Document Detail


Ab Initio Calculation of the Crystalline Structure and IR Spectrum of Polymers: Nylon 6 Polymorphs.
MedLine Citation:
PMID:  22697809     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
State of the art computational methods in solid state chemistry are applied for the prediction of the structural and spectroscopic properties of the α and γ crystalline polymorphs of nylon 6. Density functional theory calculations augmented with an empirical dispersion correction (DFT-D) are used for the optimization of the two different crystal structures and of the isolated chains, characterized by a different regular conformation and described as 1D infinite chains. The structural parameters of both crystalline polymorphs are correctly predicted and a new insight on the interplay of conformational effects, hydrogen bonding and van der Waals interactions in affecting the properties of the crystal structures of polyamides are obtained. The calculated infrared spectra are compared to experimental data; based on computed vibrational eigenvectors, assignment of the infrared absorptions of the two nylon 6 polymorphs is carried out and critically analyzed in the light of previous investigations. On the basis of the comparison between the computed and experimental IR spectra, a set of marker bands is identified and proposed as a tool to detect and quantify the presence of a given polymorph in a real sample: several marker bands adopted in the past are confirmed, while some of the previous assignment are criticized. In addition, some new marker bands are proposed. The results obtained demonstrate that accurate computational techniques are now affordable for polymer characterization, opening the way to several applications of ab initio modelling to the study of many families of polymeric materials.
Authors:
Claudio Quarti; Alberto Milani; Bartolomeo Civalleri; Roberto Orlando; Chiara Castiglioni
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-6-14
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  -     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-6-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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