J. Sep. Sci. 2017, 40, 2170–2177
DOI: 10.1002/jssc.201601376
The cover picture shows the distinction between packing chromatographic particles that are already modified with polymer (left) vs. packing particles modified with only a small‐molecule initiator for polymerization (right). For the latter, the in situ polymer occurs by adding the monomer and catalyst after packing is complete. The idea is that polymer‐modified particles would pack with softer, mechanically unstable contacts between particles, whereas particles bearing only a small‐molecule initiator would pack with stable hard‐sphere contacts. This idea was tested here, confirming higher column stability for the case of in situ polymer growth. Specifically, a silane initiator bearing a benzyl chloride initiator was used in both cases to grow a polyacrylamide layer by atom‐transfer radical polymerization. In situ polymer growth was performed by pumping reagents into the column after packing, and the polymer growth was monitored by the gradual increase in column back pressure. A polyacrylamide film on the order of 20 nm in thickness was obtained for both the ex situ and in situ growth, and the in situ growth was found to reduce bed collapse. In addition, hydrophilic interaction chromatography of a model glycoprotein, ribonuclease B, gave higher resolution for the in situ growth.