37,269 research outputs found
Hierarchical dual-sized film surface morphologies self-generated from fluorinated binary latex blends boost hydrophobicity and lipophobicity
No full textLatex films with controlled dual-level nanorough surfaces were obtained by casting from binary blends of fluorinated copolymer particles with a nanostructured core-shell morphology, narrow size dispersity and large size ratios. For this purpose, particles with different size, a common unfluorinated acrylic core copolymer of the self-crosslinking trimethoxysilylpropyl methacrylate (TSPMA) and a hard shell copolymer of either 2,2,2-trifluoroethyl methacrylate (TFEMA) or 1H,1H,2H,2H-heptadecafluorodecyl methacrylate (FMA) were synthesized by multistage emulsion polymerization. The FMA-based particles showed patchy morphologies dictated by the type of β-cyclodextrin used as FMA phase carrier in their synthesis. Four series of binary blends of either TFEMA or FMA copolymer particles with large (3-4 diameters) size ratios were cast into latex films with controlled hydrophobicity and lipophobicity. AFM and electron microscopy results indicate that addition of the small particles disrupts the hexagonal compact packed 3D organization of the large particles, resulting in dual-level nanorough surfaces and high water contact angles (up to θ(w)=127° in the as cast films, and θ(w)=135° upon aging or thermal annealing causing surface restructuring and TSPMA sol-gel condensation) with respect to the parent single component films. The proposed approach provides a straightforward route for the fabrication of robust coatings and films with tunable lipophobic and highly hydrophobic surfaces
A Primary Probe on the County Cultural Facility’s Suitability Indicator System in Eastern Northwest China — Case Analysis on Chengcheng County, Shaaxi Province
No full textIn relation to comprehensive living standard and public interests, urban cultural facility poses major influence on urban life. Compared with urban cultural facility, county cultural facility is the vinculum linking the cultural undertakings between urban and regional area, which requires rational guidance to break through the gap between urban and rural development. This thesis observed the current situation of cultural facility in Chengcheng County of Shaanxi Province, finding that the particularity of county cultural facility development and the inconsistency between supply and demand have exceeded the capacity of present development criterion. The in-depth analysis on Chengcheng County’s cultural facility is based on the influential observation of indicator system, standing on a wider perspective in consideration with resident’s demand, probing the suitable indicator system of cultural facility in Chengcheng County in consistency with the developing feature and trend combing with national standard and developing situation.</jats:p
Facile hydrophobic modification of hybrid poly(urethane-urea)methacrylate aqueous dispersions and films through blending with novel waterborne fluorinated acrylic copolymers
No full textAqueous dispersions of fluorinated particles (PBF) based on copolymers of butyl acrylate (BA) with 2-(perfluorononenyloxyl)ethyl methacrylate (FNEMA), 2,2,3,3-tetrafluoropropyl acrylate (TFPA), and 2,2,3,3,4,4,5,5-octafluoropentyl acrylate (OFPA), respectively, were synthesized by emulsion polymerization in the presence of unfluorinated and fluorinated anionic surfactant binary mixtures. These fluorinated dispersions showed good to excellent colloidal stability, as determined by freeze-thaw, centrifugation, and critical coagulation concentration measurements. Blending of small amounts (1-10 wt%) of PBF latex particles with a waterborne hybrid poly(urethane-urea)-methacrylate (PUUA) resulted in a series of slightly fluorinated modified PUUA (MPUUA) with good film forming properties and low surface energy. The precursor PUUA had been synthesized separately by simultaneous chain extension of a poly(ester-urethane)-diisocyanate with ethylenediamine and soapless free radical polymerization of methyl methacrylate (MMA) swelling the resulting branched or slightly crosslinked poly(urethane-urea) (PUU) self-dispersible ionomer particles. The results of dynamic light scattering and Zeta potential measurements suggest that merging of PUUA and PBF particles and either engulfing or interdiffusion of the incompatible macromolecular phases occurred to some extent already in the colloidal state. Highly hydrophobic films with surface energy as low as 17 mJ/m2 were obtained upon hybridization of PUUA with the FNEMA copolymer. Thermal annealing allowed to minimize the effects of fast surface dynamics leading ultimately to water absorption, and to promote synergistic enhancement of the resulting hybrid film hardness, as required for coating applications
Hydrophobic Film Surfaces from Self-Organizing Asymmetric Blends of Water-Borne Nanostructured Fluorinated Polymer Particles
No full textCore-shell latexes composed of at least two different kinds of (co)polymer particles may exhibit peculiar
physical and chemical properties. Fabrication of well defined core-shell nanoparticles fluorinated in the
shell combined with appropriate blending of particles with different size (asymmetric blend) is a strategy to
obtain required surface and bulk properties for super-hydrophobic coating applications as well as to
reduce the amount of fluorochemicals for cost and environmental reasons.
In this work, latexes with different particle size and core-shell structure using a BA/MMA-based copolymer
for the core (BA=butyl acrylate, MMA=methyl methacrylate), and TFEMA (2,2,2-trifluoroethyl
methacrylate), FNEMA (2-[(perfluorononenyl)oxyl] ethyl methacrylate) or FMA (1H,1H,2H,2Hheptadecafluorodecyl
methacrylate) for the shell, as well as TSPMA (3-trimethoxysilylpropyl methacrylate)
as a crosslinker and compatibility enhancer, were synthesized by seeded semi-continuous starved-feed
procedure. Binary blends of these small and large fluorinated nanoparticles with different size ratios were
prepared to form stable low free energy surfaces. The latter are influenced by the geometric feature of
particles and crosslinking from TSPMA components. Role of particle size, composition and structure on
film morphologies and surface properties were studied by using light scattering, DSC, TEM and contact
angle goniometry.
In order to improve the transport/diffusion of highly fluorinated comonomers in the water phase and the
stablity of the final colloidal particles, several strategies were pursued such as using cationic fluorinated
surfactants,1 more amphiphilic F-comonomers (surfmers, or reactive surfactants), and using a
cyclodextrin2 as a carrier (phase transfer agent).
Well defined core-shell fluorine-containing reactive nanoparticles, latex blends with bimodal particle size
distribution and the resulting latex films were designed and prepared using TFEMA as fluorocomonomer.
Improved hydropobicity is obtained on the surfaces of films without significant change of bulk properties.
More highly fluorinated comonomers and non-migrating or fluorinated surfactants are needed, however,
to fabricate super-hydrophobic film surfaces. Unfortunately, it is very difficult to obtain stable latex system
from highly fluorinated acrylate comonomers with long perfluoroalkyl side chain such as FNEMA and FMA
due to their extremely low solubility in water. Some coaglulation were generally observed upon
polymerization with the procedure mentioned above
Three Different ß-Cyclodextrins Direct the Emulsion Copolymerization of a Highly Fluorinated Methacrylate Towards Distinctive Nanostructured Particle Morphologies
No full textStable colloidal dispersions of nanostructured semifluorinated acrylic particles with an unfluorinated core and an
outer layer consisting of copolymers of the highly hydrophobic and lipophobic heptadecafluorodecyl methacrylate (FMA) were
successfully synthesized with the assistance of three different cyclodextrins as phase-transfer catalysts: beta-cyclodextrin (beta-CD),
hydroxypropyl beta-cyclodextrin (HpCD), and methyl beta-cyclodextrin
(MeCD). While all the cyclodextrins form a stable inclusion complex (IC) with FMA, only the ICs with the more hydrophilic HpCD and MeCD are soluble in water. Nevertheless, incorporation of
FMA in the particle shell copolymer could be achieved also when using beta-CD. On the other hand, the morphology of the nanostructured particles was characterized by a ‘‘patchy’’ fluorinated shell dependent on the cyclodextrin used, the best results being obtained with MeCD. A monomer-starved semicontinuous emulsion polymerization procedure was essential to favor the
CD-mediated incorporation of FMA into the copolymer structure and to achieve a stable colloidal dispersion even in the presence of small amounts of mixed anionic–nonionic surfactants. The
thermal and surface properties of the latex films showed a good correlation with the shell composition and patchy nanostructured
morphology of the particles
Dataset for paper: The spread of low-credibility content by social bots
No full text<p>Data for the paper <em>The spread of low-credibility content by social bots </em>by Chengcheng Shao, Giovanni Luca Ciampaglia, Onur Varol, Kai-Cheng Yang, Alessandro Flammini, and Filippo Menczer</p>
<p>Code is available at https://github.com/IUNetSci/HoaxyBots</p>
Kinetics of acid hydrolysis of k-Carrageenan by in situ rheological follow-up
No full textWater based solutions of κ-Carrageenan (1.5% weight concentration), a high molecular weight polysaccharide, were subjected to acid-catalyzed hydrolysis under controlled pH (≈3) and temperature (from 40 to 70 °C). The hydrolysis process involves selective attack of the Carrageenan glycosidic bonds α(1–3) and β(1–4), determining changes in the weight average molecular weight of the macromolecule and, as a consequence, on the gelling behavior. In this study we used transient rheological tests to monitor the hydrolysis reaction and its consequences on both the sol-gel transition and the final gel properties. Hydrolysis reaction has been modelled using a bi-exponential kinetics. To this end, a rotational rheometer was equipped with a batch reactor configuration, consisting of a cylindrical vessel and a double helix mixing tool. Both viscous and viscoelastic properties of the samples were measured quantitatively and related to the biopolymer molecular weight, replacing more complex molecular weight determinations by an easier methodology. By using the above experimental approach, kinetic constants and activation energies for the κ-Carrageenan hydrolysis were obtained as a function of the hydrolysis temperature. The latter, along with the hydrolysis reaction time, was also shown to be a relevant parameter in determining the possibility of gel formation and of the gel mechanical strength (in the range 10–600 Pa)
A New Magnetizer for Measuring the Two-Dimensional Magnetic Properties of Nanocrystalline Alloys at High Frequencies
No full textNanocrystalline alloys are used extensively in high-frequency electromagnetic applications for their low magnetic losses and high saturation flux densities. To characterize their vector magnetic properties over a broad frequency range, a new magnetizer with a compact flux density-field B-H sensor was developed for two-dimensional testing up to 10 kHz
Hierarchically Structured Films with either Surfaces or Bulk Morphology Patterned by Fluorinated Latex Particle
No full textDS1_JVDI_10.1177_1040638719868274 – Supplemental material for Histologic findings and viral antigen distribution in natural coinfection of layer hens with subgroup J avian leukosis virus, Marek’s disease virus, and reticuloendotheliosis virus
No full textSupplemental material, DS1_JVDI_10.1177_1040638719868274 for Histologic findings and viral antigen distribution in natural coinfection of layer hens with subgroup J avian leukosis virus, Marek’s disease virus, and reticuloendotheliosis virus by Hongmei Liu, Kui Ma, Miaomiao Liu, Chengcheng Yang, Xueting Huang, Yu Zhao and Kezong Qi in Journal of Veterinary Diagnostic Investigation</p
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