2‐Nitro‐1,4‐diaminobenzene‐Functionalized Poly(vinyl amine)s as Water‐Soluble UV‐Vis‐Sensitive pH Sensors

Abstract

Abstract Summary: Nucleophilic aromatic substitution of 2,6‐ O ‐dimethyl‐ β ‐cyclodextrin ( β ‐DMCD)‐complexed 4‐fluoro‐3‐nitroaniline derivatives with poly(vinyl amine) (PVAm) in water results in 2‐nitro‐1,4‐benzenediamine‐functionalized water‐soluble PVAms in one step. The 2‐nitro‐1,4‐benzenediamine moiety linked to the polymer is solvatochromic and undergoes protonation and deprotonation as function of pH as shown by UV‐Vis spectroscopy. The occurrence of an isosbestic point in the UV‐Vis spectrum is suitable to directly determine the p K a value using the Henderson‐Hasselbalch equation. The influence of the methyl group substitution of the polymer and the 2‐nitro‐1,4‐benzenediamine moiety on the p K a is discussed. Structure of the 4‐ N , N ‐dimethyl‐2‐nitro‐1,4‐benzenediamine‐functionalized PVAm and its solution in water at varying pH. magnified image Structure of the 4‐ N , N ‐dimethyl‐2‐nitro‐1,4‐benzenediamine‐functionalized PVAm and its solution in water at varying pH.