A series of salicylic acid-derived poly(anhydride-esters) were synthesized by melt polymerization methods, in which the components linking the salicylic acids were varied. In this work, we define the "linker" as the structure that connects the two salicylate units. As the goal was to determine the relationship between the linker structure and the properties of the polymer, several linkers were evaluated for their inclusion into the polymeric backbone. The linkers were chosen based on their chemical structure and include linear aliphatic, aromatic and aliphatic branched structures. Polymer properties such as molecular weight, thermal decomposition temperature, glass transition temperature and contact angle were measured. For the linear aliphatic linkers, the molecular weight increased as the linker chain length (or number of methylenes) increased. Polymers with the most hindered linkers were more difficult to polymerize, yielding lower molecular weights. The thermal decomposition temperature also increased with the alkyl chain length but the glass transition temperature decreased, likely due to the enhanced flexibility of the polymer. The highest glass transition temperatures were displayed when using aromatic linkers due to the increased p-p interactions between the polymer chains. Drug loadings of 62-74 % by weight were obtained by modifying the linker structure. Water contact angles were measured to study the relative hydrophobicity of the polymers, which influences hydrolytic degradation rates. The ability to manipulate the physical properties of the polymers is relevant for tissue engineering, as well as drug delivery applications.
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