Interfacial layering in a three-component polymer system

We study theoretically the temporal evolution and the spatial structure of the interface between two polymer melts involving three different species (A, A* and B). The first melt is composed of two different polymer species A and A* which are fairly indifferent to one another (Flory parameter chi_AA* ~ 0). The second melt is made of a pure polymer B which is strongly attracted to species A (chi_AB 0). We then show that, due to these contradictory tendencies, interesting properties arise during the evolution of the interface after the melts are put into contact: as diffusion proceeds, the interface structures into several adjacent "compartments", or layers, of differing chemical compositions, and in addition, the central mixing layer grows in a very asymmetric fashion. Such unusual behaviour might lead to interesting mechanical properties, and demonstrates on a specific case the potential richness of multi-component polymer interfaces (as compared to conventional two-component interfaces) for various applications.Comment: Revised version, to appear in Macromolecule

Photolithographic patterning of conducting polyaniline films via flash welding

In this work, two significant advances in photolithographic patterning of polyaniline (PANI) films are reported. Firstly, flash welding was enhanced through the use of polymeric substrates, enabling complete penetration of the welding of PANI films with thicknesses ranging from 5 to over 14 mu m, significantly thicker than reported previously. Masking of parts of the PANI films during flash welding enabled the formation of adjacent conducting and insulating regions as the welding changes the electrical properties of the film. Raman spectroscopy was used to determine the sharpness of these edges, and indicated that the interface between the flash welded and masked regions of the PANI films was typically less than 15 mu m wide. Secondly, using longpass filters, light with a wavelength less than 570 nm was found not to contribute to the welding process. This was confirmed by the use of a 635 nm laser diode for welding the PANI films. This novel approach enabled patterning of PANI films using a direct writing technique with a narrow wavelength light source