Solvent-Free Mechanochemical Synthesis of Highly Charged Microgels

Abstract Recently, ball milling has emerged as a versatile tool for solvent-free polymer transformations. Here, a mechanochemical strategy is presented for the synthesis of stimuli-responsive microgels under solvent-free conditions. The approach relies on mechanically induced chain scission of linear polymers during ball milling, generating macroradicals that initiate copolymerization in the presence of monomers and crosslinker. This process yields microgel-like colloidal particles without initiator-derived end groups. Time-resolved analysis of polymerization and particle formation provides new insights into the mechanism of microgel formation under mechanochemical conditions. The resulting particles are characterized by dynamic and electrophoretic light scattering and electron microscopy, confirming their colloidal nature, tunable size, charge, and swelling behavior. A key advantage of this method is the efficient incorporation of charged co-monomers, enabling significantly higher ionic contents than those accessible by conventional precipitation polymerization. This results in highly charged microgels and establishes mechanochemistry as a versatile platform for the design of functional soft colloids.