Small-angle X-ray scattering from polystyrene polymacromonomers with relatively short main chains

Abstract

Synchrotron small-angle X-ray scattering measurements were made on polystyrene polymacromonomers F33 and F110 with 33 and 110 styrene residues, respectively, in each side chain in toluene at 298.2 K and cyclohexane at 307.7 K. Two F33 samples with different weight-average degrees of polymerization of main chain Nw of 37 and 17 (F33-13 and F33-14, respectively) and two F110 samples with Nw of 61 and 27 (F110-10 and F110-11, respectively) were used. The z-average mean-square radii of gyration of these polymacromonomers were explained by the wormlike chain with finite diameter when we considered the contribution of side chains near the main chain to the contour length. This model was also applied to calculate the particle scattering function P(θ), giving satisfactory agreements between calculated and experimental k2P(θ) for F33-13 and F110-10 plotted against the magnitude of the scattering vector k = (4π/λ0)sin(θ/2), where λ0 and θ denote the wavelength of the incident X-ray and the scattering angle, respectively. The data for F33-14 and F110-11, which have short main chains relative to the side chains, cannot be explained by the same model. However, these data were closely fitted by the theoretical values for a comb polymer model with semiflexible main and side chains. The stiffness parameter for side chains in toluene was larger than that in cyclohexane, suggesting that the side chains in the former solvent are more stretched than those in cyclohexane.