Can I divorce my husband if he takes a second wife in Islam??
As per Sharia, a Muslim man may have up to four wives, making it impossible to insert a clause that bans him from taking a second wife. However, you can add a condition (at the time of and) that gives the woman the right to divorce her husband, should he choose to take a second wife without her permission.
However,If a woman in a multiple marriage situation finds herself mistreated or treated unjustly, she has a right to seek divorce from her husband. It is also permissible for a woman to make this as a condition of the marriage that her husband will not take another wife during his marriage (and to be documented) to her. https://fiqh.islamonline.net