ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Nanocapsule dispersions are investigated by 1H–13C cross polarization experiments. The capsule walls, made up from polybutylcyanoacrylate, are detectable merely as a solid state signal, whereas the triglyceride forming the liquid core and the surfactant on the outside of the capsules give rise to narrow resonance lines in the cp-spectrum indicating their mobility. In order to clarify the mechanism of cross polarization for the mobile components, the time-resolved polarization of the corresponding 13C-signals is investigated. Further, the spin-lattice relaxation times for the proton magnetization in the rotating frame are studied under direct excitation as well as under cross polarization conditions. Based on the results, we propose a special mechanism of cross polarization which is initiated by a temporary adsorption of mobile molecules to the more rigid capsule surface. During this short period of immobilization, the polarization is transferred from 1H to 13C nuclei. After desorption, the freshly generated 13C-signal is essentially conserved, now being motionally averaged by a high molecular mobility and detectable as a narrow line in the corresponding spectrum. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.480970
