345 research outputs found
Orthogonal modification of polymer chain-ends via sequential nitrile oxideâalkyne and azideâalkyne Huisgen cycloadditions
The α- and Ï-chain-ends of well-defined polystyrene chains were functionalized using consecutive Huisgen cycloadditions. Firstly, an α-alkyne, Ï-azido heterotelechelic polystyrene precursor was synthesized in three steps: (i) atom transfer radical polymerization in the presence of (1,1,1-trimethylsilyl)-2-propynyl 2-bromo-2-isobutyrate, (ii) deprotection of the alkyne function of the initiator and (iii) nucleophilic substitution of the bromine chain-end of the polymer with sodium azide. Afterwards, the chain-ends of the polymer were modified by successive nitrile oxideâalkyne cycloaddition (NOAC) and copper-catalyzed azideâalkyne cycloaddition (CuAAC). 2 Model building blocks were tested for NOAC, while 4 building blocks were studied for CuAAC. In all cases, the orthogonal combination of NOAC and CuAAC allowed the preparation of tailored heterotelechelic polymers
In silico based design of nitroxide mediated polymerization: from homopolymers to sequence controlled polymers
Synthesis of Macromolecules Containing Phenylalanine and Aliphatic Building Blocks
Aiming at developing efficient interfacial agents for fiberâreinforced composite materials, macromolecules are designed to have different components able to stick to the fiber and be compatible with the polymer matrix, respectively. Herein, macromolecules are prepared by solidâphase synthesis considering phenylalanine residues to promote adsorption of the macromolecule on aramid fibers and aliphatic building blocks to interact with a hydrophobic polymer matrix. Using phenylalanine as building block for the preparation of macromolecules by iterative synthesis has been shown to be challenging. Thus, the screening of various parameters for the optimization of the synthesis of these macromolecules is discussed in this communication. A preliminary thermal study by thermal gravimetric analysis is conducted to evaluate their thermal stability
Comma-free Codes Over Finite Alphabets
Comma-free codes have been widely studied in the last sixty years, from points of view as diverse as biology, information theory and combinatorics. We develop new methods to study comma-free codes achieving the maximum size, given the cardinality of the alphabet and the length of the words. Specifically, we are interested in counting the number of such codes. We provide (two different proofs for) a closed-formula. The approach introduced is further developed to tackle well-known sub-families of comma-free codes, such as self-complementary and (generalisations of) non-overlapping codes. We also study codes that are not contained in strictly larger ones. For instance, we determine the maximal size of self-complementary comma-free codes and the number of codes reaching the bound. We provide a characterisation of-letter non-overlapping codes (over an alphabet of cardinality n), which allows us to devise the number of such codes that are not contained in any strictly larger one. Our approach mixes combinatorial and graph-theoretical arguments
Convergent synthesis of digitally-encoded poly(alkoxyamine amide)s
International audiencea Binary-encoded poly(alkoxyamine amide)s were prepared by oligomer ligation. These polymers contain digital sequences based on two monomers defined as 0 and 1 bits. A library of oligomers containing all possible dyads 00, 01, 10 and 11 was prepared and used to construct long coded sequences
Histoire et philologie du Japon ancien et médiéval
Programme de lâannĂ©e 2009-2010 : I. La vie quotidienne dans le Japon mĂ©diĂ©val dâaprĂšs le « Rouleau de peinture des pĂ©rĂ©grinations dâIppen » (1299). â II. Le Iken jĂ»nikajĂŽ (914), texte en kanbun
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