Monomers for adhesive polymers, 8a crosslinking polymerization of selected N-substituted bis(acrylamide)s for dental filling materials



The free-radical polymerization of bis-(N-ethylacrylamido)-ethylenglycol (I), N,N′-dimethyl-1,6-bis (acrylamido)-hexan (II), and N,N′-diethyl-1,3-bis(acrylamido)-propan (III) were investigated. The cross-linking polymerization was followed in bulk by using the ampoules technique and gravimetry. Polymerizations exhibited an abnormal kinetic behavior. For the monomer II, for example, the reaction order to 2,2′- azobisisobutyronitril (AIBN) initiator of 1.28, and the polymerization overall activation energy of 151 kJ/mol between 50 and 75°C were determined. The increasing temperature and decreasing initiator concentration resulted in an increase of double bonds consumption in the formed polymer network. At 75°C the residual unsaturation was under 2%, compared with 9.9% at 50°C. The monomer conversion-time dependences were complemented also with differential scanning calorimetry (DSC) recording the heat released during polymerization. The extension of peak time with decreasing the instant heat flow rate at this point sort the studied bis(acrylamide)s according the reactivity in the following sequence: monomer III > I >II. The polymer samples sol–gel analyses in ethanol allowed the determination of the molecular weight Mc between the network crosslinks. The presence of microgel particles at the very beginning of polymerization and the changes in chain conformation with temperature we consider as the way in which was affected the polymerization kinetics of these monomers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009