SEC-MALS, small-angle X-ray scattering (SAXS), and viscosity measurements were made on tetrahydrofuran (THF) and n-hexane of a series of 4-vinylbenzyl and methacrylate ended poly(n-hexyl isocyanate) (PHIC) macromonomers (VB-HIC-n and MA-HIC-n, where n is a degree of polymerization of HIC and in a range from 21 to 192), together with higher molecular weight PHIC chains than the macromonomers. The molecular weight dependence of z-average mean-square radius of gyration < Rg(2)>(z) and intrinsic viscosity [eta] of the macromonomers and PHIC chains in THF at 25 degrees C were quantitatively described by the wormlike chain model with the stiffness parameter (lambda(-1)) = 63 nm, the molecular weight per unit contour length (M-L) = 725 nm(-1), and the hydrodynamic diameter (d(B)) = 1.6 nm. The SAXS scattering profile of VB-HIC-57 in n-hexane at 25 degrees C was also perfectly described in terms of the straight cylinder model. The results imply that the macromonomers may be regarded as a rigid rod molecule in THF and n-hexane. Cylindrical brushes consisting of polystyrene as a main chain and PHIC chains as a side chain were prepared by homopolymerizations of VB-HIC-46 and their dimensional properties were investigated in THF at 25 degrees C by SAXS and SEC-MALS measurements. The molecular weight dependence of < Rg(2)>(z) of the brushes was quantitatively explained by the wormlike cylinder model with the parameters of lambda(-1) = 48 nm, M-L = 2.40 x 10(4) nm(-1), the cross-sectional radius of gyration of the cylinder < Rc(2)>(0) (1/2) = 4.66 nm, and the end effect (delta = 16.7 nm) arising from side chains near the main-chain ends. It was concluded, therefore, that the main chain stiffness of the brush remarkably increases by the presence of densely located rodlike side chains. Direct observation of single brush of the poly(VB-HIC-46) deposited on a mica was made by scanning force microscopy (SFM) to reveal the cylindrical brushes consisting of rodlike side chains with ca. 15 nm in a thickness.