Expanding the Alternating Propagation–Chain Transfer-Based Polymerization Toolkit: The Iodo–Ene Reaction

Abstract

Analogous to the thiol−ene and phosphane−ene polymerizations, radical-mediated iodo−ene reactions are described here that proceed via alternating propagation and chain transfer (i.e., APT) reactions between perfluoroiodide-and vinyl-bearing monomers. The thermal polymerization of a diiodo/tetraene formulation yielded a cross-linked, homogeneous polymer that was approximately seven times as radiopaque as aluminum owing to its high iodine content. Visible-light photopolymerizations of model iodo−ene monomers were monitored using mid-IR spectroscopy, revealing that the perfluoroiodide functional group consumption exceeded that of the vinyl, a discrepancy that decreased with increasing irradiation intensities and hence polymerization rates. The functional group conversions in resin formulations with a large initial perfluoroiodide excess exacerbated secondary side reactions that led to off-stoichiometric functional group consumption; nevertheless, photopolymerization of resin formulations with excess vinyl stoichiometry proceeded according to the ideal APT mechanism.

Growth of a Surface-Tethered, All-Carbon Backboned Fluoropolymer by Photoactivated Molecular Layer Deposition

“…Between monomer exposures, unreacted monomer vapors are purged away to avoid continuous polymerization onto the surface. This sequential process of monomer dosing and purging allows for monomer-by-monomer polymerization of the fluoropolymer. ,− …”

“…68,69 However, other studies indicate that secondary alkyl iodides are less likely to undergo ITP, depending on the reaction conditions used. 33,34 Reactions (b) and (c) result from the next dose of DIOFB without a cyclization step. The DIOFB may bond either to the C−I within the chain (b) or to the terminal alkene (c).…”

“…Polymerization can continue by reinitiating a radical by C−I cleavage; however, as noted previously, secondary alkyl iodides are potentially less favorable to react. 33,34 Pathway (c) occurs with another C−I addition to the terminal alkene by ITP reaction, resulting in a linear chain. Linear chain formation between diiodoperfluoroalkyl and dienes has also been reported.…”

Silane–Acrylate Chemistry for Regulating Network Formation in Radical Photopolymerization

“… 19 However, drawbacks such as strong odor of thiols 20 and limited storage stability of the thiol–ene formulations 21 , 22 have motivated further development of these materials. Inspired by thiol–ene chemistry and its vast potential, phosphane–, 23 germane–, 24 and iodo–ene 25 polymerizations have recently been introduced as possible alternatives.…”

Light-Triggered Radical Silane-Ene Chemistry Using a Monosubstituted Bis(trimethylsilyl)silane

“…Powerful alternatives to the thiol‐ene approach have been developed with the implementation of phototriggered copper catalysed alkyne‐azide cycloaddition or addition fragmentation chain transfer reagents (e.g., β‐allyl sulfides, β‐allyl sulfones, and vinyl sulfonate esters) yielding a rapid formation of bulk photopolymers without the aforementioned drawbacks. Additionally, phosphane‐ene and iodo‐ene chemistry have been investigated as powerful concepts for new crosslinked photopolymer networks. All of these approaches show great potential for the formation of new spatially resolved functional materials.…”