Does a patent assignment need to be notarized?

Generally, no.  Assignments are transfers of the entire interest in a patent from one entity to another.  They are distinguished from licenses, which give another person a limited right to the patent.  In the US, there is no requirement that an assignment be notarized.  To the US Patent Office, it is irrelevant whether an assignment is notarized or not.  The important thing is that the patent assignment is recorded with the Patent Office, as an unrecorded assignment doesn’t protect against a third party who may buy the rights from the original assignor without any knowledge that the patent had already been assigned.

Note, however, that in many foreign countries, an assignment must be notarized to be valid.