A novel high-frequency resistance coating by utilizing nano titania particle

In this paper, a liquid-phase hydrolization method to synthesize nanometer rutile titania directly without transformation from anatase is proposed. By utilizing this method, the particle size of the rutile titania nanoparticles can be controlled by adjusting the reaction conditions, e.g. the concentration of sodium hydroxide solution, reaction temperature, and calcining temperature of the powder. These titania nanoparticles have been used for the preparation of a novel composite insulation coating for magnet wires. First results showed that the lifetime of the modified nanomagnet wire in the inverter-fed motor could be prolonged to eight times compared with the non-modified wire.     

Molecular design of polymer coatings capable of photo-triggered stress relaxation via dynamic covalent bond exchange

Polymer coatings are frequently used to modify surface properties of inorganic substrates. However, the disparity in physical properties between polymer film and substrate often leads to residual stress development, which can be deleterious to the overall performance of coated materials. This work reports the molecular design of polymer films that dissipate stress upon irradiation with ultraviolet (UV) light. These polymers are synthesized by post-polymerization modification of the reactive polymer, poly(2-vinyl-4,4-dimethyl azlactone), to introduce dynamic crosslinks capable of light-initiated addition transfer fragmentation chemistry. Using a custom-built optical cantilever, contrasting film stress responses are observed between films containing dynamic bonds and analogous control films after UV light irradiation, which indicate successful stress relaxation. Further experiments demonstrate the complete relaxation of residual stress in dynamic films after an extended exposure, thereby generating a “stress-free” film. Films fabricated using this approach can be easily tailored to incorporate additional moieties to introduce desired surface properties for future application in a wide array of coatings.     

Controlled processing of polymer nanoribbons: Enabling microhelix transformations

Flow‐coated, two‐dimensional polymer ribbon structures undergo a shape‐transformation into a three‐dimensional helix upon their release into a solution. Driven by surface forces and due to geometric asymmetry, the helix radius and spring constant depend upon the ribbon cross‐section dimensions, surface energy, and material elastic modulus. Such spring‐like microhelices offer multiple functionalities combined with mechanical stretching and shape recovery. Fabricating such microhelices requires a sequence of processing steps, beginning with flow‐coating of ribbons on a substrate, followed by etching of a “scum layer” to allow for an independent release into a solution, upon which shape‐transformation occurs. During the deposition‐etch‐release sequence, various control parameters influence the nanoribbon size and geometry, hence the helix properties. The experimental study presented here focuses on the influence of meniscus height, substrate velocity, substrate surface energy, and etch time on nanoribbon size (height and width), scum layer thickness, and helix radius. The results show that meniscus height and contact angle dictate flux toward the meniscus edge and volume available for spatial assembly, allowing control over the aspect ratio of ribbons. We vary the aspect ratio by two orders of magnitude, while maintaining geometric asymmetry needed for helix shape‐transformation. We provide robust scaling for the nanoribbon size and geometry and report the advantages and disadvantages of different parameters, in the control of polymer nanoribbon and helix fabrication. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1270–1278     

纳米SiO2的修饰改性及其在紫外光固化涂料中的性能研究

以对-甲基苯磺酸为催化剂，用丙烯酸羟乙酯和纳米SiO2进行酯化反应制备改性纳米SiO2用红外光谱仪和热失重分析仪对产物分析表明：纳米SiO2中约70．5％的Si-OH基团和丙烯酸羟乙酯发生了酯化反应。将改性前后的纳米SiO2应用于紫外光固化涂料中，研究了对涂料黏度和固化速率、涂料固化膜的铅笔硬度和耐磨性能等的影响。结果...     

Facile synthesis and responsive behavior of PDMS‐b‐PEG diblock copolymer brushes via photoinitiated “thiol‐ene” click reaction

We present herein a mild and rapid method to create diblock copolymer brushes on a silicon surface via photoinitiated “thiol‐ene” click reaction. The silicon surface was modified with 3‐mercaptopropyltrimethoxysilane (MPTMS) self‐assembled monolayer. Then, a mixture of divinyl‐terminated polydimethylsiloxane (PDMS) and photoinitiator was spin‐coated on the MPTMS surface and exposed to UV‐light. Thereafter, a mixture of thiol‐terminated polyethylene glycol (PEG) and photoinitiator were spin‐coated on the vinyl‐terminated PDMS‐treated surface, and the sequent photopolymerization was carried out under UV‐irradiation. The MPTMS, PDMS, and PEG layers were carefully identified by X‐ray photoelectron spectroscopy, atomic force microscopy, ellipsometry, and water contact angle measurements. The thickness of the polydimethylsiloxane‐block‐poly(ethylene glycol) (PDMS‐b‐PEG) diblock copolymer brush could be controlled by the irradiation time. The responsive behavior of diblock copolymer brushes treated in different solvents was also discussed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Modulation of cell responses by creating surface submicron topography and amine functionalities

The incorporation of biological function into synthetic polymers provides particular potential for advances in studying the complex interactions between biomolecules and materials. We developed a simple method to create polymer with submicron features on surface of polystyrene‐co‐maleic anhydride (PSMAA) using a combination of phase‐separation and spin coating method. The nanostructured PSMAA which was rarely utilized as biomaterials was further functionalized by doping with dopamine or by treating with nitrogen containing plasma. This study demonstrated a straightforward method that the creation of topographical cues alone improves the biocompatibility of PSMAA thin film. The cell proliferation increased more significantly to ～1.8‐ and 2.5‐fold on dopamine blended and N₂/H₂ plasma treated PSMAA films when compared to that on the flat sample, respectively. The overall results showed that the integration of microenvironment and chemical functionalities into materials provide promising effects for promoting mammalian cell growth. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Effective syntheses of per-2,3-di- and per-3-O-chloroacetyl-β-cyclodextrins: A new kind of ATRP initiators for star polymers

Selective chloroacetylations at per-2,3- and per-3-positions of β-cyclodextrin have been achieved via protection-deprotection methods. The reaction condition of pH >4 controlled by appropriate proton scavenger is essential for obtaining designed chloroacetylation degree under effective protection, as well as for high yield with less side-products. The β-cyclodextrin derivatives with 14 or 7 chloroacetyl groups are useful initiators for synthesizing star polymers with well-defined structure by atom transfer radical polymerization.     

Optimizing glass coating lines: MIP model and valid inequalities

Glass coating is a specific transformation aiming at improving glass performance. The work presented in this paper deals with the determination of the optimal configuration of the production lines used to perform this operation. We propose a first MIP formulation of the problem and then discuss several types of valid inequalities for improving it. The main idea is to exploit explicit or implicit binary exclusion constraints to derive stronger valid inequalities: the maximal clique constraints. Efficient (polynomial time) separation algorithms exploiting special structure of the problem are described, giving rise to a cutting-plane generation procedure for strengthening the initial formulation. The computational study carried out shows that, with the enhanced formulation, good solutions can be obtained within reasonable computation times using currently available integer programming software.     

Optimization of surface coating condition using vapor form of alkanethiol on Cu nano powders for the application of oxidation prevention

There has been a growing interest in metal nano powders recently, and researches on Copper (Cu) nano particles are actively pursued due to its good electrical conductivity and its low prices. However, its easiness to oxidation and corrosion has delayed its research progress in Cu nano particles to be applied in inkjet printed electronics and other related research area. To overcome these problems, new surface coating method on Cu nano particles has been developed using dry process instead of conventional wet coating method. Octanethiol was used as a dry coating material because it has sulfur at the end of monolayer to chemically bond to the surface of fresh non-oxidized Cu nano particles to prevent oxidation. Octanethiol does not bond to oxidized surface of Cu nano particles. Previously, bonding between octanethiol and Cu nano particles, more specifically bonding between Cu surface and Sulfur (S) was analyzed using X-ray Photoelectron Spectroscopy (XPS). As a result, S peak was detected on the coated Cu nano particles, indicating that octanethiol chain has been successfully coated on the surface of Cu nano particles.In this study, optimization of dry coating condition was studied by varying coating time and cycles. XPS was used to analyze the composition of coated material to monitor the change in amount of S and O peaks for each condition. It was found that as the amount of Sulfur increased, the amount of Oxygen decreased and vice versa. This finding indicates that dry coating has suppressed the formation of oxygen on the surface of Cu nano powders by surrounding Cu surface with Sulfur end of octanethiol chain. Based on these experiments, the optimum coating condition for suppressing Cu oxidation was found to be 5 min and 6 cycles. For future work, the lifetime of octanethiol layer on the surface of Cu surface needs to be studied.