화학공학소재연구정보센터
Macromolecules, Vol.49, No.5, 1890-1902, 2016
How Supramolecular Assemblies Control Dynamics of Associative Polymers: Toward a General Picture
The dynamics of supramolecular networks made up of partially hydrolyzed poly(n-butyl acrylate) [PnBA] is investigated. These linear entangled random copolymers [PnBA-AA] self-assemble via hydrogen bonding interactions between carboxylic acid groups. Two types of supramolecular assemblies are revealed, i.e., binary assembly of carboxylic acid dimers and collective assembly of dimers into distinct poly(acrylic acid) [PAA] domains. The latter is proved by emergence of new relaxation processes in broadband dielectric spectroscopy while the former is evident by an increase of the glass transition temperature as well as retardation of segmental mobility observed by rheology. Therefore, a "sea-island" morphology containing geometrically confined PAA nanodomains embedded in a PnBA-rich matrix is suggested for the supramolecular network. Thermodynamic theories are employed to rationalize the existence of an interlayer with restricted mobility between the two phases. A fraction of PnBA-AA segments that are trapped between more than one PAA domain are considered to describe the low-frequency plateau in storage modulus that is seen beyond the plateau modulus of PnBA as well as strain hardening in both shear and elongation fields. Finally, based on the observation in this work and wealth of literature on supramolecular networks, a general microstructure is proposed for associating polymers in which supramolecular moieties are situated along the contour length. This microstructure appropriately describes different dynamic observations made by rheology, calorimetry, and dielectric spectroscopy.