Pendant chains, degradable

B. Solubilization via Pendant Chain Degradation. "In the biological environment, side chain degradation occurs so that the chemical bonds holding the pesticide within its polymeric prison are sequentially broken to provide a sustained release of the pesticide over an extended period of time. The rate of release will clearly be determined by the nature of the pesticide-polymer bonds, the chemical characteristics of the pesticide and polymer, as well as the dimensions and structure of the resultant macromolecular combination".2=... 

Degradable implants, shape-memory polymers in, 22 355 Degradable-pendant-chain hydrogels, 13 741... 

Molecular weights of 30,000-60,000 could be obtained. The polymers showed outstanding thermal stability (TGA 550°C. break, air or nitrogen), are all soluble in common organic solvents (up to 15 wt. % ), form clear films, are colorless, and amorphous. The thermal decomposition of these polymers has been shown to take place by the loss of pendant phenyl groups as phenyl radicals. Thus, the thermal treatment of a film under nitrogen produces a crosslinked film which is still amorphous but insoluble no appreciable main chain degradation takes place. 

Another example of a non degradable pendant chain system involves the chemical linkage of catecholamines, such as dopamine, to amino-aryloxy side groups by diazo-coupling techniques (Allcock et al, 1983) (Figure 26). 

Ebdon and coworkers22 "232 have reported telechelic synthesis by a process that involves copolymerizing butadiene or acetylene derivatives to form polymers with internal unsaturation. Ozonolysis of these polymers yields di-end functional polymers. The a,o>dicarboxy1ic acid telechelic was prepared from poly(S-s tot-B) (Scheme 7.19). Precautions were necessary to stop degradation of the PS chains during ozonolysis. 28 The presence of pendant carboxylic acid groups, formed by ozonolysis of 1,2-diene units, was not reported. 

Biodegradable polyurethanes have been proposed and studied before (9-72). The difference in our study is the inclusion of a phosphoester linkage instead of the commonly used polyester component. This seems to provide more flexibility as the side chain of the phosphate or phosphonate can be varied. For controlled drug delivery applications, drugs can be linked to this site to form a pendant delivery system. Moreover, for certain medical applications, fast degradation rate is obtainable by the introduction of these hydrolyzable phosphoester bonds. With the LDI based polyurethanes, drugs or other compounds of interest can also be coupled to the ester side chain of the lysine portion. 

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