功能性离子液体及其修饰石墨烯对聚偏氟乙烯的晶型调控与机理研究

发布时间：2018-10-19 18:54

【摘要】：本文通过溶液共混与真空热压法分别将含有PEG长链的咪唑基离子液体、甲基丙烯酸甲酯与烯丙基咪唑离子液体共聚物修饰石墨烯(Gra)以及长链烷基离子液体修饰Gra混入聚偏氟乙烯(PVDF)中,制备了高极性晶体含量与功能化薄膜,系统地研究了功能性离子液体与离子液体共聚物修饰Gra对PVDF的晶型与性能的影响,并用结晶动力学研究了 PVDF结晶机制的变化,获得创新性研究成果。论文的研究内容主要包括以下三个部分:(1)在PVDF中混入含有PEG长链离子液体后,离子液体的咪唑阳离子和PVDF 的CF2-基团之间的相互作用可以促进极性的β/γ晶体生成,在热退火作用下,离子液体的PEG链段与PVDF的CF2-基团之间的相互作用可以促进处于无定形区域的PVDF分子链按照模板继续折叠为极性晶体。通过共混物的介电频率谱,发现基体中混入离子液体和热退火作用可以提高直流电导率和MWS极化,而MWS极化、离子极化和直流电导可以提高介电常数。(2)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P[MMA-IL]共聚物,用于修饰Gra,制备了三元纳米复合薄膜。数据表明P[MMA-IL]会通过咪唑阳离子-偶极子作用诱导β晶体;通过咪唑阳离子-π强相互作用,P[MMA-IL]对模板剂Gra表面进行修饰,协同诱导作用增强。POM照片表明α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β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P[MMA-IL]修饰Gra诱导的β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。(3)研究溴化1-十六烷基-3-甲基咪唑修饰Gra对PVDF结晶动力学的影响,测量等温和非等温结晶的动力学参数如相对结晶度(Xt)、半结晶时间(t1/2)、结晶速率常数(Z)、Avarami指数(n)和活化能(Ea)。对PVDF/0.5IL/0.5Gra等温和非等温结晶过程分析可得出结论,离子液体和Gra能促进成核降低Ea;此外,离子液体和Gra的协同作用可形成β晶抑制α晶的形成。咪唑阳离子和碳环结构的相互作用对PVDF结晶有很大影响,主链CF2-基团与咪唑离子的相互作用对PVDF结晶也有影响。
[Abstract]:Imidazolyl ionic liquids containing long chains of PEG were prepared by solution blending and vacuum hot pressing respectively. High polar crystal content and functionalized films were prepared by blending methyl methacrylate with allyl imidazole ionic liquid copolymer modified graphene (Gra) and long chain alkyl ionic liquid modified Gra into polyvinylidene fluoride (PVDF). The effects of functional ionic liquids and ionic liquid copolymers modified Gra on the crystal structure and properties of PVDF were systematically studied. The crystallization mechanism of PVDF was studied by means of crystallization kinetics, and the innovative research results were obtained. The main contents of this paper are as follows: (1) the interaction between imidazole cations of ionic liquids and CF2- groups of PVDF can promote the formation of polar 尾 / 纬 crystals by mixing PEG long chain ionic liquids in PVDF. Under thermal annealing, the interaction between the PEG segment of ionic liquids and the CF2- group of PVDF can promote the PVDF chains in the amorphous region to be folded into polar crystals according to the template. Through the dielectric frequency spectrum of the blend, it is found that the DC conductivity and MWS polarization can be improved by adding ionic liquid and thermal annealing into the matrix, while the MWS polarization can be improved. Ion polarization and direct current conductance can improve the dielectric constant. (2) the copolymer of P [MMA-IL] was synthesized from methyl methacrylate (MMA) and 1-vinyl-3-ethylimidazolium bromide (IL) as monomers. The ternary nanocomposite films were prepared by modified Gra,. The data show that P [MMA-IL] can induce 尾 crystal by imidazole cationic-dipole interaction, and P [MMA-IL] modifies the surface of template Gra by imidazole cation- 蟺 strong interaction. The synergistic inductive effect was enhanced. POM photos showed that during the growth of 伪 crystal, the MMA chain segment was embedded into the gap of spherulite wafer, resulting in loose structure, and the nucleation of ion-dipole and IL led to the smaller size and faster crystallization of 尾 crystal. The study of dielectric behavior showed that PMMA and its modified Gra decreased the crystallinity and chain concentration of PVDF, resulting in weak interfacial and orientation polarization and weak dielectric response, while P [MMA-IL] modified 尾 -crystal induced by Gra. The ionic polarization of the IL segment at the interface enhances the interfacial polarization and the dielectric response. (3) the effect of 1-hexadecyl-3-methylimidazolium bromide modified Gra on the crystallization kinetics of PVDF was studied. Kinetic parameters such as relative crystallinity (Xt), half crystallization time (t 1 / 2), crystallization rate constant (Z), Avarami exponent (n) and activation energy (Ea). Were measured for isothermal and non isothermal crystallization. It is concluded that ionic liquid and Gra can promote nucleation and decrease Ea;. In addition, the synergistic effect of ionic liquid and Gra can form 尾 -crystal to inhibit 伪 -crystal formation. The interaction between imidazole cations and carbon ring structure has great influence on the crystallization of PVDF, and the interaction between the main chain CF2- group and imidazole ion also affects the crystallization of PVDF.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O632.21

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