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首页> 外文学位 >Surface Modification and Characterization of Polymeric Materials for Targeted Functionality.
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Surface Modification and Characterization of Polymeric Materials for Targeted Functionality.

机译：用于目标功能的高分子材料的表面改性和表征。

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摘要

We have investigated the surface modification of polymeric materials as a viable means by which to create novel functional surfaces for use in a wide range of (nano)technologies, including the development of nanocomposites.;Improvement of the barrier properties of rPET is the overarching theme of this project. It is known that inorganic fillers introduced into a polymer matrix tend to decrease gas permeation by increasing the diffusive path length of penetrant species through the material. Nanoclays as filler materials are ideal for this purpose because of the high aspect ratio of the clay platelets. Therefore, we have sought to generate rPET/clay nanocomposites by two different protocols in this study: attachment of natural clay platelets on functionalized rPET surface, and mechanical alloying of rPET flakes with natural clay platelets.;We have shown that PET surfaces can be chemically modified while avoiding chemical degradation. Specifically, we find that brief exposure of PET substrates to ultraviolet/ozone (UVO) generates a large surface concentration of hydrophilic moieties.;Chemical surface modification routes have also been explored due to the irregular and 3D nature of rough rPET flakes. Polyethyleneimine (PEI), as "molecular glue", increases the adsorption of clay platelets on modified rPET surface. Subsequent characterization reveals that the presence of PEI molecules permits adsorption of 1-2 clay platelets/layer on the modified rPET surface. Extrusion of these surface-modified materials yields polymer/clay nanocomposites, but the high melting point of PET causes considerable degradation under non-optimized conditions. Hence, we have substituted rPET with a low melting poly(ethylene- co-octene) to perform PEI and clay adsorption multiple times and thus adjust the concentration of clay platelets in the polymer matrix. The presence of clay platelets results in a decrease in O2 and CO 2 permeabilities, which compares favorably with calculations from the Neilsen model. In addition, the thermal stability of the nanocomposites increases with increasing clay loading due to the presence of the inorganic platelets.;Electrospun PET fiber surfaces have also been chemically functionalized with polymer brushes composed of poly(N-isopropyl acrylamide) (PNIPAAm), poly(dimethylaminoethyl methacrylate) (PDMAEMA) and poly(hydroxyethyl methacrylate) (PHEMA) via surface-initiated polymerization. These fibers can be used as functional filters to 1) capture metal salts or cyanide ions from water, 2) prepare antibacterial or antifouling fibers, and 3) produce fibers responsive to temperature or pH.;We have also investigated the formation of rPET/clay nanocomposites via mechanical alloying by using high-energy ball milling as an alternative route to melt processing. Solid-state mechanical alloying was conducted using natural clay and rPET at ambient temperature. Specifically, polymer and clay powders were mixed in a steel vial in the presence of steel balls designed to induce considerable and repeated shear, fracture and welding and thus exfoliate the clay platelets in the rPET matrix. The molecular weight of mechanically milled rPET and virgin-PET is found to decrease with increasing milling time, reaching ≈45% of their original values after 16 h of milling. Characterization of the resulting nanocomposites by x-ray diffractometry and transmission electron microscopy confirm exfoliation of clay platelets irregardless of milling time.;The development of a universal polymer coating has been achieved by chemically coupling trichlorosilane (TCS) to the vinyl groups of poly(vinylmethyl siloxane) (PVMS) via hydrosilylation. The resultant PVMS-TCS coating can be deposited as a functional organic layer on a variety of substrates ranging from hydrophobic to hydrophilic. Spin-coating PVMS-TCS onto a substrate yields a uniform coating layer and exposing the coating to minute amounts of moisture generates a large density of surface-bound hydroxyl groups. Moreover, treating the PVMS-TCS substrates with UVO further increases the density of hydroxyl groups on the surface. The elastic modulus of the coating can be regulated by adjusting the TCS concentration. Several case studies demonstrating the remarkable properties of these PVMS-TCS functional coatings are presented.;Decreasing supplies of fresh water and increasing population necessitate the development of water cleaning technologies that would expedite the removal of pollutants. To assist water purification processes, we have synthesized functionalized macromolecules that contribute to decontamination by scavenging detrimental chemicals. Epitomizing this role, the thioimide unit enables chemical flexibility that facilitates reversible catch-release of the ions on the basis of subtle reduction-oxidation environmental changes. Chemical tunability of the thioimide moiety enables synthesis of thioimide-based monomers and post-polymerization modification agents. Two distinct synthetic pathways, polymerization and post-polymerization modification, have been explored, leading to functional thioimide-based macromolecules. The presence of thioimide units on macromolecular chains decreases the concentration of cyanide ions in water from 24 to 3 ppm in less than 1 h.
机译：我们已经研究了聚合物材料的表面改性方法，以此作为一种可行的方法来创建新颖的功能性表面，以用于各种（纳米）技术，包括纳米复合材料的开发。;提高rPET的阻隔性能是首要主题这个项目。已知引入到聚合物基质中的无机填料趋于通过增加渗透剂穿过材料的扩散路径长度来降低气体渗透。由于粘土薄片的高长径比，作为填充材料的纳米粘土是理想的。因此，我们试图通过两种不同的方法在本研究中生成rPET /粘土纳米复合材料：将天然粘土血小板附着在功能化的rPET表面上，以及将rPET薄片与天然粘土血小板进行机械合金化。进行修饰，同时避免化学降解。具体而言，我们发现将PET基材短暂暴露于紫外线/臭氧（UVO）会产生较大的亲水部分表面浓度。由于粗糙的rPET薄片的不规则和3D性质，还探索了化学表面改性途径。聚乙烯亚胺（PEI）作为“分子胶”，可增加粘土血小板在改性rPET表面上的吸附。随后的表征表明，PEI分子的存在允许在改性的rPET表面吸附1-2个粘土血小板/层。这些表面改性的材料的挤出产生聚合物/粘土纳米复合材料，但是PET的高熔点在未优化的条件下导致相当大的降解。因此，我们用低熔点的聚（乙烯-共辛烯）取代了rPET，以多次进行PEI和粘土吸附，从而调节聚合物基质中粘土血小板的浓度。粘土薄片的存在导致O2和CO 2渗透率降低，这与Neilsen模型的计算结果相比具有优势。此外，由于存在无机片晶，纳米复合材料的热稳定性会随着粘土含量的增加而增加。；静电纺PET纤维表面也已通过由聚（N-异丙基丙烯酰胺）（PNIPAAm），聚（甲基丙烯酸二甲基氨基乙酯）（PDMAEMA）和聚甲基丙烯酸羟乙酯（PHEMA）通过表面引发的聚合反应。这些纤维可用作功能性过滤器，以：1）从水中捕获金属盐或氰化物离子； 2）制备抗菌或防污纤维； 3）产生对温度或pH敏感的纤维。我们还研究了rPET /粘土的形成通过使用高能球磨作为熔融加工的替代途径，通过机械合金化制备纳米复合材料。在室温下使用天然粘土和rPET进行固态机械合金化。具体地，将聚合物和粘土粉末在钢球存在下混合在钢瓶中，该钢球设计为引起大量重复的剪切，断裂和焊接，从而使rPET基体中的粘土薄片剥落。发现机械研磨的rPET和纯PET的分子量随研磨时间的增加而降低，在研磨16小时后达到其原始值的约45％。通过X射线衍射法和透射电子显微镜对所得纳米复合材料进行表征，证实了不考虑研磨时间的粘土片状剥落。;通过将三氯硅烷（TCS）与聚（乙烯基甲基硅氧烷）（PVMS）进行氢化硅烷化。所得的PVMS-TCS涂层可以作为功能性有机层沉积在从疏水性到亲水性的各种基材上。将PVMS-TCS旋涂到基材上可得到均匀的涂层，并将涂层暴露于微量的湿气中会产生高密度的表面结合羟基。此外，用UVO处理PVMS-TCS基材可进一步增加表面上羟基的密度。涂层的弹性模量可以通过调节TCS浓度来调节。提出了一些案例研究，以证明这些PVMS-TCS功能涂料的卓越性能。淡水供应的减少和人口的增加，需要开发可加快污染物去除速度的水净化技术。为了协助水净化过程，我们合成了功能化的大分子，这些大分子通过清除有害化学物质有助于净化。体现这一角色硫酰亚胺单元具有化学柔韧性，可根据细微的还原-氧化环境变化促进离子的可逆捕集释放。硫酰亚胺部分的化学可调性使得能够合成基于硫酰亚胺的单体和聚合后的改​​性剂。已经探索了两种不同的合成途径，即聚合和后聚合修饰，从而产生了功能性的基于硫酰亚胺的大分子。大分子链上存在硫酰亚胺单元，可在不到1小时的时间内将水中氰化物离子的浓度从24 ppm降低至3 ppm。

著录项

  • 作者

    Ozcam, Ali Evren.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Engineering Chemical.;Plastics Technology.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 416 p.
  • 总页数 416
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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