Fluoropolymers have found broad applications
for many decades.
Considerable efforts have focused on expanding access toward main-chain
fluorinated polymers. In contrast to previous polymerizations of gaseous
fluoroethylenes conducted at elevated temperatures and with high-pressure
metallic vessels, we here report the development of a photoorganocatalyzed
reversible-deactivation radical alternating copolymerization of chlorotrifluoroethylene
(CTFE) and vinyl ethers (VEs) at room temperature and ambient pressure
by exposing to LED light irradiation. This method enables the synthesis
of various fluorinated alternating copolymers with low Đ and high chain-end fidelity, allowing an iterative switch of the
copolymerization between “ON” and “OFF”
states, the preparation of fluorinated block alternating copolymers,
as well as postsynthetic modifications.
Continuous-flow chemistry represents
a robust setting for photochemical
reactions. We have developed the first computer-aided droplet-flow
platform for photocontrolled radical polymerization. This method allows
precise and scalable living polymerizations of monomers at high concentrations
in flow, even when solids are generated. The consistent good performance
of polymerization during the programmed change of reaction conditions
demonstrates the reliability and utility of this method. Furthermore,
the droplet-flow approach not only streamlines an automated high-throughput
living polymerization (275 droplets of samples in 11 min), which enables
the rapid generation of copolymer libraries for low-cost structure–property
relationship screening, but also allows on-line switching to desirable
reaction conditions for the scale-up (co)polymerization purpose.
Aromatic sulfonyl halides are readily accessible from many sources. With newly synthesized N-arylphenothiazine catalysts, organocatalyzed photoredox polymerization has been developed with arylsulfonyl halides initiators using white or purple LEDs light sources. This method allows the preparation of poly(meth)acrylates and poly(meth)acrylamides possessing a broad scope of (hetero)aryl chain ends without metal-contamination concern. Investigations such as MALDI-TOF analysis, chain extension, and "ON/ OFF" control experiments confirmed the fidelity of the polymer structure and reliability of this method. Moreover, this method facilitates the two-step preparation of brush polymers from polystyrene through an electrophilic aromatic substitution/ organocatalyzed photopolymerization sequence.
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