Effects of Chain Length on the Thermotropic and LYotroPic Phase Behaviours of Maltosides by Small-angle X-ray Diffraction Study Hairul A,A. Hamid, Rauzah llashim, John M. Seddon and Nicholas J. Brooks Abstract Indusfiially useful surfactants such as alkyl polyglucosides (APGs) and synthetic branched-chain glycosides are interesting biosurfactants and offer an interesting insight into life-science applications. Hence, research presented here a study of rhe thermoropic and lyotropic phase of 2-hexyldecyl B-D-maltoside (P-Mal-CroCJ and the corresponding 2-decyltetradecyl f-D-maltoside @-iv{al- Cr+Cro) over a range of temperatures (O-80 'C). Small-angle X-ray diftaction (SAXS) and optical polarizing microscopy (OPM) have been used to characterize the mesophase behaviour. This study has shown that in dry conditions p-Mal-C16C6 and p-Mal-C1aC16 adopt a lamellar crystalline phase (L"), on the other hand, in excess water these compounds form a fluid lamellar phase (L") upon heating and cooling. The study also reported the effects of temperature (0-80 'C) on the d- spacing value usilg SAXS, and we estimated the surface alea per molecule and water content of the fluid lamellar phase (LJ in the fully hydrated state for both B-Mal-C10C6 and/-Mal-C1aC1s. The former gave the surface area per molecule and *u*r "onl* of SZ A'*a ZS wt 7o respectively, however, the latter forms 69 A2 and 2O wt Vo. Keywords Therrnotopic phase ' Lyotropic phase ' Lamellar phase H.A.A. Hamid (X) School of Chemistry and Environment, Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Malaysia e-mail: h.amani@ salam.uitrn.edu.my H.A.A. Hamid.R. Hashim Deparffnent of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia e-mail: rauzah @ um.edu.my J.M. Seddon . N.J. Brooks Departrnent of Chemistry, Imperial College London, London SW7 2AZ, UK e-mail: j.seddon@imperial.ac.uk N.J, Brooks e-mail: nicholas.brooks@imperial.ac.uk @ Spnnger Science+Business Media Singapore 2015 M.A. Hashim (d.), ICGS C E 20 t 4, DOI 1 0. 1 007D78-98 I -287 -505 -1 -42 315 h.amani @ salarx.ult*l.edu. nrY