Contents

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

Primary surface measurement reported

Water contact angle (wettability) of electrospun polystyrene fiber mats (and a PS film reference surface) using water droplets.

How the paper credits the instrument

The authors state: “The contact angle was analyzed on Tabletop goniometer, 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
DOI
10.1002/marc.202400403
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)
CiteScore 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)
SNIP 2024
1.078
Scopus metrics (Elsevier / Scopus rating 2024)
SJR 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.

Instruments Mentioned

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.

Method Snapshot

Method Snapshot Table

Series / samples PS solution (as prepared) Solvent ratio (chloroform:DMF, v:v) Applied voltage (kV) Surface measurement outputs reported Instruments Conditions (as reported)
Smooth-surface reference (shown in contact-angle images) PS film (used as “smooth surface” in Figure 6) — — Contact-angle image used for comparison “tabletop goniometer from Droplet Lab” —
Electrospun PS mats (Table 1 nomenclature) PS dissolved at 0.15 g mL⁻¹ 70:30 15.0, 17.5, 20.0, 22.5 Measured: water contact angle (Table 5; Figure 7). Derived, not measured: Cassie–Baxter f (Table 6), computed from the contact angle under the paper's stated assumption that water does not penetrate the fibres. “tabletop goniometer from Droplet Lab” Not reported for the contact angle measurement. The paper states the liquid (water) and the instrument, and reports standard deviations of ±0.6° to ±2.9° implying repeat measurements, but gives no replicate count, droplet volume, dispense rate, measurement temperature, humidity, drop settling time, number of positions per mat, or fitting algorithm. (Work distance 6 cm, flow rate 1.0 mL h⁻¹, collector rotation 600 rpm, 21–22 °C and 11–12% RH are the Section 2.3 electrospinning conditions — fibre production, not measurement.)
Electrospun PS mats (Table 1 nomenclature) PS dissolved at 0.15 g mL⁻¹ 50:50 15.0, 17.5, 20.0, 22.5 Measured: water contact angle (Table 5; Figure 7). Derived, not measured: Cassie–Baxter f (Table 6), computed from the contact angle under the paper's stated assumption that water does not penetrate the fibres. “tabletop goniometer from Droplet Lab” Not reported for the contact angle measurement. The paper states the liquid (water) and the instrument, and reports standard deviations of ±0.6° to ±2.9° implying repeat measurements, but gives no replicate count, droplet volume, dispense rate, measurement temperature, humidity, drop settling time, number of positions per mat, or fitting algorithm. (Work distance 6 cm, flow rate 1.0 mL h⁻¹, collector rotation 600 rpm, 21–22 °C and 11–12% RH are the Section 2.3 electrospinning conditions — fibre production, not measurement.)
Electrospun PS mats (Table 1 nomenclature) PS dissolved at 0.15 g mL⁻¹ 30:70 15.0, 17.5, 20.0, 22.5 Measured: water contact angle (Table 5; Figure 7). Derived, not measured: Cassie–Baxter f (Table 6), computed from the contact angle under the paper's stated assumption that water does not penetrate the fibres. “tabletop goniometer from Droplet Lab” Not reported for the contact angle measurement. The paper states the liquid (water) and the instrument, and reports standard deviations of ±0.6° to ±2.9° implying repeat measurements, but gives no replicate count, droplet volume, dispense rate, measurement temperature, humidity, drop settling time, number of positions per mat, or fitting algorithm. (Work distance 6 cm, flow rate 1.0 mL h⁻¹, collector rotation 600 rpm, 21–22 °C and 11–12% RH are the Section 2.3 electrospinning conditions — fibre production, not measurement.)

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." No contact angle hysteresis, advancing or receding angle, sliding angle or roll-off measurement was made to distinguish Cassie–Baxter from the Wenzel state the paper names as the alternative.

Solvent ratio controls 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 internal pores of 20–50 nm, larger pores near 100–200 nm, and external porosity around 100 nm on the 70:30 blend.

Thresholds / Regimes

The paper frames rough-surface wetting using Cassie–Baxter and Wenzel models, and reports Cassie–Baxter fractional projected area (f) values (Table 6); the authors state that f is less than 0.3 for all samples under their Cassie–Baxter assumption. Note that Cassie–Baxter Equation (3) requires θ, the contact angle on a smooth polystyrene film, as its input. The paper shows the smooth PS film only as an image in Figure 6 and does not report its numeric contact angle anywhere — not in Table 5, not in the text. Every f value in the table below therefore rests on an input that is not published, and cannot be independently recomputed from the paper.
Solvent ratio (chloroform:DMF) f at 15.0 kV at 17.5 kV f at 20.0 kV f at 22.5 kV
70:30 0.206 0.189 0.173 0.161
50:50 0.255 0.225 0.209 0.160
30:70 0.185 0.171 0.168 0.143

Figures & Visuals

What it shows

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

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, which produced four of the paper's seven figures.

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.

Internal inconsistencies in the source

Two figures conflict within the paper. The abstract reports surface area as "≈35 m² g⁻¹" while Section 3.3 gives 135.78, 23.59 and 21.39 m² g⁻¹ for the 70:30, 50:50 and 30:70 ratios — irreconcilable with ≈35 by any averaging. And the Section 3.1 conductivity values (0.61, 0.42 and 0.40 μS cm⁻¹ for 70:30, 50:50 and 30:70) are assigned to solvent ratios in the reverse order of Table 3. Neither affects the contact angle data, but both are worth knowing before citing figures from this paper.

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 generally increased with applied voltage (Figure 7 and Table 5) — the paper's own wording is "Generally, the contact angle increases as applied voltage increases" — though not monotonically in every series. The 30:70 series runs 137.9 → 139.6 → 139.9 → 143.2°, and the 0.3° step at 20.0 kV is smaller than that sample's own standard deviation of ±1.3°.

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 estimate the air fraction beneath the droplet conditional on the wetting-state assumption — the paper assumes rather than demonstrates that water does not penetrate the fibre mat, and reports no hysteresis, sliding angle or advancing/receding measurement that would test it.

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.