STUDY OF DELAYED GELATION OF A RIGID SPIRO AROMATIC DICYANATE, 6,6'-DICYANATO-3,3,3', 3'-TETRAMETHYL-1,1'-SPIROBI-INDANE

rigid spiro aromatic dicyanate, 6,6'-dicyanato-3,3,3 ',3'-tetramethyl- 1, 1'-spirobi-indane (DCSI), was synthesized and its polycyclotrimeriz ation investigated. The critical gel point (alpha(gel)) during polycyc lotrimerization of DCSI was studied by gravimetric analysis. The resul ting value of alpha(gel) ( = 65 +/- 2%) deviates greatly from the theo retical value of 50%. To explore the possible reason for this high dev iation, partially cured samples were analysed by fast atom bombardment mass spectrometry (FAB-MS). The predominant formation of trimer at a conversion ' 50% is responsible for the delayed gelation. In addition to the small amounts of side products such as dimer and carbonate imin e, the formation of products with internal cycles (i.e. tetramer and h examer) is another reason for the high alpha(gel). (C) 1998 Elsevier S cience Ltd. All rights reserved.