【作者】 王忆铭；

【导师】 吕小兵；

【作者基本信息】 大连理工大学 ， 应用化学， 2008， 博士

【摘要】 通用高分子材料如聚丙烯、聚乙烯的功能化接枝改性是改善其性能提高附加值的重要途径之一。目前，最常用的溶液和熔融接枝方法存在诸如使用大量有机溶剂、反应温度偏高和非接枝均聚物多且难以除去等问题。本论文结合γ-射线预辐射聚合物形成的陷落自由基引发接枝聚合和超临界CO₂溶胀聚合技术的优势，提出一种在较低温度下对聚合物材料进行整体化学接枝改性新方法。其基本路线是：将聚合物基体置于具有高穿透能力的γ-射线场中辐照，整体高聚物材料将产生较为均匀并具有稳定性的大分子陷落自由基。然后，在辐照场外与溶解在超临界CO₂中的单体进行接枝聚合反应。由于超临界CO₂对高聚物的溶胀作用，使得单体不仅在材料表面而且还渗透到材料内部参与接枝反应，达到整体接枝改性目的。接枝改性程度可以通过辐照剂量、接枝时间、温度等实验参数来调控。成功实现了苯乙烯、甲基丙烯酸甲酯、N-乙烯基吡咯烷酮和甲基丙烯酸β-羟乙酯等乙烯基单体对聚丙烯、低密度聚乙烯和硅橡胶等聚合物膜的整体化学接枝改性。接枝过程中无需使用有机溶剂，同时还避免了接枝单体及其均聚物在改性聚合物材料中残留。采用红外光谱、元素分析、扫描电镜、透射电镜和动态接触角测定等方法对接枝共聚物进行表征。透射电镜分析表明接枝聚合物链是以纳米尺寸均匀分布在整个改性聚合物基体中。DSC和XRD分析表明接枝聚合反应主要发生在聚合物基体的无定型部分，而且接枝聚合物链也是无定型的。针对大分子陷落自由基不稳定，不易保存等缺点，将预辐射过氧化物接枝法与超临界CO₂溶胀聚合方法有机地结合起来，提出了超临界CO₂中大分子过氧自由基引发聚合物整体化学接枝改性新方法。以苯乙烯为模式乙烯基单体，探讨了聚乙烯和聚丙烯在超临界CO₂中过氧自由基引发苯乙烯接枝反应中的反应时间、温度、压力和单体浓度对接枝率的影响。改性聚合物膜在各个层面碳含量分析表明：接枝聚苯乙烯链均匀分布在整个改性聚合物膜。较之前一种方法，本方法更容易操作，也易获得高接枝率；接枝聚合物中未接枝均聚物低于5％；改变实验参数，容易对接枝过程进行控制。改性聚合物膜内、外层的红外光谱和切面电镜分析也充分表明整体接枝的均匀性。在上述工作基础上，结合氮氧基活性自由基聚合方法的优势，初步实现了苯乙烯和甲基丙烯酸甲酯对聚烯烃膜的整体活性接枝聚合改性。更多还原

【Abstract】 Functional graft-modification of general-purpose polymer materials such as polypropylene or polyethylene is one of important routes for providing the desired properties in connection with higher added value applications. Usually, grafting reaction is carried out in organic solvent or melts extrusion. The limitation in these methods is that the need for organic solvent or/and the requirement for high temperature lead to the formation of ungrafted homopolymer, which along with organic solvent and unreacted monomer trapped in polymer substrate is very difficult to remove.In this thesis, a green and versatile route for uniform bulk graft-modification of vinyl monomers to polymer materials at relatively low temperature was presented by combining gamma （γ）-ray preirradiation-induced graft copolymerization and supercritical CO₂-swelling polymerization techniques. The polymer substrates were first irradiated withγ-rays originated from cobalt-60 resource under nitrogen atmosphere at ambient temperature, and thereby leading to uniform formation of trapped radicals on polymer backbone. Then, the produced polymer trapped-radicals were utilized to initiate graft-polymerization of vinyl monomers dissolved in supercritical CO₂ within polymer substrates. Finally, the un-reacted monomers trapped in polymer matrix were further removed via supercritical CO₂ extraction. Altering irradiation dose, reaction time and temperature can control the grafting process. The present method was succeeded in applying to bulk chemical graft-modification of various vinyl monomers such as styrene, N-vinylpyrrolidone （N-VP）, methyl methacrylate （MMA） and 2-hydroxyethyl methacrylate （HEMA） to polypropylene, low-density polyethylene and silicon rubber membranes. The grafting process did not require any organic solvent, and the resulting modified polymer materials did not remain unreacted monomer as well as ungrafted homopolymer. The bulk graft-modification of polymer materials were confirmed by fourier transform infrared spectroscopy （FTIR）, element analysis, dynamic contact angles determination, scanning electron microscope （SEM） and transmission electron microscopy （TEM） analyses. SEM and TEM micrographs indicated that the side graft-chains in nano size were uniformly dispersed in the polymer matrix throughout the thickness of the modified sample. Differential scanning calorimetry （DSC） measurements showed that the graft predominately occured in amorphous part of the polymer substrate and the resulting graft-chains were also amorphous.In consideration of their low stability of polymer trapped-radicals, a novel method for bulk graft-modification of polymer materials was presented by combining gamma （γ）-ray preirradiation-induced polymer-diperoxide graft-copolymerization and supercritical CO₂-swelling polymerization techniques. With styrene as model vinyl monomer, the influences of reaction time, temperature, pressure and monomer concentration on grafting yield were investigated in the graft-modification of styrene to polypropylene and low-density polyethylene membranes initiated by polymer-diperoxide with supercritical CO₂ both as solvent and swelling agent. As comparing with the former route, this method has some advantages such as easily controlling the reaction process and obtaining relative high grafting yield. Although ungrafted homopolymer was found in the modified polymer materials, its content was usually less than 5% with regard to that of the side graft-chains. FTIR analyses for comparing characteristic peak intensity of side graft chain of the modified polymer membranes at outer and inner layer, as well as SEM and TEM observations of a cross-section all demonstrated the uniformly bulk grafting property.On the basis of the work mentioned above, bulk living graft-copolymerization modification of styrene or MMA to polyolefin membranes was initially performed by combining the advantages of nitroxide-mediated living free radical polymerization.更多还原