Synthesis and micellization of cationic trisiloxane surfactants with poly (ethylene glycol)

PEG based cationic trisiloxane surfactants (Si(3)min-EO3, Si(3)min-EO4, and Si(3)pyr-EO4), containing poly(ethylene glycol) and imidazolium/pyridinium headgroups, were prepared through thiol-ene reaction and confirmed by 1HNMR and FT-IR. Their micellization in aqueous solution were investigated using surface tension measurements, electrical conductivity measurements, dynamic light scattering (DLS), and transmission electron microscope (TEM). Owing to the introduction of ethylene glycol segments onto both end of trisiloxane hydrophobic parts, the PEG based cationic trisiloxane surfactants may adopt the ethylene glycol groups with a suitable conformational structure on the air/water interface resulted in their lower pi(CMC) values, larger gamma(CMC) (similar to 33 mN m(-1)) and A(min) values compared with permethyltrisiloxane surfactant, even their corresponding monomeric surfactant (Vi-Si(3)minCl and Vi-Si(3)PyrCl). Meanwhile, in aqueous solution, the micellization process of Si(3)min-EO3, Si(3)min-EO4, and Si(3)pyr-EO4 were enthalpy driven and spherical aggregates were observed by TEM.

Automated summary

Cationic trisiloxane surfactants based on PEG were synthesized and their micellization behavior in aqueous solution was studied. The introduction of ethylene glycol segments resulted in lower CMC values and larger surface tension compared to permethyltrisiloxane surfactants, forming spherical aggregates driven by enthalpy.