Laser Induced Natural Fiber Welding of Cellulosic Substrates

Abstract

As excellent solvents for cellulose and silk, certain ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium acetate (EMIAc),1,2 can be used for biopolymer modification and manipulation. Full dissolution and regeneration using IL solvents often results in biomaterials with inferior properties compared to the native material. When natural substrates are only partially dissolved and regenerated through a process we call Natural Fiber Welding (NFW), much of the native biomaterial structure can be maintained while still allowing for significant material modification. NFW enables the structural modification of the surface and incorporation of functional materials through the binding capability of the portion of dissolved biopolymer3-5. In the present work we have employed a laser as the heat source to initiate partial dissolution of a cellulose substrate causing NFW in a spatially-specific manner. By using a non-solvent for cellulose (e.g., water) with the ionic liquid as a means of inhibiting the dissolution process, heat becomes the controlling factor necessary to obtain significant biopolymer dissolution and mobilization. A CO2 laser was used to raster a specific pattern onto a cellulosic paper substrate coated with IL solution. Raster power, concentration of the ionic liquid and the number of laser passes affect the amount of heat absorbed into the biopolymer and the level of NFW. Through tensile testing, confocal microscopy, ATR-IR, and SEM imaging, the resulting modification of the biopolymers was characterized. References Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am Chem Soc, 2002, 124, 4974.Phillips, D. M.; Drummy, L. F.; Conrady, D. G.; Fox, D. M.; Naik, R. R.; Stone, M. O.; Trulove, P. C.; De Long, H. C.; Mantz, R. A. J Am Chem Soc., 2004, 126, 14350.Haverhals, L. M.; Reichert, W. M.; De Long, H. C.; Trulove, P. C. Cellulose, 2010, 2985, 425.Haverhals, L. M.; Sulpizio, H. M.; Fayos, Z. A.; Trulove, M. A.; Reichert, W. M.; Foley, M. P.; De Long, H. C.; Trulove, P. C.Cellulose, 2012, 19, 13.Haverhals, L. M.; Nevin, L. M.; Foley, M. P.; Brown, E. K.; De Long, H. C.; Trulove, P. C. Chem.Commun., 2012, 48, 6417.