I'm aware this is similar to questions which have been asked previously (e.g. this question about PhD supervisor requests), however I believe due to the specific nature of the supervisor-student relationship in this case it differs enough to be a valid question in its own right.
Last week I submitted my PhD thesis. One of the chapters was based on work which hasn't been published, and my supervisor has been asking me to work on this now to get this finished off, and I'm not sure if I have an obligation to do so.
On one hand, the work in this chapter is quite interesting and new stuff. My supervisor thinks it could go in quite a highly rated journal. I've put a lot of effort into it, and I think it would make for an interesting paper.
On the other hand, this is a paper which I have been working on for the past three years, without very much feedback from my supervisor. I've sent them about 6-7 drafts, including about 3 full rewrites (I'd write it, they wouldn't read it, and then they'd decide it should go in a different journal with different style, rinse and repeat), but I've only had feedback from them on it once. On another paper, which effectively disproved one of their pet projects (the paper is now published), this supervisor didn't read the paper or provide any feedback for a year while simultaneously belittling me with passive aggressive comments about it. This continued until they finally read the paper, and realised that they were actually wrong.
Where it gets complicated is to do with my thesis. From previous PhD students, I was aware that this supervisor tended to leave giving feedback on theses to the last few days, if at all. I suggested to them that I could finish my thesis early (~3 months before submission), and then work on finishing this project after the thesis was ready. While this did mean that they read my thesis earlier than they had with previous students, they only began to give me feedback 1-2 months before submission (on a draft I sent 4 months prior to submission), which meant that in completing these changes I haven't been left with enough time to finish off the project.
We are the only two authors on the paper (so there's no obligation to other co-authors who have put work in), and my new job is not in academia (so the publication is unlikely to directly aid my own career). They haven't given any feedback on the current draft of the paper, so I do not know how much work would be needed to finish it off.
Ideally I would prefer not to work on it to have a clean break, and in my opinion this paper could have been published had my supervisor actually read it and provided feedback during my PhD. It feels to me that my supervisor has essentially caused me a great deal of stress over the past years by providing very little feedback and effectively leaving me on my own*, just to wait until the end and then expect me to do unpaid work for her once I've left.
Do I have an obligation to continue with this project? Am I at any risk if I say no in terms of my viva/graduation (this is in the UK system)?
*In the sense that I enjoy working on my own independently -- I have no problem with that. But then once I've written a paper independently, to then have to wait years to get any feedback on it seems excessive.