Curing reactions in acetylene terminated resins—III. DSC, TGA and TMA study of catalyzed cure of an ethynylaryl-terminated monomer

Abstract

DSC shows that the curing of the ethynylaryl-terminated monomer (1,4-(1,3-HCCC 6H 4-CH 2O)C 6H 4) 2CMe 2 (II) in the presence of (η-Cp)Co(CO) 2, (η-Cp) 2Ni, (PPh 3) 2NiCl 2, (PPh 3) 2PdCl 2, or (PPh 3) 3RhCl takes place at lower temperatures than in the absence of the catalysts. The enthalpies of polymerization are also lower except in the case of the (η-Cp)Co(CO) 2-catalyzed system which shows a value similar to that for the uncatalyzed resin. Comparison with calculated polymerization enthalpies suggests that crosslinking occurs by cyclotrimerization in the presence of (η-Cp)Co(CO) 2, but predominantly by non-aromatic conjugated linear polyene formation with the other catalysts. TG analysis indicates that the resulting resins, crosslinked in the presence of catalysts, are all of similar thermal stability, this property being determined by the structure of II rather than by that of the crosslinks. The T g values determined by TMA are similar except for a low value for the (η-Cp)Co(CO) 2-catalyzed resin which is therefore less rigid.