Effect of Hydrophobic Modification of a Nonionic Cellulose Derivative on the Interaction with Surfactants. Rheology

Abstract

The interactions between various surfactants (anionic, cationic, and nonionic) and a nonionic ethyl(hydroxyethyl)cellulose (EHEC) polymer or a hydrophobically modified analogue (HM-EHEC) have been examined. The study has been performed as a comparative investigation between the hydrophobically modified polymer and the unmodified parent polymer using rheology. The rheological results have been analyzed with the aid of a simple modified Maxwell model. Information about the low-frequency behavior was extracted from this model, and the rheological features were presented in terms of the complex viscosity and a characteristic relaxation time. In the presence of an ionic surfactant, the rhelogical measurements revealed significant polymer/surfactant interaction for both EHEC and HM-EHEC, but the interaction peak, observed in the different rheological quantities, was more pronounced and located at a lower surfactant concentration for the hydrophobically modified polymer. In the presence of a nonionic surfactant, the polymer/surfactant interaction was weaker. By considering the temperature effect, an important difference in the polymer dynamics between the hydrophobically modified polymer and the unmodified analogue was established. The hydrophobically modified polymer shows a normal temperature dependency, while the motion of the unmodified analogue is slowed down with increasing temperature. The finding for the unmodified polymer is attributed to increased polymer/polymer attractions with an increased temperature. It has also been shown that the hydrophobically modified polymer has features regarding the formation and breakdown of the polymer/surfactant complex in common with other hydrophobically modified polymers (both nonionic and ionic). At a certain surfactant concentration the network starts to lose its connectivity, however, because of an increased surfactant aggregation number of the mixed micelles, the breakdown process is postponed when the surfactant chain length is increased.

Nonionic Cellulose Ethers as Potential Drug Delivery Systems for Periodontal Anesthesia

“…Moreover, it has been found that as the chain length of the surfactant increases, there is a widening of the viscosity maximum as a result of an increase in the number of binding sites (41). This phenomenon can be seen in Fig.…”

Role of the Preparation Procedure in the Formation of Spherical and Monodisperse Surfactant/Polyelectrolyte Complexes

“…pharmaceutical, biomedical application, detergency, enhanced oil recovery, paints, and food and mineral processing). [1][2][3] However, most of the studies focused on the structure of the aggregates made of surfactants and neutral polymers [4][5][6][7][8][9][10] or charged surfactants and oppositely charged polyelectrolytes in dilute solution, that is, systems in which phase separation does not occur. [11][12][13][14][15] The general picture about the interaction between surfactant and polyelectrolyte emerging from these studies is that the surfactant molecules adsorb on polyelectrolyte chains as micellar or micelle-like clusters.…”

Rheological properties of hydrophobically modified polyelectrolyte systems: Concentration effects

“…[7][8][9][10][11][12][13][14] The complexity in the rheological properties of the associative polymer with hydrophobes attached as pendant side groups compared to the end-capped hydrophobic system is related to the steric hindrance of the polymer backbone that prevents the formation of hydrophobic junctions, yielding hydrophobic clusters with a polydispersed associative junctions. 3,9,11,[15][16][17][18] On the other hand, the combed-type polymer possesses a better viscosity enhancement characteristic than the end-capped system. 15,19 This is because the combed system is more efficient in creating bridges between micelles, yielding higher intermolecular associative junctions compared to HEUR system.…”

“…This is due to the low molecular weight (as compared to HEUR system) of the polymer where chain entanglements are negligible at low to moderate concentrations. Several models such as the exponential stretch and multiple modes Maxwell model 15,16,22 were used to describe the behavior of such combed polymer system. However, they are unable to provide the qualitative and quantitative description of polymer system.…”