Publishers do not legally require the complete transfer of copyright in order to publish your work, though of course they prefer it. You, as an author, have other options now. You can retain specific rights when you transfer copyright to a publisher, allowing you to use your original work in ways that support your educational and research goals.
Various scholarly institutions have written “author amendments” or “author addenda.” These agreements can be used to modify publishing contracts, allowing authors to keep specific rights.
The University of Connecticut Libraries endorse the following author amendment:
This agreement is derived from an amendment developed at MIT and has been approved by the Connecticut Office of the Attorney General for use by University of Connecticut authors.
Using this agreement will allow you, the author, to use your original work in teaching and scholarship and make derivatives for teaching and scholarship. It allows you to post the post-print copy of the manuscript to institutional repositories.