Solution properties of biobased hyperbranched polyols investigated by multiple-detection size exclusion chromatography

We used multiple-detection size exclusion chromatography and batch-mode light scattering to follow the structural development of hydroxylated fatty acid methyl esters of soybean oil into hyperbranched (HB) polyol during polymerization by analyzing samples, collected at different times, in dilute solutions in tetrahydrofuran. The size of HB molecules was, as expected, smaller and more compact than that of their linear analogues of the same molecular weight (MW). Additionally, HB polyols were roughly spherical in shape. Plots of MW as a function of retention time and plots of the radius of gyration (R _g) as a function of MW showed an upturn; this indicated mixing of the high-MW components in late-eluting fractions, caused by either adsorption onto or trapping by the pore. For region of the plot before the turning points, the exponent in the Mark-Houwink equation was between 0.3 and 0.4. The exponent in the power relationship between R_g and MW was also below 0.5. It appeared that the shape of molecules for the same MW varied with the progress of the synthesis, as observed by a slope change in the viscometric radius dependence on MW for different HB polyol samples.