Am I legal bound to inform my employer about it in Poland?
If you got your resident permit because of marriage with a Polish citizen, you need to inform the voivodship government about divorce.
praworozwodowe.opole.pl/sprawy-skomplikowane/rozwod-cudzoziemca-a-prawo-pobytu/
It is worth remembering about the obligation to inform the competent voivode about the issuance of a final judgment of the divorce court. A foreigner with the right of temporary residence is required to notify the voivode of the cessation of the reason for granting the permit within 15 working days. In the event of a divorce, this period will run from the date of the divorce decree becoming final (Article 113 (1) of the Act on foreigners).