Molecularly defined (L)‐lactic acid oligomers and polymers: Synthesis and characterization

Abstract

The synthesis of (L)‐lactide oligomers from dimer to 64mer via an exponential growth strategy is described. By careful selection of orthogonal protective groups, the synthesis were conducted using a t‐butyldimethylsilyl (TBDMS) ether as the protective group of the hydroxyl group and benzyl (Bn) ester as the protective group of the carboxylic acid group. The yields of both the deprotection steps and coupling reactions using 1,3‐dicyclohexylcarbodiimide or 1‐[3‐(dimethylamino)propyl]‐3‐ethylcarbodiimide hydrochloride were high (70–100%) and the absence of a requirement for conducting the majority of reactions under an inert atmosphere permitted a robust and efficient synthetic strategy to be developed. This allowed monodisperse dimer, tetramer, octamer, 16mer, 32mer, and 64mer materials to be prepared in gram quantities and fully characterized using mass spectrometry and size exclusion chromatography. Evaluation of the thermal and physical properties using thermogravimetric analysis, differential scanning calorimetry, and small angle X‐ray scattering demonstrated a close correlation between the molecular structure of the well‐defined Poly(lactide) oligomers and their physical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5977–5990, 2008

Precise Synthesis of Molecularly Defined Oligomers and Polymers by Orthogonal Iterative Divergent/Convergent Approaches

“…Small-angle Adapted from ref. [49] Copyright 2008, Wiley Periodicals, Inc. X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements confirmed a lamellae structure was observed for the 16-mer through the 64-mer, with the lamellae thickness (D) being very close to the theoretical molecular lengths in the case of the 16-mer and 32-mer. This indicates that the molecules are extended in the lamellae structures.…”

“…In 2008, [49] the Hawker group applied the same geometrical growth approach as Seebach and coworkers, [45] to synthesize perfectly defined oligomers of L-lactic acid up to the 64-mer 67 64 , using (t-butyl)dimethylsilyl (TBDMS) and Bn protecting groups for the carboxylic acid and alcohol chain-ends, respectively (Scheme 24). The starting key intermediate was the orthogonally protected dimer 67 2 which was obtained in three steps starting from sodium Llactate.…”

Synthesis and characterization of well-defined l-lactic acid-caprolactone co-oligomers and their rhenium (I) and technetium(I) conjugates

“…Significant effort has been devoted to the development of length-controlled polymerization process in recent years [8,9]. Although there is growing academic and industrial interest in PLA, PCL, or their copolymers (PLA-PCL), the synthesis of well-defined PLA or PCL oligomers have been scarcely reported [10,11].…”

Synthesis of Polylactide-b-Poly (Dimethyl Siloxane) Block Copolymers and Their Blends with Pure Polylactide

“…They offer attractive properties for biomedical, drug delivery, tissue engineering and packaging applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Among them, polylactide (PLA) possesses good barrier properties and excellent transparency.…”