Effect of Nanostructures Addition and Enhancement of Poly (Vinylidene Difluoride) (PVDF) Energy Harvesting

With concerns in energy crisis and global warming, researchers are actively investigating alternative energy renewable solutions. Among the various methods, piezoelectric transduction stands out due to its impressive electromechanical coupling factor and coefficient. As a result, piezoelectric energy harvesting has garnered significant attention from the scientific community. In this study, we explored methods to enhance the piezoelectric properties of polyvinylidene fluoride (PVDF) through two distinct approaches. The first approach involved applying external high voltages at various stages during the mixture reaction. The goal was to determine whether this voltage application could alter or enhance PVDF’s piezoelectric conformation by improving the alignment of polarized dipoles. In the second part of our study, we investigated the effects of incorporating various nanostructures (including Iron Oxide, Magnesium Oxide, and Zinc Oxide) into PVDF. To analyze changes in PVDF’s crystalline structure, we utilized Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) techniques. Additionally, we measured the electric polarization of samples using a Precision LC Meter and examined the morphology of nanofibers through Scanning Electron Microscopy (SEM).

Crystallization Behavior and Mechanical Properties of Poly(vinylidene fluoride)/multi-walled Carbon Nanotube Nanocomposites

Poly（vinylidene fluoride）（PVDF）/multi-walled carbon nanotube（MWCNT） nanocomposites were prepared by means of ultrasonic dispersion method. X-ray diffraction（XRD） results indicate that incorporating MWCNTs into PVDF caused the formation of β phase. A thermal annealing at 130 ℃ confirmed that the β phase was stable in the nanocomposites. Differential scanning calorimetry（DSC） results indicate that the melting temperature slightly increased while the heat of fusion markedly decreased with increasing MWCNT content. The tensile strength and modulus of PVDF were improved by loading the MWCNTs. The scanning electron microscopy（SEM） observations showed that MWCNTs were uniformly dispersed in the PVDF matrix and an interfacial adhesion between MWCNT and PVDF was achieved, which was responsible for the enhancement in the tensile strength and modulus of PVDE.

Poly(vinylidene fluoride)/Clay Nanocomposites by Melt Compounding

The crystalline structures, morphologies, and mechanical properties of poly（vinylidene fluoride）/clay nanocomposites were studied using X-ray diffraction（XRD）, transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FTIR）, polarized optical microscopy（POM）, and tensile tests. The results of XRD and TEM show that organoclays are dispersed in the poly（vinylidene fluoride）（PVDF） matrix. A clay-induced crystal transformation from α-phase to β-phase of PVFD was confirmed by XRD and FTIR. Clay layers restricted the growth of spherulite. The tensile tests indicate that the tensile modulus and yield strength as well as the elongation at break decrease when clay is loaded.

Fabrication of poly(vinylidene fluoride) membrane via thermally induced phase separation using ionic liquid as green diluent

Ionic liquid(IL),1-butyl-3-methylimidazolium hexafluorophosphate([BMIM]PF6)as a new and environmentally friendly diluent was introduced to prepare poly(vinylidene fluoride)(PVDF)membranes via thermally induced phase separation(TIPS).Phase diagram of PVDF/[BMIM]PF6 was measured.The effects of polymer concentration and quenching temperature on the morphologies,properties,and performances of the PVDF membranes were investigated.When the polymer concentration was 15 wt%,the pure water flux of the fabricated membrane was up to nearly 2000 L·m-2·h-1,along with adequate mechanical strength.With the increasing of PVDF concentration and quenching temperature,mean pore size and water permeability of the membrane decreased.SEM results showed that PVDF membranes manufactured by ionic liquid(BMIm PF6)presented spherulite structure.And the PVDF membranes were represented asβphase by XRD and FTIR characterization.It provides a new way to prepare PVDF membranes with piezoelectric properties.

RHEOLOGICAL PROPERTIES OF POLY(VINYLIDENE FLUORIDE) IN MOLTEN STATE

The theological behavior of poly(vinylidene fluoride)(PVDF)samples of different molecular weights was investigated by means of high pressure capillary rheometer and rotational rheometer.Information on the rheological properties of such materials above melt temperatures is of interest as this can lead to an improved understanding of polymer behavior in processing and fabrication technologies.Shift factors derived from time-temperature superposition showed good fit to the Arrhenius equation with a flow activa...

A FACILE APPROACH FOR THE SURFACE MODIFICATION OF POLY(VINYLIDENE FLUORIDE) MEMBRANE VIA SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

A novel approach for the surface modification of poly(vinylidene fluoride)(PVDF)membrane was successfully realized through alkaline treatment,UV-induced bromine addition,and followed by surface-initiated atom transfer radical polymerization(ATRP)of methyl methacrylate(MMA).Chemical changes on the PVDF membrane before and after modification were analyzed with attenuated total reflectance Fourier transform infrared spectroscopy(ATR/FT-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revealed...

Molecular Modulation of Structure and Ferroelectric Performance of Poly(vinylidene fluoride)Free Standing Films from Aspects of Molecular Weight and Crystallization Temperature

Ferroelectric polymer poly(vinylidene fluoride)(PVDF)has received great research interest because of its special electroactive properties which are strongly dependent on the crystalline structures and in turn processing conditions.The effect of molecular weight and crystallization temperature on the micro-structure and macro-properties of PVDF films casted from dimethyl sulfoxide(DMSO)solvent is investigated.The results demonstrated that a low molecular weight(180 kg/mol)and a low evaporation temperature(50℃)favored the formation of polarγ-phase,while a high molecular weight(1000 kg/mol)and a high evaporation temperature(125℃)made PVDF crystallize intoα-phase.Compared with films casted at 50℃,films casted at 125℃exhibited higher dielectric loss at a low electric field and less loss conductivity at a high electric field,which was due to their low degrees of crystallinity and fine evaporation of the solvent,respectively.PVDF with a molecular weight of 180 kg/mol casted at 125℃exhibited the highest remnant polarization(0.062 C/m^(2))among all of the solution-processed films,being a result of high chain mobility resulted from the low molecular weight.

Highly efficient and stable perovskite solar cells with strong hydrophobic barrier via introducing poly(vinylidene fluoride)additive

Perovskite solar cells(PSCs)have become the promising next-generation photovoltaic devices due to their excellent photoelectric performances,and the power conversion efficiencies(PCEs)have experienced unprecedented rapid increase in recent years.However,to realize the practical application of PSCs,high performance and long-term stability are required and the preparation of high-quality perovskite film is the key.Herein,we adopt a simple and effective method to prepare high-quality perovskite films by introducing the poly(vinylidene fluoride)(PVDF)polymer additive with abundant hydrophobic F.As the growth template,the PVDF promotes the growth of perovskite crystal,improves the crystallinity and film morphology,thus reducing defect density and inhibiting carrier recombination.The results show that the photovoltaic performances of the perovskite device with PVDF are meaningfully improved,and a high PCE of 21.42%is achieved with an improvement of 10.87%,More importantly,the PVDF-based perovskites display greatly enhanced humidity and heat stability due to the protection of strong hydrophobic barrier from F and PVDF long chain.Aging at 45%±5%relative humidity(RH)for 2400 h and 850 C for300 h,respectively,the unsealed PVDF devices can maintain over 90%of the initial PCE.It indicates that suitable polymer additives can improve the film quality to acquire high-performance and stable PSCs and lay a foundation to design new perovskite light absorption layer with different polymers for the further development of PSCs.

Fabrication of Poly(vinylidene fluoride) /Polysulfone Flat Blend Membranes via Thermally Induced Phase Separation Process for Water Treatment

Poly(vinylidene fluoride) /polysulfone(PVDF/PSF) flat blend membrane was prepared via thermally induced phase separation(TIPS) technique.The membrane formation mechanism and membrane structure were investigated and the effects of PSF/PVDF weight ratio on morphology,crystallinity,porosity,and mechanical properties of the membrane were discussed.The relationship between membrane structure and performances,such as pure water flux and the rejection of carbonic black,was also discussed.It was found that solid-liquid(S-L) phase separation occurred for the PVDF/PSF/diluent system.The addition of PSF influences structure and crystallinity of the membrane,which in turn influences mechanical properties and performances of the membrane.The results reveal that it is possible to obtain network structure via S-L phase separation by blending the polymer,which has a partial compatibility with PVDF.

Determining the degree of grafting for poly(vinylidene fluoride) graft-copolymers using fluorine elemental analysis

Acrylic acid (AAc) and styrene (St) were grafted onto poly(vinylidene fluoride) (PVDF) powder or membrane samples by pre-irradiation graft copolymerization.The grafted chains were proved by FT-IR spectroscopy analysis.The degree of grafting (DG) of the grafted PVDF was determined by fluorine elemental analysis (FEA) method,and was compared with the DGs determined by weighing method,acid-base back titration method and quantitative FT-IR method.The results show that the FEA method is accurate,convenient and universal,especially for the grafted polymer powders.

Effects of Stretching Ratio and Temperature on Phase Transition of Melt-spun Poly(Vinylidene Fluoride) Fibers

The effects of stretching ratio and stretching temperature on pbase transition of melt-spun poly （ vinylidene fluoride ） fibers were investigated and analyzed by using scanning electron microscopy, wide angle X- ray diffraction, differential scanning calorimetry and Fourier transfer infrared spectroscopy. The β phase exists in the as-spun fiber. The β phase content increases as the stretching ratio increases. When the stretching temperature is lower than 100 ℃ , enhancing temperature is good for the transition of phase a to ft. By contrast, when the stretching temperature is higher than 100 ℃ , enhancing temperature is unfavourable for the transition of phase a to β. Increasing the draw temperature increases the α-phase content.

The Effects of Radiationon Crystal Transformationsof Poly（vinylidenefluoride）

his paper covers the effects of γ-radiation on crystal transformations of Poly-(vinylidene fluoride)before and after drawing as well as during annealing process.The results show that the drawing results in a drastic increase in both crystallinityalong the meridian direction and β-form crystal content for the irradiated samples.When the drawn samples were irradiated under appropriate dose and then annealedat 140℃ , transformation from β-form to a-form was subjected to an inhibition.The transformation mechanisms between the two types of crystals are discussed onthe basis of results of WAXD and DSC.

High permeability poly(vinylidene fluoride)ultrafiltration membrane doped with polydopamine modified TiO_(2) nanoparticles

In order to improve the water permeability of poly(vinylidene fluoride)(PVDF)ultrafiltration(UF)membranes with low molecular weight cut-off(MWCO),polydopamine(PDA)was employed in the membrane preparation process.Owing to itsmerits of material-independent adhesion,PDAwas coated on inorganic particles or added in coagulation bath to tailor the final membrane structure and property.The introduction of PDA broke through the permeability/selectivity trade-off of the PVDF membrane.By adding the PDA coated titaniumdioxide(PDA/TiO2)nanoparticles,water flux increased by 287% while MWCO kept similar with the pristine PVDF membrane.Thermodynamics and Kinetics of the PVDF/additives/non-solvent were analyzed and shown that nanoparticles reduced the thermodynamic stability and increased the phase separation speed,and the speed can be adjusted using different nanoparticles.Additionally,X-ray diffraction(XRD)test indicated that PVDF crystalline form changed fromαphase to β phase after adding different nanoparticles.Permeability/selectivity trade-offwas broken through by DA addition in coagulation bath.Compared with the original PVDF membrane,when the DA concentration of the coagulation bath was 2.0 g·L^−1,water flux increased by 312%,and MWCO of the PVDF membrane ranged in 10,000 to 20,000 Da as well as contact angle decreased from 81.4°to 45°.

Preparation and characterization of the antifouling porous membranes from poly(vinylidene fluoride)-graft-poly(N-vinyl pyrrolidone) powders

Porous membranes were prepared using the phase inversion method from poly(vinylidene fluoride)-graftpoly(N-vinyl pyrrolidone)(PVDF-g-PVP) powders, which were synthesized via γ-ray induced graft polymerization(pre-irradiation). Chemical compositions, thermal behavior, morphology and hydrophilicity of the membranes were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, element analysis, thermalgravimetric analysis, differential scanning calorimetry, scanning electron microscopy and contact angle measurements, respectively. Permeation experiments were conducted to evaluate the water flux,and the dynamic BSA fouling resistance performances were investigated, too. All the experimental results indicate that the PVDF-g-PVP membranes demonstrate better separation performances over the pristine PVDF membrane.

聚偏氟乙烯流延膜的制备与性能

含β晶体的聚偏氟乙烯(PVDF)的极性较强,是一种重要的压电和铁电材料,受到人们的广泛关注。在该工作中,选择了PVDF的3种β晶体成核剂,首先用傅里叶红外光谱(FTIR)比较了3种成核剂对PVDF流延膜中β晶体含量的影响,随后选择成核效率最高的成核剂四苯基溴化膦(TPPB),通过调整流延工艺制备了高β晶体含量的PVDF流延膜,最后利用广角X射线衍射(WAXS)及小角X射线散射(SAXS)技术研究了PVDF流延膜以及其在后拉伸过程中的结晶结构,同时研究了流延膜的力学性能以及弹性回复性能等。研究结果表明,PVDF/TPPB流延膜的β晶体含量和片晶取向程度随着流延膜牵伸比的增加而增大。随着牵伸比的增加,PVDF/TPPB流延膜的屈服应力和杨氏模量增大,弹性回复能力增强。同时,在流延膜的后拉伸过程中,随着拉伸应变的增加,流延膜出现空洞结构,并且温度越低,空洞出现的临界应变越小,这对含β晶体PVDF微孔膜的制备具有指导意义。

Modification on crystallization of poly（vinylidene fluoride） （PVDF） by solvent extraction of poly（methyl methacrylate） （PMMA） in PVDF/PMMA blends

The crystallization modification of poly（vinylidene fluoride） （PVDF） was investigated for the blend films of PVDF and poiy（methyl methacrylate） （PMMA）. The mass crystallinity （Xc） and further, the β-phase content （F（β）） of PVDF, were studied for the asprepared blend films with different mass ratios. In addition, the variations of Xc and F（β） were systematically probed once the PMMA component was removed from the related blend systems. DSC, FTIR and XRD measurements all indicated that 1）Xc, F（β） and even the content of a-phase （F（a）） decreased with the addition of PMMA; 2） with the extraction of PMMA, both Xc and F（β） increased while F（a） decreased. It is worth noting that the increase of Xc and F（β） depended on the relative amount of extracted PMMA （EpMMA）, i.e., the more PMMA was removed, the more Xc and F（β） increased. These results reveal the hindrance effect from the PMMA constituent to the crystallization of PVDF, and consequently, this restriction would be released when the PMMA was extracted.

EFFECT OF POLY(BUTYLENE SUCCINATE) ON THE MORPHOLOGY EVOLUTION OF POLY(VINYLIDENE FLUORIDE) IN THEIR BLENDS

The effect of PBS on the morphological features of PVDF has been investigated by optical and atomic force microscopies under various conditions. It was found that neat PVDF forms large γform spherulites with extraordinarily weak birefringence at 170℃. Adding 30% PBS makes PVDF exhibit intrigued flower-like spherulitic morphology. The growth mechanism was explained by the decrease of the supercooling and the materials dissipation. Increasing the PBS content to 70% favors the formation of ring banded spherulites. Temperature dependent experiments verify the α→γ phase transition occurs from the junction sites of the ot and y crystals, while starts from the centers of α spherulites in the blends. Ring banded structures could be observed in neat PVDF, 70/30 blend and 30/70 blend when crystallized at 155℃, without γ crystals. The band period of PVDF α spherulites increases with crystallization temperature as well as the amount of PBS content. At 140℃, spherulites in neat PVDF lose their ring banded feature, while coarse spherulites consisting of evident lamellar bundles could be found in 30/70 blend.

Polyaniline-poly(vinylidene fluoride) blend microfiltration membrane and its spontaneous gold recovery application

Structural regular polyaniline was synthesized via a modified-chemical oxidative polymerization reaction. Highly hydrophilic polyaniline(PANi) and polyaniline-poly(vinylidene fluoride) blend(PANi-PVDF) membranes were prepared by solution casting and phase inversion techniques. Both of the mechanical and filtration properties of the membranes depend on the polymer composition and doping level of the blends. The elasticity of the membrane is greatly improved upon introducing poly(vinylidene fluoride) into the blend. The water permeability of the blend membranes is further enhanced when the membranes are doped with hydrochloric acid. The PANi-PVDF blend membranes are capable of recovering metallic gold from the acid/halide leaching streams spontaneous and sustainably, and are promising candidates for wastewater treatments in electronic industries.

Preparation and characterization of poly （vinylidene fluoride）/ Ti02 hybrid membranes

Poly（vinylidene fluoride） （PVDF）/titanium dioxide （TiO2） hybrid membranes were prepared using nano-TiO2 as the modifier, and characterized by Transmis- sion Electron Microscope （TEM）, Fourier transform infrared spectroscopy （FT-IR）, scanning electron micro- scope （SEM）, atomic force microscope （AFM）, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. The characterization results demonstrated that nano-sized TiO2 particles dispersed homogeneously within the PVDF matrix, contributing to more hydroxyls and smoother surfaces. Moreover, permeate flux, retention factor, porosity, contact angle and anti-fouling tests were carried out to evaluate the effect of TiO2 concentration on the performance of PVDF membranes. Among all the prepared membranes, PVDF/TiO2 membrane containing 10 vol.% TiO2 exhibited the best hydrophilicity with an average pure water flux up to 237 L.mE.h1, higher than that of unmodified PVDF membranes （155L.m2.h ）. Besides, the bovine serum albumin rejection of the hybrid membrane was improved evidently from 52.3% to 70.6%, and the contact angle was significantly lowered from 83° to 60°, while the average pore size and its distribution became smaller and narrower.

Electrospun poly（vinylidene fluoride-trifluoroethylene）/ zinc oxide nanocomposite tissue engineering scaffolds with enhanced cell adhesion and blood vessel formation

Piezoelectric materials that generate electrical signals in response to mechanical strain can be used in tissue engineering to stimulate cell proliferation. Poly （vinylidene fluoride-trifluoroethylene） （P（VDF-TrFE））, a piezoelectric polymer, is widely used in biomaterial applications. We hypothesized that incorporation of zinc oxide （ZnO） nanoparticles into the P（VDF-TrFE） matrix could promote adhesion, migration, and proliferation of cells, as well as blood vessel formation （angiogenesis）. In this study, we fabricated and comprehensively characterized a novel electrospun P（VDF-TrFE）/ZnO nanocomposite tissue engineering scaffold. We analyzed the morphological features of the polymeric matrix by scanning electron microscopy, and utilized Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry to examine changes in the crystalline phases of the copolymer due to addition of the nanoparticles. We detected no or minimal adverse effects of the biomaterials with regard to blood compatibility in vitro, biocompatibility, and cytotoxicity, indicating that P（VDF-TrFE）/ZnO nanocomposite scaffolds are suitable for tissue engineering applications. Interestingly, human mesenchymal stem cells （hMSCs） and human umbilical vein endothelial cells cultured on the nanocomposite scaffolds exhibited higher cell viability, adhesion, and proliferation compared to cells cultured on tissue culture plates or neat P（VDF-TrFE） scaffolds. Nanocomposite scaffolds implanted into rats with or without hMSCs did not elicit immunological responses, as assessed by macroscopic analysis and histology. Importantly, nanocomposite scaffolds promoted angiogenesis, which was increased in scaffolds pre-seeded with hMSCs. Overall, our results highlight the potential of these novel P（VDF-TrFE）/ZnO nanocomposites for use in tissue engineering, due to their biocompatibility and ability to promote cell adhesion and angiogenesis.