Polymerization mechanisms

Photo-controlled living polymerization has received great attention in recent years but the reports on photo-controlled living cationic polymerization are limited. Here, the authors demonstrate a metal-free and visible light-controlled living cationic polymerization using a photocatalyst and a phosphate as the chain transfer agent for the polymerization of 4-methoxystyrene.

Mannich-type polycondensation of diamines, bisphenols and PF was conducted in CHCl₃, CHCl₃/triethylamine, and CHCl₃/triethanolamine, respectively. The products were greatly affected by the solvents used. Owing to the combination of alkalinity and solvation effect of triethanolamine, CHCl₃/triethanolamine was preferable for Mannich-type polycondensation which gave main-chain benzoxazines possessing M_n up to 10,000, oxazine content >80.0% and yield >96.0%.

No new chemical compounds were found in the copolymer acrylamide – acrylonitrile – sodium 2-acrylamido-2-methylpropanesulfonate with the composition of [72]:[10]:[18] that was subjected to thermohydrolysis at temperatures up to 160 °C, with the exception of carboxyl groups in place of amides. Thermohydrolysis up to 200 °C causes partial degradation and changes in the acrylate copolymer. The intrinsic viscosity, molecular weight and average sizes of the solvated copolymer macromolecular coils were found to decrease with increasing hydrothermal treatment temperature.

Photo- and thermo-activated polymerization and melting processes are dominant in Additive Manufacturing (AM) while ultrasound activated sonochemical reactions have not been explored for AM so far. Here, the authors demonstrate 3D printing of structures using acoustic cavitation produced directly by focused ultrasound which creates sonochemical reactions in highly localized cavitation regions.

In situ scanning tunnelling microscopy reveals the dynamic nature of the early stages of two-dimensional (2D) polymer formation and crystallization at the solid–liquid interface.