Crosslinking Overview

When it comes to polymers, “crosslinking” simply means adding bonds between polymer chains to join them together, improving the rigidity and mechanical properties of the polymer. Crosslinking can also be used in this way to functionalize polymer surfaces, making them more receptive to adhesives, dyes and coatings. While there are many ways to crosslink polymers, each is typically custom designed for a specific polymer. XlynX’s goal was to develop a way to crosslink almost any polymer, even nonfunctionalized or unreactive polymers, in a controlled manner using a single set of conditions.

The Wulff Group at the University of Victoria, headed by Professor Jeremy Wulff, took their cue from chemical biologists who have been using diazirines for decades to attach small molecules to proteins. Wulff and his team took this concept and designed a molecule that could attach itself in two places at the same time. After successfully demonstrating the exceptional crosslinking ability of their new molecule on a number of different polymers (including polypropylene, a saturated hydrocarbon polymer with very low functionality), it was clear that this breakthrough could have wide-ranging practical and commercial implications.

How Diazirines Work

Diazirines are three-membered rings with one carbon and two double-bonded nitrogen atoms.

On exposure to near UV-light or moderate heat, diazirines rapidly break down into carbenes, which insert themselves into C–H, N–H, and O–H bonds. When two diazirine units are present in a single molecule, the resulting bis-diazirine acts as a crosslinker, covalently bonding two polymer chains together at the same time.

Diazirines react with even the most unreactive polymers, such as polyethylene and polypropylene, functionalizing surfaces and textiles for a variety of purposes: forming strong bonds, adding material strength and making materials responsive to dyes and coatings.

Research Papers