Lactides, nomenclature

Many investigators have studied the in vivo degradation kinetics of lactide/glycolide materials (5,35-39). There has been some confusion in the interpretation of results primarily because of lack of consistency in nomenclature and careful attention in describing the specific stereoisomers evaluated. Nevertheless, the overall degradation kinetics are fairly well established for the entire family of homopolymers and copolymers. At the present, this common knowledge of the in vivo lifetimes of various lactide/glycolide polymers is a primary reason for their popularity. 

The polymers are synthesised via two routes direct polycondensation of lactic and glycolic acids or ring-opening polymerisation of the cyclic lactide and glycolide dimers.The nomenclature for polymers prepared by different routes is full of contradictions, but polymers prepared from lactic acid by polycondensation are strictly referred to by the acid, as in poly(lactic acid), and those prepared by ring-opening polymerisation by the dimer, as in polylactide (PLA). ... 

PLA can be obtained in two ways through direct polycondensation of the hydroxy acid or by ROP of cyclic lactide monomer. The different reaction pathways to PLA are depicted in Scheme 6.3. Different nomenclatures of polymers obtained by the different routes are often observed in the literature those obtained from lactic acid by direct polycondensation are referred to as poly (lactic acid), while those obtained from lactide monomer by ROP are referred to as poly (lactide). The general abbreviation used in both cases is PLA. 

Poly(L-lactide)- -poly(e-caprolactone) (PLLA-fe-PCL) diblock copolymers were synthesized by controlled/ living sequential block copolymerization as initiated by aluminum trialkoxides in toluene solution. These procedures were reported in detail previously [50,98]. Table 11.6 lists the molecular weight characterization data obtained by size exclusion chromatography (SEC) and by NMR. The diblock nomenclature we have used denotes the PLEA block as L and the PCL block as C, the subscripts indicate the approximate composition in wt% and the superscripts the approximate number average molecular weight of the entire block copolymer in kg/mol. 

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