The stability of lead stearate layers in alternating Langmuir-Blodgett (LB) films of lead stearate/lead deuterated stearate with and without poly(tert-butyl methacrylate) (PtBMA) layers at each interface was measured from the magnitude of the splitting of the CH2 or CD2 scissoring band in transmission FT-IR spectra. Before annealing, the extent of splitting of the CH2 or CD2 bending mode in the alternating LB film with PtBMA layers was larger than that in the alternating LB film without PtBMA layers. However, the opposite trend was observed after annealing. This suggests that PtBMA does not function as a barrier to interlayer mixing on annealing. The results presented here represent the first report that PtBMA has two important roles: before annealing it stabilizes the fatty acid layers, and after annealing it disturbs these layers. PtBMA is expected to act as a substrate when it is inserted between fatty acid layers. This PtBMA substrate can stabilize the fatty acid layers at room temperature. However, external reflection FT-IR spectra indicate that annealing causes the reorientation of PtBMA. This reorientation of PtBMA could disturb the fatty acid layers.
Hyeon Suk Shin, Junhoe Cha, Taihyun Chang, and Seung Bin Kim, "Stability and Disturbance of Fatty Acid Layers by Polymer in Lead Stearate/Poly(tert-Butyl Methacrylate) Alternating Langmuir-Blodgett Films," Appl. Spectrosc. 56, 1176-1179 (2002)