Influences of the structure of long-chain diynoic acids on their polymerization properties in Langmuir—Blodgett multilayers

Abstract

Acids of the general formula CH 3 − (CH 2) m−1 − CC − CC −(CH 2) n − COOH with m = 10, n = 8; m = 16, n = 2 and m = 16, n = 0 were investigated concerning their spreading behavior in monomolecular layers and their polymerizability in Langmuir—Blodgett multilayers. Influences of the aliphatic chain lengths m and n and the cadmium salt formation on their solid-state reactivity are discussed. Acids with the diacetylene unit amidst the aliphatic chain are highly photoreactive, but their monomolecular layers are of low stability. Acids with the diacetylene unit near the polar headgroup form more stable monolayers, but the packing is less favorable for a polymerization reaction. The cadmium salt formation in the multilayers can influence the reactivity and cause even photoinactivity, as shown for the acid with m = 16, n = 2.