Silicone surfactants are chemical compounds, acting as active agents to reduce the surface tension between two different kinds of substances. There are different types of silicone surfactants available in the market. Surfactants consist of two distinct components in their molecular structure: a hydrophobic (water-repelling) part and a hydrophilic (water-attracting) part.
The unique combination of these hydrophobic and hydrophilic segments within a single molecule is responsible for lowering surface tension and contributing to the essential properties associated with this group of chemical compounds.
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Types of silicone surfactants
1. Cationic silicone surfactant:
When the R group incorporates structural units like alkyl quaternary ammonium compounds, amido quaternary ammonium compounds, and imidazoline derivative quaternary ammonium compounds, it is known as cationic silicone surfactant. Among cationic surfactants, the cationic polysiloxane quaternary ammonium salt surfactant stands out as the most widely utilized.
This surfactant boasts a substantial molar mass, compatibility with anionic surfactants, non-irritating properties to human skin and eyes, and a notable antibacterial capacity, contributing to effective stabilization. The macromolecules within this product feature hydrophobic long-chain polysiloxane chains, delivering outstanding smoothness and softness.
2. Anionic silicone surfactant:
When the R group includes structural units like phosphate salt, sulfate, carboxylate, sulfonate, and sulfosuccinate ester, it is known as an anionic silicone surfactant. Specifically, when R represents the structure mentioned below, it qualifies as an anionic polysiloxane phosphate surfactant. If R' takes the form of a fatty acid functional group, the surfactant transforms into a polysiloxane phosphate betaine amphoteric surfactant.
This unique molecule combines the structural and property features of both phosphate betaine and polysiloxane. The choice of low molar mass polysilane results in weaker polysiloxane characteristics, whereas opting for a high molar mass polysiloxane enhances the remarkable traits of polysiloxane. These products exhibit low toxicity, antibacterial properties, resistance to hard water, and excellent compatibility with various surfactants.
3. Nonionic silicone surfactant:
When the R group incorporates units like polyether, alkanolamide, ester, glycoside, and similar components, it is known as a non-ionic silicone surfactant. Among them, polyether silicone surfactant stands out as the most widely employed. The nonionic polyether silicone surfactant comprises a polysiloxane segment and a polyether segment. Various combination modes exist, including AB type, ABA type, bab type, (AB) n type, branched-chain type, and side chain type.
The connection between polyether and siloxane segments can occur through Si-O-C type and Si-C type. The former is less stable and falls under the hydrolytic category, while the latter is water-stable and referred to as non-hydrolytic.
4. Amphoteric silicone surfactant:
When the R group encompasses a structure like a phosphate betaine or betaine, it qualifies as an amphoteric silicone surfactant.
Performance of silicone surfactants
Among the different types of silicone surfactants, trisiloxane surfactants not only make oil and water mix better by reducing the tension between them but can also make things spread out well on surfaces that don't like water much, like those with low-energy hydrophobic properties. This special ability is called "super-wettability" or "super-spreadability." Scientists believe this happens because of specific groups of surfactant molecules in the solution.
The reason why polydimethylsiloxane chains (a type of silicone) spread easily on surfaces like water, metals, or fibers is that the oxygen in the silicone can make bonds with polar molecules or groups of atoms. This makes the silicone chain stick better to the surface, and it spreads out into a super thin layer. So, instead of sitting upright like regular surfactants, the hydrophobic silicone lies flat on the surface in a unique "stretched chain" shape.
Methods for synthesis of silicone surfactants
1. Synthesis of cationic silicone surfactants:
The process is performed in an inert solvent such as benzene, acetone, carbon tetrachloride, and xylene.
2. Synthesis of nonionic silicone surfactants:
Based on the copolymerization preparation method, hydrolysis, and considerations of chemical stability, the synthesis process can be categorized into two distinct methods: one involving copolymers interconnected by Si-O-C chains, and the other featuring copolymers linked by Si-C chains. This synthetic journey unfolds in two pivotal steps. Firstly, we embark on the synthesis of polysiloxane. Subsequently, in the second step, we guide the polysiloxane to seamlessly integrate into block copolymers with polyoxoalkane, adopting the structural motif of Si—O—C/Si—C.
Conclusion
In this article, we learned about the classification of silicone surfactants and their composition. Silicone surfactants have numerous applications across a wide range of industries. There are four classifications of silicone surfactants: cationic, anionic, nonionic, and amphoteric. The chemical composition of all these classifications is very different from each other.
Frequently Asked Questions
What is the classification of surfactant?
There are mainly four classifications of surfactant: ionic, cationic, non-ionic, and amphoteric.
What type of surfactant is dimethicone?
Dimethicone is a type of silicone surfactant.
What are the 3 components of surfactant?
The 3 components of surfactant are 0% to 80% phospholipids, approximately 10% protein, and 10% neutral lipids.