Reaction kinetics and chemical changes during polymerization of multifunctional (meth)acrylates for the production of highly crosslinked polymers used in information storage systems

Crosslinked polymer samples of a wide range of triacrylates, tetraacrylates, pentaacrylates and of their corresponding methacrylates were prepared by u.v. photopolymerization of the monomers using 2,2dimethoxy-2-phenyl-acetophenone as a photoinitiator. The monomers studied varied in rank, pendant group size and structure, and functionality or number of double bonds. The reaction kinetics was followed by differential photocalorimetry. Autoacceleration and autodeceleration phenomena were observed depending on the structure and molecular complexity of the monomer used. Conversion after 1 h, conversion at peak reaction rate, induction time, and time at peak reaction rate were dependent on the rank and functionality of the monomers used. Volume shrinkage during the reaction was measured by a modified thermomechanical analysis experiment and correlated to calorimetric data. A delay in volume shrinkage during polymerization was observed and correlated to rank and functionality. Dynamic mechanical studies were used to determine a, fl, 7 relaxations and linear expansion coefficients which were correlated to the polymer network structure. © 1997 Elsevier Science Ltd.