Encapsulation of catalyst in block copolymer micelles for the polymerization of ethylene in aqueous medium

Abstract

The catalytic emulsion polymerization of ethylene has been a long-lasting technical challenge as current techniques still suffer some limitations. Here we report an alternative strategy for the production of semi-crystalline polyethylene latex. Our methodology consists of encapsulating a catalyst precursor within micelles composed of an amphiphilic block copolymer. These micelles act as nanoreactors for the polymerization of ethylene in water. Phosphinosulfonate palladium complexes were used to demonstrate the success of our approach as they were found to be active for hours when encapsulated in micelles. Despite this long stability, the activity of the catalysts in micelles remains significantly lower than in organic solvent, suggesting some catalyst inhibition. The inhibition strength of the different chemicals present in the micelle were determined and compared. The combination of the small volume of the micelles, and the coordination of PEG appear to be the culprits for the low activity observed in micelles.

Remote Perfluoroalkyl Substituents are Key to Living Aqueous Ethylene Polymerization

“…Considering the particle formation process, the generation of very small (<100 nm) particles requires a high degree of dispersion of the catalyst precursor, and under ideal conditions an entire particle is grown by a single active site . With the catalysts studied here, stable dispersions with a single well‐defined particle population were obtained as observed by DLS (Figure ).…”

A Graphene‐Based Supramolecular Nanoreactor for the Fast Synthesis of Imines in Water

“…This may be the result of the following phenomena: i) stabilization of the transition state of the reaction due to a favorable interaction with the surfactant, ii) a combined polarity, microviscosity, and charge effect inside the micelle, and iii) an increased local concentration of the reactants at the surface or in the core of the micelle. [13][14][15][16] In these systems, polymeric surfactants are used as constituting element of the confined space where the reaction takes place and, at the same time, as stabilizer for the catalyst in the case of reactions that are not kinetically favored. Indeed, one of the most challenging aspect in the production of micellar reactors is the stabilization of the catalyst and its uniform dispersion in the adopted solvents.…”

Remote Perfluoroalkyl Substituents are Key to Living Aqueous Ethylene Polymerization

“…Considering the particle formation process,the generation of very small (< 100 nm) particles requires ah igh degree of dispersion of the catalyst precursor, [26] and under ideal conditions an entire particle is grown by asingle active site. [10] With the catalysts studied here,stable dispersions with asingle well-defined particle population were obtained as observed by DLS ( Figure 5).…”