Structure and Dynamics of Poly(methacrylic acid) and Its Interpolymer Complex Probed by Covalently Bound Rhodamine-123

The dynamics and structural characteristics of polymethacrylic acid bound rhodamine-123 (PMAAR123) and its interpolymer complex with poly(vinylpyrrolidone) were investigated using single molecular fluorescence studies. The time resolved fluorescence anisotropy decay of PMAA-R123 at different pH exhibits an associated anisotropy decay behavior characteristic of two different environments experienced by the fluorophore and decays with one shorter and another longer lifetime components. The anisotropy decay retains normal bi-exponential behavior under neutral pH. Fluorescence correlation spectroscopic investigation reveals that the attached fluorophore undergoes hydrolysis under basic condition which results in the release of the fluorophore from the polymer backbone. Shrinkage in the hydrodynamic radius of PMAA is observed on addition of the complementary polymer PVP which is attributed to the formation compact solubilized nanoparticle like aggregates. The size of particle further decreases on the addition of NaCl. The detailed results show that these complexes have potential for use as drug-delivery system under physiological conditions.