It is possible that a defined curvature at the membrane interface controls its pH/polarity to exhibit specific bioactivity. By utilizing an interface-interacting spiro-rhodamine pH probe and the Schiff base polarity probe, we have shown that the pH deviation from the bulk phase to the interface (Delta pH)/interfacial dielectric constant (kappa(i)) for amphiphilic self-assemblies can be regulated by the curvature geometry (positive/negative) and its radius. According to H-1 NMR and fluorescence anisotropy investigations, the probes selectively interact with an anionic interfacial Stern layer. The Delta pH/kappa(i) values for the Stern layer are estimated by UV-vis absorption and fluorescence studies. For the anionic sodium bis-2-ethylhexyl-sulfosuccinate (AOT) inverted micellar (IM) negative interface, the highly restricted water and proton penetration into the Stern layer owing to tight surfactant packing or a reduced water-exposed headgroup area may be responsible for the much lower Delta pH approximate to -0.45 and kappa(i) approximate to 28 in comparison to similar to-2.35 and similar to 44, respectively, for the anionic sodium dodecyl sulfate (SDS) micellar positive interface with a close similar Stern layer. With increasing AOT IM water-pool radius (1.7-9.5 nm) or [water]/[AOT] ratio (w(0)) (8.0-43.0), the Delta pH and kappa(i) increase maximally up to similar to-1.22 and similar to 45, respectively, due to a greater water-exposed headgroup area. However, the unchanged Delta pH approximate to -0.65 and kappa(i) approximate to 53.0 within radii similar to 3.5-8.0 nm for the positive interface of a mixed Triton X-100 (TX-100)/SDS (4:1) micelle justify its packing flexibility. Interestingly, the continuously increasing Delta pH trend for IM up to its largest possible water-pool radius of similar to 9.5 nm may rationalize the increase in Delta pH (similar to-1.4 to -1.6) with the change in the curvature radii (similar to 15 to 50 nm) for sodium 1,2-dimyristoyl-sn-glycero-3-phosphorylglycerol (DMPG)/1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) (2:1) large unilamellar vesicles (LUV) owing to its negative interface. Whereas, similar to the micellar positive interface, the unchanged Delta pH at the positive LUV interface was confirmed by fluorescence microscopic studies with giant unilamellar vesicles of identical lipids composition. The present study offers a unique and simple method of monitoring the curvature-radius-dependent interfacial pH/polarity for biologically related membranes.