Can you disconnect iMessage from multiple devices?

You can do it by getting a different AppleID for your work phone.

You can still have the same iTunes Store account on both phones so you can share apps and purchases. But you'll have to create a different AppleID and log into iCloud with it on your work phone. You will however end up with separate Contacts on both phones....modifying one won't change the other, etc.

 

Messages > Preferences > Accounts > Settings: "You can be reached for messages at:" There will be check-boxes for each phone number and email address. Un-check the business phone number.