Controlled radical initiators, such as ATRP or RAFT initiators, have become commonplace for the synthesis of a variety of polymeric materials. The use of these initiators allows one to more easily control the molecular weight and/or the polydispersity of the resultant solution polymers. Attachment of controlled radical initiators to solid substrates, however, is quite difficult, involving multiple synthetic steps, and is often very substrate dependent. We have designed a simple method for attachment of RAFT agents or iniferters to membranes and other solid substrates by taking advantage of the hydrogen abstracting ability of Type II photoinitiators such as benzophenone. Irradiation of nylon membranes coated with a solution of benzophenone and a xanthate-functional compound results in H-abstraction from the membrane surface. The free radical is trapped by transfer of the xanthate ester, resulting in a xanthate-functional membrane. This reaction process can be extended to other types of thiocarbonylthio-containing agents, such as dithioesters, dithiourethanes, and trithiocarbonates. E-beam irradiation provides an alternative and simple mechanism for generating radicals on substrates, which can subsequently be trapped by an appropriate thiocarbonylthio-containing compound. The functionalized substrates can be coated with free radically polymerizable monomers, then irradiated with UV or LED sources, to provide polymer-grafted substrates. We have grafted a variety of ionic monomers out of aqueous solution to provide ion exchange membranes for protein purification applications. However, a variety of other applications can be envisioned, and the entire process is potentially amenable to roll-to-roll manufacturing operations.

Polymeric substrates with attached controlled radical initiators

2019 Spring National Meeting

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