Vibrational sum frequency studies of Langmuir monolayers

COLL 277

Marc C. Gurau, Chemistry Department, Texas A&M University, College Station, UT 77843 and Paul S. Cremer, Department of Chemistry, Texas A&M University, MS 3255, College Station, TX 77843.
Langmuir monolayers and their associated water structures were perturbed by changing the pressure of the monolayer along with the temperature and ionic content of the subphases. Sum frequency spectra provided insights into the structural changes induced both in the monolayer's alkyl region and the hydrogen bonding network of the near surface water molecules. The methods developed allowed for the experimental determination of the enthalpy of gauche defect formation in an amphiphile's alkyl chain. Additionally, a definitive assignment of the 3400 cm-1 VSFS feature was made, which involved the solvation of the monolayer's headgroups.