TM-Free and TM-Catalyzed Mechanosynthesis of Functional Polymers

Mechanochemically induced methods are commonly used for the depolymerization of polymers, including plastic and agricultural wastes. So far, these methods have rarely been used for polymer synthesis. Compared to conventional polymerization in solutions, mechanochemical polymerization offers numerous advantages such as less or no solvent consumption, the accessibility of novel structures, the inclusion of co-polymers and post-modified polymers, and, most importantly, the avoidance of problems posed by low monomer/oligomer solubility and fast precipitation during polymerization. Consequently, the development of new functional polymers and materials, including those based on mechanochemically synthesized polymers, has drawn much interest, particularly from the perspective of green chemistry. In this review, we tried to highlight the most representative examples of transition-metal (TM)-free and TM-catalyzed mechanosynthesis of some functional polymers, such as semiconductive polymers, porous polymeric materials, sensory materials, materials for photovoltaics, etc.

Atom Transfer Radical Polymerization: A Mechanistic Perspective

Since its inception, atom transfer radical polymerization (ATRP) has seen continuous evolution in terms of the design of the catalyst and reaction conditions; today, it is one of the most useful techniques to prepare well-defined polymers as well as one of the most notable examples of catalysis in polymer chemistry. This Perspective highlights fundamental advances in the design of ATRP reactions and catalysts, focusing on the crucial role that mechanistic studies play in understanding, rationalizing, and predicting polymerization outcomes. A critical summary of traditional ATRP systems is provided first; we then focus on the most recent developments to improve catalyst selectivity, control polymerizations via external stimuli, and employ new photochemical or dual catalytic systems with an outlook to future research directions and open challenges.

Solvent-Free Mechanochemical Post-Polymerization Modification of Ionic Polymers

Despite their superior stability and facile handling, ionic polymers have limited solubility in most organic solvents, restricting the range of substrates and reaction conditions to which they can be applied. To overcome this solubility issue, the present study presents a solvent-free mechanochemical reaction. Specifically, a post-polymerization modification of ammonium-functionalized polyether was demonstrated using a solvent-free vibrational ball-milling technique. The formation of imine bonds between the ionic polymer and an aromatic aldehyde led to the complete conversion to imine within 1 h without any bond breakage on the polymer backbone. The viability of this approach for a wide range of aldehydes was also evaluated, highlighting the potential of the mechanochemical post-polymerization modification of polymers that are inaccessible by conventional solution approaches.