Utilizing exfoliated clay–poly(norbornene) nanocomposite prepared by metal-mediated surface-initiated polymerization as model end-tethered polymers on an organoclay substrate

Abstract

Current interest in dispersion strategies for nanoparticle fillers is driving research into covalently attached polymer brushes. The primary need for these “hairy nanoparticles” is for testing and developing new technologies based on polymer nanocomposites. To that end, we have prepared polymer nanocomposites with covalently tethered chains on a naturally occurring montmorillonite clay template via a metal-mediated surface-initiated ring opening metathesis polymerization approach. The nanocomposites were characterized in terms of polymer:clay composition and of various chain architecture parameters such as molecular weight, polydispersity index, and grafting density.

Surface Chain-Transfer Ring-Opening Metathesis Polymerization

“…Surface-initiated polymerization (SIP) has been widely used for surface modification because it affords high graft density, − controllable graft thickness, − well-tuned surface characteristics, , and the possibility of secondary polymerization. , Among various types of SIP methods, surface-initiated ring-opening metathesis polymerization (SI-ROMP), first reported in 1999 by Weck et al, allows for the grafting of olefinic backbones to the surface and attracts great research attention. Different types of ROMP monomers including norbornenes, , cyclooctenes, , cyclooctadienes, , cyclopentenes, , as well as macromonomers with norbornenes end-groups, , are used for surface modification via SI-ROMP. Linear, branched, and bottlebrush polymers are grafted to substrates like gold nanoparticles, clays, silica nanoparticles, silica wafers, etc., to afford unique surface structures and properties. ,− …”

“…However, grafting the catalyst and monomer to the surface via SI-ROMP requires multiple synthetic steps. The commonly adopted norbornenyl silane substrates for catalyst grafting are not commercially available and must be synthesized first . Besides, the olefin metathesis between surface grafted olefin and the catalyst must be controlled carefully to achieve a stoichiometric reaction, otherwise the surfaces would be linked together that could hinder further modification reactions .…”

“…The commonly adopted norbornenyl silane substrates for catalyst grafting are not commercially available and must be synthesized first. 12 Besides, the olefin metathesis between surface grafted olefin and the catalyst must be controlled carefully to achieve a stoichiometric reaction, otherwise the surfaces would be linked together that could hinder further modification reactions. 29 Therefore, developing a different surface ROMP method with fewer steps and enhanced efficiency should be beneficial and promising for practical applications.…”