Search results for "Note"

Poly(S-ethylsulfonyl-l-cysteines) for Chemoselective Disulfide Formation

2016

The amino acid cysteine possesses a unique role in nature due to its ability to reversibly cross-link proteins. To transfer this feature to polypeptides and control the process of disulfide formation, a protective group needs to provide stability against amines during synthesis, combined with chemoselective reactivity toward thiols. A protective group providing these unique balance of stability and reactivity toward different nucleophiles is the S-alkylsulfonyl group. In this work we report the polymerization of S-ethylsulfonyl-l-cysteine N-carboxyanhydride and kinetic evaluations with respect to temperature (−10, 0, and +10 °C) and monomer concentration. The polymerization degree of poly(S…

Polymerization of long chain alkyl glycidyl ethers: a platform for micellar gels with tailor-made melting points

2018

Controlled polymerization of long-chain alkyl glycidyl ethers (AlkGE) under anionic ring opening polymerization conditions is enabled by the addition of a crown ether (18-crown-6, K+). Homopolymers with molecular weights in the range of 4000 to 9000 g mol−1 and side chain melting temperatures of 14 °C (C12-AlkGE) and 43 °C (C16-AlkGE), respectively were synthesized. Furthermore, a series of amphiphilic ABA polyether triblock copolymers with polyethylene glycol (PEG) as the hydrophilic central block (Mn = 6k, 10k, and 20k g mol−1) with total molecular weights in the range of 7000 to 28 000 g mol−1 and narrow dispersity (1.12 to 1.34) were prepared. Separate melting endotherms of the triblock…

A road less traveled to functional polymers: epoxide termination in living carbanionic polymer synthesis.

2010

Functional polymers possess tremendous potential both in academia and in industry. In particular, oxiranes offer manifold possibilities for the introduction of single hydroxyl or multiple orthogonal functionalities in carbanionic polymerization. Here, we present a brief overview of the fascinating possibilities arising from the employment of common as well as individually designed epoxide derivatives for the synthesis of end-functional polymers. Continuous flow techniques can be utilized for the rapid generation and screening of precisely defined hydroxyl-modified polymers. The utilization of functionalized polymers as precursors for the formation of complex macromolecular architectures (e.…

Living Anionic Polymerization Celebrates 60 Years: Unique Features and Polymer Architectures

2017

The Next 100 Years of Polymer Science

2020

International audience; The year 2020 marks the 100th anniversary of the first article on poly merization, published by Hermann Staudinger. It is Staudinger who realized that polymers consist of long chains of covalently linked building blocks. Polymers have had a tremendous impact on the society ever since this initial publication. People live in a world that is almost impossible to imagine without synthetic polymers. But what does the future hold for polymer science? In this article, the editors and advisory board of Macromolecular Chemistry and Physics reflect on this question.

Oxidation-responsive polyether block copolymers lead to non-ionic polymer surfactants with multiple amine N-oxides

2019

Block copolymers consisting of a nonpolar poly(propylene oxide) block and a poly(glycidyl amine) block were prepared by anionic ring-opening polymerization (AROP). The tertiary amine groups of the block copolymers were quantitively transformed into the corresponding zwitterionic amine N-oxides, as confirmed by 1H NMR and 15N NMR spectroscopy. This leads to strongly amphiphilic polyether block copolymers with multiple N-oxides. Full oxidation of the amine groups was also possible in situ in an emulsion, demonstrating the oxidation-responsive character of this new class of non-ionic polymeric surfactants.

Multi-stimuli responsive polymers – the all-in-one talents

2014

Stimuli-responsive polymers have gained increasing attention, which is attributed to the manifold applications they can be used for. Several years' intensive research was invested in stimuli-responsive polymers. Their stimuli-responsiveness led not only to novel responsive groups, which enabled the translation of an external physical impact into a change of a material property, but also to polymers that are equipped with more than one responsive group. The integration of several responsive moieties within one polymer yields smart polymers exhibiting complex responsive behaviour of the polymers. This review summarises recent developments in the area of multi-stimuli responsive polymers, layi…

Single molecule probing of dynamics in supercooled polymers

2011

6 pages; International audience; Fluorescence experiments with single BODIPY molecules embedded in a poly(methyl acrylate) matrix have been performed at various temperatures in the supercooled regime. By using pulsed excitation, fluorescence lifetime and linear dichroism time trajectories were accessible at the same time. Both observables have been analyzed without data binning. While the linear dichroism solely reflects single particle dynamics, the fluorescence lifetime observable depends on the molecular environment, so that the dynamics from the polymer host surrounding a chromophore contributes to this quantity. We observe that the lifetime correlation decays slightly faster than polar…

Effect of the elongational flow on morphology and properties of polypropylene/graphene nanoplatelets nanocomposites

2018

Abstract In this work the effect of the presence of graphene nanoplatelets (GnP) on the morphology and mechanical properties of polypropylene/GnP nanocomposites has been investigated when these polymer systems are subjected to non-isothermal elongational flow in a melt spinning operation. The presence of the GnP magnifies the effect of the elongational flow. Indeed, the elastic modulus and the tensile strength of nanocomposites increases with the orientation more than that observed for the pure matrix. Moreover, the elongation at break increases at low values of the draw ratio for the nanocomposites, while, the matrix shows the expected decrease in deformability. These effects have been cor…

Pleiotropic Role of Recombinant Silaffin-Like Cationic Polypeptide P5S3: Peptide-Induced Silicic Acid Stabilization, Silica Formation and Inhibition …

2016

Silica-mineralizing organisms such as diatoms manage several aspects of silica chemistry when polymerizing monomeric silicic acid into amorphous silica. Silicic acid is undersaturated in the diatoms’ habitats and mechanisms of enrichment and prevention of uncontrolled mineralization are not well understood. Diatom-biosilica is associated with organic compounds, including polycationic, post-translationally modified peptides termed silaffins, which induce the condensation of silicic acid under supersaturated conditions. Here, we report the pleiotropic action of the designed silaffin-like peptide P5S3, which (i) stabilizes 4–8x silicic acid (in supersaturated conditions of 8.3 mm), (ii) decele…