Cu(0)/2,6-bis (imino)pyridines catalyzed single-electron transfer-living radical polymerization of methyl methacrylate initiated with poly(vinylidene fluoride-co -chlorotrifluoroethylene)

PVDF-Based Fluoropolymer Modifications via Photoinduced Atom Transfer Radical Polymerizations

Graft modifications of PVDF fluoropolymers have been identified as the efficient route to improve the properties and expand the applications. Taking advantage of C-F and C-Cl bonds in the repeat units, atom transfer radical polymerizations (ATRP) were widely used for graft modification. Recently, photoinduced ATRP has shown good spatial and temporal control over the polymerization process in contrast to thermal activation mode. This minireview highlights the progress in PVDF-based fluoropolymer modifications by using photoinduced Cu(II)-mediated ATRP and organocatalyzed ATRP. The challenges and opportunities are proposed with the aim at advancing the development of synthesis and applications of fluoropolymer.

Photoinduced Cu(II)-Mediated RDRP to P(VDF-co-CTFE)-g-PAN

Photoinduced Cu(II)-mediated reversible deactivation radical polymerization (RDRP) was employed to synthesize poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-polyacrylonitrile (P(VDF-co-CTFE)-g-PAN). The concentration of copper catalyst (CuCl₂) loading was as low as 1/64 equivalent to chlorine atom in the presence of Me₆-Tren under UV irradiation. The light-responsive nature of graft polymerization was confirmed by "off-on" impulsive irradiation experiments. Temporal control of the polymerization process and varied graft contents were achieved via this photoinduced Cu(II)-mediated RDRP.

Poly(vinylidene fluoride-co-chlorotrifluoroethylene) Modification via Organocatalyzed Atom Transfer Radical Polymerization

To address the challenge of metal contamination, a "graft from" approach via organocatalyzed atom transfer radical polymerization (O-ATRP) is developed to synthesize poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) graft copolymers. N-phenylphenothiazine is utilized as a model organic photoredox catalyst for catalyzing the (co)polymerization of methyl methacrylate (MMA), methacrylate (MA), and n-butyl acrylate (BA). By employing this technique, high temporal control of polymerization and graft content are achieved. A series of P(VDF-co-CTFE)-g-PMMA, P(VDF-co-CTFE)-g-PMA, and P(VDF-co-CTFE)-g-PBA is prepared under mild conditions. The resultant graft copolymer can be used as macroinitiator to re-initiate O-ATRP to synthesize P(VDF-co-CTFE)-g-(PMMA-b-PMA), which might exhibit the potential application as novel dielectric material.

Recent Developments in the Synthesis of Biomacromolecules and their Conjugates by Single Electron Transfer-Living Radical Polymerization

Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile tool for the synthesis of vinyl polymers with well-defined topology and chain end functionality. The crucial step in SET-LRP is the disproportionation of the Cu(I)X generated by activation with Cu(0) wire, powder, or nascent Cu(0) generated in situ into nascent, extremely reactive Cu(0) atoms and nanoparticles and Cu(II)X₂. Nascent Cu(0) activates the initiator and dormant chains via a homogeneous or heterogeneous outer-sphere single-electron transfer mechanism (SET-LRP). SET-LRP provides an ultrafast polymerization of a plethora of monomers (e.g., (meth)-acrylates, (meth)-acrylamides, styrene, and vinyl chloride) including hydrophobic and water insoluble to hydrophilic and water soluble. Some advantageous features of SET-LRP are (i) the use of Cu(0) wire or powder as readily available catalysts under mild reaction conditions, (ii) their excellent control over molecular weight evolution and distribution as well as polymer chain ends, (iii) their high functional group tolerance allowing the polymerization of commercial-grade monomers, and (iv) the limited purification required for the resulting polymers. In this Perspective, we highlight the recent advancements of SET-LRP in the synthesis of biomacromolecules and of their conjugates.

Direct surface modification of poly(VDF-co-TrFE) films by surface-initiated ATRP without pretreatment

A NMR study revealed that the surface-initiated ATRP of tBA occurred due to fluorine abstraction from the TrFE units of poly(VDF-co-TrFE).

Continuous flow SET-LRP in the presence of P(VDF-co-CTFE) as macroinitiator in a copper tubular reactor

A green, highly effective and energy-saving route to the grafting modification of P(VDF-co-CTFE) was developedviacontinuous flow SET-LRP with significant advantages over batch reactors.