Morphological Studies of Lightly Sulfonated Polystyrene Using 23Na NMR: Effects of Polydispersity in Molecular Weight

Humidity-modulated phase control and nanoscopic transport in supramolecular assemblies

Supramolecular assembly allows for enhanced control of bulk material properties through the fine modulation of intermolecular interactions. We present a comprehensive study of a cross-linkable amphiphilic wedge molecule based on a sulfonated trialkoxybenzene with a sodium counterion that forms liquid crystalline (LC) phases with ionic nanochannel structures. This compound exhibits drastic structural changes as a function of relative humidity (RH). Our combined structural, dynamical, and transport studies reveal deep and novel information on the coupling of water and wedge molecule transport to structural motifs, including the significant influence of domain boundaries within the material. Over a range of RH values, we employ (23)Na solid-state NMR on the counterions to complement detailed structural studies by grazing-incidence small-angle X-ray scattering. RH-dependent pulsed-field-gradient (PFG) NMR diffusion studies on both water and the wedge amphiphiles show multiple components, corresponding to species diffusing within LC domains as well as in the domain boundaries that compose 10% of the material. The rich transport and dynamical behaviors described here represent an important window into the world of supramolecular soft materials, carrying implications for optimization of these materials in many venues. Cubic phases present at high RH show fast transport of water (2 × 10(-10) m(2)/s), competitive with that observed in benchmark polymeric ion conductors. Understanding the self-assembly of these supramolecular building blocks shows promise for generating cross-linked membranes with fast ion conduction for applications such as next-generation batteries.

Nature and properties of ionomer assemblies. II

The principle subject in the current paper is to summarize and characterize the ionomers based on polymers and copolymers such as polystyrene (PSt), polyisoprene (PIP), polybutadiene (PB), poly(styrene-b-isobutylene-b-styrene) (PSt-PIB-PSt), poly(butadiene-styrene) (PB-PSt), poly(ethylene terephthalate) (PET), poly(butylene adipate) (PBA), poly(butylene succinate) (PBSi), poly(dimethylcarbosiloxanes), polyurethane, etc. The self-assembly of ionomers, models concerning ionomer morphologies, physical and rheological properties of ionomer phase and percolation behavior of ionomers were discussed. The ionomer phase materials and dispersions have been characterized by differential scanning calorimetry (DSC), small-angle X-ray catering (SAXS), small-angle neutron scattering (SANS), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), etc. The wide range of compositions, molecular architectures, and morphologies present in ionomeric disperse systems are of great interest. The research is particularly devoted to the potential application of these materials and an understanding of the fundamental principles of the ionomers. They are extremely complex systems, sensitive to changes in structure and composition, and therefore not easily amenable to modeling and to the derivation of general patterns of behavior. The reviewed data indicate that a large number of parameters are important in influencing multiplet formation and clustering in random ionomers. Among these are the ion content, size of the polyion and counterion, dielectric constant of the host, T(g) of the polymer, rigidity or persistence length of the backbone, position of the ion pair relative to the backbone, steric constraints, amount and nature of added additive (plasticizer), thermal history, etc.