Sequence-defined multifunctional polyethers via liquid-phase synthesis with molecular sieving

Synthetic chemists have devoted tremendous effort towards the production of precision synthetic polymers with defined sequences and specific functions. However, the creation of a general technology that enables precise control over monomer sequence, with efficient isolation of the target polymers, is highly challenging. Here, we report a robust strategy for the production of sequence-defined synthetic polymers through a combination of liquid-phase synthesis and selective molecular sieving. The polymer is assembled in solution with real-time monitoring to ensure couplings proceed to completion, on a three-armed star-shaped macromolecule to maximize efficiency during the molecular sieving process. This approach is applied to the construction of sequence-defined polyethers, with side-arms at precisely defined locations that can undergo site-selective modification after polymerization. Using this versatile strategy, we have introduced structural and functional diversity into sequence-defined polyethers, unlocking their potential for real-life applications in nanotechnology, healthcare and information storage

Über einige zweidimensionale Analoga der klassischen orthogonalen Polynome

The paper deals with some families of polynomials in two variables-eigenfunctions of a linear operator in partial derivates of second order with polynomial coefficients. These polynomials have certain orthogonality properties with respect to a scalar product defined in the space of polynomials by means of a double sequence of moments. In greater detail is investigated a special class of operators when the corresponding polynomials form two biorthogonal sequences analogical to the classical orthogonal polynomials. An enumeration of all operators belonging to the special class is given

Sequence-controlled methacrylic multiblock copolymers via sulfur-free RAFT emulsion polymerization

Translating the precise monomer sequence control achieved in nature over macromolecular structure (for example, DNA) to whole synthetic systems has been limited due to the lack of efficient synthetic methodologies. So far, chemists have only been able to synthesize monomer sequence-controlled macromolecules by means of complex, time-consuming and iterative chemical strategies such as solid-state Merrifield-type approaches or molecularly dissolved solution-phase systems. Here, we report a rapid and quantitative synthesis of sequence-controlled multiblock polymers in discrete stable nanoscale compartments via an emulsion polymerization approach in which a vinyl-terminated macromolecule is used as an efficient chain-transfer agent. This approach is environmentally friendly, fully translatable to industry and thus represents a significant advance in the development of complex macromolecule synthesis, where a high level of molecular precision or monomer sequence control confers potential for molecular targeting, recognition and biocatalysis, as well as molecular information storage

How can xanthates control the RAFT polymerization of methacrylates ?

International audienceA xanthate bearing S-cyanoisopropyl and O-2,2,2trifluoroethyl groups was identified as a potential RAFT agent for sequential polymerization of methyl methacrylate and vinyl acetate. The intrinsic low reactivity of the xanthate for MMA polymerization was compensated by implementing a semibatch emulsion process with a thorough adjustment of the process parameters to keep MMA concentration to a minimum during polymerization. In a second stage, the xanthate-capped PMMA seed was chain extended during batch vinyl acetate polymerization at room temperature, yielding a well-defined PMMA-PVAc diblock copolymer

Description and release of Australian gravity field model testing data

Gravimetric geoid and/or quasigeoid models are routinely evaluated using co-located GPS-levelling and/or astrogeodetic vertical deflections, globally and regionally. This short note describes these ground-truth data for Australia as of August 2017, which are provided as Electronic Supplementary Material. We provide ~7500 GPS-derived ellipsoidal heights, normal-orthometric heights from the 1971 adjustment of the Australian Height Datum, normal heights from a readjustment of levelling constrained to a model of the ocean's mean dynamic topography, and ~1000 historical astrogeodetic vertical deflections. Updates to these data will be posted on the Intergovernmental Committee on Surveying and Mapping GitHub repository (https://github.com/icsm-au), together with a readme.txt file describing them