title: Neutron reflectivity and external reflection FTIR studies of DL-aspartic acid crystallization beneath nylon 6 spread films.
abstract: The crystallization of DL-aspartic acid beneath nylon 6 spread films has been studied for 150% supersaturated systems using neutron reflectivity and external reflection FTIR. The neutron reflectivity data showed the gradual incorporation of DL-aspartic acid within a nylon 6 spread film layer over a period of 6-8 h, culminating in over 50 vol % of the "film" layer comprising DL-aspartic acid. Accumulation of further DL-aspartic acid material to produce microscopic/macroscopic surface crystals occurred, but on a more limited scale, resulting in approximately 1-5% surface coverage of crystals over the same period. External reflection FTIR studies revealed very weak bands attributable to DL-aspartic acid in surface regions devoid of visible crystals, in agreement with the neutron reflectivity studies. In regions with visible crystals, much larger and sharper DL-aspartic acid bands were seen. Changes in the intensity of the nylon 6 NH stretch band were often observed during the visible crystallization and dissolution of DL-aspartic acid and were consistent with the reversible accumulation of nylon 6 around the growing crystals.
authors.affiliation: Department of Chemistry, University of Durham, UK.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Jamieson
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Cooper
authors.forename: Aline F
authors.initials: AF
authors.lastname: Miller
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Holt
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry*; D002209:Caprolactam / Q000031:analogs & derivatives* / Q000737:chemistry; D003460:Crystallization; D009502:Neutrons; D011108:Polymers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D011108:Polymers; C009916:nylon 6; D001224:Aspartic Acid; D002209:Caprolactam