I co-founded a company with a friend, we didn't sign any paper work, though he paid for a llc. I'm leaving the company and he says he owns all my desi

It all depends if you were an employee or an independent contractor. The employer owns the copyright work product of its employees (unless there is a written agreement with a "work made for hire" clause) but an independent contractor owns the copyright of work made under contract, again absent a work make for hire provision in a written contract.