Characterization of polybutadiene-poly(ethyleneoxide) aggregates in aqueous solution: A light-scattering and small-angle neutron-scattering study

Abstract

For diblockcopolymers of polybutadiene-poly(ethyleneoxide) (PB-PEO) type, water is a selective solvent. In dependence of the length of both blocks and the block length ratio, these polymers form a multitude of self-assembled structures in solution. In the present work scattering methods are used to investigate the water-soluble polymer ${\mathrm{PB}}_{125}\text{\ensuremath{-}}{\mathrm{PEO}}_{155}$. It is found to form long rodlike micelles, which are characterized with respect to the aggregate length $L$, the cross sectional radius ${R}_{\mathrm{CS}}$, the radial scattering length density profile $\ensuremath{\sigma}(r)$, and the radial aggregation number ${N}_{\mathrm{rad}}$. Model-independent as well as model-based approaches are used for the scattering data analysis. From dynamic light scattering (DLS) and static light scattering (SLS) experiments the weight averaged length ${L}_{w}$ of these stiff elongated aggregates is determined to ${L}_{w}=350\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. Small angle neutron scattering (SANS) reveals a cross sectional radius of ${R}_{\mathrm{CS}}=17\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ and in combination with results from the SLS the radial aggregation number is found to be ${N}_{\mathrm{rad}}=70$.