Water-Resistant Surface Modification of Hydrophobic Polymers With Water-Soluble Surfactant Additives

Water-soluble nonionic surfactant, pentaethylene glycol monododecyl ether, C12E5, spontaneously blooms to the surface of spin-cast hydrophobic polyiso-prenes, generating hydrophilic surfaces. This system represents a simple model for hydrophilic chemical modification of rubbery polymers yet demonstrates surprisingly rich, complex and unexpected behaviour. The ver-tical depth profiles were quantified using neutron reflectometry (NR) and deuterated surfactant, and the surface properties were characterized using con-tact angle analysis and atomic force microscopy (AFM). Despite the low surface tension of the toluene solvent used in film preparation and the low surface en-ergy of the PI matrix, NR depth profiles revealed clear evidence of surfactant segregation. This surface layer was typically thicker than a monolayer, but incomplete, yet was remarkably stable with respect to dissolution, even when exposed to hundreds of thousands of times the volume of water required to dissolve all the surfactant on the surface. Despite the apparent resistance to removal from the surface, water exposure does alter the subsequent wettabil-ity of the surface, with a hydrophilic-to-hydrophobic transition occurring after rinsing. Complementary AFM images of these C12E5 / cis-PI films showed unexpected strand-like features on the surface of the film, which we attribute to a non-uniform lateral distribution of some of the surfactant. This surface structure becomes more evident after rinsing, and it appears that there are two distinct populations of surfactant on the PI film surface. We conclude that some of the bloomed surfactant exists as layers, which are relatively inert with respect to rinsing or surface modification, and some is laterally inhomogene-ous. This latter population is primarily responsible for surface wetting be-havior, but is not detected by specular NR.

ZnO Nanoflakes on Pb Plates with Antibacterial Effects by Electrochemical and Hydrothermal Deposition

ZnO nanoflakes were grown on the lead (Pb) plates using the electro- hydrothermal deposition methods. To investigate the influence of electrodeposition current, the ZnO seed layer was electrodeposited on the lead plates at a larger current of 160 mA (current density of 40 mA/cm2) and a smaller current of 12 mA (current density of 3mA/cm2), respectively. Then, ZnO nanoflakes were grown on top of the seed layer. Multiple analyses including field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), photoluminescence (PL) were performed on the ZnO nanostructures/Pb plates. Furthermore, surface con-tact angle measurements were conducted to study the hydrophobic properties and OD 600 antibacterial tests were used to investigate the antiseptic effects. Results indicate that the ZnO nanoflakes with the seed layer grown at a lower current of 12 mA exhibited good hydrop-hobic properties and strong antibacterial effects. ZnO nanoflakes/Pb plates show promising for future anti-radiation, antibacterial, and waterproof lead clothing applications.