My husband was diagnosed with bipolar a little over three years ago, and I've spent some time on online message boards off and on since. I've seen lots of posts like yours--it seems like emotionally abandoning spouses is very common in those with bipolar.
My husband did emotionally abandon me, too, during a psychotic spell before we were married. I fled to my parents' home 2,500 miles away, and was pretty sure I would have to rebuild my life without him. I wasn't aware he was psychotic at the time, but I was aware he was bipolar and very, very sick--and that there wasn't anything I could do to help him. (He wouldn't talk to me, and he told his psychiatrist that I was lying to her about what was going on and ordered her not to speak to me).
Believe it or not, his meds started working--at least enough for him to "come back to life" and realize what he'd done to our relationship. He came back to me, and we rebuilt our life together.
But then sometimes it doesn't work out. There was one woman on a message board whose fiance told her he never loved her--even though he had proposed months earlier.
It's painful beyond words, and I know most stories don't end as well as mine. (And three years later, we're still dealing with residual bipolar issues. My husband is stable, but the meds have left him without a sex drive--yet another issue to work out with the shrink. Sigh.)
If I could offer you any advice, it would be this: do your very best to move on and heal. Don't linger and hope he'll come back to you. I started to do that, and I got lucky: he got well and came back to me. But whether your (ex?) husband does or not, you need to take care of yourself and your children. You can't demand rational behavior from a man who's incapable of it.
By the way, with regard to your husband maintaining relationships with his other kids, but not with the daughter you had together: When my husband was psychotic and had completely written me out of his life, he was willing to talk to some of his friends (but not others) and, occasionally, his mom. He told all of them that I had destroyed his life and I was a wretched woman. Sound familiar? Unstable bipolar patients are just not rational. Take peace in knowing the "stable version" of your spouse wouldn't choose to hurt you.
Good luck! I know how unbelievable painful it is, but you will come out stronger and wiser.