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Cationic Polymerization Initiators

IP.com Disclosure Number: IPCOM000110762D
Original Publication Date: 1994-Jan-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 4 page(s) / 102K

Publishing Venue

IBM

Related People

Kuczynski, J: AUTHOR

Abstract

Disclosed is the use of organometallic amine complexes, as shown in Table 1, as photoinitiators for cationic polymerization. Examples of typical ligands are provided in Table 2. With these photoinitiators, exposure to visible light generates a relatively long lived (t > 0.5 microseconds) excited state that ultimately leads to the production of acid. The acid is capable of initiating polymerization of numerous cationically curable monomers, such as epoxies and vinyl ethers, used in photolithographic formulations.

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Cationic Polymerization Initiators

      Disclosed is the use of organometallic amine complexes, as
shown in Table 1, as photoinitiators for cationic polymerization.
Examples of typical ligands are provided in Table 2.  With these
photoinitiators, exposure to visible light generates a relatively
long lived (t > 0.5 microseconds) excited state that ultimately leads
to the production of acid.  The acid is capable of initiating
polymerization of numerous cationically curable monomers, such as
epoxies and vinyl ethers, used in photolithographic formulations.

      For more than a decade, onium salt photoinduced cationic
polymerization of epoxy resins, and other cationically curable
monomers, has been the industry mainstay [1].  Unfortunately, onium
salts are active only in ultraviolet light, requiring dye
sensitization to function at visible wavelengths [2].  An attractive
alternative to onium salt chemistry focuses on redox reactions of
organometallic complexes.  Oxidation of coordinated diamine complexes
of Ru(II)bis(bipyridyl) has been determined to readily occur at a Pt
electrode surface, as shown in Scheme 1 [3].

      Intramolecular oxidation of the bound diamine to the diimine
liberates a strong Bronsted acid, H+, capable of initiating cationic
polymerization of epoxy monomers.  For practical applications,
electrochemical oxidation of the organomatallic complexes is not
feasible.  However, photoinduced electron transfer reactions of
Ru(II)tris(bipyridyl) with suitable receptors have been extensively
used in energy storage systems, as shown in Scheme 2 [4].

      The absorbtion maximum of Ru(II)tris(bipyridyl) in acetonitrile
solution is 450 nm, clearly in the visible region of the spectrum.
In the systems depicted in Scheme 2, the Ru(III) cation is invariably
repaired with an appropriate el...