In the info on modifying startup scripts it talks about how the weblogic classpath is no longer used. The section, quoted below had links to other documentation, but I'm not going to include all those links:
The weblogic.properties converter created a new startup script (called startdomainName.cmd or .sh) for your new WebLogic Server 8.1 domain. If you need to edit this script to specify your domain startup preferences, keep the following in mind.
The WebLogic classpath is no longer used; use the Java system classpath as described in the preceding section, Classloading in WebLogic Server 8.1.
WebLogic Server 8.1 is started from the domain directory. Paths in the startup script assume that the script is located in the domain directory.
It is no longer necessary to include the license file in the classpath. There is now a distinction between an Administration Server and Managed Servers (see The Administration Server and Managed Servers in Configuring and Managing WebLogic Server). Scripts that start servers may need to be rewritten according to how you plan to administer your servers. For the new commands and their required arguments, see Starting and Stopping WebLogic Servers in the Configuring and Managing WebLogic Server.
You could take a look at the startup scripts created in a new 8.1 domain.