scholarly journals pH-Dependent Foam Formation Using Amphoteric Colloidal Polymer Particles

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 511 ◽  
Author(s):  
Sayaka Fukui ◽  
Tomoyasu Hirai ◽  
Yoshinobu Nakamura ◽  
Syuji Fujii
Keyword(s):  
Foam Stability ◽  
Aqueous Media ◽  
Carboxyl Groups ◽  
Foam Formation ◽  
Surface Charges ◽  
Air Water Interface ◽  
Free Radical Initiator ◽  
Ph Dependent ◽  
Soap Free Emulsion Polymerization ◽  
Positively Charged

Near-monodispersed micrometer-sized polystyrene (PS) particles carrying amidino and carboxyl groups on their surfaces were synthesized by soap-free emulsion polymerization using an amphoteric free radical initiator. The resulting amphoteric PS particles were characterized in terms of diameter, morphology, disperibility in aqueous media and surface charge using scanning electron microscopy (SEM), optical microscopy (OM), sedimentation rate and electrophoretic measurements. At pH 2.0, where the amidino groups are protonated (positively charged), and at pH 11.0, where the carboxyl groups are deprotonated (negatively charged), the PS particles were well dispersed in aqueous media via electrostatic repulsion. At pH 4.8, where the surface charges are neutral, the PS particles were weakly aggregated. Furthermore, it was confirmed that the PS particles can function as a pH-sensitive foam stabilizer: foamability and foam stability were higher at pH 2.0 and 4.8, where the PS particles can be adsorbed to the air–water interface, and lower at pH 11.0, where the PS particles tend to disperse in bulk aqueous medium. SEM and OM studies indicated that hexagonally close-packed arrays of PS particles were formed on the bubble surfaces and moiré patterns were observed on the dried foams. Moreover, the fragments of dried foams showed iridescent character under white light.

scholarly journals Anomalous Laterally Stressed Kinetically Trapped DNA Surface Conformations

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Valery V. Prokhorov ◽  
Nikolay A. Barinov ◽  
Kirill A. Prusakov ◽  
Evgeniy V. Dubrovin ◽  
Maxim D. Frank-Kamenetskii ◽  
...  
Keyword(s):  
Electrostatic Interaction ◽  
Mechanical Response ◽  
Persistence Length ◽  
Strong Impact ◽  
List Type ◽  
Surface Charges ◽  
Monomolecular Films ◽  
Chain Approximation ◽  
The Impact ◽  
Positively Charged

Highlights DNA kinking is inevitable for the highly anisotropic 1D–1D electrostatic interaction with the one-dimensionally periodically charged surface. The double helical structure of the DNA kinetically trapped on positively charged monomolecular films comprising the lamellar templates is strongly laterally stressed and extremely perturbed at the nanometer scale. The DNA kinetic trapping is not a smooth 3D—> 2D conformational flattening but is a complex nonlinear in-plane mechanical response (bending, tensile and unzipping) driven by the physics beyond the scope of the applicability of the linear worm-like chain approximation. Abstract Up to now, the DNA molecule adsorbed on a surface was believed to always preserve its native structure. This belief implies a negligible contribution of lateral surface forces during and after DNA adsorption although their impact has never been elucidated. High-resolution atomic force microscopy was used to observe that stiff DNA molecules kinetically trapped on monomolecular films comprising one-dimensional periodically charged lamellar templates as a single layer or as a sublayer are oversaturated by sharp discontinuous kinks and can also be locally melted and supercoiled. We argue that kink/anti-kink pairs are induced by an overcritical lateral bending stress (> 30 pNnm) inevitable for the highly anisotropic 1D-1D electrostatic interaction of DNA and underlying rows of positive surface charges. In addition, the unexpected kink-inducing mechanical instability in the shape of the template-directed DNA confined between the positively charged lamellar sides is observed indicating the strong impact of helicity. The previously reported anomalously low values of the persistence length of the surface-adsorbed DNA are explained by the impact of the surface-induced low-scale bending. The sites of the local melting and supercoiling are convincingly introduced as other lateral stress-induced structural DNA anomalies by establishing a link with DNA high-force mechanics. The results open up the study in the completely unexplored area of the principally anomalous kinetically trapped DNA surface conformations in which the DNA local mechanical response to the surface-induced spatially modulated lateral electrostatic stress is essentially nonlinear. The underlying rich and complex in-plane nonlinear physics acts at the nanoscale beyond the scope of applicability of the worm-like chain approximation.

Adsorption of tetracycline on kaolinite with pH-dependent surface charges

2010 ◽  
Vol 351 (1) ◽  
pp. 254-260 ◽  
Author(s):  
Zhaohui Li ◽  
Laura Schulz ◽  
Caren Ackley ◽  
Nancy Fenske
Keyword(s):  
Surface Charges ◽  
Ph Dependent

scholarly journals Layer-by-Layer 3D Constructs of Fibroblasts in Hydrogel for Examining Transdermal Penetration Capability of Nanoparticles

2016 ◽  
Vol 22 (4) ◽  
pp. 447-453 ◽  
Author(s):  
Xiaochun Hou ◽  
Shiying Liu ◽  
Min Wang ◽  
Christian Wiraja ◽  
Wei Huang ◽  
...  
Keyword(s):  
Transdermal Delivery ◽  
Three Dimensional ◽  
Layer By Layer ◽  
Surface Charges ◽  
Skin Model ◽  
Collagen Hydrogel ◽  
Penetration Ability ◽  
Charged Nanoparticles ◽  
Transdermal Penetration ◽  
Positively Charged

Nanoparticles are emerging transdermal delivery systems. Their size and surface properties determine their efficacy and efficiency to penetrate through the skin layers. This work utilizes three-dimensional (3D) bioprinting technology to generate a simplified artificial skin model to rapidly screen nanoparticles for their transdermal penetration ability. Specifically, this model is built through layer-by-layer alternate printing of blank collagen hydrogel and fibroblasts. Through controlling valve on-time, the spacing between printing lines could be accurately tuned, which could enable modulation of cell infiltration in the future. To confirm the effectiveness of this platform, a 3D construct with one layer of fibroblasts sandwiched between two layers of collagen hydrogel is used to screen silica nanoparticles with different surface charges for their penetration ability, with positively charged nanoparticles demonstrating deeper penetration, consistent with the observation from an existing study involving living skin tissue.

scholarly journals The interfacial structure and Young's modulus of peptide films having switchable mechanical properties

2007 ◽  
Vol 5 (18) ◽  
pp. 47-54 ◽  
Author(s):  
A.P.J Middelberg ◽  
L He ◽  
A.F Dexter ◽  
H.-H Shen ◽  
S.A Holt ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Self Assembly ◽  
Molecular Design ◽  
Foam Stability ◽  
Young's Modulus ◽  
Interfacial Structure ◽  
Water Interface ◽  
Air Water Interface ◽  
Peptide Dissociation

We report the structure and Young's modulus of switchable films formed by peptide self-assembly at the air–water interface. Peptide surfactant AM1 forms an interfacial film that can be switched, reversibly, from a high- to low-elasticity state, with rapid loss of emulsion and foam stability. Using neutron reflectometry, we find that the AM1 film comprises a thin (approx. 15 Å) layer of ordered peptide in both states, confirming that it is possible to drastically alter the mechanical properties of an interfacial ensemble without significantly altering its concentration or macromolecular organization. We also report the first experimentally determined Young's modulus of a peptide film self-assembled at the air–water interface ( E =80 MPa for AM1, switching to E <20 MPa). These findings suggest a fundamental link between E and the macroscopic stability of peptide-containing foam. Finally, we report studies of a designed peptide surfactant, Lac21E, which we find forms a stronger switchable film than AM1 ( E =335 MPa switching to E <4 MPa). In contrast to AM1, Lac21E switching is caused by peptide dissociation from the interface (i.e. by self-disassembly). This research confirms that small changes in molecular design can lead to similar macroscopic behaviour via surprisingly different mechanisms.

The Effect of Halide Counter Ions and Methanol on the Foaming Behavior of Cationic Surfactants and a Mechanism Study

2021 ◽  
Vol 58 (4) ◽  
pp. 278-286
Author(s):  
Yun Bai ◽  
Jie Zhang ◽  
Sanbao Dong ◽  
Shidong Zhu ◽  
Manxue Wang ◽  
...  
Keyword(s):  
Surface Activity ◽  
Cationic Surfactants ◽  
Foam Stability ◽  
Micelle Formation ◽  
Methanol Concentration ◽  
Effect Of Temperature ◽  
Ammonium Bromide ◽  
Foam Formation ◽  
Mechanism Study ◽  
Cetyltrimethyl Ammonium

Abstract In this work, four quaternary ammonium cationic surfactants including cetyltrimethyl ammonium fluoride (CTAF), cetyltrimethyl ammonium chloride (CTAC), cetyltrimethyl ammonium bromide (CTAB) and cetyltrimethyl ammonium iodide (CTAI) were investigated to study the effect of halide anions on the surface activity and foaming performance. The result showed that CTAF had superior surface activity, which could reduce the surface tension of water to 33.15 mN/m at a low CMC (critical micelle formation concentration) of 1.65 mmol/L. Based on the calculation of Amin (the minimum occupied area per surfactant molecule), we assumed that this higher surface activity was related to the small ionic radius of the fluorine ion (F–). The foamability and foam stability of CTAF has great advantages over other surfactants studied. On this basis, the factors affecting the formation and stabilization of the CTAF foam were investigated. The results showed that foam formation benefited from high temperatures and low methanol concentration, while high salinity was beneficial for foam stability. When CTAF at a concentration of 0.2% was used as a foaming agent, foaming was excellent at a methanol concentration of 10%, a salinity of 22 ⨯ 104 mg/L, and a temperature of 90°C. With this study, uncertainties that existed in the literature regarding the effect of anion on surface activity and foam performance were explained and the effect of temperature, methanol and salinity on foam generation and stabilization was understood.

scholarly journals Investigation of Surfactant AOT Mediated Charging of PS Particles Dispersed in Aqueous Solutions

Coatings ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 471 ◽  
Author(s):  
Huiying Cao ◽  
Baichao An ◽  
Yong Wang ◽  
Kun Zhou ◽  
Naiyan Lu
Keyword(s):  
Zeta Potential ◽  
Aqueous Solutions ◽  
Particle Surface ◽  
Water System ◽  
Submicron Particles ◽  
Foam Formation ◽  
Preferential Adsorption ◽  
Aqueous Salt Solutions ◽  
Air Water Interface ◽  
Charging Mechanism

Nano/submicron particles can be activated by surfactants and aggregate at the air-water interface to generate and stabilize foams. Such systems have been applied extensively in the food, medicine, and cosmetic industries. Studying particle charging behavior in a particle/surfactant/water system is a fundamental way to understand the activation of the particle surface. This paper presents an investigation of the charging behavior of polystyrene (PS) particles dispersed in aqueous solutions of the surfactant sodium di-2-ethylhexylsulfosuccinate (AOT). The results showed that zeta potential of PS was related to the AOT concentration with two different concentration regions. Below the critical micelle concentration (CMC), the charging of PS particles was effected by AOT ions; while above the CMC, it came from both AOT ions and AOT micelles. This behavior was different from that observed for PS in aqueous salt solutions. Additionally, the particle concentration and size were found to affect the zeta potential differently in the two AOT concentration regions. By analyzing these results, the charging mechanism of the PS/AOT/water system was revealed to be preferential adsorption. In summary, the study disclosed the internal connection between the PS charging in aqueous AOT solution and the activation of PS particles, as well as their influence to foam formation and stability.

scholarly journals The Effects of Salts on the Stability of the Collagen Helix Under Acidic Conditions

1968 ◽  
Vol 21 (4) ◽  
pp. 821 ◽  
Author(s):  
Anne FW oodlock ◽  
BS Harrap
Keyword(s):  
Thermal Stability ◽  
Carboxyl Groups ◽  
Neutral Ph ◽  
Acid Ph ◽  
Helix Stability ◽  
Acidic Conditions ◽  
Anions And Cations ◽  
The Stability ◽  
Thermal Stability Of ◽  
Positively Charged

In the acid pH region, the relative effects of various salts on the thermal stability of the collagen helix are quite different from their effects at neutral pH. The magnitude of the decrease in thermal stability brought about by the salts studied depends mainly on the nature and concentration of the anion and very little on the nature of the cation, whereas at neutral pH the nature of both anions and cations affects the collagen helix stability, the effects of the two ions being roughly additive. The magnitude of the effect of salts at acid pH is much greater than that at neutral pH whereas for a non-ionized denaturant, urea, the magnitudes at both neutral and acid pH are similar. The data are discussed in terms of possible interactions between salts and the positively charged protein with particular consideration of the effects of salts on the pKa of protein carboxyl groups.

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