Using the Permutive MailChimp integration you can keep Permutive segments synced with Interest Groups in MailChimp.
This means you can trigger emails when users enter / leave groups. Or have them in the correct groups when manually sending campaigns.
It's worth pointing out here, you might want to use Permutive Webhooks with MailChimp's webhook trigger, if you're looking to trigger workflows.
For help getting this method set up, get in touch.