Perfluoropolyalkylether Maleimides for Protection From Oxygen Inhibition and Surface Modification of Photoinitiator-Free UV-Cured Polymers

Abstract

Maleimides are attractive systems for photopolymerize for two major reasons: (1) they follow a radical mechanism without requiring a photoinitiator and (2) their rate of polymerization corresponds similarly to acrylates, which are commonplace in the industry. In this work, bismaleimide polypropylene oxide was cured under UV light forming thin films. Their surface properties were modified by copolymerization them with fluorinated comonomers. To this goal, perfluoropolyalkylethers (PFPAEs) with maleimide groups were synthesized, varying their chain structure, their functionality degree and consequently their intrinsic viscosity. These PFPPAE comonomers were highlighted to segregate at the surface, assuring omniphobic properties and acting as a protective layer against oxygen inhibition. These phenomenon were observed even when added at a concentration ≤5% w/w with respect to the main polypropylene oxide monomer. XPS analyses confirmed the segregation of the fluorine atoms at the surface during the UV-curing process of the coatings.

Diversity of Synthetic Approaches to Functionalized Perfluoropolyalkylether Polymers

“…In a similar manner to α,β-unsaturated ester PFPAEs, maleimide PFPAEs were afforded via the same Steglich esterification conditions to afford photoreactive macromonomers that do not require a photoinitiator to cure (Scheme ). , The absence of photoinitiator would be a main advantage in the industry, and they would easily compete with methacrylate-type monomers more sensitive to oxygen inhibition. Nonetheless, their use for other applications besides microfuluidics could be foreseen, because they possessed better thermal stability, for example.…”

“…Nonetheless, the insulation created by the insertion of ethylene oxide units (Fluorolink or Fomblin ZDOLTX) between the electron-withdrawing effect of the fluoropolymer (Fomblin ZDOL) and the alcohol group provides similar reactivity to hydrogenated alcohols. Consequently, in recent years, Fluorolink products were widely used. ,,,, …”

“…Priola et al in 1997 released the first paper describing the photoinduced radical polymerization of PFPAE methacrylates, obtaining polymers suitable for protective coatings . In the following years, many publications of the same group have been dealing with the photoinduced copolymerization of PFPAE derivatives. ,,− It has also been demonstrated the photopolymerization of PFPAEs bearing other functional groups than methacrylates such as maleimides , and α,β-unsaturated esters in combination with a vinyl ether PFPAE . As for methacrylates, their mechanism is radical; however, it is worthwhile to quote that the photopolymerization of epoxy and alcohol PFPAEs was performed through a cationic mechanism. ,, …”

A review on self-initiated and photoinitiator-free system for photopolymerization

“…Because of its remarkable properties, they find application in protective coatings, quick-setting adhesives and composites [116]. A wide range of applications is derived by modifying the acceptor monomer [36,123] or combining both acceptor and donor group in the same molecule [124] or by replacing it with acrylates/acrylic acid depending on aimed properties [122]. Electron donor/acceptor concept is used in photopolymerization application for the development of hydrogel [118], coating, adhesive [118], interpenetrating penetrating network [120], hydrogel [121] and for the development of composite [119], etc.…”

Novel perfluoropolyalkylethers monomers: synthesis and photo-induced cationic polymerization

“…For these reasons, PFPAEs have previously been explored containing functionalization with acrylic [23,24], methacrylic [10,[25][26][27][28], or maleimidic [29,30] end-groups to be used in radical photopolymerization. It is well known that this process suffers from oxygen inhibition; this drawback is even more severe for fluorinated products, as they show a high oxygen solubility.…”