Document Detail

Structural changes in a polyelectrolyte multilayer assembly investigated by reflection absorption infrared spectroscopy and sum frequency generation spectroscopy.
MedLine Citation:
PMID:  19152319     Owner:  NLM     Status:  MEDLINE    
The structure of polyelectrolyte multilayer films adsorbed onto either a per-protonated or per-deuterated 11-mercaptoundecanoic acid (h-MUA/d-MUA) self assembled monolayer (SAM) on gold was investigated in air using two surface vibrational spectroscopy techniques, namely, reflection absorption infrared spectroscopy (RAIRS) and sum frequency generation (SFG) spectroscopy. Determination of film masses and dissipation values were made using a quartz crystal microbalance with dissipation monitoring (QCM-D). The films, containing alternating layers of the polyanion poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) and the polycation poly(ethylenimine) (PEI) built on the MUA SAM, were formed using the layer-by-layer electrostatic self-assembly method. The SFG spectrum of the SAM itself comprised strong methylene resonances, indicating the presence of gauche defects in the alkyl chains of the acid. The RAIRS spectrum of the SAM also contained strong methylene bands, indicating a degree of orientation of the methylene groups parallel to the surface normal. Changes in the SFG and RAIRS spectra when a PEI layer was adsorbed on the MUA monolayer showed that the expected electrostatic interaction between the polymer and the SAM, probably involving interpenetration of the PEI into the MUA monolayer, caused a straightening of the alkyl chains of the MUA and, consequently, a decrease in the number of gauche defects. When a layer of PAZO was subsequently deposited on the MUA/PEI film, further spectral changes occurred that can be explained by the formation of a complex PEI/PAZO interpenetrated layer. A per-deuterated MUA SAM was used to determine the relative contributions from the adsorbed polyelectrolytes and the MUA monolayer to the RAIRS and SFG spectra. Spectroscopic and adsorbed mass measurements combined showed that as further bilayers were constructed the interpenetration of PAZO into preadsorbed PEI layers was repeated, up to the formation of at least five PEI/PAZO bilayers.
Peter J N Kett; Michael T L Casford; Amanda Y Yang; Thomas J Lane; Malkiat S Johal; Paul B Davies
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  113     ISSN:  1520-6106     ISO Abbreviation:  J Phys Chem B     Publication Date:  2009 Feb 
Date Detail:
Created Date:  2009-02-05     Completed Date:  2009-04-06     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1559-68     Citation Subset:  IM    
Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom.
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MeSH Terms
Electrolytes / chemistry*
Fatty Acids / chemistry*
Gold / chemistry
Membranes, Artificial*
Molecular Structure
Polyethyleneimine / chemistry*
Polystyrenes / chemistry*
Spectrum Analysis / methods*
Sulfhydryl Compounds / chemistry*
Surface Properties
Reg. No./Substance:
0/11-mercaptoundecanoic acid; 0/Electrolytes; 0/Fatty Acids; 0/Membranes, Artificial; 0/Polystyrenes; 0/Sulfhydryl Compounds; 0/poly(1-(4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido)-1,2-ethanediyl, sodium salt); 7440-57-5/Gold; 9002-98-6/Polyethyleneimine

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