Interfacial Properties of Methylcelluloses: The Influence of Molar Mass

Abstract

Abstract:The interfacial interactions of four methylcelluloses having the same average degree of substitution and distribution of methyl groups, but different molar masses, are studied at ambient temperature and at very low polymer concentrations. Firstly, the surface tension σ at the water/air interface is determined for the progressive addition of methylcellulose up to 100 mg/L; σ starts to decrease over 1 mg/L up to the critical aggregation concentration (CAC) at 10 mg/L. The curves describing the influence of polymer concentration on σ are independent of the molar mass at equilibrium. Secondly, the adsorption of methylcellulose on silica particles is estimated from ζ-potential measurements. The data are interpreted in terms of an increase of the adsorbed layer thickness at the interface when the molar mass of methylcellulose increases. It is concluded that methylcellulose is adsorbed, forming trains and loops at the interface based on the equilibrium between surface free energy and solvent quality.

Methylcellulose, a Cellulose Derivative with Original Physical Properties and Extended Applications

“…Recent data obtained on methylcelluloses with different molecular weights are given in Figure 11 [24]. It demonstrates clearly that the MW has no influence on the surface activity of MC at equilibrium; the same conclusion was given on hydroxypropylmethylcelluloses by Gaonkar [75] but a slight impact was noticed for hydroxypropylmethylcelluloses by Sarkar [49].…”

“…The dependence of viscosity as a function of temperature was given at well-defined shear rates as shown in Figure 6 [24]. The behavior is Newtonian at temperatures lower than 30 °C (a critical temperature) and then becomes non-Newtonian when the shear rate increases.…”

“…The surface activity of methylcellulose (MC) has been recently studied as well as the influence of the MC molecular weight on the air/water interface properties [24]. The experiments were performed with methylcellulose having a similar microstructure but different molecular weights allowing the influence of the molecular weight on the interfacial properties to be established.…”

“…Influence of the molecular weight on the tension-active properties (σ in mN/m) of MC with different molecular weights as a function of polymer concentration at 20 °C. The lines are added to guide the eye [24]. Over 1 mg/L up to around 10 mg/L, the surface tension is decreased in relation to the progressive packing of amphiphilic molecules at the interface and to the orientation of highly hydrophobic blocks.…”

“…This review covers particularly the influence of the MW of methylcelluloses on their most original physical properties using MC with the same degree of substitution as described in our recent works [20,24].…”