Synthesis of Advanced Nanoreinforced Polyurethane with Thiolene Photografted Organo-Modified Layered Double Hydroxide

New bionanocomposites with strongly intertwined structures based on polyurethane and layered double hydroxides (LDH) were obtained by using two different intermolecular thiolene coupling strategies in which the modification of LDH with oleic acid was either performed first and then followed by the thiolene photografting using 2-mercaptoethanol, or the initial thiolene photografted oleic acid/2-mercaptoethanol product was subsequently used to modify the LDH platelets. The resultant photografted oleate/LDH was condensed with diisocyanate and the addition of poly(ethyleneglycol) yielded a final hybrid polymer. The interleaved LDH materials were characterized by X-ray diffraction and thermogravimetric analysis, underlining the possible commutative steps between photografting and organo-modification processes. The resultant polyurethanes were characterized by FTIR spectroscopy, nuclear magnetic resonance, differential scanning calorimetry and rheology. Furthermore, the durability of the resultant polymers was assessed by photo-FTIR. The results showed that strongly intermingled polyurethanes were processed by both strategies. Enhanced mechanical properties as well as more prolonged durability were found after anchoring LDH sheets and this was even more amplified when using the photografted acid direct intercalation into the LDH during the first synthesis step.