Hydrophobic cotton fabric surfaces modified with 2, 2, 2-Trifluoroethyl Methacrylate (TFEM) by admicellar polymerization
Sourav Mondal1, Sukanta pal1, Jayanta Maity1*
1*Department of Chemistry, Sidho-Kanho-Birsha University, Purulia, West Bengal, India, 723104 ([email protected])
Abstract: We report a simple procedure to prepare hydrophobic cotton textiles by admicellar polymerization. The hydrophobic cotton surface is facilely fabricated by an easy novel method through adsorption of fluorosurfactant on the cotton surface and then polymerization of low-surface-energy fluoromonomer in presence of an initiator under an ambient temperature with short time. By in situ introducing fluoropolymer on cotton fibers to generate a dual-size surface roughness, followed by hydrophobization with Trifluoroethyl Methacrylate (TFEM), normally hydrophilic cotton has been easily turned hydrophobic, which exhibits static water contact angle of 1320 average for a 10 µL droplet and also water droplet can roll off the cotton surface easily. The rough micro/nano-textured surface morphology, after surface fluorination, results in simultaneous hydrophobicity and superoleophilicity. The hydrophobic character was confirmed by simple drop test and contact angle measurement. Surface composition was evaluated by SEM, FT IR, and EDS analysis to confirm the fluoropolymeric layer on the cotton surface.
Keywords: Fluoropolymer; Contact angle; Admicellar Polymerization.
Inspired from the lotus phenomenon 1 construction of such special superhydrophobic (water contact angle is greater than 1500) surfaces are increasingly attractive in various potential application fields both in academic research and practical application such as self-cleaning, anti-contamination and anti-sticking. Superhydrophobicity is an extraordinary wettability with high water contact angle and low sliding angle. Neinhuis et al have elaborated that water drops rolling off on the lotus leave surfaces is due to the presence of a combination of rough micro-nanostructure and low surface energy waxy materials on their surfaces. Based on the principle, scientists and researchers have endeavored various methods to fabricate such special hydrophobic and superhydrophobic surfaces by constructing hierarchical micro/nanostructures with low surface energy materials 2. Cotton, a soft fluffy fiber has low production cost, low density, and good strength in both wet and in dry condition and other unique properties such as comfortability; breathability makes them even more attractive for future applications. It is extremely used raw material to make garments for many years. Cotton is composed of almost pure cellulose which contains hydroxyl groups. In spite of the many advantages of cotton, the hydroxyl groups make them tremendous water loving adsorbent i.e. hydrophilic. The excessive water absorbability allows the cotton textile to be easily stained and dirtied. Sometimes the cotton textiles are also wetted and contaminated by blood, oily appearance and even bacteria which are undesired in their use as cloths particularly in hospitality. Thus in recent years, nonwettable cotton textile with high water contact angle value and dirt resistant cotton textile has long been an interesting subject in research. Modifying textile with hydrophobic chemicals to make surface hydrophobicity is a well-established technology developed in early 1940 (Roach et al. 2008). For example, a patent published by Gao and McCarthy et al (2006) on the basis of hydrophobization with silane 3. They were successfully fabricated artificial lotus leaf-like polyester fabric. Two factors (1) surface chemical composition and (2) surface structure (roughness) promotes the special nonwettable effects on fabrics. A variety of approaches are reported to enhance the surface roughness such as introduction of nanotechnology through electrospinning 4, plasma treatment 5,6 and sol-gel technology 7-9, chemical vapor deposition 10. Silicone compound is also reported to coat on fabric surfaces for many years. Beside nanotechnology, polymer technology 11,12 plays also an important role to create a surface thin film with high hydrophobic character. Among known chemical methods,?uorine is the best element to be used to lower the surface free energy and make fabric hydrophobic 13. Fluorine has a small radius and a high electronegativity, thus the covalent bond between ?uorine and carbon is extremely stable. When ?uorine is replaced by other H and C, the surface free energy is increased in the order –CF3