Degradation rate, poly alkyl

Malhotra studied the effect of alkyl substituent on the ultrasonic degradation of poly (alkyl methacrylate) [197]. He prepared poly(isopropyl methacrylate) and poly (octadecyl methacrylate) of identical contour length (Fig. 23a). In an acoustic field, he failed to see any dependence of the rate constant on the size of side groups. Recently, May revisited the effect of side group using a spiropyran... 

Poly(amino acids) are insoluble in common solvents, are difficult to fabricate due to high melting point, and absorb a significant amount of water when their acid content reaches over 50 mol%. To solve these problems, polyesters derived from amino acids and lactic acids [e.g., poly (lactic acid-co-lysine) PLAL] are developed. The PLAL system is further modified by reaction with lysine A-carboxyanhydride derivatives. Another modification of poly(amino acids) includes poly(iminocarbon-ates), which are derived from the polymerization of desaminotyrosyl tyrosine alkyl esters. These polymers are easily processable and can be used as support materials for cell growth due to a high tissue compatibility. Mechanical properties of tyrosine-derived poly(carbonates) are in between those of poly(orthoesters) and poly(lactic acid) or poly(gly-colic acid). The rate of degradation of poly(iminocarbonates) is similar to that of poly (lactic acid). 

Beside inhibiting thermooxidative ageing, phosphorus containing additives increase radiation resistance of polyimides and poly(alkyl terephthalates) the rate of evolution of the aromatic ring radiation degradation product - CH4 reduces two-fold. 

The rate of degradation of PCAs is much faster than PLGAs which do not necessitate the overloading of the body with excess polymer that is still present long after initial treatment (Lherm et al. 1992). The alkyl cyanoacetate that is formed and the rate of formation are dependent on the length of the alkyl chain of the monomer used to produce the microparticles. The degree of toxicity is also dependent on the length of the alkyl chain. Poly(cyanoacrylates) have been approved by the FDA in several systems, so it is one of the more acceptable of the polymeric systems. 

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