Plasma polymerized hexamethyldisiloxane (HMDS) barrier layers

Abstract

The number of applications employing polymeric optical materials is growing rapidly due to recent advances in telecommunications, display, and laser markets. For a number of these applications, organic dyes (chromophores) are added to the polymer host to add linear or nonlinear optical properties to the system. In homogeneous systems, dye diffusion is not an issue; however in multiple stacks of polymer films with different dye concentrations or in films with a spatially varying dye concentration, diffusion becomes important. We report here on initial studies to control the diffusion of the dye, zinc octabromylporpyhrin (ZnOBP), doped in poly(dimethylsiloxane) films, from diffusing into other layers in multiple stack systems. Plasma enhanced chemical vapor deposition (PECVD) was utilized to deposit thin films (60–240nm) of hexamethyldisiloxane (HMDS) at the interface of two separate polymer layers, one with and one without ZnOBP. The diffusion of the chromophore to the outside surface of the undoped layer was examined with and without the plasma polymerized barrier layer. The thin but highly crosslinked interlayer is found to be an effective barrier to diffusion as measured using X-ray photoelectron spectroscopy to track bromine diffusion.