Oriented nanometer surface morphologies by thermal relaxation of locally cross-linked and stretched polymer samples

We present a technique to fabricate polymer substrates with locally structured surfaces in the nanometer scale. By ion projection direct cross-linking the surface of a stretched polymer is locally cross-linked and afterwards annealed above the glass transition temperature to induce surface rippling. The rippling periodicity depends on the thickness of the cross-linked surface layer, formed through hydrogen vacancies, which are generated by the ion bombardment. We systematically studied the effect of the projectile mass on the hydrogen vacancy distribution in polystyrene (PS) samples. Simulations revealed a decreasing depth of the maximum hydrogen vacancy numbers by increasing projectile mass. This value can be correlated to the thickness of the cross-linked PS layer, which directly determines the ripple periodicity. An additional An capping layer was used to further reduce the cross-linked layer thickness to a few nanometers. By this, defined structures with a ripple periodicity of 250 nm were fabricated. In addition, the technique allows inferring the Young's modulus of thin cross-linked PS layers

Guided phase separation of polymer blend thin films on ion beam-induced pre-patterned substrates

A technique for fabricating pre-pattern induced phase-separated polymer blend films is presented. The gold layer coated silicon substrates were bombarded with focused ion beams (FIB) to sputter away Au grains in the irradiated regions and expose silicon oxide surface underneath, thereby creating pre-patterns of relatively hydrophobic (Au)/hydrophilic (silicon oxide) regions. In the pre-patterned regions, the spin-coated films consisting of immiscible PS (polystyrene) and PtBA (poly-tert-butyl acrylate) blend exhibited phase separation induced by the underlying pre-patterns and formed two distinct ordered morphologies with periodicities much smaller than that of the pre-patterns. The influence of varying periodicities of the pre-patterned structures, blending ratios and spin-coating paramet ers on the resulting morphologies are presented

Particle size and lime addiction on properties of wood-cement composites produced by the method of densification by vibro compaction

This paper aimed to evaluate the effects of particle size and the use of lime as a pretreatment of Pinus spp wood particles on the production of wood-cement composites by vibro-compaction densification. Specimens for internal bond and static bending were produced with two different particle sizes: G1, particles that pass through a 4mm screen and were retained at 2mm screen, and G2, particles that pass through a 2mm screen and were retained at 0.84mm screen. The use of lime was also tested in two different methods as pretreatment of wood particles: carbonatation of wood particles before being used in the composite mixture; and addition of hydrated lime directly to the composite mixture. Use of larger particles (G1) presented higher values of internal bond and MOR than composites produced with smaller particles (G2). About the pretreatments, the use of hydrated lime resulted in composites with higher density and better internal bond