Copolymers of glycolide and lactide

Most of the commercially available biodegradable devices are polyesters composed of homopolymers or copolymers of glycolide and lactide. There are also devices made from copolymers of trimethylene carbonate and e-caprolactone, and a suture product made from polydioxanone. 

Polygalactin 910 is a copolymer of glycolide and lactide, obtained from glycolic and lactic acid in 9 1 ratio. The multi-fiber threads, called Victyl or Pohsorb, are coated, transparent, or dyed purple. For Vicryl Rapid threads a material with smaller relative molecular mass is used, and as a result is absorbed more rapidly. 

Fredericks, R., Melveger, A. and Dolegiewitz, L., Morphological and structural changes in a copolymer of glycolide and lactide occurring as a result of hydrolysis, /. Polym. Sci. Polym. Phys. Ed., 22, 57, 1984. 

The third class primarily consists of polymers of 1,3-dioxane-2-one otherwise known as trimethylene carbonate (TMC) and its copolymers with glycolide and lactide. PTMC degrades at a much slower rate than PGA. In addition, it softens between 40 °C and 60 °C, has low mechanical strength [5], and is reported to improve handling properties in copolymers with PGA [4]. Some thermal and mechanical properties of PTMC are shown in Table 55.1. 

Copolymers of glycolide L(-)lactide have been commercialized for biomedical applications and are high strength biodegradable thermoplastic materials. Poly(glycolic acid) and copolymers with D,L-lactides are presumed to be biodegradable, although the role of chemical hydrolysis vs. enzymatic depolymerization in this process remains open to debate. 

The rate and duration of steroid release is affected by (1) polymer composition, (2) drug/polymer ratio (3) microsphere size distribution, and (4) microsphere quality (75). The ratio of glycolide to lactide in the copolymer has been found to be more dominant than the polymer molecular weight in the design of controlled release formulations. Microspheres of smaller size provide in vivo drug profiles of higher levels and shorter durations because of greater surface area. 

Gardner, D. L., Battelle Development Corp., Process of preparing microcapsules of lactides or lactide copolymers with glycolides and/or c-caprolactones, U.S. Patent 4,637,905, A,... 

Poly-p-dioxanone and copolymers Poly-p-dioxanone (PDS) Copolymers of PDS and 1-lactide Copolymers of PDS and glycolide Poly-p-dioxanone-co-morpholine-2,5 dione Copolymers of p-dioxanone and polyethlyene-p-phenylene diglycolate Copolymers of polytrimethylene malonate and p-dioxanone A, B, F, G A, B, G A, B, G A, B, G A, B, G, J A, B, G, H... 

One approach is the copolymerization of caprolactone with other cyclic monomers that nndergo ROP, namely, lactide, glycolide [70], or fnnctionalized epoxides [62,63]. In these systems, the second monomer is considered to bear the desired functionality or chemical moiety, and therefore, a wide range of novel functionalities and polymer properties are accessible. Statistical copolymers of caprolactone with lactides and glycolides are discussed earlier [70]. Beside these commonly used polyester monomers, a variety of other functional cyclic esters are described. Cyclic esters... 

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