Unique domain for each organic group
You can accomplish this with the Rules module, and the Domain Rules module.


  Adding Rules module actions related to Domain Access module.
  Allowing automation of different actions needed to create/modify/delete domains.
  
  First version includes:
  
  
  rules_action_create_domain - create new domain using given arguments
  rules_action_delete_domain - delete existing domain
  rules_action_set_user_defaults_domain - set a given role access to a given domain
  rules_action_set_node_domain - set domain to a node
  rules_action_set_domain_theme - set a theme to a given domain