Exotic smooth structures on small 4-manifolds with odd signatures

Let M be (2n - 1)ℂℙ²#2nℂℙ̄² for any integer n≥1. We construct an irreducible symplectic 4-manifold homeomorphic to M and also an infinite family of pairwise non-diffeomorphic irreducible non-symplectic 4-manifolds homeomorphic to M. We also construct such exotic smooth structures when M is ℂℙ²#4ℂℙ̄² or 3ℂℙ²#Kℂℙ̄² for k=6,8,10.