A liquid crystalline (LC) azobenzene homopolymer brush film of poly[4-(10-methacryloxydecyloxy)-4-pentylazobenzene] (P5Az10MA), and two diblock copolymer brushes consisting of the same LC azobenzene (Az) block connected with poly(hexyl methacrylate) block (PHMA-b-P5Az10MA) have been synthesized on initiator-immobilized quartz surfaces by atom transfer radical polymerization. In the diblock polymer brushes, the length of PHMA blocks tethering to the substrate surface were changed (26nm and 51nm). The orientation and structural features of the liquid crystalline block, containing an Az mesogenic group of the polymer brushes were evaluated by UV-vis spectroscopy and grazing incident X-ray diffraction measurements. Upon irradiation with 436nm linearly polarized light (LPL), the levels of photoinduced in-plane anisotropy and reorienting behavior among the brushes showed significant differences as a result of degree of freedom of the flexible buffer chain spacers.