Catastrophic desorption

The isotherm of H-Beta is reported in figure 4 and exhibits an hyterisis loop indicating that mesopores are present, the closer point of the hyterisis loop is found to be close to P/Po=0.42. Catastrophic desorption of mesopores is seen as generally found for dealuminated HY zeolites (ref. 8), one can discuss about the origin of this phenomenon. It is certainly due to mesopores, evidenced in transmission electron microscopy, which are not directly connected to the exterior of the crystals. The formation of these mesopores is probably related to the presence of faults in the stacking sequence of polytypes as mentioned in ref. 9. 

Their formation is certainly due to the presence of a high density of defects in the structure, clearly visible in high resolution micrographs as an apparent distorsion of the lattice planes (figure 4). These mesopores seem not to be connected to the exterior of the crystals as indicated by the catastrophic desorption at P/Po about 0.42. 

Since desorption depends only on the outer barrier layers, multiple lamination offers no advantage in controlled release other than perhaps a safety factor. That is, damage to a single laminate might produce catastrophic dumping, while damage to the outer layer of a multilaminate would only result in a minor disruption of the release. Provided vesicles do not fuse or burst, liposomes and unilamellar vesicles should have identical release properties. 

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