Manufacturing homogenous PVC/graphene nanocomposites using a novel dispersion agent

The goal of the study was to prepare a graphene (GN) dispersion in a poly (vinyl chloride) (PVC) solution with enhanced stability of the nanofiller thanks to the application of curcuma extract (CE). The stable dispersion was used to obtain PVC/GN nanocomposites with more homogeneous graphene by the solvent evaporation method. The CE effectiveness was compared with two commercially available dispersants in the form of oleic acid (OA) and polysorbate 80 (P80).The chemical composition of the CE was examined by Fourier-transform infrared spectroscopy. The dispersion stability was tested by the multiple light scattering method (Turbiscan Lab) and evaluated visually over a period of 40 days. The homogeneity of the filler's dispersion in the PVC matrix was evaluated by scanning electron microscopy and Raman spectroscopy.The application of the dispersing agents led to improved stability of the graphene dispersion in PVC solution. CE was the agent that most effectively improved the homogeneity of graphene dispersion, both in dispersions in a PVC solution and in PVC/GN nanocomposite films.     

Poly(vinyl alcohol) physical hydrogels: new vista on a long serving biomaterial

Poly(vinyl alcohol), PVA, and physical hydrogels derived thereof have an excellent safety profile and a successful history of biomedical applications. However, these materials are hardly in the focus of biomedical research, largely due to poor opportunities in nano- and micro-scale design associated with PVA hydrogels in their current form. In this review we aim to demonstrate that with PVA, a (sub)molecular control over polymer chemistry translates into fine-tuned supramolecular association of chains and this, in turn, defines macroscopic properties of the material. This nano- to micro- to macro- translation of control is unique for PVA and can now be accomplished using modern tools of macromolecular design. We believe that this strategy affords functionalized PVA physical hydrogels which meet the demands of modern nanobiotechnology and have a potential to become an indispensable tool in the design of biomaterials.     

Preparation and characterization of cationic poly vinyl alcohol with a low degree of substitution

The cationization of polymers has been regarded as an effective method to improve their performance for various applications. In this work, the cationization of poly vinyl alcohol (PVA) was investigated under different conditions, i.e., various glycidyl-trimethylammonium chloride (GTMAC) to PVA ratios, reaction temperatures, times, PVA and NaOH concentrations and solvent compositions. The results showed that the overall efficiency of the cationic modification was rather low, which was due to the hydrolysis of both GTMAC and cationic-modified PVA (CPVA) under the strong alkaline conditions employed. The results also showed that the optimum GTMAC/PVA ratio depended on the solvent composition. The cationization was confirmed by means of ¹H NMR and FTIR analyses. The maximum efficiency in water was obtained under the conditions of 95 °C, 1 h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration, while that in the ethanol/DMSO mixture (1.25 v/v) was obtained under the conditions of 70 °C, 1 h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration. Additionally, the interaction of CPVAs with a silicon wafer (as a substrate) was determined by employing an atomic force microscope (AFM) in water and air.     

Finite element simulation for yield stress of hard poly(vinyl chloride)/acrylonitrile-butadiene-styrene blends at different crosshead speeds

Hard poly(vinyl chloride)(PVC)/acrylonitrile-butadiene-sryrene(ABS) blends were prepared using injection-molding and influence of crosshead speed on mechanical properties was examined.Based on morphology parameters obtained from transmission electron microscopy photography and the material parameters from true stress-strain curves of neat PVC and ABS,yield stresses of the blends at different crosshead speeds were simulated employing a two-dimensional nine-particle model based on the finite element analysis(FEA).The FEA results were compared with the experimental yielding stress and the good agreement validated the simulation approach.The FEA approach allowed establishing a yielding criterion related to local yielding of the interstitial matrix between ABS particles.     

η-Cyclopentadienylpalladium(II) complexes: Synthesis, characterization and use for the vinyl addition polymerization of norbornene and the copolymerization with 5-vinyl-2-norbornene or 5-ethylidene-2-norbornene

Dinuclear complexes of palladium(II), containing two bridging halogen (Cl or Br) ligands, [NⁿBu₄]₂[(X₅C₆)₂Pd(μ-Cl)₂Pd(C₆X₅)₂] and [(X₅C₆)(L)Pd(μ-Y)₂Pd(C₆X₅)(L)] (X = F, Cl; Y = Cl, Br), readily react with cyclopentadienylthallium, C₅H₅Tl, to give the corresponding air stable half-sandwich, pseudo-trigonal η⁵-cyclopentadienylpalladium complexes, [NⁿBu₄][(η⁵-C₅H₅)Pd(C₆X₅)₂] (X = F 1, Cl 2) and (η⁵-C₅H₅)Pd(C₆X₅)(L) (X = F, L = CNBu^t3, PPh₃4, PMe₂Ph 5, PEt₃6, AsPh₃7, SbPh₃8; X = Cl, L = PMe₂Ph 9, PEt₃10), respectively. With tetraphenylcyclopentadienylthallium, C₅Ph₄HTl or pentabenzylcyclopentadienylthallium, C₅Bn₅Tl (Bn = CH₂Ph) the air stable half-sandwich complexes (η⁵-C₅Ph₄H)Pd(C₆F₅)(AsPh₃), 12 and (η⁵-C₅Bn₅)Pd(C₆F₅)(AsPh₃), 13 are synthesized accordingly. The molecular structures were verified by NMR-spectroscopy, X-ray crystallography (7, 12, 13) and electron impact-mass spectrometry (EI-MS). The precatalysts 4 and 7 can be activated with methylalumoxane (MAO) for the homopolymerization of norbornene (NB) and 5-ethylidene-2-norbornene (ENB) and for the copolymerization of NB with 5-vinyl-2-norbornene (VNB) or ENB with activities of more than 10⁶ g_PNB/(mol_Pd·h). The higher activity of 7/MAO over 4/MAO towards NB homopolymerization was reversed when the olefin-substituted VNB or ENB were added. Then, the more strongly bound PPh₃ ligand of 4 (versus AsPh₃ of 7) can compete with the olefin functionality of VNB or ENB and assume a directing role for the insertion of the ring double bond. As a consequence 4/MAO shows almost the same activity in NB and ENB homopolymerization.     

pH值对硅烷偶联剂表面改性稀土长余辉发光材料的影响

为提高稀土长余辉发光材料SrMgAl4 O8:Eu2+,Dy3+在非极性树脂中的分散性和相容性,用硅烷偶联剂YDH-570在强酸条件下对其进行了表面改性.通过质量变化、比表面积、ATR-FTIR、SEM(能谱分析)和发光性能分别研究了该条件下不同ptH值改性对材料表面组成、形貌和性能的影响.结果发现:强酸条件下改性效果十分显著;当pH值由0.6增加到0.72时,样品增重率达23.3％,33.3％,53.3％,比表面积净增75.6％,215.2％,265.4％;对于改性效果较明显的pH为0.72的样品,能谱分析证实是一种片状有机包覆层结构;余辉衰减曲线表明,表面改性对材料发光性能影响不大.     

Solid‐Phase Organic Synthesis of Aryl Vinyl Ethers Using Sulfone‐Linking Strategy

A novel facile solid‐phase organic synthesis of aryl vinyl ethers by reaction of polystyrene‐supported 2‐phenylsulfonylethanol with phenols under Mitsunobu conditions and subsequent elimination reaction with DBU has been developed. The advantages of this method include straightforward operation, good yield and high purity of the products. Alternatively, a typical example of Suzuki coupling reaction on‐resin was further applied to prepare 4‐phenylphenyl vinyl ether for extending this method.     

Anionic synthesis of binary random in-chain multi-functionalized poly(styrene/butadiene/isoprene and dimethyl [4-phenylvinyl)-phenyl]silane)(PS-DPESiH,PB-DPESiH,PI-DPESiH) copolymers

The binary random in-chain silyl-hydride multi-functionalized poly(styrene/butadiene/isoprene and dimethyl[4-(1-phenylvinyl) phenyl]silane)(PS-DPESiH,PB-DPESiH,PI-DPESiH) copolymers were successfully synthesized.These functionalized copolymers were prepared in hexane with n-BuLi as the initiator at 50℃for 4 h.The silyl-hydride groups were introduced into polymer backbones quantitatively by living anionic polymerization.The copolymers were determined through ’H NMR,size exclusion chromatography(SEC) and differential scanning calorimetry(DSC) techniques,while the number of silyl-hydride groups was calculated and discussed.