonium and carboxyl groups), the HPP-NH₃⁺ showed a significant pH-dependent equilibrium adsorption capacity, which increased dramatically from 59 mg/g to 449 mg/g as the solution pH decreased from 9 to 2. This uniqueness makes the dye-adsorbed HPP-NH₃⁺ can be facilely regenerated under mild condition (in weak alkaline solution, pH 10) to recover both <i>a</i>-MB and the HPP-NH₃⁺, whereas the recovery of conventional adsorbents is commonly performed under particularly severe conditions. The regenerated HPP-NH₃⁺ can be reused for dye removal and the dye removal efficiency remained above 98% even after five adsorption–desorption cycles. Because of its high adsorption capacity, pH-sensitivity, easy regeneration, and good reusability, the HPP-NH₃⁺ has great potential for the application in the field of water treatment, controlled drug release, and pH-responsive delivery

UV-Induced Thiol–Ene “Click” Surface Grafting Polymerization on BOPP Substrate and Its Postmodifying for Hydrophilic and Antibacterial Applications

This paper proposed a novel and versatile surface modification route by integrating UV light-mediated thiol–ene “click” surface grafting polymerization and postmodification via the reactions of the surface thiol groups. At first, poly(thiol ether) layers with tunable thiol group density, up to 8.2 × 102 ea/nm3 for cross-linked grafting layers, were grafted from biaxially oriented polypropylene (BOPP) film. Then, the surface −SH groups reacted with epoxy compounds to introduce quaternary ammonium salt. With the immobilized quaternary ammonium salt and coordinated Zn2+ ions, the modified film demonstrated 99.98% antibacterial rate against Staphylococcus aureusafter soaking in DI water for 21 days and in a highly alkaline environment (0.1 M NaOH aqueous solution) for 3 days, and the surface water contact angle decreased to 39°. At last, the polymethacrylate chains were also successfully grafted from the surface thiol groups of the cross-linked poly(thiol ether) under visible light irradiation. With 2-(dimethyldodecylammonium) ethyl methacrylate as the grafting monomer, the modified BOPP film had shown a 99.99% antibacterial rate against both Escherichia coliand S. aureus. Meanwhile, with 2-methacryloxyethyl phosphoryl choline as grafting monomer, the modified surface showed an excellent antibioadhesion of living S. aureus, and the surface water contact angle was as low as 48°

Image_1_Involvement of 5-HT1A receptors of the thalamic descending pathway in the analgesic effect of intramuscular heating-needle stimulation in a rat model of lumbar disc herniation.JPEG

BackgroundIntramuscular (IM) heating-needle therapy, a non-painful thermal therapy, has been found to exert an analgesic effect via the thalamic ventromedial (VM) nucleus, solely by reducing the triggering threshold for descending inhibition; this could be modulated by intracephalic 5-hydroxytryptamine-1A (5-HT1A) receptors, rather than via the regular analgesia pathway. In this study, the effect and the potential serotonergic mechanism of IM heating-needle stimulation at 43°C were explored in the case of the pathological state of lumbar disc herniation (LDH).MethodsA modified classic rat model of LDH, induced via autologous nucleus pulposus implantation, was utilized. IM inner heating-needles were applied at the attachment point of skeletal muscle on both sides of the L4 and L5 spinous processes. WAY-100635 and 8-OH-DAPT, 5-HT1A receptor antagonist and agonist, were separately injected into the bilateral thalamic mediodorsal (MD) and VM nucleus via an intrathalamic catheter. Nociception was assessed by bilateral paw withdrawal reflexes elicited by noxious mechanical and heat stimulation.ResultsIM heating-needle stimulation at a temperature of 43°C for 30 or 45 min significantly relieved both mechanical and heat hyperalgesia in the rat model of LDH (P 0.05). Injection of 8-OH-DAPT into the thalamic MD nucleus exerted no modulating effects on either mechanical or heat hyperalgesia (P > 0.05).ConclusionIM heating-needle stimulation at 43°C for 30 min may activate 5-HT1A mechanisms, via the thalamic VM nucleus, to attenuate hyperalgesia in a rat model of LDH. This innocuous form of thermal stimulation is speculated to selectively activate the descending inhibition mediated by the thalamic VM nucleus, exerting an analgesic effect, without the involvement of descending facilitation of the thalamic MD nucleus.</p

Emulsion copolymerization of vinyl chloride with poly (ethylene glycol) methyl ether methacrylate

In this work, we reported a novel emulsion copolymerization of vinyl chloride monomer (VCM) with amphipathic monomer poly (ethylene glycol) methyl ether methacrylate (PEGMA) by using sodium dodecyl sulfate (SDS) as emulsifier and K2S2O8/NaHSO3 as redox initiator. Owing to the multifunctionality of PEGMA that can serve as co-monomer and ‘emulsifier’, the emulsion copolymerization is achieved successfully and the interesting results demonstrate quite different features such as:(1) the stable P[(VC)-co-(PEGMA)] latex is obtained only when the mass ratio of PEGMA > 10% (to total monomer mass), (2) a small amount of ionic emulsifier SDS is required to achieve a stable latex, and (3) the mechanism of the micellar formation is different from the typical emulsion polymerization. Unexpectedly, the obtained copolymer formed high content of gel fraction which is mainly caused by the chain transfer reaction of the PVC growth chain radical to the hydrogen atom of the methylene from alkoxy (-OCH2CH2-) of the PEGMA oligomer chain. However, it could be inhibited effectively by the addition of chain transfer agent 2-mercaptoethanol (2-MCE). Subsequently, the properties of as-obtained P[(VC)-co-(PEGMA)] copolymer are evaluated carefully and it exhibited unique features such as self-plasticization, lower Tg (decreased from 83.1 to 59.6 °C), higher heat resistance (increased from 270 to 290 °C), hydrophilic, and high transparent in comparison to pure PVC. These outstanding features of the P[(VC)-co-(PEGMA)] copolymer offered a potential route for the functional modifications of PVC and broadened its further use.</p

Copolymers of Vinyl Acetate and Vinyl Carboxylates Bearing Branched C₇–C₉ Chains: Synthesis, Alcoholysis, and Properties

This contribution reported the radical copolymerization of vinyl acetate (VAc) with vinyl carboxylates bearing branched C7–C9 chains, including vinyl neononanoate (VV-9), vinyl neodecanoate (VV-10), and vinyl 2-ethylhexanoate (VV-EH), and the VAc units of the as-prepared copolymers were subsequently hydrolyzed to vinyl alcohol units in a base medium. With reactivity ratios of r1 = 0.94 (VV-9) and r2 = 0.96 (VAc), the copolymerization of VV-9 and VAc demonstrates an ideal azeotropic copolymerization. By simply adjusting the initial feed ratios, terpolymers of VV-9, VAc, and vinyl alcohol (PVVOH) with different compositions have been successfully prepared. As a proof-of-concept, their application as modifiers to improve the adhesive, hydrophilic, and oxygen barrier properties of low-density polyethylene (LDPE) was evaluated. When the PVVOH with 40 wt % VV-9 units was blended with LDPE, the dispersed PVVOH phase formed microdomains with a size of about 1 μm, and there was no observable two-phase structure. The water contact angles of the PVVOH/LDPE blends were reduced from 103.7 ± 0.9° to 51.1 ± 1.3° and retained after being soaked in water at ambient conditions for 30 days. PVVOH is also effective in improving the adhesion between LDPE and aluminum alloys. With the addition of 25 wt % PVVOH (20 wt % VV-9), the ultimate shear strength of the lap joint was effectively enhanced from 3.60 ± 0.17 MPa (pristine LDPE) to 4.87 ± 0.02 MPa. Furthermore, the addition of 20 wt % PVVOH reduced the oxygen transmission rates (OTR) of LDPE film from 145.3 to 52.2 cm3·mm·m–2·day–1·bar–1