Tethering vapor-phase deposited GLYMO coupling molecules to silane-crosslinked polyethylene surface via plasma grafting approaches

Abstract

Herein, an attempt was made to deposit and graft GLYMO (3-glycidyloxypropyltrimethoxysilane) self-assembled layers on silane-crosslinked polyethylene (Si-XLPE). The principal objective was to create an anchoring layer on the pristine surface of Si-XLPE to modify its poor surface bonding properties. Since attachment of the GLYMO self-assembled layers to the partially non-polar surface of Si-XLPE seemed challenging, plasma post-irradiation and syn-irradiation grafting methods were utilized separately for activating the substrate and the deposited GLYMO molecules to provide the necessary condition for grafting and fabrication of uniform self-assembled layers. According to surface chemistry analyses, plasma grafting methods appeared to be beneficial tools for enhancing grafting of GLYMO molecules and reducing the self-condensed GLYMO aggregates and its self-assembled multilayer structures. Morphology investigations confirmed the positive role of plasma grafting in decreasing the self-condensed aggregated GLYMO structures on the surface. Moreover, GLYMO plasma grafting flattened the surface owing to the special orientation of the deposited molecules during the grafting and plasma etching. Surface wettability studies, along with chemistry outcomes, demonstrated the tendency of GLYMO molecules to tether to the surface with their trimethoxysilane groups, while their closed epoxide rings aligned to the out of surface. Overall, the plasma post-irradiation grafting approach exhibited higher grafting density.