Azeotropic Dehydrative Polycondensation of LA

Takasu et al. [24] reported that scandium trifluoromethanesulfonate [Sc(OTQ3] and scandium trifluoromethanesulfonimide [Sc(NTf2)s] are effective for one-step dehydration polycondensation of L-lactic acid. Bulk polycondensation of L-lactic acid was carried out at 130-170°C to give PLLA with Mn of 5.1 xlO -7.3xl0 (yield 32%-60%). However, the solution polycondensation was 

Ajioka et al. [26] have synthesized PLA with a higher than 300 000 by azeotropic dehydrative polycondensation of LA in the presence of a catalyst and an organic solvent. These polymers have good mechanical properties and can be processed into products such as cups, film, and fiber, which can be used as compostable materials. 

The polymerization process by azeotropic dehydrative condensation of LA seems promising for obtaining a high molecular weight PLA with improved cost performance. However, the use of solvents such as diphenyl ether results in multiple reactors and complex facilities of the process control, leaving the price of PLA expensive. Also, it is hard to remove solvent completely from the end product. Meanwhile, the azeotropic dehydrative condensation process inherits the 

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Figure 3.3 Flow diagram of the azeotropic dehydrative polycondensation of LA...

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