UV curing of epoxy functional hybrid silicones

Abstract

Several epoxy difunctional hybrid alkylene‐silicone telomers with different silicone characters and organic spacers (linkers) were prepared via the platinum‐catalyzed polyhydrosilylation of α,ω‐dihydrosiloxanes and α,ω‐dienes. Thereafter, the resulting SiH‐terminated prepolymers were terminally functionalized with 4‐vinyl‐1,2‐epoxycyclohexane or allyl glycidyl ether. In the presence of a lipophilic cationic photoinitiator, the terminally epoxy‐functionalized hybrid alkylene–silicone telomers were photopolymerized to give crosslinked, soft, elastomeric, and transparent films. The progress of the photoinitiated cationic ring‐opening epoxide polymerizations was monitored using optical pyrometry. Potential applications for these novel photocurable epoxy‐functional telomers are as modifiers for UV curable coatings, printing inks, adhesives, and release coatings. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Sequential Functionalization of a Natural Crosslinker Leads to Designer Silicone Networks

“…Crosslinking compounds 2 with telechelich ydrosilicones in the presence of Karstedt's Pt catalyst in the same pot (without workup)l ed to bubble-free elastomers of type 3 (Scheme 3ACF,T able 1). These experiments showedt hat the presence of B(C 6 F 5 ) 3 did not affect the catalytic behavior of the platinum catalyst;w ithoutp latinum, hydrosilylation was not observed.…”

“…The platinum catalysti ns tep 2d oes not appear to be affectedb y the presence of B(C 6 F 5 ) 3 and C=Ch ydrosilylation was observed. However, the PR reactioni ns tep 3w as slower than other PR reactions, suggesting boron catalyst degradation or inhibition along the way, but addition of as econd bolus of BCF without any intervening workup led to cleanr eaction in the same pot.…”

“…The resulting networks reflect the specific batch of pendant-functional polymers used. It is, therefore, difficult to reproducibly preparep recise networks from commercial materials.It is possible to create networks containing av ariety of silicone precursors in as omewhat controlledm anner by using ac ombinationo fo rthogonal cure technologiess elected from silicone and organic chemistry;d ual cure systemst hat combine any of the cure technologiesn oted above with amine/ epoxy, [2] cationic epoxy polymerization, [3] thiol-ene click, [4] or azide/alkyne click [5] allow complex network materials to be prepared. Most of thesep rocesses, however,s till suffer from random placement of crosslinking groups along as ilicone backbone.…”

“…In all cases, the complexf ormed between B(C 6 F 5 ) 3 (BCF) and ah ydrosilane reacts with siloxonium ions to form siloxane bondsa nd either H 2 or an alkane (RH) byproduct (shownf or phenolics, Scheme 2B). BCF will also catalyzet he hydrosilylation reaction with alkenes, [9] but only using high concentrations of catalyst ( % 5mol %).…”

“…Eugenoli sareadily available organic material extracted from cloves and other plants. [10] It has three different functional groups that should react with SiH with very different efficiencies using either platinum catalysts or B(C 6 F 5 ) 3 .P latinums hould preferentially promote SiH reactions with RHC=CH 2 groups, and react much less efficientlyw ith ArOH, [11] while BCF will catalyze reactions between SiHa nd ArOH or ArOMe, respectively. Use of this crosslinker would allow up to three different silicones to be sequentially linked to the central aromatic core, permitting the preparation of precise networks from commercial telechelic silicones;t he products' properties could be tuned by selection of the chain lengths of the three silicones, backbone functionalization, and which silicone chain grafts via hydrosilylation.…”