Thiol-ene grafting from polylactic acid, polycaprolactone, and polyhydroxybutyrate

Thiol-ene additions of different monomers from multi-thiol functionalized biodegradable polymers are analyzed in this study. These monomers include quaternary ammonium groups known for their biological activities; and also methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA), which are used to control the hydrophilic-hydrophobic balance in the issued copolymers. Monomer conversion and the resulting polymer structures are confirmed principally by 1H nuclear magnetic resonance (NMR) spectra. Model reactions are first conducted with thiophenol, and then polylactic acid (PLA), polycaprolactone (PCL), and polyhydroxybutyrate (PHB) multi-thiol functionalized polymers are successfully used. The structures of the obtained products are analyzed by 1H NMR spectra: all the reactions are kinetically controlled and monomer additions are controllable. Chain transfer constants of the used monomers to the multi-thiol functionalized PLA are between 1.4 and 1.9. The obtained products were also characterized by size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA).