Monodispersed two-dimensional nanoclusters of CF3(CF2)(3)(CH2)(22)COOH on the aqueous Cd2+ subphase investigated by polarization modulation infrared spectroscopy

Polarization modulation infrared reflection absorption spectroscopy was app lied to investigate two-dimensional nanoclusters of CF3(CF2)(3)(CH2)(22)COO H (C27F9) on the aqueous Cd2+ subphase in a Langmuir trough at 288 K. The - (CH2)(22)- long axis was always inclined on the subphase and had triclinic parallel packing with compression from 0.60 to 0.30 nm(2). In contrast, beh enic acid, without the CF3(CF2)(3)- tail, formed orthorhombic micrometer do mains on the Cd2+ subphase with its hydrocarbon chain vertically aligned. I t is concluded that the steric hindrance imposed by the bulky CF3(CF2)(3)- tail is responsible for the specific orientation and packing of the -(CH2)( 22)- part as well as the formation of the nanometer-size clusters. (C) 2000 Elsevier Science B.V. All rights reserved.