[en] A direct probe of the single chain conformation in associating low polarity model telechelic ionomer solutions has been obtained using small-angle neutron scattering. A contrast matching technique was employed utilizing a solution of hydrogenated and deuterated ionomer chains in a mixture of labeled and unlabeled solvent molecules. The scattering data at all concentrations and ionic levels examined show an excellent fit to the wormlike chain model. Single chain scattering patterns were obtained for two sodium-neutralized carboxy−telechelic polystyrene ionomers that differ by a factor of 2 in their molecular weight, in a concentration range from the dilute to the concentrated solution regime. The single chain dimensions were found to be influenced by both the ionic interactions and the extent of association. Both ionomer systems showed a contraction of the chain dimensions in the dilute solution regime which is more pronounced for the lower molecular weight telechelic ionomer. As concentration increases, the single chain dimensions increase until they reach a plateau value in the concentrated solution regime. This plateau value is very close to the chain dimensions of the ionomer in the bulk, as was found from a previous SANS study on similar ionomer systems. This plateau value chain dimension is also the same as the unperturbed dimension of the nonionic parent polymer in the bulk. The effect of concentration on the ionomer chain dimensions is attributed to the influence of ionic interactions as the nonionic form of the material shows larger chain dimensions in the concentration regime studied. These results indicate that intramolecular interactions with the formation of self loops prevail in the dilute solution regime. Intermolecular interactions with ionic groups connecting to different chains prevail in the concentrated solution regime, as evidenced by an extension of the chain dimensions.
Research center :
Center for Education and Research on Macromolecules (CERM)
Disciplines :
Materials science & engineering Chemistry
Author, co-author :
Karayianni, Eleni; University of Wisconsin-Madison, USA > Department of Chemical Engineering
Jérôme, Robert ; Université de Liège - ULiège > Department of Chemistry > Center for Education and Research on Macromolecules (CERM)
Cooper, Stuart L; University of Wisconsin-Madison, USA > Department of Chemical Engineering
Language :
English
Title :
Small-angle neutron scattering studies of low polarity telechelic ionomer solutions. 2. Single chain scattering
Publication date :
01 December 1997
Journal title :
Macromolecules
ISSN :
0024-9297
eISSN :
1520-5835
Publisher :
Amer Chemical Soc, Washington, United States - Washington
BELSPO - SPP Politique scientifique - Service Public Fédéral de Programmation Politique scientifique The Department of Energy through Grant DE-FG02-88ER45370
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