Materials with highly ordered molecular arrangements have the capacity to display unique properties derived from their nanoscale structure. Here, the synthesis and characterization of azobenzene (AZO)-functionalized siloxane oligomers of discrete length that form photoswitchable supramolecular materials are described. Specifically, synergy between phase segregation and azobenzene crystallization leads to the self-assembly of an exfoliated 2D crystal that becomes isotropic upon photoisomerization with UV light. Consequently, the material undergoes a rapid athermal solid-to-liquid transition which can be reversed using blue light due to the unexpectedly fast 2D crystallization that is facilitated by phase segregation. In contrast, enabling telechelic supramolecular polymerization through hydrogen bonding inhibits azobenzene crystallization, and nanostructured pastes with well-ordered morphologies are obtained based on phase segregation alone, thus demonstrating block copolymer-like behavior. Therefore, by tailoring the balance of self-assembly forces in the azobenzene-functionalized siloxane oligomers, fast and reversible phase-changing materials can be engineered with various mechanical properties for applications in photolithography or switchable adhesion to lubricant properties. In these materials, contraction along the LC director occurs with isomerization of the planar trans-azobenzenes to the bent cis-azobenzenes. By limiting the depth of photoactivity, generally through utilizing the inherently high absorption coefficient of the azobenzenes, this contraction can give rise to anisotropic bending in poly mer films, [7,8] gels, [9] fibers, [10][11][12] and even crystals. [13] Different modes of motion arise with more complex molecular arrangements. For example, expansion of chiral nematic LCs along the helical axis has been utilized to create polymer coatings with photoswitchable topologies [14][15][16][17] and polymer films with macroscopic helical motion. [18] Additionally, polymer films with splay-bend configuration, in which LC-mesogens gradually change orientation throughout the film cross-section, have shown to exhibit inherently anisotropic bending as well as achieve significantly faster and larger bending when compared to uniaxially aligned films. [19][20][21] The ability of azobenzene photoisomerization to generate anisotropic dimension change and motion in LC networks typically results from increased molecular disorder caused by bent cis-azobenzene relative to networks with rod-like transazobenzene. Such photocontrol of order/disorder has been used to induce rapid nematic-to-isotropic phase transitions in LC films for applications in optical image storage [22] and holography. [23] The reversibility of azobenzene photoisomerization is beneficial for such applications, and the ability of azobenzene materials to undergo many trans-cis photoisomerization cycles without noticeable degradation in performance has been demonstrated. [24,25] Furthermore, few examples have demonstrated the photocontrolled swit...

Highly ordered nanopatterns are obtained at sub‐5 nm periodicities by the graphoepitaxial directed self‐assembly of monodisperse, oligo(dimethylsiloxane) liquid crystals. These hybrid organic/inorganic liquid crystals are of high interest for nanopatterning applications due to the combination of their ultrasmall feature sizes and their ability to be directed into highly ordered domains without additional annealing.

Dendritic cell‐wall mimics: Choline‐binding proteins from Streptococcus pneumoniae recognize distinctive multivalent choline architectures on the bacterial cell wall. Choline‐functionalized dendrimers are potent inhibitors of these essential enzymes, with a 103–104‐fold higher affinity than free choline, resulting in inhibition of autolysis and cell separation in bacterial cultures at low micromolar concentrations (see picture).

Background: Pneumococcal virulence factors common to all serotypes, such as choline-binding proteins (CBPs), are promising therapeutic targets in pneumococcal infections. We studied the effect of a choline dendrimer with maximized binding affinity/specificity for CBPs on microglia-mediated pneumococcal phagocytosis. Methods: Pneumoccocal cultures were exposed to dendrimers containing 8 choline end groups or amino groups as controls, either from the beginning of bacterial growth or at the late exponential phase. The effect of long/short co-incubation was assessed in terms of bacterial morphological changes and increase in bacterial uptake by primary microglial cultures. Results: Inhibiting CBPs by micromolar concentrations of a choline dendrimer caused the formation of long pneumococcal chains that were readily phagocytosed by microglia. Enhanced phagocytosis was dendrimer dose-dependent. Long bacteria-dendrimer co-incubation (14 h) resulted in a higher bacterial uptake than short co-incubation (2 h; p < 0.001). Conclusions: Multivalent dendrimers containing choline end groups are promising antimicrobial agents for the management of pneumococcal diseases.

Díez-Martínez, R.; Maestro, B.; García-Fernández, E.; de Waal, B.F.M.; Meijer, E.W.; García, P.; Sanz, J.M.