This website uses cookies to give you the best user experience. If you continue
without changing your settings we'll assume you are happy to receive all RSC cookies.
You can change your cookie settings by navigating to our Privacy and Cookies page and following the instructions. These instructions
are also obtainable from the privacy link at the bottom of any RSC page.
Dipartimento di Chimica, Dipartimento di Fisica and Research center SOFT-INFM-CNR, Sapienza Università di Roma, P.le A. Moro 5, Roma, Italy
E-mail: l.galantini@caspur.it
; Fax: (+39) 06 490631
b
Departamento de Química Física, Facultad de Ciencias, Universidad de Santiago de Compostela, Avda. Alfonso X El Sabio s/n, Lugo, Spain
c
Escuela de Quimica, Universidad de Costa Rica, San Josè, Costa Rica
Soft Matter, 2009,5, 3018-3025
DOI:
10.1039/B905531B
Received
19 Mar 2009,
Accepted
11 May 2009
First published online
19 Jun 2009
We report a kinetic study of the supramolecular tubule formation of the bile salt derivative [3β,5β,7α,12α]-3-(4-t-butylbenzoilamine)-7,12-dihydroxycholan-24-oic acid sodium salt (Na-tbutPhC). At high bicarbonatebuffer concentration (pH10) this salt shows gelator properties. Starting from gels or viscous solutions, the tubule formation is triggered by increasing the temperature beyond the critical value of 34–36 °C. For gels, when the process takes place, the transition to sols occurs. The process is easily triggered and can be followed by several techniques. We used static light scattering (SLS), circular dichroism (CD), small angle X-ray scattering (SAXS) along with transmission electron (TEM) and optical microscopies. The CD results show that fibrils with a clockwise arrangement of the bile salt derivative are present in the samples at room temperature. When the tubule formation starts, evolutions of the CD and SLS profiles are observed indicating that the formation process begins with the aggregation of the fibrils accompanied by a simultaneous peculiar reciprocal reorientation of the surfactant molecules. After that, as pointed out by the long time evolution of the curves, a slow transformation towards the final well defined tubules occurs, involving an adjustment of the molecular packing. In the meanwhile, the slow ordering of the tubule walls in well spaced layers takes place, as inferred by SAXS. The TEM images show that short disordered tubules are formed, because of the aggregation of fibrils, in the beginning. Moreover they highlight a final elongation of the tubules taking place without a further aggregation of fibrils. Optical microscopy frames, collected during the process, point out that the tubules grow singly even at quite a high concentration, thus supporting the data interpretation.
Fetching data from CrossRef. This may take some time to load.