Sleep straightening? Answers!!?

Alright, so i've got curly hair. Like ringlets. I dont want to burn it by flat ironing it, but i want it to be straight or wavy SO BAD. Last night when i put my hair in a braid, this lock of it kept falling out so i pinned it tightly against the braid and tied it in with an extra hair tie, and when i woke up, it was only slightly wavy and stayed like that all day. Do you guys have any suggestions for hairstyles i could sleep in that would do this???