Optical properties of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-phenylene vinylene) deposited on porous alumina substrates

Thin films of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-phenylene vinylene) (MEH-PPV) were deposited from solutions prepared with different solvents, on alumina-1%Mg substrates with different pore sizes from 18 to 118 nm to study the effects of the size on the optical properties of the polymer. The photoluminescence (PL) spectra of films cast from solutions using chloroform, toluene or xylene are almost similar, suggesting that the solvents have little effect on the solid films. In the composite systems, a blue shift of the polymer PL spectra was observed when the pore size decreases. Raman spectra recorded on these samples did not show significant changes compared to that of the polymer, suggesting that the structure of the polymer was preserved. The modifications observed in the PL spectra are attributed to the nanosize effect of the polymer deposited in the pores resulted from the chain conformation, which depends on the nature of the solvents used.