As a powerful synthetic tool, ruthenium-catalyzed ring-opening metathesis polymerization (ROMP) has been widely utilized to prepare diverse polymers. In this contribution, we demonstrated the polymerization of cyclooctene in the presence...
Comprehensive Summary
Introducing covalently crosslinked network to telechelic polymers can enable the formation of advanced polymeric materials with enhanced material properties. In this contribution, well‐defined telechelic polymers bearing acetoacetate groups were synthesized via Ru‐catalyzed ring‐opening metathesis polymerization of cyclooctene in the presence of chain transfer agents. Given the unique feature of muti‐site reactive acetoacetate end groups, several crosslinked networks were constructed using different crosslinkers under mild conditions. In the Michael addition reaction system, the introduction of di/trifunctional aliphatic acrylate as crosslinkers significantly enhanced the mechanical properties of the generated crosslinked network (tensile strength up to 27 MPa, elongation at break up to 500%). On the other hand, vitrimers with dynamic covalent crosslinked networks were accessed via transamination of vinylogous urethane reaction using telechelic polymers and tris(2‐aminoethyl)amine. These vitrimers presented great mechanical properties and reprocessing properties. These strategies can be potentially applied to construct other types of high‐performance polymeric materials.
Stimulus responsive catalysts have received increasing attention. Photoresponsive catalytic polymerization is particularly attractive because the noninvasive and versatile nature of light. Most photoresponsive ROP catalytic systems exhibit low activities, allowing ROP to be completed within several hours to 10 h. In this contribution, a series of (thio)ureas bearing dithienylcyclopentene optical molecular switch moiety are designed, synthesized, and characterized.The photoresponsive effects in (thio)urea/alkoxide mediated ROP of L-lactide are investigated. These catalysts allow the ROP reactions of L-lactide to be completed within a few minutes to 1 h and the resulting polyesters have narrow molecular weight distributions. The dithienylcyclopentene moiety allows photoisomerization to be completed within 1 min. The catalytic activity of the ROP catalyst can be altered by the photoisomerization of the dithienyl cyclopentene moiety by exposure to ultraviolet or visible light, respectively.
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