Electrospinning is a versatile technique that can utilize a wide range of materials to produce nanofibers. Polymers, both synthetic and natural, are the most common materials used in this process.
Polymers:
Synthetic polymers such as polycaprolactone (PCL), poly(lactic acid) (PLA), polystyrene (PS), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and polyvinylpyrrolidone (PVP) are frequently employed due to their tunable properties and ease of processing. Natural polymers, including cellulose, chitosan, gelatin, and silk fibroin, offer biocompatibility and biodegradability, making them suitable for biomedical applications.
Synthetic Polymers:
- Polycaprolactone (PCL): A biodegradable and biocompatible polymer with excellent mechanical properties. It's often used in tissue engineering and drug delivery applications.
- Poly(lactic acid) (PLA): A biodegradable and biocompatible polymer derived from renewable resources. It's widely used in biomedical applications, such as tissue engineering and drug delivery.
- Polystyrene (PS): A versatile polymer with good mechanical properties and thermal stability. It's used in various applications, including filtration and sensors.
- Polyvinyl alcohol (PVA): A water-soluble polymer with good film-forming properties and biocompatibility. It's used in various applications, including wound dressings and drug delivery.
- Polyacrylonitrile (PAN): A high-strength polymer with excellent thermal stability. It's used in various applications, including filtration and protective clothing.
- Polyvinylpyrrolidone (PVP): A water-soluble polymer with good film-forming properties and biocompatibility. It's used in various applications, including drug delivery and tissue engineering.
Natural Polymers:
- Cellulose: A natural polymer with excellent mechanical properties and biocompatibility. It's used in various applications, including filtration and tissue engineering.
- Chitosan: A natural polymer with antimicrobial and wound-healing properties. It's used in various applications, including wound dressings and drug delivery.
- Gelatin: A natural polymer with good biocompatibility and film-forming properties. It's used in various applications, including tissue engineering and drug delivery.
- Silk Fibroin: A natural polymer with excellent mechanical properties and biocompatibility. It's used in various applications, including tissue engineering and wound healing.
In addition to polymers, inorganic materials like silica, titania, alumina, and zirconia can also be electrospun. These materials often possess unique properties, such as high strength and thermal stability, which can be exploited in various applications. Composite materials, combining polymers and inorganic materials, further expand the possibilities of electrospinning.
The choice of solvent is equally crucial in the electrospinning process. The solvent's volatility, viscosity, and polarity significantly influence the fiber morphology and diameter. Common solvents used in electrospinning include chloroform, dichloromethane, dimethylformamide (DMF), and acetic acid. The selection of the solvent depends on the solubility of the polymer, the desired fiber properties, and environmental considerations. By carefully selecting the polymer and solvent, researchers can tailor the properties of the resulting nanofibers to meet specific requirements.
Other solvents used include:
- Alcohols: Ethanol, methanol, and isopropanol are often used for water-soluble polymers and to achieve specific fiber morphologies.
- Ketones: Acetone and methyl ethyl ketone (MEK) are versatile solvents for a range of polymers, particularly those with moderate polarity.
- Ethers: Tetrahydrofuran (THF) is a common solvent for many polymers, especially those with moderate to high polarity.
- Esters: Ethyl acetate is a relatively green solvent used for some polymers, such as poly(methyl methacrylate) (PMMA).
- Ionic Liquids: These are molten salts that can dissolve a wide range of polymers, offering unique opportunities for electrospinning.