Self-assembly in the bulk complexes of poly(ethylene oxide) with amphiphilic dodecylbenzenesulfonic acid

We studied the self-assembly behavior in the bulk complexes of poly(ethylene oxide) (PEO) with an amphiphilic dodecylbenzenesulfonic acid (DBSA) formed through hydrogen bonding. In the hydrate state, PEO-DBSA complexes self-organized into a lamellar morphology consisting of alternating stacks of polar and nonpolar layers. The interlamellar distance increased with decreasing binding fraction of DBSA due to increasing inclusion of unbound monomer units into the polar layers. In the disordered state the comblike structure persisted and a "correlation hole" peak was present in the corresponding small-angle X-ray scattering (SAXS) profile. Complexation with PEO greatly promoted the thermal stability of the mesophase and the dynamics of mesophase formation as compared with those in pure DBSA. The faster mesophase formation in the complexes was proposed to stem from the higher isotropization temperature as well as the existence of comblike structure in the disordered melt.