UV VIS AND NMR SPECTROSCOPIC STUDIES ON THE STRUCTURE OF CATIONICALLYPOLYMERIZED CYCLOPENTADIENE ON THE SURFACE OF SILICA PARTICLES/

The cationic polymerization of cyclopentadiene (CPD) in the presence o f silica gel particles is initiated by triphenylmethyl chloride, triph enylmethyl bromide, and methyl triflate in 1,2-dichloroethane. The sus pension polymerization yields soluble colourless polycyclopentadiene ( PCPD) and intensively blue coloured silica particles (PCPD+ silica). T he formation of the polymer structure on the silica surface in suspens ion is followed by transmission UV/VIS spectroscopy and solution (H-1 and C-13) NMR spectroscopy. The structure of the novel solid materials (PCPD modified silica particles) is additionally investigated by DRIF T spectroscopy, solid-state C-13 CP/MAS NMR spectroscopy and scanning electron microscopy (SEM). The blue colour of the PCPD+ silica particl es is caused by polyenylium sequences with five or six conjugated doub le bonds along the isomerized PCPD chains. The PCPD+ structures are co mpared with similar ionic model compounds derived from retinol and ret inal, respectively. The remaining of the PCPD layer including the conj ugated sequences on the surface is attributed to the formation of cova lent Si-O-C bonds. Model reactions of the cationically active PCPD+ si lica particles with benzyltriethyl-ammonium chloride and hexachloroant imonate, as well as charge transfer complex formation of the PCPD poly mer layer with carbenium salts, (C6H5)(3)C+AsF6- and C7H7+BF4-, are al so investigated. A possible mechanism for the formation of crosslinked PCPD layers on the silica surface is suggested.