Off‐center Mechanophore Activation in Block Copolymers

Abstract

Block copolymers (BCPs) are used in numerous applications in modern materials science. Yet, like homopolymers, BCPs can undergo covalent bond scission when mechanically stressed (mechanochemistry), which could lead to unexpected consequences in such applications. BCPs’ heterogeneity may affect force transduction, perhaps changing force distribution and localization. To verify this, a gem‐dichlorocyclopropane (gDCC) embedded linear chain is prepared and extended with a poly(methyl methacrylate) block. When stressed in solution, the mechanochemical ring‐opening of gDCC is accelerated compared to homopolymers, even though the mechanophores are at the chain ends. Moreover, a higher mechanophore activation selectivity is obtained. These results indicate that mechanochemical response outside, and even far from the chain center is quite prominent in BCPs, and that forces along the polymer chain can efficiently activate multi‐mechanophores regions, even when far from the polymer midchain.

Macromolecular Postpolymerization of Siloxane Exchange to Assemble Multiple Siloxane Linkages

“…The possibilities of polymerization, and the variety of products that can be gained, are greatly increased when polymerization is carried out in a mixture of two or more monomers, for the copolymer chain can now contain arrangements of various monomer units. − Moreover, copolymerization brings flexibility to tailor polymer properties (such as Tg , surface energy, rheological properties, and so on) to meet the needs of a wide range of applications. − However, copolymerization is a more challenging research topic than homopolymerization, because it requires a comprehensive consideration of the relative polymerization activity of monomers, monomer feeding ratios, and dosing methods, and the distribution of monomers (random, block, or alternating) in the polymer chain. − Therefore, numerous efforts have been devoted to the development of catalysts and polymerization methods to surmount the varied polymerization activity of the monomers and to achieve the controllability of the copolymerization, thus modulating the properties of the synthesized polymers. , Such challenges are also encountered with polysiloxanes, − a polymer formed out of silicon and oxygen atoms alternately arranged in the backbone and organic groups attached to the silicon atoms, which serve as a critically important material bridge between inorganic and organic polymers.…”