Efficient synthesis and characterization of new photoactive dextran esters showing nanosphere formation

Different types of photoactive dextran derivatives with high degree of substitution were prepared by an efficient and mild esterification of the biopolymer with 2-methoxycinnamic acid, [(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetic acid, and azobenzene-4-carboxylic acid via in situ activation of the carboxylic acid groups with N,N'-carbonyldiimidazole. The structures of the novel dextran esters were evaluated by means of NMR spectroscopy applying the perpropionylated samples. Perpropionylation yields samples soluble in chloroform and acetonitrile that are very useful solvents not only for NMR but also for UV-vis spectroscopic studies. The photochemistry was studied by NMR and UV-vis spectroscopy in the dissolved state and the changes observed may be used to control the properties. The photoactive dextran esters form spherical nanoparticles of a size below 200 nm that are of interest in the design of smart materials.