We report a simple and versatile method for the fabrication of superhydrophobic inorganic-organic thiol-ene coatings via sequential spray-deposition and photopolymerization under ambient conditions. The coatings are obtained by spray-deposition of UV-curable hybrid inorganic-organic thiol-ene resins consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), triallyl isocyanurate (TTT), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles. The spray-deposition process and nanoparticle agglomeration/dispersion provide surfaces with hierarchical morphologies exhibiting both micro- and nanoscale roughness. The wetting behavior, dependent on the concentration of TMTVSi and hydrophobic silica nanoparticles, can be varied over a broad range to ultimately provide coatings with high static water contact angles (>150°), low contact angle hysteresis, and low roll off angles (<5°). The cross-linked thiol-ene coatings are solvent resistant, stable at low and high pH, and maintain superhydrophobic wetting behavior after extended exposure to elevated temperatures. We demonstrate the versatility of the spray-deposition and UV-cure process on a variety of substrate surfaces including glass, paper, stone, and cotton fabric.
Superamphiphobic surfaces, exhibiting high contact angles and low contact angle hysteresis to both water and low surface tension liquids, have attracted a great deal attention in recent years because of the potential of these materials in practical applications such as liquid-resistant textiles, self-cleaning surfaces, and antifouling/anticorrosion coatings. In this work, we present a simple strategy for fabricating of superamphiphobic coatings based on photopolymerization of hybrid thiol-ene resins. Spray-deposition and UV photopolymerization of thiol-ene resins containing hydrophobic silica nanoparticles and perfluorinated thiols provide a multiscale topography and low-energy surface that endows the surface with superamphiphobicity. The wettability and chemical composition of the surfaces were characterized by contact-angle goniometry and X-ray photoelectron spectroscopy, respectively. The hierarchical roughness features of the thiol-ene surfaces were investigated with field-emission scanning electron microscopy. Droplet impact and sandpaper abrasion tests indicate the coatings respectively possess a robust antiwetting behavior and good mechanical durability.
A new family of poly(ethylene glycol)
(PEG) based membranes for
CO2 separation was developed using thiol–ene photopolymerization.
Compared to photopolymerized PEG-containing acrylate membranes, these
new thiol–ene based membranes offer improved mechanical properties
and processing advantages. The starting material, a combination of
a trithiol cross-linker and a PEG diene, was gradually modified with
a PEG dithiol while maintaining 1:1 thiol:ene stoichiometry. This
approach made it possible to decrease the network cross-link density,
resulting in simultaneous increases in free volume and PEG content.
Materials with high concentrations of dithiol were very stretchable,
with largely, up to 500%, improved elongation at break, yet they exhibited
commendable CO2/N2, O2, H2, and CH4 permeability-selectivity performance. The average
molecular weight of polymer chains between cross-links, M
c, was determined experimentally by fitting the classic
network affine model to stress–strain data obtained via tensile
testing. M
c was also calculated assuming
an ideal, lattice-like, network structure based on monomer stoichiometry.
The effect of M
c on glass transition temperature
and gas permeation behavior was studied. A free volume based model
was employed to describe experimental gas permeability (diffusivity)
trends as a function of M
c.
Most recent developments in polymers from renewable resources have focused on thermoplastics, whereas there has been no comparable development of plastics with elastomeric properties. Here we evaluate the possibility of developing renewable elastomers based on starch. Potato starch plasticized with glycerol (called plasticized starch, or PLS) was melt-blended with small quantities (5 wt % or 15 wt%) of maleated polypropylene (MAPP). The maleic anhydride groups of the polypropylene are expected to react with the hydroxy groups of starch under melt blending conditions. The resulting blends of MAPP and PLS were characterized by mechanical testing, SEM, DMA, and DSC. SEM, solubility and adhesion tests indicate that the blends are two-phase materials, in which the continuous phase PLS is physically crosslinked by polypropylene domains. The materials showed rubbery properties as judged by a low glass transition temperature ($À50 C independent of polypropylene content), and a wide rubbery plateau in DMA experiments that extended from room temperature to as high as 170 C. The tensile properties are also characteristic of elastomers. However, slow aging due to starch crystallization, and extraction of glycerol upon water exposure remain two challenges that must be overcome before the materials can be used as practical elastomers.
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