偏氟乙烯的聚合反应

本文研究了用有机引发剂引发偏氟乙烯的水相聚合,并对制得的聚偏氟乙烯的性质进行了研究。有机引发剂引发聚合的聚偏氟乙烯的热稳定性、强度、结晶度和熔点均比用过硫酸盐引发聚合的聚偏氟乙烯高。     

葡萄糖对聚偏氟乙烯膜的共混改性研究

以葡萄糖为共混剂,聚乙烯吡咯烷酮为添加剂,用相转化法获得了聚偏氟乙烯/葡萄糖共混膜。研究了聚偏氟乙烯浓度,葡萄糖与偏氟乙烯的共混比例和添加剂含量等各项制膜条件对微孔膜的结构和性能的影响。结果显示当聚偏氟乙烯的固含量为10wt%,葡萄糖含量为4wt%,聚乙烯吡咯烷酮为固含量的2wt%,溶液蒸发时间为30min时,能够得到性能理想的微孔膜。     

聚偏氟乙烯薄膜压电性的研究

本文研究了聚偏氟乙烯的压电性。聚偏氟乙烯薄膜是用DMA溶剂浇铸而成,然后进行单轴拉伸,并采用热驻极的方法使薄膜成极。实验结果表明,压电活性依赖于拉伸比、极化电场、极化温度和极化时间。此外,还研究了聚偏氟乙烯压电薄膜的稳定性和某些使用特性。     

铁电高分子聚偏氟乙烯-三氟乙烯的凝聚态结构与性能调控研究进展

高分子的凝聚态结构具有多层次性,在微纳米尺度上有效地控制高分子的凝聚态结构,进而探索在微纳米尺度上凝聚态结构与性能的关系,将为高分子分子层次和宏观层次的结构与性能之间架起桥梁。本文综述了近年来我们课题组在铁电高分子聚偏氟乙烯-三氟乙烯共聚物方面的研究及其进展。发展了在纳米尺度上控制高分子片晶取向的新方法并应用到聚偏氟乙烯-三氟乙烯体系,构筑了取向高度有序的铁电高分子纳米结构阵列,分析了片晶取向与聚偏氟乙烯-三氟乙烯微观铁电和压电性能之间的关系,有效降低了以聚偏氟乙烯-三氟乙烯为主要材料的有机铁电非易失性存储器的读写电压。     

等离子体改性的聚偏氟乙烯表面结构的XPS研究

采用5种气氛等离子体处理聚偏氟乙烯(PVF_2)基片,用XPS研究了PVF_2表面结构的变化。结果表明,处理后的PVF_2基片表面嵌入了C—O,C—NH_2,—CHF和COOH基团,因而改变了表面性质。     

碳纳米管对聚偏氟乙烯膜的共混改性研究

用相转化法制备了聚偏氟乙烯/碳纳米管共混膜,研究了共混膜的表面结构、水通量、孔隙率、接触角和机械性能。结果显示碳纳米管的加入提高了聚偏氟乙烯膜的亲水性和水通量,当聚偏氟乙烯浓度为10wt.%,碳纳米管含量为1.5wt.%时,共混膜的水通量和孔隙率最高,从243 L/m2·h和86.2%提高到365 L/m2·h和91.4%;接触角也由82°减小为67°;同时,共混膜的机械性能也得到显著提高。     

聚偏氟乙烯/蒙脱土纳米复合材料的形态结构

采用有机改性的蒙脱土与聚偏氟乙烯熔融共混, 制备了聚偏氟乙烯/蒙脱土纳米复合材料. 利用X射线衍射分析、透射电子显微镜(TEM)和Molau实验研究了复合材料的微观结构. 通过X射线衍射、傅里叶变换红外光谱(FTIR)以及差热扫描(DSC)研究了有机改性蒙脱土对聚偏氟乙烯结晶结构的影响. 结果表明, 有机改性蒙脱土在聚偏氟乙烯中以插层、剥离和碎片的形式存在. 在X射线衍射谱中发现蒙脱土的(001)峰向低角方向移动, 在TEM中可见到剥离的片层碎 片.蒙脱土的引入改变了聚偏氟乙烯的结晶结构, 导致了具有压电性能的β相形成, 引起α相内应力的产生, 同时也导致了聚偏氟乙烯基体的结晶度下降, 球晶尺寸随蒙脱土含量明显减少. 蒙脱土引起的β相在 160℃退火表明是相当稳定的. 根据这些实验结果, 对由于蒙脱土的引入引起的聚偏氟乙烯结晶结构的变化提出了可能的解释.     

偏氟乙烯-三氟乙烯共聚物的分子链结构与多晶型现象

偏氟乙烯-三氟乙烯共聚物(PVDF/TrFE)的合成及物性研究,是改善聚偏氟乙烯(PVDF)压电性的一种尝试。据文献报道,PVDF/TrFE 有明显的铁电性,以及强的压电性     

聚氟代单烯烃的~(19)F核磁共振波谱研究

本文研究了聚偏氟乙烯(PVF_2),偏氟乙烯-全氟丙烯(VF_2-HFP)共聚物和偏氟乙烯-四氟乙烯-全氟丙烯(VF_2-TFE-HFP)共聚物的~19F核磁共振谱。由谱线的化学位移和强度归纳出二单元组和三单元组链节的序列分布,并计算出两者的相互比例。     

聚偏氟乙烯膜三维离子传输通道的构建及其在全钒液流电池中的性能研究

随着新能源技术的不断发展, 大规模储能技术受到了广泛的关注. 全钒液流电池因其容量和功率设计灵活、安全可靠、寿命长等优势成为发展较快的储能电池之一. 离子膜作为液流电池的关键部件, 对电池的能量转化效率、寿命和成本具有显著影响. 本工作以高化学稳定性的聚偏氟乙烯作为膜材料, 利用聚乙二醇和聚乙烯吡咯烷酮分别作为模板和稳定剂, 在聚偏氟乙烯膜内成功构建了具有较好H/V离子选择性的三维离子传输通道. 电池性能测试表明, 该聚偏氟乙烯(PVDF)离子膜有着出色的化学稳定性, 在100 mA•cm^-2电流密度下, 具有98%以上的电流效率和83.5%的能量效率. 此外, 聚偏氟乙烯具有价格低的显著特点, 使其在全钒液流电池中有较好的应用前景.     

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 revea...     

Electromechanical properties of poly(vinylidene fluoride‐trifluoroethylene) networks

Random copolymers of 65% vinylidene fluoride and 35% trifluoroethylene were reacted with an organic peroxide, in combination with a free‐radical trap, to yield networks of high crosslink density. Crystallization subsequent to the crosslinking yielded ferroelectric materials exhibiting large electrostrictive strains. The magnitude of the electromechanical response increased with an increasing degree of crosslinking, even though this reduced the crystallinity. For the most crosslinked sample, longitudinal (thickness) strains as high as 12% were induced at an electric field of 9 MV/m. This electrostrictive performance exceeded that obtained to date with any poly(vinylidene fluoride) material. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1975–1984, 2002     

A FACILE APPROAC0H 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(AIR/Fr-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revealed that the chain growth of poly(methyl methacrylate)(PMMA)from the PVDF surface is consistent with a"controlled"process.     

表面引发的原子转移自由基聚合法在聚偏二氟乙烯表面制备可控的聚甲基丙烯酸甲酯刷

采用表面引发的原子转移自由基聚合法(ATRP)在聚偏二氟乙烯(PVDF)表面制备结构可控的聚甲基丙烯酸甲酯刷。通过碱处理和紫外光照溴代的方法,将ATRP引入到PVDF表面; 然后采用ATRP法将甲基丙烯酸甲酯接枝到溴代的PVDF表面。采用傅里叶变换红外光谱和X-射线光电子能谱对改性前后PVDF表面的结构进行了表征。结果表明甲基丙烯酸甲酯成功地接枝到了PVDF表面。     

低头-头链含量的聚偏氟乙烯合成

研究了偏氟乙烯的聚合条件与其聚合物的头-头链含量的关系。实验表明聚合物的头-头链的含量与聚合温度有关,而与引发剂的种类无关。因而,可以在较低的聚合温度下聚合制得带有低的头-头结构(约3％)的聚偏氟乙烯。将聚合物链的A结构含量对其熔点作图,得一直线,可表示为方程式A=24.8+0.362T_m(％)。     

SYNTHESIS OF POLY(VINYLIDENE FLUORIDE) WITH LOW CONTENTS OF HEAD-TO-HEAD CHAIN

The relations between polymerization conditions of vinylidene fluoride and contents of head-tohead chain in the polymer have been studied. It shows that the contents of head-to-head chain of the polymer are related to its polymerization temperature, but are not related with the kinds of initiators used. Therefore, poly(vinylidene fluoride) with low contents of head-to-head chain (ca. 3%) can be prepared under lower polymerization temperature. Plot of the contents of A chains against melting points of the polymer is linear, which can be expressed by an equation: A=24.8 + 0.362 T_m(%).     

Structure and properties of nanocomposites based on zinc sulfide and poly(vinylidene fluoride)

The structure and properties of nanocomposites based on zinc sulfide and poly(vinylidene fluoride) were studied. The nanocomposite material was prepared by the matrix isolation technique: ZnS nanoparticles are formed by chemical reactions in a poly(vinylidene fluoride) powder of particle size 0.5–1.0 μm.     

Piezoelectricity,pyroelectricity, and the electrostriction constant of poly(vinylidene fluoride)

A new device for measuring the electrostriction constant of polymer films is described. Observed values for various polymers except poly(vinylidene fluoride) and poly(methyl methacrylate) agree well with those calculated from the Clausius-Mosotti equation. Elongational piezoelectricity, the pyroelectric current, and the electrostriction constant are measured for undrawn and roll-drawn poly(vinylidene fluoride) films. The piezoelectricity and pyroelectric current are attributed to space charges antisymmetrically distributed along thickness direction of the film for two reasons: (1) the polarity coincides between these two phenomena for all specimens, and (2) the piezoelectricity and the electrostriction constant have the same anisotropy for drawn films. Similarity of signs between piezoelectricity and pyroelectric current is observed also in poly(vinyl chloride) films. The electrical behavior of poly(vinylidene fluoride) is interpreted in terms of the ferroelectric nature of the β-form crystal.     

Microhardness measurements of poly(methyl methacrylate) and poly(vinylidene fluoride) polyblends

The preparation of polymer blends of poly(methyl methacrylate) and poly(vinylidene fluoride) in different weight percentages is described. Vickers microhardness measurements have been made to study the effects of load and compositional ratio of the two polymers in polyblend. It is observed that poly(vinylidene fluoride) acts as a plasticizer for poly(methyl methacrylate). Evidence of increasing and decreasing strength of polyblends has been obtained for different compositional ratios of the two polymers.     

Effect of poly(ethylene glycol) on the dielectric properties of poly(vinylidene fluoride)/BiFeO<Subscript>3</Subscript>/poly(ethylene glycol) composite films for electronic applications

In the present work a series of poly(vinylidene fluoride)/BiFeO₃/poly(ethylene glycol) composite films were prepared by solvent casting method with poly(vinylidene fluoride) as polymer matrix, bismuth ferrite as ceramic filler and poly(ethylene glycol) as binding agent as well as enhancer. The structural analysis of the composite films by X-ray diffraction confirms that the composites have a distorted rhombohedral structure. The micro-structural analysis shows that the use of poly(ethylene glycol)in the composite films enhances the homogeneity as well as compatibility of BiFeO₃ particles within the poly(vinylidene fluoride) matrix. The dielectric and electrical study done by impedance analyzer reveals that with an increase in poly(ethylene glycol) concentration, there is a subsequent increase in dielectric constant as well as AC electrical conductivity. Finally, the ferroelectric behavior of the composite confirms that the ferroelectric properties of the composites are enhanced by the addition of BiFeO₃ with an increase in poly(ethylene glycol) concentrations. These preliminary results give an idea for possible applications of this type of composites in the field of electronic applications.