Document Detail


The Structure of Hydrated Poly (D, L - Lactic Acid) Studied With X-Ray Diffraction and Molecular Simulation Methods.
MedLine Citation:
PMID:  22707795     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The effect of hydration on the molecular structure of amorphous poly (D, L-lactic acid) (PDLLA) with 50:50 L-to-D ratio has been studied by combining experiments with molecular simulations. X-ray diffraction measurements revealed significant changes upon hydration in the structure functions of the copolymer. Large changes in the structure functions at ~ 10 days of incubation coincided with the large increase in the water uptake from ~1 to ~40% and the formation of voids in the film. Computer modeling based on the recently developed TIGER2/TIGER3 mixed sampling scheme was used to interpret these changes by efficiently equilibrating both dry and hydrated models of PDLLA. Realistic models of bulk amorphous PDLLA structure were generated as demonstrated by close agreement between the calculated and the experimental structure functions. These molecular simulations were used to identify the interactions between water and the polymer at the atomic level including the change of positional order between atoms in the polymer due to hydration. Changes in the partial O-O structure functions, about 95% of which were due to water-polymer interactions, were apparent in the radial distribution functions. These changes, and somewhat smaller changes in the C-C and C-O partial structure functions, clearly demonstrated the ability of the model to capture the hydrogen bonding interactions between water and the polymer, with the probability of water forming hydrogen bonds with the carbonyl oxygen of the ester group being about four times higher than with its ether oxygen.
Authors:
Xianfeng Li; N Sanjeeva Murthy; Robert A Latour
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-5-22
Journal Detail:
Title:  Macromolecules     Volume:  45     ISSN:  0024-9297     ISO Abbreviation:  -     Publication Date:  2012 Jun 
Date Detail:
Created Date:  2012-6-18     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0365316     Medline TA:  Macromolecules     Country:  -    
Other Details:
Languages:  ENG     Pagination:  4896-4906     Citation Subset:  -    
Affiliation:
Department of Bioengineering, Clemson University, Clemson, South Carolina 29634, United States.
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