Wetting of Hydrophilic Electrospun Mats Produced by Blending SEBS with PEO–PPO–PEO Copolymers of Different Molecular Weight

Abstract

The interaction of electrospun mats with water is critical for many possible applications, and the water contact angle on the surface is the parameter usually measured to characterize wetting. Although useful for hydrophobic surfaces, this approach is limited for hydrophilic mats, where wicking has also to be considered. In this case, it is still unclear how the fiber surface chemical composition and morphology will affect the wetting behavior of electrospun mats. In this work, wetting was studied with different hydrophilic membranes produced by blending thermoplastic elastomer SEBS with amphiphilic PEO-PPO-PEO molecules. Three different types of PEO-PPO-PEO, with different molar masses, PEO content and physical form were used. The effect of these differences on the wetting behavior of the electrospun mats was evaluated by contact angle goniometry, wicking measurements and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 different imaging techniques. X-ray photoelectron spectroscopy was used to characterize the surface chemical composition. The smaller molecules quickly saturated the surface at low concentrations, making the mats hydrophilic. The sheath of PEO-PPO-PEO also resulted in fast absorption of water, when comparing the saturated and non-saturated surfaces. Longer PEO chain-ends seemed to hinder complete segregation and also led to a higher activation time when in contact with water. Liquid PEO-PPO-PEO was easily leached by water.

Surface properties evolution in electrospun polymer blends by segregation of hydrophilic or amphiphilic molecules

“…These new equilibrium morphologies help to explain the remarkable segregation and the evolution towards surface enrichment and saturation in the SEBS/PEO-PPO-PEO blends. As previously proposed, the low surface energy PPO block drives the segregation of the amphiphilic PEO-PPO-PEO to the surface [13,18]. Pure PEO and F127 have a similar molecular weight but the segregation is much more effective with the amphiphilic polymer.…”

“…Similarly, the F127_15 mat that was hydrophobic right after processing also became hydrophilic, although the droplet absorption time varied greatly depending on the mat region [13]. These results led to the investigation presented in Figure 3a 1 Values taken from ref [30] The harmonic mean equation was used to calculate the interfacial tension γ 12 between the polymers 1 (SEBS or PS) and 2…”

“…To achieve hydrophilization by blending two alternatives are possible: mixing the hydrophobic matrix with either a hydrophilic or an amphiphilic polymer [5]. Examples of the former include blends with poly(vinyl alcohol) (PVA) [6][7][8][9], poly(vinyl methyl ether) (PVME) [10] or poly(glycolic acid) (PGA) [11], while examples of the latter can be found in recent studies on the hydrophilization of different hydrophobic polymers using the amphiphilic block copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) with great surface segregation [12][13][14].…”

Desired properties and corresponding improvement measures of electrospun nanofibers for membrane distillation, reinforcement, and self‐healing applications

“…[ 64 ] Kurusu designed wetting hydrophilic electrospun mats of different molecular weights and found that the fiber diameter increased with increasing molecular weight at various concentrations of the polymer solution. [ 65 ] However, for some materials (such as dextran), the molecular weight has no significant effect on the nanofiber diameter. [ 62 ]…”

Multinozzle high efficiency electrospinning with the constraint of sheath gas

“…Electrospinning is a simple and low cost way to fabricate ultrathin nanofibers, which has been a promising technique in various fields including air filtration, water purification, tissue scaffolds, catalysis, flexible electronic, microwave absorption, high sensitivity sensing, and energy storage . Nevertheless, the low productivity and nonuniform collection of nanofibers are the main limitations for its industrial applications.…”