How does a non-ionic hydrophobically modified telechelic polymer interact with a non-ionic vesicle? Rheological aspects

Abstract

The association between hydrophobically modified polyethylene glycol, HM-PEG, and non-ionic vesicles of tetraethylene glycol monododecyl ether, C 12 E 4 , was investigated. HM-PEG is in a triblock form, with an alkyl chain attached to each hydrophilic polymer-end. Such polymer structure is denoted as telechelic. The vesicle average radius was measured by self-diffusion measurements. The system exhibits both a monophasic gel and biphasic regions. The monophasic region was characterized from a rheological point of view. We argue that the gel formation is due to the presence of polymer crosslinks between different surfactant aggregates, once the polymer's hydrophobic moieties may adsorb into the vesicle bilayer. This association is strongly concentration dependent which is reflected in the monotonic increase of the storage modulus, relaxation time and shear viscosity with the addition of surfactant and/or polymer.

Rheological study of hydrophobically modified hydroxyethyl cellulose and phospholipid vesicles

“…5, the zero-shear viscosity for the HMHEC-lipid mixture does not become lower than for the pure HMHEC solution. Previous studies for mixtures of telechelic HMPs and surfactant vesicles reported increasing viscosity and elastic properties with increasing surfactant concentration [23,24]. It is not known whether the solution viscosity will decrease when the surfactant concentration becomes high enough.…”

“…Formation of a gel network with a large elastic modulus independent of frequency was reported for hydrophobically modified chitosan in catanionic vesicles [21]. For telechelic HMP, Medronho et al examined hydrophobically modified polyethylene glycol (HMPEG) with catanionic vesicles [23], while Santos et al studied HMPEG with C 12 E 4 vesicles [24]. Both studies observed phase separation and enhanced viscoelasticity due to the bridging mechanism originating from hydrophobic attraction.…”

“…Several studies have applied rheometry to investigate the interaction of HMP with surfactant vesicles [18][19][20][21][22][23][24]. For comblike HMP, Sarrazin-Cartalas et al investigated hydrophobically modified poly(sodium arcylate) (HMPA) and oligoethylene glycol monododecyl ether surfactants (C 12 E 4 , C 12 E 5 and C 12 E 8 ) [22].…”

Gels Obtained by Colloidal Self-Assembly of Amphiphilic Molecules

“…There is less work done on the fundamental properties on vesicles compared to microemulsions with added HM polymers. Such hydrophobically modified polymers can interact with vesicles and interconnect them within vesicle solutions [144,145,146,147,148] (Figure 11A). However, the vesicle/polymer systems are more complicated because, unlike in the case of microemulsions and micelles, the structure of the vesicles do not necessarily remain intact upon the addition of hydrophobically modified polymers.…”

“…In any case, the addition of hydrophobically modified linear polymers to vesicle solutions leads to the formation of networks. These networks have higher elasticity with higher polymer concentration [144,145,146]. Here again, it is necessary that the hydrophilic part of the polymer is longer than the distance between vesicle membranes to form bridges.…”