Polystyrene is a hydrophobic aromatic polymer that can be used to coat nanoparticles for compatibility with selected organic solvents and nonpolar materials. The polymer consists of a hydrocarbon backbone with pendant phenyl groups, creating a hydrophobic particle interface that can also promote passive adsorption of molecules with hydrophobic regions.
nanoComposix has used thiol-terminated polystyrene to form polymer coatings on metal nanoparticles. Polystyrene layers, typically approximately 10–20 nm thick, can provide steric stabilization while enabling larger nanoparticles to be transferred from aqueous formulations into compatible organic solvents and incorporated into hydrophobic composites.
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Polystyrene Surface Properties
- Surface character: Hydrophobic
- Stabilization: Steric stabilization from the polymer coating
- Surface interactions: Promotes passive adsorption of surfactants, proteins, and other molecules containing hydrophobic regions
- Polymer density: Approximately 1.055 g/cm3 at 20°C
- Refractive index: Approximately 1.59 at 590 nm
- Solvent compatibility: Compatible with selected organic solvents; compatibility should be evaluated for the intended formulation
Representative source material: Thiol-terminated poly(styrene) (Polymer Source, Inc., A-6.1.15.1.33.1)
Representative molecular weight: 50 kDa
Why Use a Polystyrene Surface?
The primary advantage of polystyrene is its ability to create a hydrophobic, sterically stabilized nanoparticle surface compatible with selected organic solvents and polymer matrices.
Compared with small hydrophobic ligands such as dodecanethiol, a polystyrene coating can be particularly useful for larger nanoparticles where a thicker polymer layer provides greater steric separation between particles.
The hydrophobic surface can also promote passive adsorption of molecules containing hydrophobic regions, including proteins and surfactants, when that interaction is useful for the intended application.
Applications
- Integration of nanoparticles into hydrophobic polymers and composite materials
- Transfer of nanoparticles into compatible organic solvents
- Coatings and particle-deposition applications
- Passive adsorption of molecules containing hydrophobic regions
- Custom optical and materials-engineering formulations
For optical coatings and composite applications, see Nanomaterials for Optical Engineering.
Polystyrene Solvent Compatibility
Polystyrene-coated nanoparticles can be dispersed in a range of organic solvents, but compatibility depends strongly on the solvent. The examples below summarize solvents historically evaluated or used with these formulations.
| Compatibility | Example Solvents |
|---|---|
| Compatible | Benzene, toluene (methylbenzene), chloroform, dichloromethane (DCM), tetrahydrofuran (THF), dimethylformamide (DMF), ethyl acetate, xylene |
| Not directly compatible | Acetone, hexane, butane, ethanol, ether, methanol, phenol, propanol, water |
Solvent compatibility should be confirmed for the specific nanoparticle formulation because particle size, coating thickness, polymer molecular weight, concentration, and solvent composition can all affect dispersion behavior.
Using Ethanol During Solvent Transfer
Although polystyrene-coated particles can flocculate in polar solvents such as ethanol, ethanol can be used as an intermediate during transfer between compatible solvents when the appropriate procedure is followed.
See the Polystyrene-Coated Gold Solvent Transfer Protocol for detailed instructions.
Polystyrene vs. Other Hydrophobic Surfaces
The appropriate hydrophobic coating depends on particle size, solvent, downstream material, and processing requirements.
- Polystyrene: Provides a relatively thick hydrophobic polymer layer and steric stabilization, making it useful for larger nanoparticles and incorporation into organic materials.
- Dodecanethiol: Provides a smaller hydrophobic ligand layer and has primarily been used with small metal nanoparticles that require dispersion in compatible nonpolar solvents.
See Dodecanethiol Surface Chemistry for more information about the alternative hydrophobic ligand approach.
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Talk with our technical team about polystyrene coatings, solvent transfer, hydrophobic composites, particle size, coating thickness, or other custom surface chemistries.
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