Dynamic Postpolymerization Modification Based on Knoevenagel Adducts of Meldrum’s Acid

Abstract

Postpolymerization modification using “click” reactions has been proven to be a powerful method to build functional polymers, but the way to construct dynamic functional polymers remains challenging. In this work, CC/CN dynamic exchange reaction between Meldrum’s acid condensate and aldimine was employed to establish an efficient dynamic PPM method. Under the condition of catalyst free and room temperature, the conversion of PPM based on CC/CN dynamic exchange reaction can be up to more than 90%. Furthermore, reactive polymer coatings for in situ generating dyes with different absorbance wavelengths (λmax = 360–605 nm) and rewritable fluorescent papers were successfully developed by using dynamic PPM to tune the electron donor−π-acceptor structures in MA condensates on polymers.

Mechanochemistry Enabled Inverse Vulcanization of Norbornadiene for Optical Polymers and Elastomeric Materials

“…After the reaction mixture is milled at 30 Hz for 3 h, a portion is taken for 1 HNMR, XRD, and DSC measurements to check the conversion of both monomers. As shown in Figure 2a, 1 HNMR data display that as sulfur content varies from 90 to 40 wt %, no proton signal of NBD C�C bond can be observed, whereas a slight peak from the NBD C�C bond emerges as sulfur content is 30 wt %, suggesting that full conversion of NBD can be achieved 22 for the sulfur polymer with a sulfur content from 90 to 40 wt %. Besides, as proven in Figure 2b, the phase transition peak of Correspondingly, the PXRD data (Figure 2c) also show the complete disappearance of the crystal diffraction peak of S 8 when the sulfur mass percentage reaches 80 wt %.…”

β-Triketones as Reactive Handles for Polymer Diversification via Dynamic Catalyst-Free Diketoenamine Click Chemistry

“…Conversely, the C�C/C�N associative metathesis process between a Knoevenagel compound and an imine has been introduced as a dynamic click chemistry for postpolymerization modification, allowing for room-temperature exchange (Figure 1B). 29 However, this rapid exchangeability may not be ideal for generating robust materials such as creep-resistant covalent adaptable networks. 30 β-Ketoesters have been popularized for their straightforward reactivity with amines to form β-ketoenamines, or vinylogous urethanes, which further undergo transamination in associative bond exchange.…”

“…32 Additionally, the subsequent dynamic exchange processes are illustrated: transamination involving vinylogous urethanes and a C�C/C�N associative metathesis process between a Knoevenagel compound and an imine. 29 (C) This work, wherein synthesis of vinyl polymers with pendent β-triketones is achieved using thermal RAFT and photoiniferter polymerization. These β-triketones subsequently undergo catalyst-free reactions with amines at ambient temperatures to form diketoenamines, which can then associatively exchange with amines through transamination.…”

“…Dynamic PPM approaches, which commonly employ imine groups, often suffer from poor hydrolytic stability. , Alternatively, O -alkyl hydroxylamines can yield more stable oxime linkages but their accessibility is limited. , Although the introduction of more stable dynamic linkages, such as Diels–Alder and thiol–Michael adducts, , enhances polymer properties, the substantial thermal requirements for facilitating dynamic exchange of such motifs limit their application in temperature-sensitive environments. Conversely, the CC/CN associative metathesis process between a Knoevenagel compound and an imine has been introduced as a dynamic click chemistry for postpolymerization modification, allowing for room-temperature exchange (Figure B) . However, this rapid exchangeability may not be ideal for generating robust materials such as creep-resistant covalent adaptable networks …”

“…(B) A focus on previously applied dynamic click chemistries, particularly β-ketoesters (teal) and Meldrum's acid (pink), for postpolymerization modification, showing how pendent βketoesters react with amines to form vinylogous urethanes31 and pendent Meldrum's acid reacts with aldehydes to form Knoevenagel adducts 32. Additionally, the subsequent dynamic exchange processes are illustrated: transamination involving vinylogous urethanes and a C�C/C�N associative metathesis process between a Knoevenagel compound and an imine 29. (C) This work, wherein synthesis of vinyl polymers with pendent β-triketones is achieved using thermal RAFT and photoiniferter polymerization.…”