We studied the effect of polyethylene-oxide (PEO, molecular weight from 10(5) to 4 x 10(6)) dissolved in the micellar nematic (N) and lamellar (L) phases of the surfactant system cesium perfluoro-octanoate (CsPFO)/water by microscopy and calorimetry. Replacement of water by PEO suppresses the lamellar phase above a critical concentration (w(c)) which depends on the molecular weight of the polymer by a power law. In a limited range below w(c) a reentrant nematic is observed. The N-L transitions become less sharp with increasing concentration. The observed effects are due to the disruption of the lamellar order by the polymer.
The melting of lipid-based microcylinders (tubules) has been investigated for systems with single and multiple bilayer walls using high field, magnetic birefringence, and precision microcalorimetry. The pretransitional behavior of both the magnetic birefringence and the specific heat is very different in tubules with a single bilayer wall from that of tubules with multiple bilayers.