O-三丁基锡炔基或烯基膦酸的合成及其结构表征

以三丁基氯化锡与炔基或烯基膦酸钠反应,合成了8种新的O-三丁基锡炔基或烯基膦酸类化合物,利用元素分析、IR、∧1HNMR、MS等手段对其结构进行了表征,结果表明,这些化合物具有五配位锡原子的聚合结构。     

Understanding polymorphism formation in electrospun fibers of immiscible Poly(vinylidene fluoride) blends

Effects of electric poling, mechanical stretching, and dipolar interaction on the formation of ferroelectric (β and/or γ) phases in poly(vinylidene fluoride) (PVDF) have been studied in electrospun fibers of PVDF/polyacrylonitrile (PAN) and PVDF/polysulfone (PSF) blends with PVDF as the minor component, using wide-angle X-ray diffraction and Fourier transform infrared techniques. Experimental results of as-electrospun neat PVDF fibers (beaded vs. bead-free) showed that mechanical stretching during electrospinning, rather than electric poling, was effective to induce ferroelectric phases. For as-electrospun PVDF blend fibers with the non-polar PSF matrix, mechanical stretching during electrospinning again was capable of inducing some ferroelectric phases in addition to the major paraelectric (α) phase. However, after removing the mechanical stretching in a confined melt-recrystallization process, only the paraelectric phase was obtained. For as-electrospun PVDF blend fibers with the polar (or ferroelectric) PAN matrix, strong intermolecular interactions between polar PAN and PVDF played an important role in the ferroelectric phase formation in addition to the mechanical stretching effect during electrospinning. Even after the removal of mechanical stretching through the confined melt-recrystallization process, a significant amount of ferroelectric phases persisted. Comparing the ferroelectric phase formation between PVDF/PSF and PVDF/PAN blend fibers, we concluded that the local electric field-dipole interactions were the determining factor for the nucleation and growth of polar PVDF phases.     

Effect of coagulation bath temperature on formation mechanism of poly(vinylidene fluoride) membrane

Effects of coagulation bath temperature on the membrane formation mechanism and the morphologies of the formed membranes were studied. The binodal and spinodal lines in the phase diagrams of water/DMAc/Poly(vinylidene fluoride) (PVDF) were calculated based on the thermodynamics equations of membrane formation, and the gel phase boundaries of the systems at 25°C and 60°C were determined via cloud point measurement. The obtained ternary phase diagrams of water/DMAc/PVDF contain three regions: the one‐phase region, the liquid–liquid two‐phase region, and the gel region. In the phase diagrams, the liquid–liquid demixing line (binodal) is located inside the gelation line. At low temperature, there exists a wide region between gelation line and binodal line. Gelation could occur in the absence of liquid–liquid demixing, and becomes the dominant membrane formation mechanism. At high temperatures (60°C), however, the gelation line approaches the binodal line, which results in a much smaller gelation zone. The kinetics of the solvent out‐flux and water influx were enhanced, liquid–liquid demixing is the dominant mechanism. The membrane formation mechanisms at different temperature were confirmed by the light transmission measurements during membrane forming process and the morphologies of the membranes examined by SEM imaging. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

Crosslinking of fibers via azide–alkyne click chemistry: Synthesis and characterization

There has been growing interest in fiber modification for several industrial applications. The modifications have mostly been done to improve the fiber properties. However, the information regarding fiber modification via click chemistry is still limited. In this work, two strategies of click chemistry are evaluated for modifying commercial paper without the addition of copper catalyst. The first strategy is the direct reaction between azidated fiber and propargylated fiber, and the second strategy is to bridge azidated fiber with a self‐made alkyne terminal crosslinker. Native and chemically modified fibers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and ¹H‐NMR spectroscopy. The effects of the two clicking strategies on the fiber were further investigated by making handsheets. In terms of mechanical properties, the bridge‐clicking strategy was found to produce better handsheets than the direct‐clicking strategy. These modified fibers would be an interesting application for the packaging and printing industries. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43576.     

Properties of poly(vinylidene fluoride)

The properties of fluorocarbon plastics have made them desirable for numerous new applications. Poly(vinylidene fluoride) (PVF₂) can be easily extruded into films or fibers or injection molded into a variety of shapes. It was found that crystallinity, molecular weight distribution and polymer structure are important in establishing resin properties. Highly crystalline PVF₂ with a narrow Gaussian molecular weight distribution gives specimens with optimum physical and chemical properties.     

A new approach for conductive network formation in electrospun poly(vinylidene fluoride) nanofibers

Conductive nanofibers of poly(vinylidene fluoride) (PVDF) filled with polyaniline (PANi)‐coated multi‐wall carbon nanotubes (MWCNTs) were fabricated using the electrospinning technique. PANi is an intrinsically conductive polymer. The addition of PANi‐coated MWCNTs to PVDF created short conductive strands on the surface of the nanofibers, facilitating the formation of a conductive network in the transverse direction of the nanofibers. Piezoelectricity along with electric conductivity makes these PVDF nanofibers promising for applications such as sensors and actuators. Electrospun PVDF nanofiber mats had higher piezoelectricity than melt‐processed samples produced using traditional polymer processing techniques, such as compression molding. Spectroscopic imaging techniques were employed to study the effects of the filler and processing conditions on the nanofiber structure. X‐ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry results indicated a large increase in the β‐phase crystals of the PVDF nanofibers. This higher content of β‐phase crystals enhanced the piezoelectricity of the nanofibers. © 2015 Society of Chemical Industry     

Features of structure formation and electrophysical properties of poly(vinylidene fluoride) crystalline ferroelectric polymers

The influence of intramolecular dipole–dipole interaction changes on structure formation peculiarities and some electrophysical properties were investigated with example of copolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene with different compositions. The decrease of such dipole–dipole interactions in vinylidene fluoride/tetrafluoroethylene copolymers leads to an increase of the a and b parameters of the ferroelectric phase lattice and were accompanied by a shift of the Curie point to lower temperatures. The presence of peak‐halo at angles near 2θ = 18° were attributed to a paraelectric phase localized in the interfacial domains at the crystal–amorphous phase boundaries. Similar peak‐halos for vinylidene fluoride/hexafluoropropylene copolymers crystallizing into the nonpolar α phase were associated with the presence of an antiferroelectric phase formed by the chains in the planar zigzag conformation. The temperature range where dielectric anomalies were detected was characterized by conformational changes at which the decrease in planar zigzag conformation isomers took place. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crystallization kinetics of poly(vinylidene fluoride)

Specimens of poly(vinylidene fluoride) were crystallized isothermally at a series of temperatures in the vicinity of the melting point. The -form was the only crystalline polymorph present in the crystallized samples. Crystallization rates have been measured by differential scanning calorimetry. The results were analysed in terms of the Avrami equation. The rates of crystallization depend upon the undercooling and the data agree with a process of growth of spherulites controlled by a secondary surface coherent nucleation mechanism. The equilibrium melting temperature, the Avrami exponent, the free energy of formation of a nucleus of critical dimensions and the surfaces free energy of the lamellar crystallites were determined.     

聚偏氯乙烯废弃物的利用

介绍聚偏氯乙烯生产和吹膜过程中产生的废弃物回收利用的几个实例,说明在使用聚偏氯乙烯时要充分利用其使用价值。     

The solubility of poly(vinylidene chloride)

The relative abilities of various solvents to dissolve crystalline polyvinylidene chloride were judged by comparing temperatures at which dilute suspensions became homogeneous. PVDC is not soluble in common solvents at ambient temperatures. It dissolves in solvents of matching solubility parameter only above ～130°C. An analysis of the data suggests that δ = 10.1 for PVDC. Five classes of specific solvents were observed that could dissolve PVDC at much lower temperatures. These include sulfoxides, dialkyl amides, alkyl lactams, cyclic sulfides, and cyclic ketones. PVDC acts as a weak Lewis acid in these solutions. The best solvents found, in order of decreasing activity, are: hexamethylphosphoramide, tetramethylene sulfoxide, N-acetylpiperidine, N-methylpyrrolidone, N-formylhexamethyleneimine, and trimethylene sulfide.     

Self-assembly and conductive network formation of vapor-grown carbon fiber in a poly(vinylidene fluoride) melt

The construction of vapor-grown carbon fiber (VGCF) conductive networks through the self-assembly process in a poly(vinylidene fluoride) (PVDF) melt was investigated. Depending on real-time tracing of the variation of electrical resistivity with isothermal treatment time, the properties and possible assembly mechanism of PVDF/VGCF composites were evaluated. It was found that the self-assembly velocity of VGCFs in the matrix increased with annealing temperature. Scanning electron microscopy showed that the coagulation of VGCFs formed the conductive paths in the matrix after annealing. The value for the activation energy of conductive network formation was about 144 kJ/mol, which was higher than the value for the activation energy of zero-shear-rate viscosity () of the pure polymer (62 kJ/mol), but was close to the value for the activation energy of of VGCF filled PVDF composites (135 kJ/mol). These results indicated that the conductive network of the composites was related to the interaction between PVDF molecules and VGCFs. According to a thermodynamic percolation model, a self-assembly velocity model for conductive network formation was proposed, and the result indicated that self-assembly velocity was a function of annealing time and temperature.     

In-solution structure formation of poly(vinylidene fluoride) building units influencing on the final membrane characteristics

A systematic study was carried out on the initial casting solutions of asymmetric PVDF ultrafiltration membranes to observe the aggregate structure of polymer building units in solution and the properties of the membranes in terms of microstructure morphology, crystallinity, average pore size, pore-size distribution, total porosity, hydrophobicity, wetting energy, molecular weight cut-off, and permeability. Hydrophobic membrane of higher porosity exhibiting higher flux was obtained from the solution of bigger polymer structural units while the membrane obtained from solution of smaller polymer structural units exhibited relatively rougher and hydrophilic surface and smaller uniform pores with lesser flux.     

聚偏氯乙烯-b-聚乙二醇-b-聚偏氯乙烯共聚物基多孔炭的制备及电化学性能

通过直接碳化由可逆加成-断裂链转移(RAFT)活性自由基聚合制备的聚偏氯乙烯-b-聚乙二醇-b-聚偏氯乙烯共聚物(PVDC-b-PEG-b-PVDC),制备了微孔-中孔复合多孔炭,并对其电化学性能进行了研究。凝胶渗透色谱仪表征表明通过RAFT聚合制得的PVDC-b-PEG-b-PVDC的分子量较高(MnGPC7000 g?mol-1)、分子量分布较窄(PDI1.5)。采用热重分析、扫描电镜、N2等温吸脱附法表征了嵌段共聚物的热分解特性和多孔炭的结构,发现PEG链段可完全热分解而具有形成中孔的模板作用,PVDC链段热分解形成含微孔的炭骨架,最终形成兼有微孔和中孔、最大比表面积达1242m2?g-1、孔容达0.49 cm3?g-1的多孔炭。电化学测试表明制备的多孔炭的电化学特性良好,当电流密度为0.5 A?g-1时,PVDC-b-PEG4k-b-PVDC基多孔炭的比电容达到157 F?g-1,显著优于文献报道的PVDC基多孔炭的比电容。     

Effect of crystallization rate on the formation of the polymorphs of solution cast poly(vinylidene fluoride)

A systematic study was carried out to investigate the effect of solvent type and temperature on the formation of the α and β phases from solution cast PVDF. Three solvents with different boiling points were used: N,N, dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and hexamethylphosphoramide (HMPA). Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) revealed that the type of phase formed depends on the crystallization rate of PVDF, which in turn is determined by the evaporation rate of the solvent. Low rates result predominantly in the trans-planar β phase, high rates predominantly in the trans-gauche α phase and intermediate rates in a mixture of these two phases, regardless of solvent and temperature used. Since evaporation rate of the solvent is intimately related to temperature, PVDF films can be obtained predominantly in either one of these phases, or a mixture of these, by an adequate choice of the evaporation temperature range for a given solvent. The possible solubility curves of the two polymorphs α and β of PVDF were sketched. The formation of different types of spherulites, associated with the two different PVDF polymorphs, could be verified by surface micrographs of the cast films.     

Solid state extrusion of vinylidene fluoride (VF2)/vinylidene trifluoride (VF3) copolymers. II: Structure development

Copolymers of vinylidene fluoride (VF2) and vinyltrifluoride (VF3) exhibit Curie transition temperatures well below their melting points. Above these endothermic transitions, they soften and this behavior helps in their solid state extrudability. In this paper, the effects of extrusion speed, temperature, and draw ratio on structure development in 60/40 and 72/28 VF2/VF3 copolymer compositions are presented. With the increase of extrusion draw ratio the Curie transition temperature of the extrudates decreased and melting temperature increased. This behavior suggested that the chains in the crystalline regions contain higher levels of conformational defects while overall crystallinity is increased. Unoriented polymers were optically opaque and extrudates were found to be transparent as a result of breakdown on the superstructural level which decreases the scattering effects in the visible wavelength range. The micro beam WAXS studies on the samples taken from the entrance of the dies revealed that the unoriented core is surrounded by alternating unoriented and oriented layers close to the core. The remainder of the skin layers are found to be oriented with local symmetry axes and main chain orientation being parallel to the die wall surface. The regions that are found to be oriented were also found to be optically translucent and unoriented regions were optically opaque. This structure turns uniformly transparent–and thus oriented?as the polymer enters the die. The existence of layered structure suggests that highly localized yielding occurs during early states of deformation at the converging entrance region of the die. Examination of the radial structural variation in extrudates with micro beam X-ray diffraction technique revealed that the local symmetry axes are tilted away from the extrusion direction and this tilt angle reduces at the sample macro-symmetry axis at the core of the samples. This indicated that the tilted structure developed at the converging entrance region is partially preserved through the die. While the orientation of local symmetry axes varies from skin to core in the extrudates, the orientation of chains with respect to these local symmetry axes remains relatively unaffected.     

聚偏氟乙烯熔体的流变特性

综述了聚偏氟乙烯树脂的性能、其熔体的流变特性及在熔融加工领域的广泛应用,详细介绍了剪切变稀的非牛顿流体流变行为及其影响因素。通过分子链支化、共混和共聚可改善PVDF熔体的流变性能,以满足不同性能制品的需求以及进一步拓宽熔融加工成型方法。     

Infra-red analysis of poly(vinylidene fluoride) thermoelectrets

The copolymer poly(vinylidene fluoride)—poly(tetrafluoroethylene) studied by infra-red spectroscopy during its transformation into electrets, shows structural modifications of the copolymer due to the electrostatic field action. The dielectric used is a copolymer monoaxially oriented by stretching and the paper reports on the structural changes in the molecular arrangements, relative to the induced electrical properties. These results complete and confirm data obtained previously by Raman spectroscopy^1,7.     

Synthesis of a poly(vinylidene fluoride) macromonomer

Summary Methacrylate-type poly(vinylidene fluoride) macromonomer was synthesized from vinylidene fluoride via hydroxy-ended poly(vinylidene fluoride). The macromonomer copolymerized easily with methyl methacrylate, but homopolymerization did not proceed completely.     

Toughening effect of poly(methyl methacrylate) on an immiscible poly(vinylidene fluoride)/polylactide blend

In this work, a mutually miscible third polymer, poly(methyl methacrylate) (PMMA), was incorporated into an immiscible poly(vinylidene fluoride)/polylactide (PVDF/PLA) blend (weight ratio 70:30). It was found that incorporation of PMMA in an appropriate amount (30–60 wt%) induced a marked improvement in fracture toughness. A five times enlargement of the elongation at break can be achieved by introducing 30 wt% PMMA. In order to understand the underlying toughening mechanism, SEM, dynamic mechanical analysis (DMA), XRD and DSC were applied to study the variations in morphology, the interaction between the three components and the crystallization behavior. SEM micrographs showed that the PMMA preferred to locate at the interface of PVDF and PLA, which was attributed to the mutual miscibility of PVDF with PMMA and PLA. Furthermore, a variety of thermal characteristics such as T_g and T_m induced by the entanglement of PVDF, PMMA and PLA at the interface were illustrated in DMA and DSC curves. Obviously, the interface consisting of the entanglement of PVDF, PLA and PMMA acted as a linkage to improve interfacial adhesion, which was regarded as the main toughening mechanism. This work provides a potential strategy to realize the interfacial enhancement of an immiscible blend via the incorporation of a mutually miscible third polymer. © 2016 Society of Chemical Industry