Molecular morphology of modified partially hydrolyzed polyacrylamide (MHPAM) on mica substrates and Langmuir-Blodgett films of MHPAM/CTAB complexes as observed by AFM

Direct observation of molecular morphology of modified partially hydrolyzed polyacrylamide (MHPAM) has been studied in this paper by atomic force microscopy (AFM). The MHPAM molecule chains are stretched forming worm-like coils due to the electrostatic repulsion between randomly distributed positive charges along the chain at pH 3. The further data analysis demonstrates single MHPAM molecules are being imaged. In addition, morphology of Langmuir-Blodgett films of MHPAM/CTAB complexes on mica surfaces also investigated as a function of the subphase pH. At pH 6, MHPAM/CTAB molecules covered on mica surfaces adopted the worm-like nanostructures, and at pH 7, conformational transition of polymer complexes appeared, showing the morphology of bump-like to some extent owing to aggregation of intrachains and interchains. Eventually, more compact globule morphology was formed at pH 12.