That is an interesting idea, and a creative and smart strategy to study his lectures via his powerpoint presentations. However, he may not want to share his powerpoint presentation because he's put a lot of work into developing his lectures. My intern made a copy of my powerpoint presentation at work, and I found out later that she has been using my work without my permission and passed it off as her own. If he hasn't copyrighted them, he is probably concerned that someone could possibly plagiarize his work. Also, he is probably concerned that his notes get passed on for free to other students who could get a head start on his class if future semesters, which means that he'd need to change up his lectures every semester. Who wants to do that? Lastly, while he may not have permission to pass on various graphs, pictures, etc. in print and it could be a legal issue. So, it isn't unreasonable for you to ask, but you need to be able to accept a "no" with respect to his work. It's really his choice and if he doesn't want to give you his powerpoint presentation, I don't think he should have to.