Self-Assembled Structures of Anionic Hydrophobically Modified Polyacrylamide with Star-Shaped Trimeric and Hexameric Quaternary Ammonium Surfactants

Abstract

The self-assembly of a 1% hydrophobically modified and 30% hydrolyzed polyacrylamide (C12PAM) with cationic star-shaped oligomeric surfactants has been investigated by isothermal titration microcalorimetry, turbidimetry, ζ potential, scanning electron microscopy, and (1)H NMR techniques. The oligomeric surfactants are composed of quaternary dodecyldimethylammonium ions with three or six hydrophobic chains connected by a polyamine spacer at the headgroup level, abbreviated as DTAD and PAHB, respectively. DTAD/C12PAM and PAHB/C12PAM mixed systems undergo the same aggregate transitions with increases in surfactant concentration from soluble networklike aggregates to precipitated denser and more cross-linked structures and then to soluble spherical aggregates. The networklike aggregates are generated at very low surfactant concentration. However, at the corresponding surfactant concentration without C12PAM, DTAD cannot form aggregates and PAHB forms only networklike aggregates with a very loose structure. The strong electrostatic and hydrophobic interaction of DTAD and PAHB with C12PAM and the hydrophobic interaction between the alkyl chains of DTAD and PAHB themselves evidently promote the formation of networklike aggregates. As the surfactant concentration increases, cationic surfactants become excessive. The molecular configuration is changed by the stronger hydrophobic association among the DTAD and PAHB molecules and the enhanced electrostatic repulsion between the mixed aggregates. Thus, the networklike aggregates transfer to spherical aggregates.

Transitions in the Molecular Configuration and Aggregates for Mixtures of a Star‐Shaped Hexameric Cationic Surfactant and a Monomeric Anionic Surfactant

“…Correspondingly, spherical mixed aggregates with a radius of about 25 nm were formed, as shown in Figure 3 a. A comparison of the interaction enthalpy curve between SDS and PAHB with the dilution curve of SDS indicated that the binding between SDS and PAHB and the resulting aggregate transition took place at extremely low R value, so that the critical transition concentration could not be defined . The pronounced exothermic enthalpy plateau accounted for the continuous electrostatic binding of the anionic headgroups of SDS to the positively charged quaternary ammoniums on PAHB, and to the hydrophobic association between the hydrocarbon chains of these two surfactants.…”

“…Ac omparison of the interaction enthalpy curve between SDS and PAHB with the dilutionc urve of SDS indicated that the binding between SDS and PAHB and the resulting ag-gregate transition tookp lace at extremely low R value, so that the critical transition concentrationc ould not be defined. [8] The pronounced exothermic enthalpy plateau accounted for the continuous electrostatic binding of the anionic headgroups of SDS to the positively charged quaternary ammoniumso n PAHB, and to the hydrophobic association between the hydrocarbon chains of these two surfactants. As we know,t he initial network-like pre-micellesw ith loose structures formed at extremely low c PAHB values and, in which case, their turbiditya nd z-potential values were closet oz ero.…”

“…Previously, the effects of anionic hydrophobically modified polyacrylamide (C 12 PAM) on the aggregation behavior of star‐shaped trimeric or hexameric cationic surfactants (DTAD and PAHB) have been studied . Both DTAD/C 12 PAM and PAHB/C 12 PAM form soluble network‐like aggregates, denser cross‐linked precipitated aggregates, and soluble spherical aggregates with increasing surfactant concentration.…”

Physicochemical investigation of antibacterial Moxifloxacin interacting with quaternary ammonium disinfectants

“…A c c e p t e d M a n u s c r i p t 4 The quaternary ammonium cationic surfactants belong to an important class of disinfectants, primarily due to their in vitro and in vivo compatibility and utility over a broad range of pH conditions [36][37][38][39][40]. The typical examples are Cetrimonium bromide (HTAB) and Mecetronium bromide (EHDAB) that are widely known as antiperspirant, antiseptics, antimicrobials, anticancer, bactericides and fungicides in pharmaceuticals active ingredients (For brevity basic molecular structures of HTAB and EHDAB are shown in Supporting Information, Fig.…”

Spectral-luminescent properties of pH-sensitive azo fluorophore in complexes with quaternary ammonium disinfectants

“…Among numerous surfactant types, the quaternary ammonium surfactants (Quats) belong to an important class of fast-acting disinfectants, primarily due to their in vitro and in vivo compatibility and utility over a broad range of pH conditions [17][18][19][20][21]. In terms of encapsulation strategies, cationic surfactants have been extensively used by the scientists, owing to their recognition as model system for studying different aspects of membrane interactions with drug molecules [22][23][24][25][26][27].…”