As the macromolecular version of mechanically interlocked molecules, mechanically interlocked polymers are promising candidates for the creation of sophisticated molecular machines and smart soft materials. Poly[]catenanes, where the molecular chains consist solely of interlocked macrocycles, contain one of the highest concentrations of topological bonds. We report, herein, a synthetic approach toward this distinctive polymer architecture in high yield (~75%) via efficient ring closing of rationally designed metallosupramolecular polymers. Light-scattering, mass spectrometric, and nuclear magnetic resonance characterization of fractionated samples support assignment of the high-molar mass product (number-average molar mass ~21.4 kilograms per mole) to a mixture of linear poly[7-26]catenanes, branched poly[13-130]catenanes, and cyclic poly[4-7]catenanes. Increased hydrodynamic radius (in solution) and glass transition temperature (in bulk materials) were observed upon metallation with Zn.

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Small-angle neutron scattering (SANS) is used to measure the conformation and solution thermodynamics of low dispersity, star branched poly(N-isopropylacrylamide) (PNI-PAM) in water using a newly developed form factor for starbranched polymers with excluded volume, in conjunction with the random phase approximation (RPA). Star PNIPAM is synthesized using both ATRP and RAFT, allowing the terminal group and number of arms to be precisely tuned from f = 3 to 6 arms, with bromine, phenyl, and dodecane terminal moieties. SANS measurements show that both the number of arms (f) and synthetic route (i.e., ATRP or RAFT) play a dominant role in the solution behavior of PNIPAM in relation to the interaction parameters, conformation of the arms of the polymer, and clustering/association of the polymers below the LCST. Dodecaneterminated PNIPAM polymers form small, sub-20 nm globules in solution, whereas phenyl-and bromine-terminated polymers form large, micrometer-scale clusters of nearly-Gaussian polymer chains. Multiangle light scattering (MALS) is used to probe the large clusters, finding that their size increases slightly with temperature but is largely independent of terminal group chemistry.

Aerogels based on sodium montmorillonite clay, epoxy polymer, and tannic acid as a flame retardant additive were fabricated through a simple, environmentally friendly freeze-drying process in which water is used as solvent. A one-step coating method using a coordination complex of natural polyphenols and Fe(III) ions was examined. Both the blended and the coated aerogels exhibit low flammabilities (the parameters measured are the time to ignition, the critical heat flux for ignition, and the heat release rate); the effects of tannic acid upon the aerogel compressive mechanical properties are reported.

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