?therische ?le

Ohne Zusammenfassung     

New process for the preparation of methyl carbonates

The methyl carbonate of HOBt was developed for the conversion of alcohols to carbonates. This method is superior to the use of methyl chloroformate or methyl pyrocarbonate, especially with more hindered alcohols. The reagent is a stable solid that is easily prepared on a multigram scale. [reaction: see text]     

Exploiting catalytic chain transfer polymerization for the synthesis of carboxylated latexes via sulfur‐free RAFT

We present a systematic study of incorporating carboxyl groups into latex particles to enhance colloidal stability and the physical properties of the latex. Statistical copolymers of methacrylic acid and methyl methacrylate) were synthesized via catalytic chain transfer polymerization (CCTP) in emulsion. The vinyl‐terminated oligomers were in turn successfully utilized as chain transfer agents for the formation of diblock and pseudo triblock copolymers via sulfur‐free reversible addition–fragmentation chain transfer polymerization (SF‐RAFT). These copolymers were characterized using ¹H NMR, size exclusion chromatography (SEC), dynamic light scattering (DLS), dynamic mechanical analysis (DMA), contact angle measurements and matrix‐assisted laser desorption/ionization time of flight mass spectroscopy (MALDI‐TOF‐MS) techniques. © 2019 The Authors. Journal of Polymer Science Part A: Polymer Chemistry published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, E1–E9     

Observation of a Silk-Like Crystal Structure in a Genetically Engineered Periodic Polypeptide

Abstract

A genetically engineered periodic polypeptide consisting of 36 repeats of the octapeptide sequence -(AlaGly)₃GluGly- has been crystallized from solution in aqueous lithium bromide. Analysis by solid-state nuclear magnetic resonance spectroscopy, vibrational spectroscopy, and wide-angle x-ray diffraction reveals a crystal structure analogous to that obtained when silk solutions are allowed to dry under quiescent conditions, i.e., the silk I structure. Previous analyses of the same polymer have demonstrated an antiparallel β-sheet architecture (silk II structure) in samples crystallized from formic acid. These results illustrate the potential for controlling the solid-state structures and properties of genetically engineered materials through selection of appropriate processing and crystallization conditions.