Submicron features have been formed on polymer-coated cylindrical and spherical
substrates via hot-embossing with a polydimethylsiloxane (PDMS) film stamp, without the
use of high pressure. The use of flexible PDMS moulds offers a unique advantage over
conventional methods, because they cover curved substrates easily, maintaining good
contact with the substrate even during the hot-embossing procedure. Using this approach,
uniform submicron patterns have been easily generated on curved substrates without
distortion or defect formation, eliminating the need for complex and expensive lithography
processes.
The self-assembly of colloidal spheres is an effective strategy for producing nanopatterns. To use colloidal crystals in lithographic applications, the key challenge is to fabricate a monolayer of colloidal crystals uniformly over a large area. A simple and effective method for fabricating a colloidal crystals monolayer from a 3D colloidal crystal is described. The top layer of a surface-etched 3D colloidal crystal is picked up on a PDMS stamp, and by simply heating the receiving substrate, the polymeric colloidal crystal can be easily transferred to many types of substrates, including curved or flexible materials, without utilizing a glue layer. Moreover, the colloidal spheres are deformed to hemispheres during the transfer process, which is a suitable form of a lithographic mask for both dry and wet etching processes. An array of silicon nanocones and gold dots is demonstrated by pattern transfer from an array of hemispherical polymeric particles. In addition, it is also shown that the transferred hemispherical array has good antireflective properties.
A two-step process has been invented to prepare sulfonated polypropylene from chlorinated polypropylene via thiolation and successive oxidation to enhance the dyeability of polypropylene. With a short thiolation reaction time of 3 h in an N-methyl-2-pyrrolidone solution, 1.7-20.5% sulfur can be incorporated into a polypropylene bulk effectively. Chlorine-thiol substitution and hydrosulfide conversion have been examined with elemental analysis, and their behaviors as a function of the SH/Cl ratio can be explained with an equilibrium model of hydrosulfide and accessible chlorine in a given timescale. Oxidation of thiol has been performed successfully with hydrogen peroxide. The evolution of oxidation intermediates such as sulfoxide, sulfone, sulfinic acid, and sulfonic acid can be identified by Raman and Fourier transform infrared analyses. Sulfonated polypropylene can be stained by a basic dye very effectively, and its dye uptake reaches 190 mmol of dye/kg of polymer for 3.6 mmol of sulfur/g of polymer. This dye uptake is 20 times more effective than that of chlorinated polypropylene on a molar basis. Thus, it is clear that a modification can be performed effectively to enhance the dyeability of polypropylene.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.