Free Radical Induced Acceleration of Cationic Photopolymerization

Abstract

Two new monomers based on R-terpineol were prepared, allyl R-terpineol ether epoxide (III) and 1-propenyl ether R-terpineol epoxide (IV). The photoinitiated cationic polymerizations of these two monomers as well as two model compounds, 1-propenyl R-terpineol ether and methyl R-terpineol ether epoxide, were studied using real-time infrared spectroscopy. Surprisingly, the rates of epoxide ring-opening polymerization of both monomers were greatly enhanced as compared to the model compounds. At the same time, the rate of polymerization of the 1-propenyl ether groups in IV was depressed. Two different mechanisms which involve the free radical induced decomposition of the diaryliodonium salt photoinitiator were proposed to explain the rate acceleration effects.

Interaction of epoxy and vinyl ethers during photoinitiated cationic polymerization

“…We call such compounds hybrid monomers. In three recent papers, [7][8][9] we reported that cycloaliphatic epoxy monomers bearing 1-propenyl ether groups with the structures shown below undergo photoinduced cationic epoxide ring-opening polymerization at anomalously high rates.…”

Supramolecular diaryliodonium salt‐crown ether complexes as cationic photoinitiators

“…Diaryliodonium salts are oxidants with low reduction potentials. Several research groups30–35 have taken advantage of this fact by using easily oxidized free radicals generated by both Norrish Type I and II photoreactions to generate a cationic initiating species by the chemical reduction of a diaryliodonium salt. For example, unimolecular free radical photoinitiators such as 2,2‐dimethoxy‐2‐phenylacetophenone (Irgacure 651) undergo efficient photolysis by a Norrish I type α‐cleavage reaction as shown in eq 9 of Scheme to afford the benzoyl ( VI ) and dimethoxyphenylmethyl radicals ( VII ).…”

Successful UV‐Induced RICFP of Epoxy‐Composites

“…[12][13][14] The self-sustaining propagation of the FP toward the formulation thickness is ensured by thermal decomposition www.advancedsciencenews.com www.mcp-journal.de kept at high vacuum (about 0.03 mbar) for at least 3 h until bubble formation had ceased. The apparatus developed by Bomze et al was used for the RICFP setup.…”