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We report a self-immolative polymer (SIP) that generates a fluorescent response upon metathesis depolymerization. Functionally distinct from other degradable polymers, SIPs offer the ability to release many subunits per one signal molecule, making them advantageous for a variety of applications such as molecular detection and signal amplification. Utilizing robust copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) chemistry to orthogonally functionalize alkynes, fluorophore coumarin and quencher 4-((4-(dimethylamino)phenyl)azo) (DABCYL) were efficiently installed as side chains on the SIP. The depolymerization mediated by Grubbs 3rd-generation (G3) organoruthenium initiator enabled a fluorescence turn-on response under nanomolar SIP concentrations. To demonstrate the utility of the fluorogenic SIP, we showed a temperature-dependent fluorescence turn-on of this metathesis-triggered SIP using a thermally responsive Grubbs 2nd-generation (G2) organoruthenium initiator. 

Controlling the structure and reactivity of the chain-end group is a central objective in modern polymer chemistry. Here, we introduce 3,6-anhydrogalactal as a single-addition monomer that enables efficient and versatile chain-end functionalization of metathesis polymers. Readily synthesized from biomass-derived galactal, 3,6-anhydrogalactal exhibits excellent single-addition reactivity, allowing precise chain-end modifications even when introduced simultaneously with the propagating monomer. Theoretical calculations provide mechanistic insights into the unique reactivities governing its single-addition behavior. Its broad functional group compatibility facilitates diverse applications, including block copolymer synthesis, polymer-polymer coupling, and bioconjugation, demonstrating significant potential for advancing polymer materials and bioconjugation strategies. 

Cyclic ketene acetals (CKAs) are among the most well-studied monomers for radical ring-opening polymerization (rROP). However, ring-retaining side reactions and low reactivities in homopolymerization and copolymerization remain significant challenges for existing CKAs. Here, we report that a class of monosaccharide CKAs can be facilely prepared from a short and scalable synthetic route and can undergo quantitative, regiospecific, and stereoselective rROP. NMR analyses and degradation experiments revealed a reaction mechanism involving a propagating radical at the C2 position of pyranose, with different monosaccharides exhibiting distinct stereoselectivity in the radical addition of the monomer. Furthermore, adding maleimide was found to improve the incorporation efficiency of the monosaccharide CKA in the copolymerization with vinyl monomers, producing unique degradable terpolymers with carbohydrate motifs in the polymer backbone. 

Cationic polymerization is a powerful strategy for the production of well-defined polymers and advanced materials. In particular, the emergence of living cationic polymerization has enabled pathways to complex polymer architectures inaccessible before. The use of light and electricity as external stimuli to regulate cationic polymerization represents another advance with increasing applications in surface fabrication and patterning, additive manufacturing, and other advanced material engineering. The past decade also witnessed vigorous progress in stereoselective cationic polymerizations, allowing for the dual control of both the tacticity and the molecular weight of vinyl polymers towards precision polymers. In addition, in addressing the plastics pollution crisis and achieving a circular materials economy, cationic polymerization offers unique advantages for generating chemically recyclable polymers, such as polyacetals, polysaccharides, polyvinyl ethers, and polyethers. In this review, we provide an overview of recent developments in regulating cationic polymerization, including emerging control systems, spatiotemporally controlled polymerization (light and electricity), stereoselective polymerization, and chemically recyclable/degradable polymers. Hopefully, these discussions will help to stimulate new ideas for the further development of cationic polymerization for researchers in the field of polymer science and beyond.