Microencapsulation by Complex Coacervation Notes

Microencapsulation by Complex Coacervation at Room Temperature

The invention relates to a microencapsulation process using complex coacervation at room temperature. This new method encapsulates hydrophobic liquids or particles without exposing them to temperatures exceeding 30°C for more than one minute.
This differentiates it from existing processes.
It is suited for volatile, thermolabile, or thermosensitive products that degrade above 40°C for several minutes.
The process is particularly useful for encapsulating essential oils and other products sensitive to temperatures above 40°C.

Coacervation involves the separation of a colloid-rich layer in hydrophilic sols, resembling demixing.
This phenomenon is complex and challenging to analyze using phase theory due to difficulties in determining the number of constituents and differentiating phases.
The separation of a sol into two layers may not always indicate a change in the number of phases.
The term "coacervat" refers to the colloid-rich layer, while "equilibrium liquid" or "supernatant" denotes the colloid-poor layer.
"Demixing" is often replaced by "coacervation."

Conditions for flocculation and coacervation in hydrophilic sols are similar.
Coacervation is considered a step after flocculation.
The difference between flocculation and coacervation is a matter of degree.
Coacervation involves initial flocculation, an intermediate stage between solution (isolated macromolecules) and phase separation (macromolecular aggregation).
Polymer solutions are typically clear, becoming turbid during flocculation and separating into two phases during coacervation.

By varying temperature, adding alcohol or electrolytes, or gradually inducing coagulation, pronounced liquid precipitation can be achieved instead of flocculation.
A floc should not be seen as merely aggregated micelles but as numerous adhering coacervated droplets, invisible under a microscope.
If conditions favor coalescence (low coacervat viscosity), droplets become visible microscopically.
Under more favorable conditions, separation into two distinct layers (coacervated layer and equilibrium liquid layer) can occur rapidly.

Coacervation of hydrophilic colloids is generally caused by their desolvation.
In a coacervated system, the water in the colloid-rich layer (coacervat) must be bound to the colloids; otherwise, it would move to the colloid-poor layer.
Non-colloidal matter is bound to colloids, forming a significant part of the coacervat and acting as the remaining solvating envelope of the primitive sol micelles.
Solvation stabilizes non-charged particles by surrounding the micelle with water, replacing the micelle surface with a solvating layer.
Solvating layers lack concrete boundaries, with solvation involving liquid binding to micelles, decreasing in strength outwards until merging with the free liquid of the dispersing medium.

A defined boundary is difficult to establish, suggesting a diffuse water envelope.
Factors determining coacervation make the solvating envelope less diffuse, defining the boundary between the envelope and dispersing medium more precisely, increasing surface free energy.
In a sol, particles are free and dispersed, while in a coacervat, they form a condensed system in contact only with solvent molecules involved in its constitution.
Coacervats consist of independent, touching but unbound particles.

Complex coacervation, a term coined by Bungenberg de Jong, describes the spontaneous liquid/liquid phase separation when oppositely charged polyelectrolytes mix in an aqueous medium.
This results in two layers: one rich in polymers and the other poor, due to electrostatic bonds between the two oppositely charged hydrophilic polymers.
The anionic polymer is a polyanion, while the cationic polymer is a polycation.

Not all mixtures of such polyelectrolytes form a complex coacervat.
The phenomenon is limited to polyelectrolytes with suitable charge density and chain length.
Figure 2 illustrates the electrostatic interaction between a polycation and a polyanion.
A distinction must be made between complex coacervats and