Main‐Chain Fluoropolymers with Alternating Sequence Control via Light‐Driven Reversible‐Deactivation Copolymerization in Batch and Flow

Abstract

Polymers with regulated alternating structures are attractive in practical applications, particularly for main-chain fluoropolymers. We for the first time enabled controlled fluoropolymer synthesis with alternating sequence regulation using a novel fluorinated xanthate agent via a light-driven process, which achieved on-demand copolymerization of chlorotrifluoroethylene and vinyl esters/amides under both batch and flow conditions at ambient pressure. This method creates a facile access to fluoropolymers with a broad fraction range of alternating units, low dispersities and high chain-end fidelity. Moreover, a two-step photo-flow platform was established to streamline the in-situ chainextension toward unprecedented block copolymers continuously from fluoroethylene. Influences of structural control were illustrated with thermal and surface properties. We anticipate that this work will promote advanced material engineering with customized fluoropolymers.

Organocatalyzed Controlled Copolymerization of Perfluorinated Vinyl Ethers and Unconjugated Monomers Driven by Light

“…As shown in Figure A,B, for both comonomer pairs, the adoption of PC2 provided clearly faster reaction rates than PC1 (for VPi, k app = 0.61 h –1 vs 0.29 h –1 and for NVP, k app = 0.28 h –1 vs 0.18 h –1 ), and copolymerizations exhibited linear reaction kinetics. As influenced by the homo-addition of vinyl ester and vinyl amide, degrees of polymerization (DPs) for VPi and NVP are higher than PPVE during corresponding copolymerization processes (Figure C,D), which is consistent with observations in the photo-controlled copolymerizations of chlorotrifluoroethylene (CTFE)-VAc and CTFE-NVP pairs . For two reactions, the molecular weights of copolymers determined by size-exclusion chromatography (SEC) gradually rise with monomer conversions.…”

“…57,58 Based on the results, a hexafluoroisopropyl substituted xanthate (CTA 8) was further employed as inspired by the influence of the fluorophilicity effect. 9,59 The copolymerizations generated PPVE copolymers of low To promote the copolymerization, methoxynaphthalen substituted dibenzo[a, c]phenothiazine (PC2) was synthesized (Figure 2A, Scheme S1, Figures S2 and S3) by extending the conjugated structure of PTH. 31,40,60 Although PC2 displays decreased molar absorptivity at λ max (ε = 11,788 M −1 cm −1 at 345 nm for PC1 and ε = 5876 M −1 cm −1 at 353 nm for PC2, Figure 2B), it provides stronger reductivity in the photoexcited state (E ⊖ (PC •+ /PC*) = −2.05 V vs −1.94 V) and higher oxidative potential after donating an electron (E ⊖ (PC •+ /PC) = 0.89 V vs 0.76 V) when compared to PC1.…”

“…As influenced by the homo-addition of vinyl ester and vinyl amide, degrees of polymerization (DPs) for VPi and NVP are higher than PPVE during corresponding copolymerization processes (Figure 3C,D), which is consistent with observations in the photo-controlled copolymerizations of chlorotrifluoroethylene (CTFE)-VAc and CTFE-NVP pairs. 59 For two reactions, the molecular weights of copolymers determined by size-exclusion chromatography (SEC) gradually rise with monomer conversions. Although detected M n,SEC values are lower than calculated values (M n,calc , filled rhombuses in Figure 3E, eq S3), a multiangle laser light scattering (MALLS) detector was employed to measure the absolute molecular weights (M n,MALLS, empty rhombuses), providing M n,MALLS that are close to M n,calc results.…”

“…From CTAs 5 to 7 , the xanthates generate primary, secondary, and tertiary carbon radicals, respectively, during their activations by the photo-excited catalyst (PC*) and RAFT equilibrium. The gradually increased stability of carbon radicals retards polymerization and causes lowered monomer conversion. , Based on the results, a hexafluoroisopropyl substituted xanthate (CTA 8 ) was further employed as inspired by the influence of the fluorophilicity effect. , The copolymerizations generated PPVE copolymers of low dispersities ( D̵ = 1.14 for VAc and D̵ = 1.19 for NVP, entries 18 and 19) at moderate UCM conversions (58–63%).…”

RAFT-Mediated 3D Printing of “Living” Materials with Tailored Hierarchical Porosity

“…The “living” character of the 3D materials is offered by the incorporated RAFT functionalities within the constituting structure of 3D materials that are capable of reversibly deactivating the propagating polymer chains. , The dormant RAFT species can be reactivated (thermally or under light exposure) in a post-printing stage to allow spatiotemporal insertion of new monomers/polymers into the strands of existing 3D polymers, surface functionalization, ,, welding/self-healing, , and/or expansion of an already fabricated material. − From the viewpoint of sustainability and recyclability, materials that can undergo controlled changes in a post-printing stage can address the challenges associated with 3D-printed waste polymers and pave the way for future advancements and scaling-up of the 3D technology. Taking a step back, RAFT is a family of reversible deactivation radical polymerization reactions that has become progressively popular as it can offer controlled synthesis of well-defined polymer chains with high chemical fidelity, − micro- and nanoparticles of different architectures, surface functionalization, sequence-defined polymers, etc …”