PH induced tuning of size, charge and viscoelastic behavior of aqueous micellar solution of Pluronic ® P104–anthranilic acid mixtures: A scattering, rheology and NMR study

Abstract

• SANS and rheology data for AA loaded P104 micelles at different pH are reported. • Uniaxial growth was seen with [AA] which suppressed in strongly acidic and alkaline pH. • The pH dependent growth in the presence of AA is accounted for charged micelles. • NOESY showed the location of AA in micelles at core–shell interface. A moderately hydrophilic ethylene oxide–propylene oxide triblock copolymer (EO 27 –PO 63 –EO 27 ) Pluronic ® P104 hereafter referred to as P104 forms spherical core–shell micelles in water. The pH dependence on the influence of anthranilic acid (AA) on P104 micelles was investigated by cloud point (CP), viscosity, dynamic light scattering (DLS), small angle neutron scattering (SANS), nuclear Overhauser enhancement spectroscopy (NOESY) and rheology. SANS results showed the remarkable effects on the structure of micelles and are discussed in terms of micellar growth and transition. NOESY revealed the location of AA close to the core–corona region of the micelle. These micelles develop ionic nature by changes in pH which affects micelle hydration and inter-micellar interaction. This was further supported by changes in viscosity, cloud point and DLS. The storage/loss modulus and other rheological parameters for selected viscoelastic solutions were evaluated and discussed.