Dramatic Effect of Alkali Metal Alkoxides on the Anionic Copolymerization of Styrene and Isoprene
Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide The effect of lithium, sodium, and potassium tert -amylates on the kinetics of the statistical anionic copolymerization of styrene and isoprene in cyclohexane was investigated using in situ near-infrared (NIR) spectroscopy. The reactivity ratios and the related comonomer gradients can be adjusted over the entire range resulting in both random and inverted gradient copolymers. Lithium tert -amylate retards the polymerization at overstoichiometric concentrations. In contrast, even at low concentrations, sodium and potassium tert -amylate increase the rate of styrene polymerization due to a counterion exchange. Only 1/30 equiv of potassium tert -amylate relative to butyllithium is necessary to obtain random copolymers, which unexpectedly consist of short blocks. Remarkably, a high content of isoprene 1,4-units is maintained, leading to a low glass transition temperature of −55 °C of random or inversely tapered poly(styrene -co- isoprene). Thus, in contrast to Lewis base modifiers, the diene microstructure can be decoupled from reaction kinetics, when potassium alkoxides are used.
Source: Macromolecules
Institution: Johannes Gutenberg University Mainz
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4411344334