polyanhydrides with uniform distribution of alkyl and aromatic residues are prepared by melt polycondensation or solution polymerization of p - carboxyphenoxyalkanoic acids or p - carboxyphenylalkanoic acids . these polymers are soluble in common organic solvents and have low melting points , generally in the range of 40 °- 100 ° c . the polyanhydrides are especially well suited for forming bioerodible matrices in controlled bioactive compound delivery devices . a polymeric matrix formed according to the method described here degrades uniformly during drug release , preventing the wholescale channeling of the bioactive compound into the environment , and eliminating the problem of the presence of the polymer matrix at the site long after drug release . the polymer displays zero - order kinetic degradation profiles over various periods of time , at a rate useful for controlled drug delivery . furthermore , a desired degradation rate may be obtained by choosing the appropriate length of the aliphatic moiety .