Study of Inclusion in Phase Inversion Emulsification and Multiple Emulsions

The phenomenon of ‘inclusion’ in emulsions refers to the inclusion of continuous
phase into the dispersed phase drops and formation of multiple drops due to the
tendency of the inner phase to stabilise the outer phase. Inclusion plays an
important role in both catastrophic phase inversion (CPI) emulsification process
and preparation of multiple emulsions. In CPI, inclusion leads to formation of
abnormal multiple drops, which eventually invert to the opposite desired normal
emulsion. On the other hand, in multiple emulsions, inclusion may have an
adverse effect leading to instability of the multiple emulsions because of
coalescence of inner drops, and/or coalescence of multiple drops, or even
bursting of multiple drops. All these result in instability of multiple emulsions and
accelerate release of the active agent. In the first part of this work, we carried out
a comprehensive study on the rate and extent of inclusion in CPI emulsification at
different formulation and process conditions for the first time. We also
investigated the conditions under which the CPI emulsification method produces
finer emulsions than the direct emulsification method, which means applying less
energy could result in a finer emulsion. In the second part of this work, we
investigated the conditions under which inclusion can be ignored during the
preparation of multiple emulsions. We also carried out an extensive study on the
optimisation of the process conditions to achieve maximum encapsulation
efficiency in freshly prepared multiple emulsions.
In the last part of this work, we briefly looked at the possibility of synthesis of
macroporous alginate hydrogel particles via CPI and through inclusion of an oil
into sodium alginate drops but without success. However, we introduced a new
modified emulsification process based on addition of calcium chloride water-in-oil
emulsion to sodium alginate emulsion, which produced promising results.