Premium
Study of hydrogen bond dynamics in Nylon 6 crystals using IR spectroscopy and molecular dynamics focusing on the differences between α and γ crystal forms
Author(s) -
Brela Mateusz Z.,
Wójcik Marek J.,
Boczar Marek,
Onishi Erika,
Sato Harumi,
Nakajima Takahito,
Ozaki Yukihiro
Publication year - 2018
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25595
Subject(s) - anharmonicity , hydrogen bond , molecular dynamics , chemistry , quantization (signal processing) , infrared spectroscopy , proton , spectroscopy , crystallography , chemical physics , spectral line , ab initio , computational chemistry , molecular physics , physics , molecule , quantum mechanics , organic chemistry , computer science , computer vision
Proton dynamics of hydrogen bonds (HBs) in the α and γ form of Nylon 6 were investigated by Born–Oppenheimer molecular dynamics (BOMD). Our results show differences in the dynamic effects of interchain HB interactions between the α form and the γ form of Nylon 6. Analysis of the time course of the geometrical parameters of HBs along the BOMD simulations has shown that HBs are dynamically favored in the γ form of Nylon. The quantization of the NH stretching mode enables a detailed discussion of the strengths of HB interactions. Solving the Schrödinger equation for the snapshots of one‐dimensional proton potentials, extracted from the ab initio MD, enables the consideration of anharmonicity, thermodynamics, and approximate quantum effects on proton movement. A larger red shift of the NH stretching band was observed in the γ form compared with the α form. Our study shows that HBs are more stabilized in the γ form than in the α form, which is mainly due to the higher number of HBs. The distribution of HBs along the trajectory clearly reveals the preference of the γ form. The quantization of the NH motion enables the discussion of the differences in the IR spectra between the two forms.