Figure 1

The phase diagram in the upper left corner has two phase coexistence regions corresponding to one in each monolayer. This is consistent with our AFM data. The transition temperature in pure water of DPPC is $41.3°\mathrm{C}$ and that of SOPC is $5°\mathrm{C}$. Images of a DPPC-SOPC ($80/20\mathrm{m}\mathrm{o}\mathrm{l}\%$) bilayer on a solid mica support at various temperatures in the heating-cooling cycle: (a) at room temperature, the darkest areas are holes and the grain boundaries are clearly visible; (b) during the phase transition of the distal monolayer; (c) when the distal monolayer is completely melted; (d) during the phase transition of the proximal monolayer, and (e) when the bilayer is completely fluid. Images (f)–(i) are corresponding images obtained when the bilayer is cooled. Note the similarity between the defect structure of images (c) and (g) and of (a) and (i). All images are $2.4\times 2.4\mu {\mathrm{m}}^2$.Reuse & Permissions

Figure 2

DSC and AFM data of the solid-to-liquid transition. Filled and empty squares represent AFM data from the distal and the proximal monolayer, respectively. The fraction of melted monolayer ($\alpha$, measured by AFM) is plotted against temperature. The thick solid line represents the DSC data.Reuse & Permissions

Figure 3

Semilog plot of the width of the melted interfacial zone $w(T)$ vs reduced temperature $(T_{\mathrm{m}}-T)/T_{\mathrm{m}}$. The straight solid line is the result of a fit of the logarithmic law $w(T)=-A\ln (T_{\mathrm{m}}-T)+B$ to the data. $T_{\mathrm{m}}$ was determined from the fit to be $311.05\pm 0.65\mathrm{K}$. This temperature corresponds very well to the temperature where the distal monolayer is completely melted, i.e., the upper limit of the phase coexistence region.Reuse & Permissions