We investigated the effect of surface property of polyimide substrate on the formation of pentacene thin. film by using atomic force microscopy (AFM) and X-ray reflectivity (XRR) and diffuse scattering (XDS). Two types of polymer films were prepared: (1) polyimide (PAA-PI) from poly(amic acid) (PAA) (2) polyimide hybrid (PAA-PI-H) prepared by hybridizing the PAA and soluble polyimide (PI) with a octadecyl side chain. The hybridization ratio of PI to PAA was 2/98 in wt%. The water contact angle for PAA-PI-H and PAA-PI were around 808 and 648, respectively. Morphology of pentacene with a ropelike structure and ( 1 1 0) peak around 1.4 A in q(z) was found when it was deposited on PAA-PI thin-film. Different pentacene morphology was observed when it was deposited on PAA-PI-H thin-film. The different morphology might be due to a 5-6 nm thick additional layer (similar to 0.95 rho(film)) at the interface between pentacene and PAA-PI-H thin-film caused by a long alkyl side chain introduced to the polymer main chain. (C) 2009 Elsevier B.V. All rights reserved.