5.7 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Emulsion stabilization using polyelectrolytes | 2/2 | https://en.wikipedia.org/wiki/Emulsion_stabilization_using_polyelectrolytes | reference | science, encyclopedia | 2026-05-05T10:47:39.907152+00:00 | kb-cron |
λ
B
=
e
2
4
π
ε
r
ε
0
k
B
T
,
{\displaystyle \lambda _{B}={\frac {e^{2}}{4\pi \varepsilon _{r}\varepsilon _{0}k_{\text{B}}T}},}
where
e
{\displaystyle e}
= elementary charge,
ε
0
{\displaystyle \varepsilon _{0}}
= vacuum permittivity,
ε
r
{\displaystyle \varepsilon _{r}}
= relative dielectric constant.
=== Surface charge density === The factors discussed above can influence the charge on the surface of the polyelectrolyte. The surface charge density of these surfaces, at low surface potentials, can be modeled using a simplified version of the Grahame equation (eq. 3):
σ
=
ε
r
ε
0
ϕ
0
K
,
{\displaystyle \sigma ={\varepsilon _{r}\varepsilon _{0}\phi _{0}}{K},}
where
ϕ
0
{\displaystyle \phi _{0}}
= surface potential. Examples of polymers and their surface charge densities can be found in the table below.
== Applications ==
=== Deflocculation === Depending on the situation, polyelectrolytes can function as either flocculants or deflocculants. To stabilize emulsion, deflocculant polyelectrolytes are required. When repulsive forces between particles overcome the intermolecular forces in solution and the loose flocculated aggregates separate, deflocculation occurs. As opposed to the loose and easily separated sediments formed in flocculation, sediments formed in deflocculation are tightly packed and difficult to redisperse. The repelling forces in a deflocculation increase the zeta potential, which in turn reduces the viscosity of the suspension. Because of this reduction in viscosity, deflocculants are sometimes referred to as "thinning agents". These thinning agents are usually alkaline and raise the pH of the suspension, preventing flocculation. Deflocculants are used as thinning agents in molding plastics, making glassware, and creating clay ceramics.
=== Petroleum waste treatment === Polyelectrolytes can also act as flocculants, separating solids (flakes) and liquids in industrial processes such as solubilization and oil recovery and they usually have a large cationic charge density. Using organic materials to refine petroleum instead of iron or aluminum coagulated would greatly decrease that amount of inorganic waste produced. The waste consists of stable oil-in-water emulsions. The addition of various polyelectrolytes to petroleum waste can cause the oil to coagulate, which will make it easier to remove and dispose of, and does not significantly decrease the stability of the solution.
=== Drug delivery ===
Polyelectrolyte stabilized emulsions are important in the field of nanomedicine. To function properly, any drug delivery system must be biocompatible and biodegradable. Polyelectrolytes such as dextran sulfate (DSS), protamine (PRM) or poly-L-arginine all fulfill these requirements and may be used as a capsule with an emulsion inside. Oil in water emulsions are currently used as safe solvents for vaccines. It is important that these emulsion are stable and remain so for long periods of time. Polyelectrolyte stabilized emulsions could be used to increase the shelf life of vaccines. Researchers have been able to develop polyelectrolyte emulsions with more than six month stability. In addition to being stable for extended periods of time, polyelectrolytes may be useful for vaccines because they can be biodegradable. For example, the ester bonds of the polyelectrolyte poly(HPMA-DMAE) can undergo hydrolysis in the human body and VERO cells envelope DSS and use poly-L-arginine to break them down. Once the polylelectroyte capsule has been degraded, the emulsion containing drug is released into the body. Researchers have been investigating this drug delivery method to target leukemia cells.
=== Food technology === Because polyelectrolytes may be biocompatible, it follows that they can be used to stabilize emulsion in foods. Several studies have focused on using polyelectrolytes to induce mixing of proteins and polysaccharides in oil-in-water emulsions. DSS has been successfully used to stabilize these types of emulsions. Other studies have focused on stabilizing oil-in-water emulsions using β-lactoglobulin (β-Lg), a globular protein, and pectin, an anionic polysaccharide. Both β-lactoglobulin and pectin are common ingredients in the food industry. β-lactoglobulin is used in whey protein, which can act as an emulsifier.
== References ==