Structure determination of hyperbranched polyester BOLTORN H40 by 1D- and 2D-NMR spectroscopy

Hyperbranched polyester BOLTORN H40 is a perspective core molecule for synthesis of biodegradable block copolymers for drug delivery systems. NMR spectroscopy is the key method to study molecular structure of BOLTORN H40; however, interpretation of the 1 H-NMR spectrum is still ambiguous. To determine the polyester structure precisely, a combination of 1D and 2D-NMR methods ( 1 H, 13 C, TOCSY, HSQC, HMBC) was suggested. These methods allow detecting signals from hydroxyl groups, whose correlations are crucial for identification of different types of units. The proportions of the terminal, linear, and dendritic monomeric units in BOLTORN H40 polyester were estimated to be 31, 53, and 16%, respectively. The degree of branching of the polyester is 0.47. According to this value, BOLTORN H40 belongs to a family of hyperbranched polyesters capable of forming micellar nanocontainers. These properties are critical for further precise characterization of block copolymers for various drug delivery applications.