Document Detail


Cooperativity and selectivity in chemomechanical polyethylenimine gels.
MedLine Citation:
PMID:  17824717     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
Gel particles obtained from polyethylenimine (PEI) cross-linked with 10% ethylene glycol diglycidyl ether show considerable selectivity in size changes if exposed to solutions of different effector compounds. Monocarboxylic acids induce contractions of, e.g., -9% for benzoate and -40% for 2-naphthoate (all values in one dimension such as length). With diacids, the contractions increase to -29% for 1,4-benzene and -68% for 2,6-naphthalene disulfonate, indicating the significant contributions of noncovalent ionic cross-linking and of interactions with aromatic residues. A striking cooperativity is observed if aromatic compounds such as naphthoic acid are used simultaneously with amino acids as effectors. The combination with, e.g., 2-naphthoic acid and phenylalanine induces, e.g., 69% contraction, whereas the single effector compounds induce only 40% and 8%, respectively. As expected with contraction of chemomechanical polymers, the kinetics of effector absorption is significantly slower than that of the size changes, which take, e.g., 5 min to reach one-half of the final contraction; with smaller gel particles, the rates are significantly increased. Gravimetric determinations show that release of solvation water is largely responsible for the observed volume contractions. Copper or zinc ions induce small contractions, also in experiments with PEI solutions, but show no evidence of cooperativity in combination with amino acids or peptides. MAS NMR spectra of the gels induced by aromatic effector compounds exhibited moderate upfield shifts of the polymer backbone signals, as a result of ring current effects.
Authors:
Kazuaki Kato; Hans-Jörg Schneider
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Publication Detail:
Type:  Journal Article     Date:  2007-09-08
Journal Detail:
Title:  Langmuir : the ACS journal of surfaces and colloids     Volume:  23     ISSN:  0743-7463     ISO Abbreviation:  Langmuir     Publication Date:  2007 Oct 
Date Detail:
Created Date:  2007-10-02     Completed Date:  2007-11-13     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9882736     Medline TA:  Langmuir     Country:  United States    
Other Details:
Languages:  eng     Pagination:  10741-5     Citation Subset:  -    
Affiliation:
FR Org. Chemie der Universität des Saarlandes, D 66041 Saarbrücken, Germany. kato@molle.k.u-tokyo.ac.jp
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