Self-assembly modulation in star block copolymers by amphiphilic diol: A scattering insight

Abstract

The present study offers a better insight into the alteration in the aggregation characteristics of ethylene oxide-propylene oxide (EO-PO)-based star block copolymers Tetronics® T1304 and T1307 induced by an amphiphilic diol Surfynol® 104 (hereafter C14 diol) using scattering (dynamic light scattering and small angle neutron scattering) with complementary physical property measurement viz. solution viscosity and cloud point (CP). It is the hydrophobic interaction that drives C14 diol molecules to penetrate inside copolymer micelles resulting in dehydration that lowered the CP and markedly increase in solution viscosity. Quite interestingly, initial lowering in CP is followed by sudden increase at higher level of solubilization. A significant increase in the apparent hydrodynamic diameter (Dh) divulges the growth of micelles which is equally supported by SANS measurements. The micellar parameters obtained from SANS analysis for T1304 and T1307 in the presence of C14 diol are described. The preferential partitioning of C14 diol into the copolymer micelles is the driving force for morphological changes from spherical to unilamellar vesicles. Also, the effect of temperature and NaCl was examined with the aim to observe various micellar transitions. The observed changes are clarified in terms of the hydrophobic interaction of C14 diol with Tetronic® micelles and HLB value of copolymers. The perception of C14 diol stabilised Tetronic® micelles is anticipated and correlated with optimal parameters obtained from computational simulation approach, providing a clear understanding of the correlation between the molecular orbital energy levels of Tetronic® and C14 diol. The present manuscript thus sheds light on C14 diol induced dehydration causing the micelle growth for both Tetronics® with varied hydrophobicity. Such hydrophobic diol-induced spherical to vesicular transition is observed for the first time in Tetronic®-diol mixed system.