Polymer (N, N-dimethyl-ethylamine methacrylate)-block-poly{6-[4-(4-methoxy phenyl-azo) phenoxy] hexylacrylate} p(DMAEMA(m)-b-AZOM(n)) was synthesized by successive reversible addition-fragmentation chain transfer polymerization in the hydrothermal reactor. The products were characterized by hydrogen nuclear magnetic resonance, differential scanning calorimetry, gel permeation chromatography, and ultraviolet and visible absorption spectroscopy (UV-vis). In H2O/THF mixture, we found amphiphilic p(DMAEMAm-b-AZOMn) self-assembles occurred. p(DMAEMA(79)-b-AZOM(7)) self-assembled into rods, p(DMAEMA(79)-b-AZOM(5)) self-assembled into giant microspheres with rods wind around, p(DMAEMA(79)-b-AZOM(2)) self-assembled into microspheres. Photochromic behaviors of the polymers in different environments were investigated. We found the colors of diblock copolymers in films changed from yellow to orange after irradiation by ultraviolet and visible (UV) light. The rates of trans-cis photoisomerization in films were almost the same for the three p(DMAEMA(m)-b-AZOM(n)) copolymers. The rates in aqueous micellar solutions were only marginally faster than those in films for all the three diblock copolymers. The observation of a sizable rate difference in different environments for p(DMAEMA(m)-b-AZOM(n)) suggested that a rotational mechanism might be operative for these water-soluble amphiphilic diblock copolymers. The self-assembly behaviors of three copolymers and the application of p(DMAEMA(79)-b-AZOM(2)) microspheres in biochemistry were investigated in present work. POLYM. ENG. SCI., 51: 1662-1668, 2011. (C) 2011 Society of Plastics Engineers