GRAFT COPOLYMER WITH PH DEPENDENT BEHAVIOUR

摘要

A graft copolymer with pH dependent behavior of formula 1 Comprises, (i) a backbone having the formula 1 [A(X) B(Y) C(z)] wherein (A) is diol, (B) is dicarboxylic acid or acid anhydride and (C) is monomer containing pendent unsaturation such that (x) = 41-45 %, (y) = 49-53 % (z) = 4-7 % by mole; and (ii) a graft which is a polymer of the basic monomer (D) which comprises "w" weight percent of the total weight of said graft copolymer such that 'w' is 22-52 %. The graft copolymers do not swell / dissolve at neutral and basic pH and swell / dissolve at acidic pH. The polymers are useful as protective coating for pharmaceutical dosage forms and as excipient in the development of extended release drug delivery systems.