Photochemically Enabled Iodine Degenerative Transfer Controlled Radical Homo- and Block Copolymerization of Vinylidene Fluoride at Ambient Temperatures with Mn₂(CO)₁₀and Visible Light

Universal Group 14 Free Radical Photoinitiators for Vinylidene Fluoride, Styrene, Methyl Methacrylate, Vinyl Acetate, and Butadiene

“…To verify the free radical nature of the polymerization (FRP), a set of reactions using [VDF]/[Me 6 Sn 2 ] = 25, 50, 100 and [VDF]/[Bu 6 Sn 2 ] = 50 were investigated kinetically in acetone under BLB irradiation at 40 °C (Table S1, Figure ). As expected, M n remained independent of conversion ( M n ∼ 4–5000) with rather narrow PDI values of ∼1.3–1.5, partially attributable to MeOH precipitation of oligomers. ,− , Interestingly, both M n and the reaction rates ( k p ,Me6Sn2 app = ∼6 × 10 –2 h –1 , k p ,Bu6Sn2 app = ∼2 × 10 –2 h –1 ) remained relatively independent of the [VDF]/[Sn] ratio. However, despite a superficial resemblance with the cobalt hydride mediated catalytic chain transfer polymerization of acrylates, R 3 Sn· does not act catalytically as a dual H abstractor and donor vs the solvent, VDF, or PVDF.…”

“…As expected, M n remained independent of conversion (M n ∼ 4−5000) with rather narrow PDI values of ∼1.3−1.5, partially attributable to MeOH precipitation of oligomers. 1,[39][40][41][42][43][44][45][46]53 Interestingly, both M n and the reaction rates…”

“…The assignments of typical PVDF–FRP peaks were made as previously described. ,− ,− Since VDF propagation involves both 1,2 and 2,1-additions, the backbone head–tail (H–T) and head–head (H–H) units are seen (Figures and S1–S7) as −CF 2 –[C H 2 –CF 2 −] n –CH 2 – ( a H , δ = 2.8–3.1 ppm) and −CF 2 –C H 2 –C H 2 –CF 2 – ,,, ( a ′H , δ = 2.3–2.4 ppm) in 1 H NMR and, respectively, as −CH 2 –CF 2 –[CH 2 – CF 2 ] n –CH 2 –CF 2 – ( a F , δ = −91.3 ppm) and −CH 2 – CF 2 –CH 2 – CF 2 – CF 2 –CH 2 –CH 2 – CF 2 –CH 2 –CF 2 – ( a ′F , δ = −113.5 ppm, a 1 ′F , δ = −115.9 ppm, a 2 ′F , δ = −95.1 ppm, and a 3 ′F , δ = −91.7 ppm) in 19 F NMR.…”

“…In fact, the very reactive PVDF • abstracts H from solvent (S–H), forming PVDF–H and solvent radicals (S • ), which if reactive enough, may add to VDF and reinitiate polymerization as S–PVDF • (i.e., chain transfer to solvent, Scheme ). − As such, H abstraction by the ∼CH 2 –CF 2 • and ∼CF 2 –CH 2 • radicals, respectively, affords the corresponding ∼ CF 2 –CH 2 – CF 2 –H ( d H , tt, δ = 6.3 ppm, 3 J HH = 4.6 Hz, 2 J HF = 54.7 Hz, d F , δ = −114.7 ppm, d 1 F , δ = −92.4 ppm) and ∼CH 2 – CF 2 –CF 2 – CH 3 ( d ′H , t, δ = 1.80 ppm, 3 J HF = 19.2 Hz, d ′F , δ = −108.2 ppm, d 1 ′F , δ = −114.1 ppm) PVDF–H chain ends.…”

“…Encouraged by initial rt VDF free radical polymerizations (FRP) initiated by t butyl peroxide under UV irradiation, we subsequently investigated a large number of other photochemical means of radical generation and trapping , under the visible light of low wattage (<30 W) white fluorescent bulbs. ,− This work led to first examples of rt free- and controlled radical photopolymerizations (FRP and IDT-CRP) initiated from alkyl, semi- and perfluorinated halides (Cl, Br, I) in the presence of photolabile transition metal carbonyl complexes (e.g., Mt 2 (CO) 10 , Mt = Mn, Re, etc. ), − as well as from photolabile hypervalent iodide carboxylate initiators (e.g., (CX 3 COO) 2 IPh, X = H, F), alone, or with I 2 or perfluoroalkyl iodides. The synthesis of well-defined PVDF block copolymers was likewise elaborated in the presence of a series of photolabile transition metal dimers. , …”