Primary surface measurement reported
Water contact angle (wettability) of electrospun polystyrene fiber mats (and a PS film reference surface) using water droplets.
Client Citation Analysis
Influence of Mixed Solvent in the Morphology and Hydrophobicity of Electrospun Polystyrene Porous Fibers
This study electrospins polystyrene (PS) from chloroform/DMF mixed solvents and uses water contact-angle measurements (via a Droplet Lab tabletop goniometer) to quantify how solvent ratio and applied voltage influence the hydrophobicity of the resulting fiber mats.
At-a-Glance Summary
How the paper credits the instrument
The authors state: “The contact angle was analyzed on a tabletop goniometer from Droplet Lab.” (model not specified)
How the contact-angle data were used in the study
Water contact angle values and images are used to compare hydrophobicity across electrospinning conditions (chloroform:DMF ratio and applied voltage) and to support a Cassie–Baxter treatment of rough-surface wettability reported as fractional projected area (f).
Paper Details
Title
Influence of Mixed Solvent in the Morphology and Hydrophobicity of Electrospun Polystyrene Porous Fibers
Authors
Guilherme Henrique França Melo; Uttandaraman Sundararaj
Journal
Macromolecular Rapid Communications
Year
2024
Volume
45
Pages / Article
2400403
License
Creative Commons Attribution-NonCommercial-NoDerivs License
Article type
Research Article, peer-reviewed. Received 30 May 2024, revised 12 August 2024, published online 26 September 2024. Issue 21.
Institution
Department of Chemical and Petroleum Engineering, University of Calgary.
Funding & interests
Funded by NSERC grant 05503/2020 and Alberta Innovates graduate scholarships. The authors declare no conflict of interest. Droplet Lab appears in no funding, acknowledgement or affiliation statement — it is named once, as an equipment source in the Characterization section.
Data availability
The paper's Data Availability Statement reads, in full: "Research data are not shared."
8.4
Scopus metrics (Elsevier / Scopus rating 2024)
Scopus metrics (Elsevier / Scopus rating 2024)
CiteScore subject ranks (CiteScore 2024)
- Q1 - Chemistry: Organic Chemistry (29/212)
- Q1 - Materials Science: Polymers and Plastics (32/167)
- Q1 - Materials Science: Materials Chemistry (63/324)
0.833
Scopus metrics (Elsevier / Scopus rating 2024)
1.078
Scopus metrics (Elsevier / Scopus rating 2024)
What Was Measured
Primary surface / interfacial measurement
Water contact angle of electrospun PS fiber mats with water, presented as contact-angle images and contact angle versus applied voltage for multiple chloroform:DMF solvent ratios.
Supporting measurements
Fiber morphology (including fiber and pore dimensions) by SEM, plus solution electrical conductivity and viscosity; surface area and porosity were obtained via gas adsorption and discussed alongside wettability results.
Electrical conductivity
Electrochemistry Meter Orion VersaStarPro (Thermo Scientific)
Viscosity
Rheometer Anton-Paar MCR 302 (coaxial cylinder system, ISO 3219)
Morphology imaging
Scanning Electron Microscope (SEM) Zeiss SIGMA VP
Fiber and pore sizing
ImageJ
Contact angle
“tabletop goniometer from Droplet Lab”
Surface area / porosity
ASAP 2460 (Micromeritics)
Role of the Droplet Lab goniometer
The paper uses the Droplet Lab tabletop goniometer to analyze water contact angle on electrospun PS fiber mats, with representative droplet images (including a PS film shown as a smooth-surface reference) and quantitative contact-angle values reported across electrospinning conditions.
These contact-angle outputs are used to compare hydrophobicity trends with solvent ratio and applied voltage and to parameterize a Cassie–Baxter-based calculation of fractional projected area (f) reported for the fiber mats.
Bring This Measurement Into Your Lab
If you need water contact angle on electrospun fiber mats or other rough hydrophobic surfaces, we can show you the same measurement on your samples.
Key Findings
High hydrophobicity across electrospun mats
The fiber mats are described as highly hydrophobic based on water contact-angle characterization, with reported contact angles spanning from 130.1° to 143.2° across the studied conditions.
Voltage-dependent increase in contact angle
The authors report: “Generally, the contact angle increases as applied voltage increases,” based on the contact angle versus voltage comparison for multiple solvent ratios (Figure 7 and Table 5).
Highest reported contact angle at 30:70 and 22.5 kV
The highest contact angle value in Table 5 is 143.2 ± 0.6° for the chloroform:DMF ratio of 30:70 at 22.5 kV.
Morphology-based interpretation of contact-angle changes
The paper explains the voltage-driven contact-angle increase as a combined effect of reduced fiber diameter, increased bead frequency, and pores on the fiber surface, which together increase surface roughness and promote hydrophobic behavior.
Cassie–Baxter-derived f values indicate low projected solid fraction
Using the Cassie–Baxter model, the authors report fractional projected area (f) values that are less than 0.3 for all samples (Table 6), and highlight sample C:D_30:70_22.5 with f = 0.143 and an "air below the droplet" contribution of 0.857. These are calculated values, not measured air fractions: the paper states that "the Cassie-Baxter model is used, therefore, it is assumed that water does not penetrate the electrospun fibers." The f values are calculated from the measured water contact angles (Table 5) using Equation (3).
Solvent ratio influences fibre morphology (Zeiss SIGMA VP SEM)
From the Conclusion: "the solvent mixture plays an important role in the morphological formation of the fibers, with a chloroform:DMF volume ratio equal to 70:30 leading to thinner fibers in the range of 1 μm with an internal and external porosity. While the use of a chloroform:DMF volume ratio of 30:70 leads to fibers with the presence of beads and only internal porosity." Fibre diameters span 0.95 to 2.84 µm (Table 4), with pores on the fiber surface ranging from 20–50 nm nanopores to larger pores of about 100–200 nm (Abstract), and external porosity around 100 nm on the 70:30 blend.
Figures & Visuals
What it shows
Shows contact-angle images of the PS film (smooth surface reference) and electrospun samples made with different chloroform:DMF ratios at 22.5 kV.
What it shows
Plots contact angle versus applied voltage for fiber mats produced using the different chloroform:DMF ratios, supporting the stated trend of increasing contact angle with voltage.
Why It Matters
Within the paper's framing, water contact angle is the study's only wettability measurement, connecting electrospinning conditions (mixed-solvent ratio and applied voltage) to the hydrophobic performance of porous PS fiber mats. Morphology — fibre diameter, bead formation and pore structure — was characterised separately by SEM on a Zeiss SIGMA VP (Figures 2 to 4).
The authors position these hydrophobic, porous fiber mats as candidates for applications including textiles, filtration, and biomedical fields, with contact-angle results serving as the study’s primary wettability evidence alongside morphology and porosity characterization.
Surface area and conductivity values as reported
The abstract gives the BET surface area as "≈35 m² g⁻¹"; Section 3.3 reports 135.78, 23.59 and 21.39 m² g⁻¹ for the 70:30, 50:50 and 30:70 samples electrospun at 22.5 kV. Section 3.1 gives solution conductivities of 0.61, 0.42 and 0.40 μS cm⁻¹ for 70:30, 50:50 and 30:70, and Table 3 lists conductivity by solvent ratio. When citing these values, refer to the specific section or table. None of them involve the contact angle data.
Expert Perspective
Practical Takeaways
Contact angle as the hydrophobicity comparator
The study uses water contact angle (measured on a Droplet Lab tabletop goniometer) to compare hydrophobicity across mats produced with different chloroform:DMF ratios and voltages.
Voltage-driven hydrophobicity shift
Contact angle increased with applied voltage in each solvent series (Figure 7 and Table 5); the paper's own wording is "Generally, the contact angle increases as applied voltage increases". The 30:70 series runs 137.9 → 139.6 → 139.9 → 143.2°, with the smallest step (0.3°) between 17.5 and 20.0 kV.
Condition associated with the highest contact angle
The highest reported contact angle is 143.2 ± 0.6° for the 30:70 chloroform:DMF condition electrospun at 22.5 kV (Table 5).
Cassie–Baxter parameter reported from contact-angle analysis
The paper reports Cassie–Baxter fractional projected area (f) values (Table 6) and highlights C:D_30:70_22.5 with f = 0.143 and an air contribution under the droplet of 0.857. These are calculated under the paper's stated Cassie–Baxter assumption that water does not penetrate the electrospun fibers.
Morphology-linked interpretation of wettability
The authors attribute contact-angle differences to changes in fiber diameter, bead formation, and pore presence, describing these as contributors to increased roughness and hydrophobic behavior.
Frequently Asked Questions
What did the Droplet Lab instrument measure in this study?
The authors state that contact angle was analyzed on a tabletop goniometer from Droplet Lab. They measured the water contact angle of electrospun polystyrene fiber mats made with three chloroform:DMF ratios (70:30, 50:50 and 30:70) at four applied voltages from 15.0 to 22.5 kV, with a polystyrene film shown as a smooth surface reference (Figure 6).
What contact angle values were reported?
All fiber mats were highly hydrophobic, with contact angles from 130.1 ± 1.6° (50:50, 15.0 kV) to 143.2 ± 0.6° (30:70, 22.5 kV) in Table 5. The authors report that contact angle generally increased with applied voltage, and attribute this to thinner fibers, more beads and surface pores that together increase roughness.
What do the Cassie–Baxter values mean, and what was not measured?
The authors used the measured angles in the Cassie–Baxter model to calculate a fractional projected area (f) below 0.3 for all samples, with 0.143 for the 30:70, 22.5 kV mat. These f values are calculated under the stated assumption that water does not penetrate the fibers, rather than measured directly. The paper reports water contact angle only, without advancing, receding or sliding angles.