Super Photo-base initiated organic-inorganic hybrid coatings by plural-cure mechanism Himanshu Manchanda and Vijay Mannari, Eastern Michigan University, USA Abstract: Free Radical polymerisation forms the core chemistry of a majority of UV curable coatings produced today. Rapid curing at ambient temperatures using stable, single pack coating systems form the key value proposition that such coatings offer. However, owing to their limitations such as oxygen inhibition, shrinkage, toxicity profiles of reactive diluents (RD), and the limited chemistry available, efforts are being made to counter these challenges by innovating and exploring new systems that have the potential to replace the existing chemistries. Anionic polymerisation is one such promising area that has the potential to introduce a wide variety of chemistries in the field of UV curable coatings. A significant stride in this field has been the innovation of photo-labile bases in the UV industry and the diverse chemistries that these bases have brought to fore. The primary focus of this study is to employ a super photo-base generator (PBG) in catalysing concomitant but independent reactions to develop organic-inorganic hybrid (OIH) coating networks by leveraging plural-cure chemistry. The super PBG has been used to initiate both Michael-addition (MA) reaction and sol-gel reaction concurrently, upon exposure to the UV source. Coatings have been formulated using uniquely designed acrylic oligomers (MA-acceptor), acetoacetate functional reactive diluents (MA-donors) and organo-silanes (sol-gel precursors), besides super PBG. The study highlights many technical and environmental benefits of these OIH coatings with potential for applications in advanced coatings and additive manufacturing. Introduction: The drive to make VOC-free coatings has paved the way for new coating technologies such as waterborne, powder coatings, UV-cure coatings etc. UV cure coatings present a striking balance of opportunities and challenges, with efforts being made each year to come up with innovative solutions to offset the latter while at the same time maintaining or improving the former. While rapid curing at ambient temperature forms the single-most important advantage these coatings offer, the phenomenon of oxygen inhibition, shrinkage, poor adhesion and the inherent inability to cure thicker films limit the out-reach of UV–curable coatings as compared to other coating systems. While several approaches are being developed to deal with these issues, a satisfactory approach eliminating all these challenges is yet to be found [1-3]. A novel approach to offset these limitations has been found by exploiting chemistries that form cross- linked networks using photo-triggered base catalysed reactions instead of photo-induced free-radical polymerisation. The mechanism of base-catalysed polymerisation eliminates the usage of free- radicals by using anions and therefore, the problem of oxygen inhibition is directly solved [2-5]. Efforts are being made to use such chemistries and contain problems such as high shrinkage and poor adhesion to metals. The photo-latent base (PLB) catalysts that have lately been developed for use in the UV curing industry use tertiary amines that are modified with alkyl or benzyl groups. Sufficient literature on photo-latent primary amines is available too, however, they find limited usage in catalysing addition/condensation reactions. Crosslinking reactions requiring amines of higher basicity than tertiary amines use amidines such as DBU (1, 5-diazabicyclo [4.3.0] undec-5-ene) and DBN (1, 5-diazabicyclo [4.3.0] non-5-ene). These bases are known to have basicity of a magnitude of 12-13 [4, 5]. The use of these bases as photolatent precursors was initially made possible through the use of their corresponding ketoprofen salts. But owing to their insufficient stability, the research is now underway to come up with non-ionic photo-base generators that release DBN or DBU upon UV exposure [2-6].