Blend compatibilizers for alkyne-containing hydrogen “getters” in crosslinked siloxanes

Abstract

Low molar mass multi-alkynes, commonly called hydrogen getters, continue to receive attention due to their ability to irreversibly sequester hydrogen gas in sensitive environments such as ultra-high vacuum and electronics. 1,4-bis(phenylethynyl)benzene (DEB) bisalkyne offers suitable reactivity as an evaporable getter due to efficient stoichiometric hydrogen uptake. However, as expected, poor dispersibility in polymer matrices and crystallization upon hydrogenation restrict DEB to powdered form factors. Compatibilizers will promote a more homogeneous dispersion throughout non-polar polymeric networks. Thus, this research employs styrenic graft copolymers to effectively disperse DEB. Free radical copolymerization of styrene with a poly(dimethyl siloxane) macromonomer (PDMS-MM) of varying molecular weights (1k and 5k) afforded effective graft copolymer compatibilizers. Furthermore, facile hydrosilylation of styrene with a hydride-terminated PDMS-MM provided an alternative phenethyl-PDMS MM 1k low molar mass compatibilizer that also effectively promoted DEB dispersion. Both high molecular weight styrenic graft copolymers and low molecular weight siloxane compatibilizers were suitable to disperse alkyne-containing hydrogen scavengers in siloxane networks.