Microscopic diffusion in cationic vesicles across different phases

Phase Behaviors of Dialkyldimethylammonium Bromide Bilayers

“…Moreover, a plateau value of S CD ≈ 0.4 demonstrates that the bilayer is in the L β phase as reported in the literature − and is much higher demonstrating that the bilayer is in the L α phase ( S CD ≈ 0.2). , In addition, the sharp peak of dihedral angle distributions at 180° (Figure c,d) also implies that most of the alkyl chains stay in trans configuration in the bilayers. That is to say, the DDAB and DPAB bilayers are in the gel phase, which are also consistent with the literature. , Some other experiments also observed that the alkyl chains stay in trans configuration in the gel phase. ,, As the temperature increases to 323 K for the DDAB bilayer and to 348 K for the DPAB bilayer, it is obvious that the peak strength at 180° weakens, which indicates that the surging thermal motion of the molecule leads to a rise of random configurations or gauche defects. The DDAB bilayers with different initial interdigitated degrees (δ int ) are almost identical at 298 K, and the area per surfactant and membrane thickness are also similar to each other (Table S2).…”

“…That is to say, the DDAB and DPAB bilayers are in the gel phase, which are also consistent with the literature. 66,67 Some other experiments also observed that the alkyl chains stay in trans configuration in the gel phase. 20,68,69 As the temperature increases to 323 K for the DDAB bilayer and to 348 K for the DPAB bilayer, it is obvious that the peak strength at 180°weakens, which indicates that the surging thermal motion of the molecule leads to a rise of random configurations or gauche defects.…”

Modulation of Phase Behavior and Microscopic Dynamics in Cationic Vesicles by 1-Decyl-3-methylimidazolium Bromide

“…This type of motion has been characterized by various models, including ballistic flow-like motion, 43 Fickian diffusion, 44 subdiffusion, 58 and localized diffusion. 59 It is found that Fickian diffusion is valid at least for distances greater than the molecular diameter, [5][6][7]11 which is the case for the length scale accessible by the present QENS experiment. Hence, we have used the Fickian diffusion model, and the scattering law for the lateral motion can be written as 41,42…”

“…57 The spatial and temporal windows accessible by the IRIS spectrometer are suitable for both lateral and internal motions of the lipids. 3,5 Generally, the relaxation time scales of these two motions are well separated and hence are considered to be independent of each other. Therefore, the model scattering law of a lipid membrane can be written as the convolution of the scattering laws corresponding to the lateral and internal motions of the lipid molecules, which can be expressed as…”

“…[3][4][5][6]11 These contrasting phase behaviors are mainly driven by the complex interplay between hydrophobic interactions between the alkyl tails and Coulombic repulsion between the charged head groups. 5 Surfactants, being amphiphilic molecules, interact with vesicles and can modulate the biophysical characteristics of these vesicles, which hold promise for their potential application in drug delivery. In this context, there has been considerable interest in the use of surface-active ionic liquids (SAILs) or ionic liquid-based surfactants (ILBSs) as alternatives to traditional surfactants due to their distinct and adjustable physicochemical and biological attributes, including enhanced surface activity.…”