Aliphatic polyesters biomaterials applications

Aliphatic polyesters occupy a key position in the field of polymer science because they exhibit the remarkable properties of biodegradability and biocompatibihty, which opens up a wide range of applications as environmentally friendly thermoplastics and biomaterials. Three different mechanisms of polymerization can be implemented to synthesize aliphatic polyesters (1) the ring-opening polymerization (ROP) of cyclic ketene acetals, (2) the step-growth polymerization of lactones, and (3) the ROP of lactones (Fig. 1). 

Strategies in Aliphatic Polyester Synthesis for Biomaterial and Drug Delivery Applications... 

Figure 1. Examples of biomaterials applications using aliphatic polyesters...

In summary, aliphatic polyesters, already an important class of synthetic degradable polymeric biomaterials, have been taken to unprecedented levels of synthetic diversity and tailoring through the efforts of many research groups in the U.S. and abroad. Some of these have been described in this brief review, with a focus on pendent or graft functionality by polymerization of functionalized lactones, and post-polymerization modification. Future efforts in this area must attempt to connect these synthetic advances to specific applications, through the collaborative efforts of experts in the chemistry, biology, and clinical use of synthetic polymer materials. 

Vert, M. and Guerin, P. (1991) Biodegradable aliphatic polyesters of the poly(hydroxy acid)-type for temporary therapeutic applications, in M.A. Barbosa (ed.). Biomaterial Degradation Fundamental Aspects and Related Clinical Phenomena, Elsevier, Amsterdam, pp. 35-51. 

Polyurethanes (PUs), one of the most commonly used polymers for various blood-contacting biomedical applications, are generally prepared by the polycondensation reactions of diisocyanates with diols or amines [35, 36]. Reactions of diisocyanates with diols result in the formation of urethane linkages while diisocyanates reactions with amines result in urea linkages. Both aliphatic, as well as aromatic diisocyanate monomers, are commonly used for preparing polyurethane biomaterials. Examples include 1,4-butane diisocyanate (BDI), 1,6-hexamethylene diisocyanate (HDI), 4,4-dicyclohexylmethane diisocyanate (HMDI), and 4,4-diphenylmethane diisocyanate (MDl) [37]. Commonly used diols (or termed as polyols) for preparing polyurethanes includes poly ethers, polycaprolactone, and polyesters with molecular weights up to 5000 Da. 

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