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Carbene polymerization provides polyolefins that cannot be readily prepared from olefin monomers; however, controlled and living carbene polymerization has been a long-standing challenge. Here we report a new class of initiators, (π-allyl)palladium carboxylate dimers, which polymerize ethyl diazoacetate, a carbene precursor in a controlled and quasi-living manner, with nearly quantitative yields, degrees of polymerization >100, molecular weight dispersities 1.2-1.4, and well-defined, diversifiable chain ends. This method also provides block copolycarbenes that undergo microphase segregation. Experimental and theoretical mechanistic analysis supports a new dinuclear mechanism for this process.

Viral Battery In developing materials for batteries, there is a trade-off between charge capacity, conductivity, and chemical stability. Nanostructured materials improve the conductivity for some resistive materials, but fabricating stable materials at nanometer-length scales is difficult. Harnessing their knowledge of viruses as toolkits for materials fabrication, Lee et al. (p. 1051; published online 2 April) modified two genes in the filamentous bacteriophage M13 to produce a virus with an affinity for nucleating amorphous iron phosphate along its length and for attaching carbon nanotubes at one of the ends. In nanostructured form, the amorphous iron phosphate produced a useful cathode material, while the carbon nanotubes formed a percolating network that significantly enhanced conductivity.

Atomically thin two-dimensional (2D) layered materials, including graphene, boron nitride, and transition metal dichalcogenides (TMDs), can exhibit novel phenomena distinct from their bulk counterparts and hold great promise for novel electronic and optoelectronic applications. Controlled growth of such 2D materials with different thickness, composition, and symmetry are of central importance to realize their potential. In particular, the ability to control the symmetry of TMD layers is highly desirable because breaking the inversion symmetry can lead to intriguing valley physics, nonlinear optical properties, and piezoelectric responses. Here we report the first chemical vapor deposition (CVD) growth of spirals of layered MoS2 with atomically thin helical periodicity, which exhibits a chiral structure and breaks the three-dimensional (3D) inversion symmetry explicitly. The spirals composed of tens of connected MoS2 layers with decreasing areas: each basal plane has a triangular shape and shrinks gradually to the summit when spiraling up. All the layers in the spiral assume an AA lattice stacking, which is in contrast to the centrosymmetric AB stacking in natural MoS2 crystals. We show that the noncentrosymmetric MoS2 spiral leads to a strong bulk second-order optical nonlinearity. In addition, we found that the growth of spirals involves a dislocation mechanism, which can be generally applicable to other 2D TMD materials.

Goal of the paper is to investigate the analogue computational capabilities of dynamic networks with mem-elements. A relevant class of networks containing memristors and (possibly) nonlinear capacitors and inductors is considered. The paper unfolds the nonlinear dynamics of these networks by highlighting some main features that are potentially useful for real-time signal processing and in-memory computing. These include the presence of bifurcations without parameters and the coexistence of different regimes and complex dynamics. The analysis is conducted by means of a recently developed technique named flux-charge analysis method.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDesign of polymeric imaging materials based on electrophilic aromatic substitution: model studiesHarald D. H. Stover, Stephen Matuszczak, C. Grant Willson, and Jean M. J. FrechetCite this: Macromolecules 1991, 24, 8, 1741–1745Publication Date (Print):April 1, 1991Publication History Published online1 May 2002Published inissue 1 April 1991https://pubs.acs.org/doi/10.1021/ma00008a009https://doi.org/10.1021/ma00008a009research-articleACS PublicationsRequest reuse permissionsArticle Views135Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

In situ time-dependent measurements using voltammetry and sum frequency generation (SFG) were carried out to study CO oxidation on a Pt(111) electrode. The scan-rate dependence of CO oxidation was measured by changing the scan rate from 50 to 0.5 mV/s. While the basic shape of the CO stripping curves was unaffected by sweep rate, the oxidation potential of CO was lowered by 0.1 V, from 0.84 to 0.74 V. The measurements of SFG spectra and CO stripping were carried out simultaneously to clarify the discrepancy between SFG and CO stripping measurements reported in earlier SFG studies. Our results showed that the SFG peak attributed to the CO stretch vanished immediately after the CO stripping current reached its maximum value. In the preignition potential region, the frequency shift of the CO stretch observed by SFG agrees with that observed by IR spectroscopy. Additionally, in the ignition potential region, a significant blue shift of CO stretching frequency was observed. For the first time, a 360% enhancement of SFG intensity coinciding with the red shift of stretching frequency was observed in the preignition potential region. While it was not observed by IR spectroscopy, it shows similar behavior to limited Raman spectroscopy measurements obtained from a roughened Pt surface.