Controlled radical copolymerization of multivinyl crosslinkers: a robust route to functional branched macromolecules

Abstract

Controlled radical polymerization (CRP) has both revolutionized the synthesis of linear polymers and enabled unprecedented topological complexity. While the synthesis of many polymeric architectures requires careful planning and specialized precursors, branched macromolecules such as segmented hyperbranched polymers (SHPs), knotted polymers, core-crosslinked stars (CCSs), and more can be synthesized through the copolymerization of vinyl monomers and divinyl crosslinkers in only a few steps. In the nearly two decades since its discovery, this strategy has helped elucidate the fundamental polymerization behavior of crosslinkers and also yielded a variety of functional and stimuli-responsive materials. The purpose of this mini-review is to therefore overview critical fundamental aspects of CRP of crosslinkers and materials derived therefrom. The process by which both SHPs and CCS polymers are synthesized, the effect of key reaction parameters and intriguing recent advances are described with the intent of both educating new researchers and inspiring new directions in this area.

Nondestructive Photo-Cross-Linking of Microphase-Separated Diblock Polymers through Coumarin Dimerization

“…We initially attempted to synthesize an all-acrylate diblock polymer; however, chain extension using coumarin acrylate resulted in a broad and multimodal molecular weight distribution (Figure S1), likely due to cross-linking through the pendent coumarin olefin by reactive acrylate radicals. While this side reaction can produce a macroscopic gel, the system likely remained below the critical gelation conversion and accordingly yielded soluble branched polymers that were amenable to chromatographic analysis . In contrast, using methacrylate derivatives resulted in well-controlled polymerization and coumarin preservation (Figure , Figure S2, and Figure S3) by virtue of the lower ground-state energies of the methacrylate radicals.…”

“…While this side reaction can produce a macroscopic gel, the system likely remained below the critical gelation conversion and accordingly yielded soluble branched polymers that were amenable to chromatographic analysis. 31 In contrast, using methacrylate derivatives resulted in well-controlled polymer-Scheme 1. Synthesis of Cross-Linkable Diblock Polymers by ATRP ization and coumarin preservation (Figure 1, Figure S2, and Figure S3) by virtue of the lower ground-state energies of the methacrylate radicals.…”

Scaling Behavior and Structure–Property Relationships of Multifunctional Ternary‐Hydrogels Based on N‐Alkyl Methacrylate Esters: Property Tunability through Versatile Synthesis

“…) X (11) in which M r is the molecular weight of repeating unit (Table 2). By taking the crosslinker ratio X = 1/76, and the apparent density of terpolymer, 𝜌 = 1.507 ± 0.016, one can determine the nominal crosslink density, i.e., DEGDMA % used in the hydrogel synthesis.…”

“…[10] An attempt has been made to identify a robust pathway to functionally branched macromolecules by CRP of multivinyl crosslinkers. [11] Because in order to predict the network topology regardless of the polymerization type, it is necessary to understand how the polymerization conditions lead to crosslinking or loop formation. Understanding how the mechanical properties of polymer networks change according to their structure is important for the design of advanced functional materials with desired properties.…”

Respecting differences

“…3 Additionally, designing more sustainable networks offers critical impact to improve performance with an opportunity of recycling, from thermosets from renewable sources to stimuli-responsive crosslinks. 4,5 Our Board members continue to demonstrate their tireless commitment to the journal and preservation of international discourse, and Professor Carmen Scholz describes polymer-coated ceramic monoliths for affinity chromatography. 6 I extend my sincerest gratitude to Carmen for her leadership, her attention to excellence, her welcoming of differences, and her immense impact on our journal.…”