Self-assembling semicrystalline polymer into highly ordered, microscopic concentric rings by evaporation

A drop of semicrystalline polymer, poly(ethylene oxide) (PEO), solution was placed in a restricted geometry consisting of a sphere on a flat substrate (i.e., sphere-on-flat geometry). Upon solvent evaporation from the sphere-on-flat geometry, microscopic concentric rings of PEO with appropriate high molecular weight were produced via controlled, repetitive pinning ("stick") and depinning ("slip") cycles of the contact line. The evaporation-induced concentric rings of PEO exhibited a fibrillar-like surface morphology. Subsequent isothermal crystallization of rings at 40 and 58 degrees C led to the formation of multilayer of flat-on lamellae (i.e., spiral morphology). In between adjacent spirals, depletion zones were developed during crystallization, as revealed by AFM measurements. The present highly ordered, concentric PEO rings may serve as a platform to study cell adhesion and motility, neuron guidance, cell mechanotransduction, and other biological processes.     

聚合物分散液晶从液体桥的组装

We report the organization of polymer-dispersed liquid crystals (PDLCs) into ordered concentric rings over large areas by drying a drop of bound PDLC toluene solution (i.e., confined between a spherical lens and an indium tin oxide (ITO)-coated glass substrate; sphere-on-ITOgeometry). The formation of regular ring-like deposits was a direct consequence of controlled "stick-slip" cycles of three-phase contact line during the course of solvent evaporation, which was effectively regulated through the use of the sphere-on-ITO geometry. This simple approach based on controlled evaporative organization may provide a new means of processing polymer/LC mixture to produce ordered surface patterns in one step, where microscopic LCs are dispersed within the polymer matrix.     

Fabrication of Patterned Conducting Polymers on Insulating Polymeric Substrates by Electric‐Field‐Assisted Assembly and Pattern Transfer

Summary: The use of electrostatically addressable templates for the directed assembly of conducting polymers and pattern transfer to another polymer substrate is demonstrated. Doped conducting polyaniline was selectively assembled on the patterned template assisted by a DC electric field. Adding an insulated silicon dioxide layer onto the surface of the silicon wafer is critical to the formation of patterned PANi rather than a PANi film. After deposition, it was demonstrated that by compression molding or solution casting methods, patterned PANi can be completely transferred to a secondary polymer substrate, such as an NBR sheet or a polyurethane film. The conductivity of PANi lines on the PU film was found to be as high as 0.87 S · cm⁻¹. The simple one‐step assembly process for patterning conductive polymers and transfer provides a promising nanomanufacturing approach for cost‐effective and high performance flexible nanoelectronics and biosensors.

Optical image of PANi‐assembled templates with patterned gold lines connected to negative electrodes at 10 V for 1 min.     

Stability of hypersurface sections of quadric threefolds

Let S be a complete intersection of a smooth quadric 3-fold Q and a hypersurface of degree d in P4.We analyze GIT stability of S with respect to the natural G=SO(5,C)-action.We prove that if d 4 and S has at worst semi-log canonical singularities then S is G-stable.Also,we prove that if d 3 and S has at worst semi-log canonical singularities then S is G-semistable.