[Hybrid] Investigating the Structure of Ionically Assembled Complexes of Polyelectrolytes with Oppositely Charged Polyelectrolytes or Surfactants by Means of Small-Angle Neutron Scattering (SANS)

by Prof. Michael Gradzielski (Department of Chemistry, Technische Universität Berlin)

Monday 24 Oct 2022, 14:30 → 15:30 Europe/Berlin

PH HS 3 (Physics Department)

Ionic assembly of oppositely charged polyelectrolytes and/or surfactant is a very powerful way to construct self-assembled colloidal systems, which are very versatile with respect to their structures and properties. For instance, in such systems one can control the rheological properties as well as the solubilisation properties, both being very important for practical applications of colloidal formulations. 
 

In this presentation we will look at various interpolyelectrolyte complexes (IPECs) and polyelectrolyte surfactant complexes (PESCs) with a particular focus on how neutron scattering can contribute to understanding their structural features. Here especially small-angle neutron scattering (SANS) and neutron spin-echo (NSE) spectroscopy have been employed. 
 

As polycation we employed for instance polydiallyldimethylammonium chloride (PDADMAC) of different Mw as polycation and complexed it with different polyanions. In particular, we addressed the effects of having different degrees of hydrophobic modification contained within the acrylate based polyanions. Such systems are potentially interesting due to their modified solubilisation properties. Their self-assembled structures can be systematically varied by the molecular design of the polycation and the resulting structures can be determined in good detail by a combination of SANS with static and dynamic light scattering. In a different direction we studied block copolymer micelles that can be formed by poly (alkyl acrylate) as hydrophobic and poly (acrylic acid) (AA) as hydrophilic part. Their structure can be modified in a systematic way by complexation with PDADMAC, thereby forming core-shell particles. Finally, we also looked at the complexes that are formed by complexing PDADMAC with anionic surfactants, like SDS. Here the formed PESC structures can be modified largely by the addition of cosurfactant. The resulting changes of the aggregate structure then is also reflected in marked changes of the rheological properties.

In summary, neutron scattering is a central tool to determine the structures of IPECs and PESCs, where such structures are very versatile and allow to tailor various macroscopic properties of importance for formulations.