Preparation Of Polyacrylamide-clay Nanocomposites By Redox Polymerization

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2006Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2006Bu çalışmada poliakrilamid-kil nanokompozitleri, akrilamidin Ce(IV)-gliserin redoks çifti ile başlatılan yerinde polimerizasyonu ile hazırlanmıştır. Kilin organik olarak modifiye edilmesinde; biri ticari, uzun alkil zincirli hekzadesiltrimetilamonyum klorür (HDTMA) ve diğeri monomerin kendisi, akrilamid, olmak üzere iki farklı tip yüzey aktif madde kullanılmıştır. Kil içeriği % 1 ile % 5 arasında değiştirilerek her bir yüzey aktif madde ile iki seri poliakrilamid-kil nanokompoziti hazırlanmıştır. HDTMA’nın tabakalar arasındaki mesafede ciddi bir artış sağladığı, akrilamidin ise tabakaların açılmasındaki etkisinin sınırlı olduğu gösterilmiştir. XRD sonuçları; akrilamidin “intercalating” ajanı olarak kullanılmasıyla hazırlanan poliakrilamid-kil nanokompozitlerinde (PAAM-ACLAY), tüm kil yüzdeleri için, “exfoliated” tipi bir yapıya işaret etmektedir. HDTMA ile modifiye edilen organofilik kille üretilen poliakrilamid-kil nanokompozitleri (PAAM-OCLAY) de yine “exfoliated” tipi bir yapı göstermektedir, fakat kil miktarı % 1’i aştığında kismi “intercalated” yapıların varlığı XRD ile ortaya konmuştur. Bütün nanokompozitler, saf polimerden daha yüksek camsı geçiş sıcaklıkları göstermiştir. Artışlar PAAM-OCLAY nanokompozitleri için daha yüksek bulunmuştur. PAAM-ACLAY nanokompozitleri için dönüşümün kil miktarıyla arttığı bulunurken, PAAM-OCLAY nanokompozitleri için ilişkinin tam tersine olduğu görülmüştür. Bu sonuçlar ışığında, akrilamidin “intercalating” ajanı olarak kullanılmasının, HDTMA gibi bilinen yüzey aktif maddelerin polimerizasyon reaksiyonu üzerindeki sınırlayıcı etkilerini ortadan kaldırdığı vargısına ulaşılmıştır.In this study, polyacrylamide-clay nanocomposites were prepared by in-situ polymerization of acrylamide initited by redox pair of Ce(IV)-glycerine. Two types of surfactants; a commercial long alkyl chained hexadecyltrimethylammonium chloride (HDTMA) and acrylamide monomer itself were used in the organically modification of clay. Two series of polyacrylamide-clay nanocomposites with each surfactant were prepared by varying the clay loading between 1 % and 5 %. It was shown that, while HDTMA results in a considerable increase in the interlayer distances, acrylamide has limited effect on expanding of the clay gallery. XRD results suggested exfoliated type structure for all clay loadings in polyacrylamide-clay (PAAM-ACLAY) nanocomposites prepared with the acrylamide as an intercalating agent. Polyacrylamide-clay nanocomposites (PAAM-OCLAY) synthesized with the organophilic clay modified with HDTMA, also showed exfoliated structure, but with the increase of clay loading above 1 %, some intercalated structure was evidenced by XRD. All nanocomposites displayed higher glass transition temperatures than the pure polyacrylamide. Increments were higher for PAAM-OCLAY nanocomposites. For PAAM-ACLAY nanocomposites conversion was found to increase with the clay loading, while relation is in an opposite manner for PAAM-OCLAY nanocomposites. With the light of these results, it can be inferred that use of acrylamide as an intercalating agent removes the restrictive effects of known surfactants like HDTMA on the polymerization reaction.Yüksek LisansM.Sc

Solid substrates decorated with Ag nanostructures for the catalytic degradation of methyl orange

There is a strong demand for development of catalytically active solid substrates for heterogeneous catalysis applications. This study reports fully solution-processable and scalable fabrication of solid substrates decorated with Ag nanostructures for the degradation of organic dyes. Ag nanostructures were prepared by direct surface-growth from Pt nanoparticles that were immobilized on Si substrates modified with a layer of end-grafted poly (2-vinylpyridine). The proper choice of the growth conditions and seed-selective growth from Pt nanoparticles were critically important in fabricating Ag nanostructures with high catalytic activity and large surface coverage. The catalytic performance of the presented platform was studied by the reduction of methyl orange by borohydride ions and monitored using UV-visible spectrometry. The substrates exhibited high catalytic activity enabling degradation of 10(-5 )M methyl orange solution in less than an hour with an apparent reaction rate constant of 33.5 x 10(-3) min(-1). The substrates can be easily removed from the degradation medium and used multiple times. Our approach presents an effective strategy for waste water management applications avoiding the agglomeration and separation issues of colloidal catalysts and overcoming the need for tedious and costly fabrication of thin films

Robust superhydrophobicity on paper: Protection of spray-coated nanoparticles against mechanical wear by the microstructure of paper

Practical applications require scalable, low cost and facile approaches to fabricate coatings that are repellent to liquids and yet are resistant to mechanical impact and abrasion which may occur during service operation of these materials. Here we report fabrication of superhydrophobic (SHP) coatings on paper substrates by one-step spray-coating of fluorinated silica nanoparticles. The coatings were extremely repellent to water and organic liquids with surface tensions higher than similar to 45 mN/m, as demonstrated by the sliding angles that are lower than 5 degrees. The coated paper substrates retained their liquid repellency behavior without any discernable change in their static contact and sliding angles following different mechanical wear tests. Mechanical robustness together with demonstrations in self-cleaning, anti-icing and food-packaging show great promise for the use of fabricated paper substrates in different applications. A significant finding of the present work is that the mechanical robustness of the spray-coated fluorinated silica nanoparticles in the absence of any polymeric matrix/binder was dramatically higher on paper in comparison to flat substrates. These results suggest that the inherent microstructure of the paper provides a suitable matrix for protecting the functionalized nanoparticles against external mechanical effects and present an effective strategy for improving the mechanical robustness of the coatings fabricated by one-step spray-coating of nanomaterials. (C) 2017 Elsevier B.V. All rights reserved