Unsaturated-LMWE monolayers

In contrast with saturated-LMWE, imsaturated-LMWE monolayers present only the liquid expanded structure and the collapse. BAM images corroborate that only the homogeneous LE phase is present during the compression of unsaturated-LMWE monolayers. From the observation with BAM along the film balance no fractures were visualized after the monolayer collapse. These monolayers collapse with the formation of lenses. 

At TT > TTg the relaxation phenomena for insoluble monolayers are caused by the transformation of a homogeneous monolayer phase into a heterogeneous monolayer-collapse phase system. However, some differences exist between saturated-LMWE and unsaturated-LMWE monolayers (Eigure 14.6b). Relaxation phenomena in saturated-LMWE monolayer are controlled predominantly by the collapse mechanism because the surface pressure relaxes to TTg. Eor these systems the monolayer collapses by nucleation and growth of critical nuclei. Unsaturated-LMWE monolayers behave differently to saturated-LMWE monolayers. As the surface pressure relaxes from the collapse value, which is close to TTg, towards values lower than TTg at longer times, the collapse competes with a desorption mechanism (Patino and Nino, 1999). 

As for unsaturated-LMWE, the domains that residues of protein molecules adopt at the air-water interface appeared to be of uniform reflectivity, suggesting homogeneity in thickness and film isotropy. I increased with tt and reaches a maximum at the collapse point. At ir < TTg, I was independent of the protein but, at the collapse point, I was higher for (3-casein and caseinate than for WPI. That is, at higher tt and especially at the collapse point, the thickness of (3-casein or caseinate monolayer is higher than that for WPI. However, for globular protein monolayers, E increased with increasing tt up to the collapse point. However, for the more disordered proteins ((3-casein and caseinate) the E-tt dependence is more complex. E increases to a maximum with tt for Structure 1, but decreases with tt and... 

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