Ester-adduct derivatives of rosin were synthesized by reacting rosin with polyethylene glycol 200 (PEG 200) and maleic anhydride (MA) at elevated temperature. The different concentrations of PEG 200 (7.5%, 15% and 25% w/w of rosin) were used with fixed concentration of MA (7.5%) to obtain derivatives. These derivatives were evaluated for acid number, glass transition temperature (Tg), solubility, FT-IR spectroscopy, molecular weight (Mw) and polydispersity. Water vapor transmission rate (WVTR) of free and applied (on tablets) derivative films was investigated. The PEG 200 concentration showed proportional increase in the molecular weight and reciprocal relation with the acid number and Tg of the rosin derivatives. The derivatives were soluble in organic solvents; aqueous solubility was pH dependent. The contact angle study revealed higher wettability of derivatives compared to rosin films. WVTR of derivative-coated tablets was much lower than for the free films. Further, the derivatives were investigated as matrix former in tablets and pellets using,diclofenac sodium (sparingly soluble in water) and propranolol hydrochloride (soluble in water) as model drugs. While the release of diclofenac sodium was retarded for 8 h in both dosage forms, propranolol hydrochloride was completely released within 2 h. The results support applications of these rosin derivatives in different drug delivery systems. (c) 2006 Elsevier B.V. All rights reserved.