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The polymerization of LA and GA can proceed by anionic, carbocationic, or coordination insertion mechanisms and is well described in the previous sections. Poly(lactic acid‐co‐glycolic acid) [poly(LA‐co‐GA) or PLGA] of varying molar masses and compositions are also available commercially.

Low molar mass PLGA, copolymers were prepared by the step‐growth polycondensation of lactic acid and glycolic acid. Such copolymers are obtained by polycondensation reaction of the desired composition of monomers in the presence of heat. The reaction is favored in forward direction by removal of evolved water by distillation at atmospheric pressure or under vacuum conditions. The copolymers thus obtained are either brittle and glassy or waxy and sticky, depending on the feed composition and the resultant molar mass of the polymer. A copolymer with a weight‐average molar mass of ≥15,000 g/mol was prepared by dehydration condensation of lactic acid and glycolic acid in diphenyl ether in the presence of tin powder [89].

On the other hand, high molar mass copolymers are prepared by ROP of LLA or DLA and 1,4‐dioxane‐2,5‐dione or GA under inert atmosphere or in vacuum. The polymerization can be carried out in bulk, solution (tetrahydrofuran (THF), toluene, dioxane, etc.), or suspension or emulsion conditions. The temperature of bulk polymerization is generally in the range of 100–160°C, whereas in solution polymerization, low temperature (0–25°C) was used to minimize the side reactions (inter‐ and intra‐molecular transesterifications). PLGA copolymers having lactoyl content of 70–90% were prepared by copolymerization at 160°C for 20 h using a desired ratio of monomers and Sn(Oct)₂ as a catalyst [21]. The weight‐average molar mass of the copolymers ranged from 9.07 to 7.95 × 10⁴ g/mol. Bulk polymerization of LLA and GA (75 : 25) using Sn(Oct)₂ at 60°C for 2 h (in vacuum to remove traces of water) and at 165°C for 4.5 h gave a polymer with weight‐average molar mass of 50,000–70,000 g/mol [18].

Block copolymers of LA and GA have been synthesized by sequential addition of monomer onto the reactive chain end of polymer produced from another monomer and by using a hydroxyl‐terminated homopolymer as a chain transfer agent [17]. Even small differences in the sequence of monomer units in PLGAs can be easily noticed and determined by (¹H and ¹³C) NMR. Especially, the diastereotopic methylene resonances for the glycolic units of the copolymers are well noticed in the ¹H NMR. Thus, NMR technique is considered as sensitive and useful technique to provide a better structure–property correlation [90].