Block copolymers, dinonylphenyl end-capped polyethylene glycol-b-polystyrene (DNPE-PEO-b-PSs) were synthesized in a one-step atom transfer radical polymerization (ATRP) of styrene. The PEO block in the DNPE-PEO-b-PS samples (volume fraction of PS: 66.8-93.2 %) was found to be amorphous, which contrasts with DNPE-PEO precursor, traditional methoxide end-capped polyethylene glycol-b-polystyrene (PEO-b-PS) and dinonylphenyl end-capped poly-(ethylene glycol)-b-poly(fluorinated methyl methacrylate)(DNPE-PEO-b-PFMAs). Meanwhile, DNPE-PEO-b-PSs display an intriguing self-assembly behavior in solution. Block copolymer particles with mesoporous internal structures are directly formed by self-assembly of DNPE-PEO-b-PS in tetrahydrofuran/water solutions. It is proposed that DNPE end group has an important effect on the crystallization of the block copolymers as well as their self-assembly behaviors in solution.