Dipolar particles via photopolymerization of 1,6-hexanediol diacrylate miniemulsion template tailored with oppositely-charged polymerizable surfactants

•1,6 hexandiol diacrylate is miniemulsified in water.•Oppositely charged polymerizable hydrophobes were employed as surfactants.•The miniemulsion drops were immobilized using agarose gel.•The immobilized oil drops were exposed to DC field for polarization.•Meanwhile, polymerization was triggered on by simultaneous exposure to UV radiation.•The dipolarity of the particles was approved via various techniques. A new technique was developed for producing dipolar colloidal particles via miniemulsification of 1,6-hexandiol diacrylate (HDDA), which was stabilized by a non-ionic surfactant, in presence of a UV initiator, and doped with different oppositely-charged polymerizable surfactants (surfmers). The surfmers were chosen of poor miscibility with water to ensure their existence at the interface between the phases while the charged moieties are exposed toward the aqueous phase. Thereafter, the miniemulsion was mixed with agarose medium, and gelation was accomplished instantly to arrest the oil drops while the charged surfmers are immobilized on their surfaces. The drops were exposed to DC-field for polarization of the charges whereas UV radiation was applied simultaneously to trigger polymerization. The well-known particle nucleation in miniemulsion systems as well as polarizability of the charged moieties of the surfmers under the effect of the field and complete conversion of UV-initiated polymerization allowed the formation of particles bearing strong dipole moment. Size and zeta potential measurements of particles confirmed the nanometric size, typical of miniemulsion technique, which was further confirmed by scanning electron microscopy (SEM). On the other hand, a net charge on the surface even in presence of both cationic and anionic surfmers, is an evidence of non-equal hemispheres of the particles under the alignment induced by the electric field. This is dependent on the molar ratio of the charged species and intensity of the electric field during polymerization. In addition, the high resistance of aqueous dispersions of the polarized particles to induced aggregation in presence of an electrolyte, compared to a weakly-polarized comparable system, approves strongly the dipolarity of the particles. Cross-polarized optical imaging of assemblies formed in presence of electrolytes indicated clusters around 30 µm in size with excellent birefringence. Nevertheless, that was not the case for the un/weakly-polarized particles, indicating the anisotropy of the p