Password Determined Redirect?

Setting up marketing library for 4 clients behind one login page, but I don't want them to be able to see each other's content.  There's no commerce involved, it's just marketing collateral to support sales on the main page.

Question: How can I redirect based on password/login? 
E.g. Login by client A lands him in Library A; Login by client B lands him in Library B etc.

(Using 7.1)