Miniemulsion
Encyclopedia
A miniemulsion is a special case of emulsion
. A miniemulsion is obtained by shearing a mixture comprising two immiscible liquid phases, one surfactant
and one co-surfactant (typical examples are hexadecane or cetyl alcohol).
The shearing proceeds usually via ultrasonication of the mixture or with a high-pressure homogenizer
, which are high-shearing processes.
In an ideal miniemulsion system, coalescence
and Ostwald ripening
are suppressed thanks to the presence of the surfactant and co-surfactant, respectively.
Stable droplets are then obtained, which have typically a size between 50 and 500 nm. The miniemulsion process is therefore particularly adapted for the generation of nanomaterials
. There is a fundamental difference between traditional emulsion polymerisation and a miniemulsion polymerisation. Particle formation in the former is a mixture of micellar and homogenous nucleation, particles formed via miniemulsion however are mainly formed by droplet nucleation.
Emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...
. A miniemulsion is obtained by shearing a mixture comprising two immiscible liquid phases, one surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
and one co-surfactant (typical examples are hexadecane or cetyl alcohol).
The shearing proceeds usually via ultrasonication of the mixture or with a high-pressure homogenizer
Homogenization (chemistry)
Homogenization or homogenisation is any of several processes used to make a chemical mixture the same throughout.-Definition:Homogenization is intensive blending of mutually related substances or groups of mutually related substances to form a constant of different insoluble phases to obtain a...
, which are high-shearing processes.
In an ideal miniemulsion system, coalescence
Coalescence
Coalescence may refer to:* Coalescence , the merging of genetic lineages backwards time to a most recent common ancestor* Coalescence , the merging of two or more phonological segments into one...
and Ostwald ripening
Ostwald ripening
right|thumb|300px|Basic schematic of the Ostwald ripening process Ostwald ripening is an observed phenomenon in solid solutions or liquid sols which describes the change of an inhomogeneous structure over time...
are suppressed thanks to the presence of the surfactant and co-surfactant, respectively.
Stable droplets are then obtained, which have typically a size between 50 and 500 nm. The miniemulsion process is therefore particularly adapted for the generation of nanomaterials
Nanomaterials
Nanomaterials is a field that takes a materials science-based approach to nanotechnology. It studies materials with morphological features on the nanoscale, and especially those that have special properties stemming from their nanoscale dimensions...
. There is a fundamental difference between traditional emulsion polymerisation and a miniemulsion polymerisation. Particle formation in the former is a mixture of micellar and homogenous nucleation, particles formed via miniemulsion however are mainly formed by droplet nucleation.