Influence of weight ratio in polymer blend film on the phase separation structure and its optical properties

National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, P.R. China

Corresponding author: muwang@nju.edu.cn

Received: 6 September 2008
Revised: 5 November 2008
Accepted: 7 November 2008
Published online: 31 January 2009

Abstract

In this paper we report the nano-phase separation structure in the polymer blend film and its optical properties. Polystyrene (PS)/polymethyl methacrylate (PMMA) blend film is spin-coated on substrate. A sandwiched structure consisting of a depleted PMMA layer, a PS/PMMA blend layer and a PS-rich top layer has been formed. By selectively dissolving the PS-rich phase, a nanoporous film is generated, and the nanoporous structure can be tuned by changing the weight ratio of PS/PMMA in the blend solution in fabrication. The optical properties of the nanoporous thin films are determined. Our results show that by introducing the nanoporous structure, the refractive index can be effectively modified. By selecting proper film thickness, the maximum optical transmission can be achieved in the specific waveband.