What causes the anomalous aggregation in pluronic aqueous solutions?. Issue 37 (3rd September 2018)

• Record Type: Journal Article
• Authors: Shih, Kuo-Chih; Shen, Zhiqiang; Li, Ying; Kröger, Martin; Chang, Shing-Yun; Liu, Yun; Nieh, Mu-Ping; Lai, Hsi-Mei
• Is Part Of: Soft matter. Volume 14:Issue 37(2018)
• Page Start: 7653
• Page End: 7663
• Publication Date: 2018-09-03
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c8sm01096j
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Anomalous aggregation of pluronic induced by weak PPO hydrophobicity can be suppressed in presence of acids or bases. Abstract : Pluronic (PL) block copolymers have been widely used as delivery carriers, molecular templates for porous media, and process additives for affecting rheological behavior. Unlike most surfactant systems, where unimer transforms into micelle with increased surfactant concentration, anomalous large PL aggregates below the critical micelle concentration (CMC) were found throughout four types of PL (F108, F127, F88 and P84). We characterized their structures using dynamic light scattering and small-angle X-ray/neutron scattering. Molecular dynamics simulations suggest that the PPO segments, though weakly hydrophobic interaction (insufficient to form micelles), promote the formation of large aggregates. Addition of acid or base ( e.g. citric acid, acetic acid, HCl and NaOH) in F108 solution significantly suppresses the aggregate formation for up to 20 days due to the repulsion force from the attached H3 O + molecules on the EO segment in both PEO and PL and the reduction of CMC through the salting out effect, respectively.