Molecular Structure of Hydrophobic Alkyl Side Chains at Comb Polymer-Air Interface. Gautam, Keshav S.; Dhinojwala, Ali. Department of Polymer Science, University of Akron, Akron, OH, USA. Macromolecules (2001), 34(5), 1137-1139. CODEN: MAMOBX ISSN: 0024-9297. Journal written in English. CAN 134:281358 AN 2001:78808 CAPLUS

In this Communication, the authors report the first spectroscopic measurement of the mol. structure of octadecyl alkyl side chains at poly(vinyl octadecyl carbamates-co-vinyl acetate) air interface using the surface sensitive sum-frequency generation (SFG) technique. The authors compare the differences in the surface structure of 65 nm thick octadecyl polymer films prepd. by spin-coating to a 7 nm polymer layer prepd. by soln. dipping on a mica substrate. In both cases, the SFG signals show strong Me asym. and sym. stretching vibrations indicating ordered Me terminal groups. For the adsorbed octadecyl films, the SFG signal assocd. with methylene vibrations is higher indicating increased gauche defects in comparison with the spin-coated thicker films. The irregularity in packing of the alkyl chains for the 7 nm polymer films is also reflected in an unstable and rapidly changing contact angle.