He went to shanghai after graduation with the purpose of looking for a better job.
＝He went to shanghai after graduation for the sake of looking for a better job.
with the purpose of =for the sake of=for one's sake"目的是.“,”为了."
当然for the sake of还有其它意思和用法.
He went to town with the purpose of buying a new television.
他进城的目的是买一台新电视机.
We all remained for the sake of keeping a house.
我们大家都留下来以便保持开会的法定人数.