Does KPS oxidize the pyridine ring during radical-initiated polymerization of 4-vinylpyridine?

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In our current system, the use of KPS as an initiator, with water as the solvent, results in polymers of 4-vinylpyridine with a good morphology; therefore, we are considering further developing this approach. However, we are facing one problem: the IR data of the synthesized poly-4-vinylpyridine always show a weak N→O vibration. Since it was previously found that oxygen in the air can rapidly oxidize the pyridine ring during the polymerization reaction, we employed a method involving the introduction of large amounts of nitrogen gas over an extended period to remove oxygen. Yet even with this approach, this pyridine oxidation vibration cannot be completely eliminated – although it appears as a weak peak in the IR spectrum, it can still be detected. This leads us to speculate that KPS, in addition to acting as an initiator for homolytic polymerization, also functions as an oxidizing agent. However, to date, no valuable information has been found regarding KPS’s ability to oxidize 4-vinylpyridine; thus, this hypothesis remains at the theoretical level only. Does anyone have more knowledge on this issue? We would appreciate any guidance you can provide. Thank you