TY - JOUR A1 - Tentschert, Jutta A1 - Jungnickel, Harald A1 - Reichardt, Philipp A1 - Leube, Peter A1 - Kretzschmar, Bernd A1 - Taubert, Andreas A1 - Luch, A. T1 - Identification of nano clay in composite polymers JF - Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films N2 - Industrialized food production is in urgent search for alternative packaging materials, which can serve the requirements of a globalized world in terms of longer product shelf lives, reduced freight weight to decrease transport costs, and better barrier functionality to preserve its freshness. Polymer materials containing organically modified nano clay particles as additives are one example for a new generation of packaging materials with specific barrier functionality to actually hit the market. Clay types used for these applications are aluminosilicates, which belong to the mineral group of phyllosilicates. These consist of nano-scaled thin platelets, which are organically modified with quaternary ammonium compounds acting as spacers between the different clay layers, thereby increasing the hydrophobicity of the mineral additive. A variety of different organically modified clays are already available, and the use as additive for food packaging materials is one important application. To ensure valid risk assessments of emerging nano composite polymers used in the food packaging industry, exact analytical characterization of the organically modified clay within the polymer matrix is of paramount importance. Time-of-flight SIMS in combination with multivariate statistical analysis was used to differentiate modified clay reference materials from another. Time-of-flight SIMS spectra of a reference polymer plate, which contained one specific nano clay composite, were acquired. For each modified clay additive, a set of characteristic diagnostic ions could be identified, which then was used to successfully assign unknown clay additives to the corresponding reference material. Thus, the described methodology could be used to define and characterize nano clay within polymer matrices. Copyright (c) 2014 John Wiley & Sons, Ltd. KW - ToF-SIMS KW - nanoparticles KW - nano clay KW - polymer KW - food contact material Y1 - 2014 U6 - https://doi.org/10.1002/sia.5546 SN - 0142-2421 SN - 1096-9918 VL - 46 SP - 334 EP - 336 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Wagner, Tom A1 - Lazar, Jaroslav A1 - Schnakenberg, Uwe A1 - Böker, Alexander T1 - In situ Electrothemical Impedance Spectroscopy of Electrostatically Driven Selective Gold Nanoparticle Adsorption on Block Copolymer Lamellae JF - Trials N2 - Electrostatic attraction between charged nano particles and oppositely charged nanopatterned polymeric films enables tailored structuring of functional nanoscopic surfaces. The bottom-up fabrication of organic/inorganic composites for example bears promising potential toward cheap fabrication of catalysts, optical sensors, and the manufacture of miniaturized electric circuitry. However, only little is known about the time-dependent adsorption behavior and the electronic or ionic charge transfer in the film bulk and at interfaces during nanoparticle assembly via electrostatic interactions. In situ electrochemical impedance spectroscopy (EIS) in combination with a microfluidic system for fast and reproducible liquid delivery was thus applied to monitor the selective deposition of negatively charged gold nanoparticles on top of positively charged poly(2-vinylpyridinium) (qP2VP) domains of phase separated lamellar poly(styrene)-block-poly(2-vinylpyridinium) (PS-b-qP2VP) diblock copolymer thin films. The acquired impedance data delivered information with respect to interfacial charge alteration, ionic diffusion, and the charge dependent nanoparticle adsorption kinetics, considering this yet unexplored system. We demonstrate that the selective adsorption of negatively charged gold nanoparticles (AuNPs) on positively charged qP2VP domains of lamellar PS-b-qP2VP thin films can indeed be tracked by EIS. Moreover, we show that the nanoparticle adsorption kinetics and the nanoparticle packing density are functions of the charge density in the qP2VP domains. KW - impedance spectroscopy KW - block copolymers KW - nanoparticles KW - electrostatics KW - adsorption kinetics Y1 - 2016 U6 - https://doi.org/10.1021/acsami.6b07708 SN - 1944-8244 VL - 8 SP - 27282 EP - 27290 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zou, Hua A1 - Schlaad, Helmut T1 - Thermoresponsive PNIPAM/Silica Nanoparticles by Direct Photopolymerization in Aqueous Media JF - Journal of polymer science : A, Polymer chemistry N2 - This article presents a simple and facile method to fabricate thermoresponsive polymer-grafted silica particles by direct surface-initiated photopolymerization of N-isopropylacrylamide (NIPAM). This method is based on silica particles bearing thiol functionalities, which are transformed into thiyl radicals by irradiation with UV light to initiate the polymerization of NIPAM in aqueous media at room temperature. The photopolymerization of NIPAM could be applied to smaller thiol-functionalized particles (approximate to 48 nm) as well as to larger particles (approximate to 692 nm). Hollow poly(NIPAM) capsules could be formed after etching away the silica cores from the composite particles. It is possible to produce tailor-made composite particles or capsules for particular applications by extending this approach to other vinyl monomers. (c) 2015 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 2015, 53, 1260-1267 KW - nanocomposites KW - nanoparticles KW - photopolymerization KW - silica nanoparticles KW - surface-initiated photopolymerization KW - thermoresponsive KW - thiol Y1 - 2015 U6 - https://doi.org/10.1002/pola.27593 SN - 0887-624X SN - 1099-0518 VL - 53 IS - 10 SP - 1260 EP - 1267 PB - Wiley-Blackwell CY - Hoboken ER -