Conformation of surfactant monolayers at solid/liquid interfaces

Infrared-visible sum-frequency (SFG) vibrational spectroscopy is used to study chain conformation of cationic surfactant monolayers (dioctadecyl dimethyl ammonium chloride, DOAC), adsorbed at various quartz/liquid interfaces at low coverage. The results show that the chains can assume many different conformations: an all-trans form if the liquid is alkane with a similarly long chain length, a bent form with significant trans-gauche defects if the liquid is CCL4 or CDCL3 or short-chain alkanes, and a highly contracted form if the liquid is water or alcohol.