Interpolymer Hydrogen Bonding in the Presence of a Low-Molecular Competitor

We examine the effect of dimethyl sulfoxide (DMSO) on binding enthalpy, strength of association between hydrogen-bonding polymers (poly(methacrylic) acid, PMAA), and polyvinylpyrrolidone, PVP) and their deposition within layer-by-layer (LbL) films, In solution, isothermal titration calorimetry (ITC) showed that the addition of DMSO to aqueous solutions resulted in a switching in enthalpy of binding from endothermic to exothermic. In good agreement with the ITC data, the growth mode of PVP/PMAA LbL films changed from linear to exponential with an increase in DMSO content. Neutron reflectometry (NR) studies showed that while LbL films constructed from DMSO-free solutions were stratified, significant layer intermixing occurred in the films constructed from polymer solutions with high DMSO content. This study demonstrates a facile means to control binding of polymer components and structure of assembled films in hydrogen-bonded systems.