P[MMA-IL]修饰石墨烯协同调控PVDF复合物结晶与介电行为

为改善石墨烯(Gra)在聚偏氟乙烯(PVDF)中的分散性和界面性质,以甲基丙烯酸甲酯(MMA)和1-乙烯基-3-乙基咪唑溴盐(IL)为单体合成PMMA-IL]共聚物,用于修饰石墨烯(Gra),并通过溶液共混、热压法制备PVDF/PMMA、PVDF/PMMA-IL]、PVDF/PMMA/Gra和PVDF/PMMA-IL]/Gra复合薄膜.采用Raman光谱、场发射扫描电子显微镜(FESEM)、傅里叶变换反射红外光谱分析仪(FTIR-ATR)、X射线衍射仪(XRD)、偏光显微镜(POM)、示差扫描量热仪(DSC)和电感电容电阻测试仪(LCR)对复合薄膜的结构形态、结晶与介电行为进行表征和分析.Raman光谱表明PMMA-IL]与Gra之间存在强相互作用;FESEM照片显示PMMAIL]能够促进Gra在基体中的分散;DSC、XRD和FTIR-ATR数据表明PMMA降低PVDF的结晶温度,PMMA和Gra未能诱导出?-PVDF极性晶体,而单独的PMMA-IL]会通过咪唑阳离子-偶极子作用诱导?-PVDF晶体;通过咪唑阳离子-π强相互作用,PMMA-IL]在模板剂Gra表面进行修饰,协同诱导作用增强.POM照片表明?-PVDF晶体在生长过程中,MMA链段会嵌入到球晶的晶片空隙中,引起结构疏松;离子-偶极子和IL成核作用导致?-PVDF晶体尺寸较小,结晶较快.介电行为研究表明PMMA及其修饰Gra降低PVDF的结晶度和链浓度,导致界面极化和取向极化较弱,介电响应较弱;而PMMA-IL]修饰Gra诱导的?-PVDF晶体、以及IL链段在界面的离子极化使得界面极化作用增强,介电响应增强.

Effect of Graphene Modified by P[MMA-IL] on the Crystallization and Dielectric Behavior of PVDF Composite Film

In order to enhance the dispersion of graphene (Gra) in PVDF matrix and improve the interface properties of the composite materials,a copolymer (PMMA-IL]) with 1-vinyl-3-ethyl imidazole bromine (IL) and methyl methacrylate (MMA) was synthesized by radical polymerization.A series of PVDF/PMMA,PVDF/PMMA/Gra,PVDF/PMMA-IL] and PVDF/PMMA-IL]/Gra were prepared using a solution-cast and hot pressing method.The morphological structure,crystallization and dielectric behavior were investigated by Raman spectrometer,field emission scanning electron microscope (FESEM),X-ray diffraction (XRD),polarized optical microscopy (POM),differential scanning calorimetry (DSC) and LCR meter,respectively.Raman spectra indicated that strong π interaction between imidazole ring and carbon ring established between PMMA-IL] and Gra,and FESEM observation showed the good dispersity of Gra in PVDF matrix due to that interaction.DSC results indicated that,Tc of PVDF was decreased by the presence of PMMA as a diluent,and that Tc and Tm of PVDF were promoted by PMMA-IL] modified Gra because of the presence of β polar crystal.Gra was modified by PMMA-IL] as a template to increase the degree of crystallinity of PVDF.XRD and FTIR-ATR results confirmed that the β-crystal was not induced by PMMA and Gra,but by PMMA-IL] due to the electrostatic interaction between the ＞ CF2 of the polymer backbone and imidazolium cation,and the strong induction was brought by the template of Gra.POM photos displayed that α-crystal with loose structure were embedded into the chip space of spherulites because the presence of MMA chain segments.The electrostatic interaction and nucleating agents of IL chain segments resulted in β crystal with small size and increased the crystallization rate.Dielectric properties study showed that PMMA and modified Gra reduced the crystallinity and concentration of PVDF chain,leading to weak interface polarization and orientation polarization of PVDF.The dielectric constant is low.While PMMA-IL] and modified Gra induced more β crystal,the strong intertace polarization was enhanced by β crystal and ion polarization of IL chain segments improved the dielectric constant.