I highlight my hair. It's usually very nice and strong but for some reason, it has become really dry and matted of late. After washing my hair, the ends get dry and frizzy before I have the chance to style them. When I wake up in the morning, some sections along the ends are matted. I read that sleeping in sateen pillowcases can help but having searched for them in Debenhams and John Lewis I'm confused. They are made of cotton. So what makes them sateen? In addition to new pillowcases, what can I do to the ends of my hair to improve their condition? By the way, I recently cut around 10cm but that's only helped slightly. Thanks.