Dispersion systems: basic components and applications

The emergence of dispersion systems - In the fields of chemistry, physics, biology and engineering and pharmaceuticals the behavior of substances is governed by a fascinating phenomenon. These systems, also referred to as dispersed phase systems, are key in many applications, from pharmaceuticals and food products to cosmetics and materials science. The core of their functionality is the complex interplay of two basic components: the dispersion medium and the dispersion phase.

What is a dispersion system?

A dispersion system encapsulates a scenario in which one substance is dispersed in another substance in the form of tiny particles or droplets. These substances are typically immiscible or partially immiscible, indicating their reluctance to mix smoothly or dissolve each other. Consequently, dispersion systems manifest themselves in different configurations depending on the nature of the substances involved and the dynamics of their interaction.

Dispersion systems

Dispersion medium (continuous phase): The dispersion medium serves as a continuous phase that surrounds the dispersed phase. It acts as a support matrix in which the dispersed particles or droplets are distributed. Depending on the particular system, the dispersion medium can appear as a gas, liquid or solid. For example, in an oil-in-water emulsion, the water serves as the dispersion medium, providing a continuous phase that encapsulates the dispersed oil droplets.

Dispersed phase: This component refers to the substance that exists in the dispersion system as small particles, droplets or solid entities dispersed in the dispersion medium. Similar to the dispersion medium, the dispersed phase can also be a gas, liquid or solid. The size and shape of the dispersed phase particles play a key role in determining the properties and behavior of the dispersion system. For example, in the context of colloidal dispersions, where solid particles are dispersed in a liquid medium, particle size significantly affects factors such as stability and optical properties.

Application of dispersion systems:

The ubiquity of dispersion systems across various fields underlines their importance and versatility. Some notable applications include:

Medicines: Dispersion systems are widely used in pharmaceutical formulations, where they serve as carriers of active pharmaceutical ingredients (API). For example, nanoemulsions increase the bioavailability of poorly soluble drugs, which facilitates their absorption and effectiveness.

Food products: In the food industry, dispersion systems play a key role in stabilizing emulsions and suspensions, improving the texture, appearance and durability of food products. Examples include salad dressings, ice cream, and beverages.

Cosmetics: Emulsions are the cornerstone of cosmetics, facilitating the incorporation of oils and water-based ingredients. Creams, lotions and serums rely on dispersion systems to provide the desired sensory properties and functional benefits.

Materials science: Dispersion systems contribute to the development of advanced materials with tailored properties. Nanocomposites, in which nanoparticles are dispersed in a matrix material, exhibit improved mechanical, electrical, and thermal properties, opening avenues for innovative applications in the electronics, aerospace, and automotive industries.

Understanding the classification of dispersion systems

In chemistry and materials science, an understanding of the classification of dispersion systems is key to understanding their behavior and applications. Dispersion systems are diverse in nature and vary depending on the particle size of the dispersed phase. They can be broadly divided into molecular dispersions, colloidal dispersions (colloids) and coarse dispersions, each exhibiting distinct characteristics and properties.

1. Molecular dispersion:

Description: Molecular dispersions contain individual molecules dissolved in the dispersion medium at the molecular level.

Dispersed phase particle size range: less than 1 nanometer (nm)

System features:

Invisible in the electron microscope.
The dispersed phase can pass through an ultrafilter and a semipermeable membrane.
Undergo rapid diffusion.
Examples: Sugar dissolved in water, oxygen molecules in air.

2. Colloidal dispersion (colloids):

Description: Colloids are characterized by dispersed phase particles ranging in size from 1 nanometer (nm) to 0.5 micrometer (μm), larger than individual molecules but smaller than particles in coarse dispersions.

Dispersion phase particle size range: 1 nm to 0.5 µm

System features:

Invisible in the ordinary microscope, but may be visible for ultramicroscopy and electron microscopy.
The dispersed phase can pass through filter paper but not through a semipermeable membrane.
Undergo very slow diffusion.
Subtypes:

Sol: Solid particles dispersed in a liquid medium (eg ink).
Gel: A liquid dispersed in a solid medium (eg jelly).
Emulsion: Drops of liquid dispersed in another liquid (e.g.
Example: Milk is an emulsion where fat globules are dispersed in water.

3. Coarse dispersions:

Description: Coarse dispersions consist of larger particles, typically ranging from 0.5 micrometers (μm) to 1000 micrometers (μm) or even larger.

Dispersion phase particle size range: Greater than 0.5 µm

System features:

Visible in an ordinary microscope.
The dispersed phase does not pass through the filter paper or the semipermeable membrane.
No diffusion was observed.
Subtypes:

Suspension: Solid particles dispersed in a liquid medium (eg orange juice with pulp).
Aerosol: Liquid or solid particles dispersed in a gaseous medium (eg mist or smoke).
Example: Paint is a suspension where pigment particles are dispersed in a liquid medium.

Conclusion:

The classification of disperse systems based on the particle size of the dispersed phase provides a structured framework for understanding their diverse characteristics and behaviors. From molecular dispersions to colloidal dispersions and coarse dispersions, each category encompasses a wide range of applications across various fields, including pharmaceuticals, food science, and materials engineering. By delving into the nuances of disperse systems, scientists and engineers continue to unravel their potential for innovation and advancement in countless domains.