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Silicon (Si) and composites thereof, preferably with carbon (C), show favorable lithium (Li) storage properties at low potential, and thus hold promise for application as anode active materials in the energy storage area. However, the high theoretical specific capacity of Si afforded by the alloying reaction with Li involves many challenges. In this article, we report the preparation of small-size Si particles with a turbostratic carbon shell from a polymer precoated powder material. Galvanostatic charge/discharge experiments conducted on electrodes with practical loadings resulted in much improved capacity retention and kinetics for the Si/C composite particles compared to physical mixtures of pristine Si particles and carbon black, emphasizing the positive effect that the core−shell-type morphology has on the cycling performance. Using in situ differential electrochemical mass spectrometry, pressure, and acoustic emission measurements, we gain insights into the gassing behavior, the bulk volume expansion, and the mechanical degradation of the Si/C composite-containing electrodes. Taken together, our research data demonstrate that some of the problems of high-content Si anodes can be mitigated by carbon coating. Nonetheless, continuous electrolyte decomposition, particle fracture, and electrode restructuring due to the large volume changes during battery operation (here, ∼170% in the voltage range of 600−30 mV vs Li+/Li) remain as serious hurdles toward practical implementation.

Dendritic core-double-shell architectures consisting of a hyperbranched polyglycerol core, a long aliphatic hydrophobic inner shell, and hyperbranched polyglycerol-based hydrophilic outer shell have been synthesized and characterized. They have been prepared from simple building blocks by applying an anionic ring-opening polymerization protocol. The obtained, well-defined, globular, nanometer-sized architectures possess the ability to host polar and nonpolar guest molecules in water. The polymer−guest molecule complexes were characterized by UV and DLS measurements. Unimolecular transport behavior was observed for nonpolar guest molecules with transport capacities of 1.5 guest molecules per nanocarrier and particle sizes of 7−10 nm. However, for polar guest molecules, the formation of uniform aggregates with a diameter of 70 nm and transport capacities up to 10 guests per nanocarrier was detected.

The ring-closing metathesis reaction of dendrimers containing allyl ether end groups is known to rigidify them significantly. Herein we report that polyallylated hyperbranched polyglycerol (HPG) 1 complexes the sodium salt of rose Bengal in chloroform solution but releases it readily to water. In contrast, extensively cross-linking 1 with Grubbs catalyst provides 2 which similarly complexes rose Bengal, but does not release it despite 12 h of shaking with water. Both 1 and 2 also complex thymol blue and exhibit the same differential complex stability when extracted with water. Neither 1 nor 2 complex Congo red sodium salt and more weakly solubilize the cesium salt of rose Bengal and thymol blue. Larger loop size cross-linked analogs HPG 5 and 6 also bind rose Bengal (RB) and thymol blue and are able to bind Congo red, but both release the dye more readily when extracted with water. In addition, a bathochromic shift is observed in the UV spectra for complex 6·RB, suggesting a changed microenvironment for the dye due to a tighter binding of the counter anion. Dihydroxylation of the alkene groups in 1, 2, 5, and 6 produced HPGs 3, 4, 7, and 8, respectively. HPGs 3 and 4 are both water-soluble, but 7 and 8 were not and could not be studied further. In water, HPG 4 solubilized less than one nonpolar guest (Nimodipine, pyrene, or Nile red) per polymer at least in part because it forms very large aggregates. Dynamic light scattering (DLS) and size exclusion chromatography (SEC) indicate aggregates with diameters of ca. 100 nm in pure water. The aggregates dissociated in high salt concentrations suggesting applications in stimuli responsive materials.

A convenient methodology for the synthesis of photolabile crosslinked hyperbranched polyglycerol nanocapsules is presented. These nanocarriers selectively and efficiently bind ionic guest molecules. The stability of the host-guest complexes formed depends on the counterion of the guest molecules. Moreover, the control over guest binding can be achieved by modification of the polymer building blocks, in particular the outer shell. In addition, photo-triggered degradation of the nanocarrier leads to efficient release of encapsulated guest molecules. This approach, using photolabile dendritic nanocarriers to bind and release guest molecules, is of particular relevance for biomedical applications where selective guest binding and controlled release are crucial.