Primary surface measurement reported
Surface tension of polymer–surfactant solutions measured at room temperature (reported as surface tension vs. surfactant concentration plots).
Client Citation Analysis
Steady Shear Rheology and Surface Activity of Polymer–Surfactant Mixtures
This study investigates how five surfactants affect steady-shear rheology and “surface activity” by tracking electrical conductivity and pendant-drop surface tension in two polymer systems (LR-400 and Praestol 2540TR) in water.
At-a-Glance Summary
Dropometer attribution in the paper
Surface tension was measured using a smartphone-based tensiometer using the ADSA (Axisymmetric Drop Shape Analysis) method
How the surface-tension data were used in the study
Surface tension vs. surfactant concentration curves (paired with conductivity curves) were used to discuss surface activity and to estimate approximate CAC (critical aggregation concentration) and PSP (polymer saturation point) based on slope changes.
Replication / reliability statement
Each solution’s surface tension was measured 12 times and averaged; the authors describe the measurements as “very consistent” and use this to support method reliability.
Paper Details
Title
Steady Shear Rheology and Surface Activity of Polymer-Surfactant Mixtures
Authors
Qiran Lu; Rajinder Pal (corresponding author)
Journal
Polymers
Year
2025
Volume
17
Pages / Article
364
License
Open access; Creative Commons Attribution (CC BY) license (CC BY 4.0)
Journal context
What it is
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How to read it
Compare metrics within category; updates are annual and lag current-year publications.
Scopus metrics (Elsevier / Scopus rating 2024)
CiteScore 2024
9.7
CiteScore subject ranks (CiteScore 2024)
- Q1 - Chemistry (all) (58/404)
- Q1 - Materials Science: Polymers and Plastics (25/167)
SNIP 2024
1.227
SJR 2024
0.918
Journal Impact Factor (Clarivate JCR)
Journal Impact Factor (JCR 2024)
4.9
5-Year Impact Factor
5.2
JCR category rank
Q1 - Polymer Science (19/94)
What Was Measured
Primary surface / interfacial measurement
Surface tension of aqueous polymer–surfactant solutions at room temperature, obtained from pendant-drop measurements analyzed using ADSA with a smartphone-based tensiometer
Supporting measurements
Electrical conductivity of polymer–surfactant solutions (used alongside surface tension to interpret concentration-dependent behavior).
Steady-shear rheology (shear stress vs. shear rate and viscosity vs. shear rate), including power-law model parameters K (consistency index) and n (flow behavior index).
Role of the Dropometer
The paper uses Dropometer by Droplet Lab a smartphone-based tensiometer to measure surface tension via the ADSA (Axisymmetric Drop Shape Analysis) method. A pendant droplet is formed at the tip of a needle or capillary, back-illuminated, imaged at high resolution using a smartphone camera, and analyzed with specialized software that calculates surface tension numerically from the droplet geometry.
These surface-tension outputs are used throughout the “surface activity” results to compare surfactant effectiveness and to estimate approximate CAC and PSP values from changes in slope of surface-tension–concentration plots (often considered alongside conductivity plots).
Key Findings
Surface tension decreases, then levels off at higher surfactant concentration
Across polymer–surfactant mixtures, the surface tension decreases as surfactant concentration increases and tends to level off at higher concentrations. The authors interpret the initial decrease as adsorption at the air–water interface and the leveling behavior as saturation of the interface by surfactant–polymer complexes and surfactant molecules.
Amphosol is the most effective surface-tension reducer in both polymer systems
In the cross-surfactant comparisons (LR-400: Figure 19b; Praestol 2540TR: Figure 25b), Amphosol is identified as the most effective surfactant in reducing surface tension at a given concentration.
LR-400 system: surface-tension ranking across surfactants at fixed concentration
For surfactant/LR-400 polymer solutions, at any given surfactant concentration, the surface tension order reported is: Stepwet > Stepanol > HTAB > Alfonic > Amphosol.
Praestol 2540TR system: surface-tension ranking across surfactants at fixed concentration
For surfactant/Praestol 2540TR polymer solutions, at any given surfactant concentration, the surface tension order reported is: HTAB > Stepanol ≥ Stepwet > Alfonic > Amphosol.
CAC/PSP values are treated as approximate based on slope changes
The authors use changes in slope of surface tension vs. concentration plots (and paired conductivity plots) to estimate CAC and PSP values, and note that the plots do not show “sharp enough breaks” to draw definite conclusions; they also mention alternative methods (e.g., calorimetry or spectroscopy) as possible validation approaches.
Figures & Visuals
Figure 14 — Example surface-tension + conductivity response with CAC/PSP annotations (LR-400)
What it shows
Shows electrical conductivity and surface tension versus Stepanol concentration in surfactant + LR-400 solutions, with CAC/PSP indicated in the plotted trends.
Figure 19 — Cross-surfactant comparison of surface tension in LR-400
What it shows
Compares surface tension behavior across the five surfactants at matched concentration in the LR-400 polymer solution, including the reported surface-tension ordering and identification of Amphosol as most effective.
Figure 20 — Example surface-tension + conductivity response (Praestol 2540TR)
What it shows
Shows electrical conductivity and surface tension versus Stepanol concentration in surfactant + Praestol 2540TR solutions, illustrating the concentration dependence used for CAC/PSP estimation.
Figure 25 — Cross-surfactant comparison of surface tension in Praestol 2540TR
What it shows
Compares surface tension behavior across the five surfactants at matched concentration in the Praestol 2540TR polymer solution, including the reported surface-tension ordering and identification of Amphosol as most effective.
Why It Matters
The paper frames polymer–surfactant interactions as important for designing advanced fluid systems used in applications such as enhanced oil recovery, drilling, and chemical processing. Within that scope, the surface-tension measurements provide the “surface activity” component of the study, enabling direct comparison of how surfactant type influences the air–water interface behavior across the two polymer systems.
By pairing surface tension with conductivity versus surfactant concentration, the authors use the Dropometer (smartphone-based tensiometer with ADSA) to interpret adsorption/saturation behavior and to estimate approximate CAC/PSP regime markers for the tested polymer–surfactant combinations.
Practical Takeaways
Most effective surfactant in these tests
Amphosol CG is identified as the most effective surfactant for reducing surface tension at a given concentration in both LR-400 and Praestol 2540TR polymer solutions.
Common concentration-response shape
The paper describes surface tension curves that drop sharply at low surfactant concentration and level off at higher concentration, interpreted as interface saturation behavior.
Use CAC/PSP values as approximate regime markers
The authors state the plots do not exhibit sharp enough breaks for definite CAC/PSP determination and present CAC/PSP values as approximate, with calorimetry/spectroscopy mentioned as potential validation approaches.
Surfactant-dependent response differences in Praestol 2540TR
The paper notes that for Amphosol and Alfonic the surface tension drops sharply then levels off, while for Stepanol, Stepwet, and HTAB the decrease is more gradual in the Praestol 2540TR system.