A new class of water-soluble, amphiphilic star block copolymers with a large number of arms was prepared by sequential atom transfer radical polymerization (ATRP) of n-butyl methacrylate (BMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA). As the macroinitiator for the ATRP, a 2-bromoisobutyric acid functionalized fourth-generation hyperbranched polyester (Boltorn H40) was used, which allowed the preparation of star polymers that contained on average 20 diblock copolymer arms. The synthetic concept was validated by AFM experiments, which allowed direct visualization of single molecules of the multiarm star block copolymers. DSC and SAXS experiments on bulk samples suggested a microphase-separated structure, in agreement with the core−shell architecture of the polymers. SAXS experiments on aqueous solutions indicated that the star block copolymers can be regarded as unimolecular micelles composed of a PBMA core and a diffuse PPEGMA corona. The ability of the polymers to encapsulate and release hydrophobic guests was evaluated using 1H NMR spectroscopy. In dilute aqueous solution, these polymers act as unimolecular containers that can be loaded with up to 27 wt % hydrophobic guest molecules.

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The integration of shear-thickening fluids (STFs) into composite structures has been investigated with the aim of tuning part stiffness and damping capacity under dynamic deformation. Results from oscillatory rheological measurements for a STF based on concentrated fused silica in polypropylene glycol were correlated with results from vibrating beam tests on model sandwich structures containing layers of the same STF sandwiched between polyvinyl chloride (PVC) beams. Above a critical amplitude, the relative motion of the PVC beams provoked shear thickening of the silica suspensions, and the vibration and damping properties were significantly modified. These changes were related to the rheological response of the STF through analytical calculations of strains in the STF layers, an approach that was verified experimentally by replacing the STF with a slow-curing epoxy resin. The potential for integrating STFs into structures exposed to dynamic flexural deformation, with the aim of controlling their vibrational response, has thus been demonstrated.