Block-copolymer controlled radical polymerization of vinylbenzylthymine (VBT): An application for controlled drug delivery devices

A. BARBARINI; D. M. MARTINO

Washington

Conferencia; 14th Annual Green Chemistry & Engineering Conference; 2010

We carried out a systematical experimental investigation on the block copolymer controlled radical polymerization of styrene (St) and vinylbenzyl thymine (VBT). Two radical capping mechanisms were compared: nitroxide-mediated living free-radical polymerization (NMP) using 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) derivatives as stable radical deactivators; and transition metal mediated polymerization or atom transfer radical polymerization (ATRP) using a copper bromide (CuBr) as catalyst. Several syntheses of block copolymers varying the comonomer composition, the nitroxide radical/catalyst concentrations and temperature were examined. Samples were taken along the reactions to determine monomer conversion, chemical composition, and molecular weight distribution. The radical nature and concentrations were measured and analyzed with the aid of electron paramagnetic resonance spectroscopy (EPR), providing important information on the mechanisms. The experimental results provide complementary information on the characteristics and properties of styrene based copolymers containing thymine, that are crucial for developing new classes of environmentally benign, non-toxic materials.