High Pressure-Solid State Polyamidation of Nylon mm Salt Crystals with Even-Even Carbon Number

摘要

Crystal structures of nylons used to be determined mainly by using drawn fibers. But the molecular chain packing in darwn fibers is not so regular due to inclusion of the undistinguished packing of asymmetrical molecular chains and so on. In addition, small crystallite size along the chain axis in nylon single crystals with regular chain folding also complicates crystal structure analysis. Therefore, thermally induced Solid Stale Polyamidation(SSP), utilizing the molecular arrangement of nylon monomer crystals, is considered effective in preparing large nylon single crystals. SSP as crystallization method was first applied to 6-amino-n-caproic acid(6ACA). 11 -amino-n-undecanoic acid( 11AUA) and nylon salt crystals from diamines-dicarboxylic acids. Though nylon 6 and 11 single crystals by SSP were observed under electron microscope, resulting nylons are macroscopically composed of randomly oriented crystallites. Then, Solid State Polyamidation of 12-amino-n-dodecanoic acid(12ADA) and 11AUA under High Pressure(HP-SSP) was conducted, for HP-SSP is sure to provide a topotactic reaction field as compared with SSP. However. HP-SSP is unable to remove the evolved H_2O from reaction field under high pressure. In addition, raising the polymerization pressure is unfavorable for polycondensation, as represented by (δIn K/δP ) = -ΔV/RT. Despite these disadvantages, well oriented Nylon 11 and 12 were easily obtained, and the mechanism of polymerization was suggested that the one-dimensional chain growth in a monocrystallitc forms longer chain crystals. This paper investigates the effects of the number of carbon atoms(m) in a monomer, polymerization temperature and pressure on HP-SSP of aliphatic nylon salts with the even carbon number (m). and discusses the mechanism of HP-SSP.