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.