Photoactive films obtained from methacrylo-urethanes tannic acid-based with potential usage as coating materials: analytic and kinetic studies

New UV-curable urethane functionalized precursors were synthesized from met hacrylic derivatives of tannic acid (TA) (m-digallic acid), using tolylene 2,4-diisocyanate (TDI) and 2-hydroxyethyl methacrylate (HEMA) as major reag ents. These products were obtained through two different procedures: two-st ep and one-step synthetic routes. Thus, Hypermonomers I and II were obtaine d. Hypermonomer I was prepared via convergent synthesis of two precursors, i.e . tannic acid methacrylate (Monomer I-A) and TDI-HEMA adduct (Monomer I-B) in a 1 : 1 molar ratio (Route I). On the other hand, Hypermonomer II was obtained in a one-step procedure; th e coupling reaction between tannic acid and TDI (Monomer IIA) was followed by HEMA addition, in a molar ratio TA-TDI-HEMA 1 :3 :3 (Route LT). To begin with, kinetic and thermodynamic parameters were defined by means o f differential photocalorimetry (DPC) to evaluate the following parameters: enthalpy (Delta H), peak maximum (PM), percent of monomer reacted at peak maximum (RPM %), induction time (IT), order of the initiation reaction (m), and rate constant (k). The hypermonomers were thermally and photochemically polymerized into films , and the resulting films were characterized by infrared spectroscopy (FT-I R), H-1 nuclear magnetic resonance spectroscopy (H-1 NMR), and thermogravim etric analysis (TGA-DTG). From all these studies, it is clear that the films obtained from Hypermonom er LI (Route LI) yield compounds of higher crosslinking extent than films f rom Hypermonomer I (Route I) readily and effectively. (C) 1999 Elsevier Sci ence S.A. All rights reserved.