Thermotropic phase behaviour of long-chain alkylmaltosides.
The thermotropic phase behaviour and phase structure of crystalline and non-crystalline n-tetradecyl-beta-D-maltoside (C14G2) and n-hexadecyl-beta-D-maltoside (C16G2) have been investigated by means of differential scanning calorimetry and X-ray techniques. Upon lyophilisation, both compounds form a solid, lamellar phase comprising disordered head groups and hexagonally packed alkyl chains that are suggested to be tilted and interdigitated. This ordered lamellar phase melts into a metastable lamellar liquid crystal, which re-crystallises to a high-temperature crystalline polymorph comprising interdigitated, non-tilted alkyl chains. Remarkably, the high-temperature polymorph of C14G2 has the same melting point as that of C16G2, namely 105 degrees C for both surfactants. A low-temperature polymorph of anhydrous C14G2 crystallises from water at room temperature, whereas the hemihydrate of C14G2 crystallises at 6 degrees C from water, or from chloroform containing trace water. X-ray data suggest both these crystalline modifications to comprise interdigitated and tilted alkyl chains.
Ericsson
Caroline A
CA
Department of Physical Chemistry 1, Centre of Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-221 00, Lund, Sweden.
Ericsson
Louise C
LC
Kocherbitov
Vitaly
V
Söderman
Olle
O
Ulvenlund
Stefan
S
D000473:Alkanes / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D018360:Crystallography, X-Ray; D005960:Glucosides / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature
D000473:Alkanes; D005960:Glucosides; D013501:Surface-Active Agents; C040358:dodecyl maltoside