Studies of monomer and polymer monolayers using optical second and third harmonic generation
Optical second harmonic generation (SHG) is a highly surface sensitive technique for studying ultrathin molecular layers. This technique has been used to study monolayers of various organic monomers - vinyl stearate, octadecyl methacrylate and some diacetylene derivatives - and their corresponding polymers spread at air/water interfaces. Different SHG signals are obtained from a pure water surface, and from water covered with monomer and polymer monolayers. During polymerization of monomer monolayers the SHG signal intensity is observed to change continuously from the monomer monolayer value to the polymer monolayer value. Monolayer polymerization of some amphiphilic diacetylenes was also studied by third harmonic generation (THG), which unlike SHG is not a surface sensitive probe. However, the extremely high third order nonlinearity of polydiacetylenes enables THG from a single monolayer to be observable above the water background signal. In addition, evaluation of surface molecular orientations and molecular nonlinear optical coefficients from monolayer SHG and THG is also discussed.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6543526
- Report Number(s):
- LBL-23267; CONF-870410-22; ON: DE87009622
- Country of Publication:
- United States
- Language:
- English
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