The interaction between hydroxypropylguar (HPG) and its dodecyl-modified derivative (HMHPG) and cationic surfactant oligomers has been investigated by measurements of the solution viscosity at constant shear rate, microviscosity of the aggregates (dipyrenylpropane fluorescence emission spectra), and aggregation number of the polymer hydrophobe and of the surfactant (time-resolved fluorescence quenching). The surfactants are dodecyltrimethylammonium bromide (DTAB, monomeric surfactant) and some of its dimers and trimers which differed by the carbon number s of the polymethylene spacer connecting the surfactant moieties (2 = s = 20). Most results refer to a polymer concentration of 1 wt%. Only a weak interaction was evidenced between HPG and these surfactants, whereas strong interactions occurred between HMHPG and the surfactant oligomers. The interaction became stronger as the degree of oligomerization of the surfactant increased. The results led us to distinguish three ranges of concentration of added surfactant. The first range corresponds to surfactant concentrations below the surfactant cmc in water. In this range mixed aggregation occurs between polymer hydrophobes and surfactant ions, and the viscosity of the HMHPG + surfactant systems goes through a maximum, as usually found for associating polymers. The second range extends from the cmc to about 10 cmc. Precipitation of a polymer/surfactant complex occurs in this range with all surfactants forming threadlike micelles. For the other surfactants the viscosity goes through a minimum. In the third range, which corresponds to surfactant concentrations above 10 cmc, resolubilization of the precipitated HMHPG/surfactant complexes occurs and a solution-to-gel transition is observed for the surfactants which form threadlike micelles or vesicles. The concentration corresponding to this transition is about the same as that for pure surfactant solutions. Some polymer hydrophobes may contribute to the formation of additional bridges between surfactant micelles. Copyright 1999 Academic Press.
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http://dx.doi.org/10.1006/jcis.1999.6438 | DOI Listing |
J Hazard Mater
January 2025
Key Laboratory of Agro-product Quality and Safety, Institute of Quality Standards & Testing Technology for Agro-products, Chinese Academy of Agricultural Sciences, Beijing 100081, China. Electronic address:
Trisiloxane ethoxylates (TSEOn) have been found in multiple agro-environmental media due to their pervasive application in agricultural production. While some studies suggested that the differences in the toxicological effects of TSEOn were closely related to their end-capping groups, the environmental behaviors and fate of TSEOn congeners with varying end-capping groups in agroecosystems remain underexplored. This study investigated the dissipation patterns of 39 oligomers across three TSEOn congeners in cucumber, leaves, and soils through field trials, including TSEOn-H (hydroxy, n = 2-14), TSEOn-CH (methoxy, n = 2-14), and TSEOn-COCH (acetoxy, n = 3-15).
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January 2025
Research Center for Water Resources and Interface Science, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China.
The mechanism of the emulsion polymerization of styrene to polystyrene nanoparticles (PSNPs) remains a subject of debate. Herein, a series of reaction parameters with different surfactant concentrations, monomer contents, temperatures, and equilibration times were investigated to understand the formation mechanism of PSNPs, which demonstrate a correlation between the properties of PSNPs and the mesostructure of the premix. Cooling the model systems with self-emulsifying nanodroplets (SENDs) in the early reaction stages resulted in the hollow polystyrene spheres (H-PSSs), ruptured PSNPs, and dandelion-like PSNPs, further indicating that the oil nanodroplets are the key sites for the formation of PSNPs.
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Institute of Biomedical Engineering and Technology, Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, PR China.
Lipid nanoparticles (LNPs) are widely used for nucleic acid delivery but face challenges like limited targeting and accelerated blood clearance (ABC) effect. We design three ionizable oligomers (IOs) that, with polylactide-polyethylene glycol (PLA-PEG), form a potential siRNA delivery system, named Ionizable Polymeric Micelles (IPMs). The siRNA encapsulated IPMs escape from lysosomes upon cellular uptake, and silence the target gene.
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November 2024
Division of Toxicology, Wageningen University and Research, Stippeneng 4, Wageningen 6708 WE, the Netherlands.
Nat Commun
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Department of Chemistry, Rice University, Houston, TX, USA.
The de novo design of self-assembling peptides has garnered significant attention in scientific research. While alpha-helical assemblies have been extensively studied, exploration of polyproline type II helices, such as those found in collagen, remains relatively limited. In this study, we focus on understanding the sequence-structure relationship in hierarchical assemblies of collagen-like peptides, using defense collagen Surfactant Protein A as a model.
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