Ring-opening polymerization of L-lactide

Braided Synthetic Absorbable Sutures. Suture manufacturers have searched for many years to find a synthetic alternative to surgical gut. The first successful attempt to make a synthetic absorbable suture was the invention of polylactic acid [26023-30-3] suture (15). The polymer was made by the ring-opening polymerization of L-lactide [95-96-5] (1), the cycUc dimer of L-lactic acid. 

Recently, Cohn and Salomon synthesized and characterized a series of PLCL thermoplastic bioelastomers by two-step synthesis procedure. First, ring-opening polymerization of L-lactide initiated by the hydroxyl terminal groups of the PCL chain. Second, chain extension polymerization of these PLA-PCL-PLA triblocks initiated by the hexamethylene diisocyanate (HDl). 

Dittrich, V. W., and Schulz, R. C., Kinetics and mechanism of the ring-opening polymerization of L-lactide, Angew. Makro-mol. Chem.. 15. 109, 1971. 

DIAMETER AND DIAMETER DISTRIBUTIONS OF POLY(l-LACTIDE) MICROSPHERES BY RING-OPENING POLYMERIZATION OF l-LACTIDE AND FROM EARLIER SYNTHESIZED POLYMERS... 

Diameter and Diameter Distributions of Poly(L-lactide) Microspheres by Ring-Opening Polymerization of L-Lactide and from Earlier Synthesized Polymers... 

Scheme 6.38 Ring-opening polymerization of L-lactide catalyzed by tertiary amine-functionalized thiourea rac-12.

Ring opening polymerization of L-lactide is generally the most preferred route for preparing high-molecular-weight PLA due to the possibility of an accurate control of the process. Lactide polymerization can be carried out using melt polymerization, bulk polymerization, solution polymerization, and suspension... 

Scheme 2.1 Synthesis of poly(L-lactide) (PLLA) by ring-opening polymerization of L-lactide.

Li et al. reported on stereo-complex hydrogels from totally aqueous PLLA/ PEG and PDLA/PEG solutions. The copolymers are synthesized by ring-opening polymerization of L-lactide or o-lactide in the presence of mono- or dihydro)q l PEG, using zinc lactate as catalyst. Hydrogels are obtained from aqueous solutions containing equimolar amounts of PLLA/ PEG and PDLA/PEG block copolymers due to the stereo-complexation between PLLA and PDLA blocks. 

Poly-(L-lactide-co-e-caprolactone) (PLCL) copolymer, was also synthesized by the ring-opening polymerization of L-lactide and e-caprolactone in the presence of Sn(Oct)2 (Fig. 3.5). PLCL is composed of a soft matrix of e -caprolactone moieties and hard domains of L-lactide units. The monomers used in this system differ greatly in mechanical properties and time to reach complete mass loss however, once physically cross-linked in specific monomer ratios, the copolymer system exhibits a rubber-like elasticity. The structure of PLCL was identified by NMR spectra in CDCI3 (Fig. 3.5). The methine protons of the lactide unit appear as two singlets at d 5.1-5.2 (a, a ) as a result of the sequence distribution of the lactyl and caproyl units, while the methylene protons of the caproyl unit adjacent to the ester group appear at d 4.0-4.2 (c, c ) and d 2.3-2.S (g, g ). 

Fujioka et al. [100] conducted the ring-opening polymerization of L-lactide by using immobilized lipase Candida Antarctica (Novozym 435) as a catalyst at a... 

Stridsberg, K. and Albertsson, A.-C. (2000) Controlled ring-opening polymerization of L-lactide and l,5-dioxepan-2-one forming a triblock copolymer. Journal of Polymer Science Part A-Polymer Chemistry, 38. 1774-84. 

---