Elsevier

Applied Surface Science

Volume 327, 1 February 2015, Pages 93-99
Applied Surface Science

Switchable hydrophobic/hydrophilic surface of electrospun poly (l-lactide) membranes obtained by CF4 microwave plasma treatment

https://doi.org/10.1016/j.apsusc.2014.11.149Get rights and content

Highlights

  • A facile method to control the surface wettability of electrospun poly (l-lactide) microfibrous membranes via CF4 microwave plasma treatment.

  • The etching and grafting process synergistically affected the final surface wettability of poly (l-lactide) membranes.

  • Both hydrophobic and hydrophilic surface could be obtained by adjusting the plasma power and treatment time during the CF4 plasma treatment.

Abstract

A switchable surface that promotes either hydrophobic or hydrophilic wettability of poly (l-lactide) (PLLA) microfibrous membranes is obtained by CF4 microwave plasma treatment in this paper. The results indicated that both etching and grafting process occurred during the CF4 plasma treatment and these two factors synergistically affected the final surface wettability of PLLA membranes. When plasma treatment was taken under a relatively low power, the surface wettability of PLLA membranes turned from hydrophobic to hydrophilic. Especially when CF4 plasma treatment was taken under 100 W for 10 min and 150 W for 5 min, the water contact angle sharply decreased from 116 ± 3.0° to ∼0°. According to Field-emission scanning electron microscopy (FESEM) results, the PLLA fibers were notably etched by CF4 plasma treatment. Combined with the X-ray photoelectron spectroscopy (XPS) measurements, only a few fluorine-containing groups were grafted onto the surface, so the etching effect directly affected the surface wettability of PLLA membranes in low plasma power condition. However, with the plasma power increasing to 200 W, the PLLA membrane surface turned to hydrophobic again. In contrast, the morphology changes of PLLA fiber surfaces were not obvious while a large number of fluorine-containing groups grafted onto the surface. So the grafting effect gradually became the major factor for the final surface wettability.

Section snippets

1 Introduction

Microfibrous structures fabricated by electrospinning are of particular interest due to their high specific surface area, high porosity and excellent mechanical properties that make them ideal candidates for polymer scaffolds [1], [2], [3], [4]. However, since some polymer surfaces, such as poly (l-lactide) (PLLA), are hydrophobic and its insufficient reactive side-chain groups on surface usually lead to low performances [5], its further application is severely limited [2], [6], [7], [8].

Materials

PLLA (biopla 6202F) was purchased from Ningbo Global Biological Material Co., Ltd. Its number-average molecular weights are 1.1 × 105 g/mol. Chloroform and ethanol were purchased from Tianjin Weichen Chemical Reagent Co. Ltd. China.

Electrospinning

The electrospinning apparatus is schematically depicted in Fig. 1, where the main components are shown. PLLA was dissolved in a mixture of chloroform and ethanol (3:1, v/v) to prepare a 7 wt% solution, which was then loaded into a plastic syringe fitted with a stainless

Surface morphology and water contact angle

Surface morphologies of the untreated and CF4 plasma treated electrospun PLLA microfibrous membranes were observed by FESEM, which are illustrated in Fig. 3, Fig. 4, and the water contact angle measurements of untreated and CF4 plasma-treated electrospun PLLA micro-fibrous membranes are given in Fig. 5. As can be seen in Fig. 3a, the as-spun PLLA micro-fibrous membrane is a highly porous nonwoven material with an average diameter of 847 ± 200 nm. More in detail, it was found that the untreated

Conclusion

A facile method to control the surface wettability of electrospun PLLA microfibrous membrane via CF4 microwave plasma treatment is investigated in this study. According to water contact angle analysis, both hydrophobic and hydrophilic surface could be obtained by adjusting the plasma power and treatment time during the CF4 plasma treatment. Moreover, plasma power is crucial for the surface wettability of PLLA membranes. FESEM results demonstrated that CF4 plasma treatment caused etching on PLLA

Acknowledgments

The work was funded by the Petrochemical Joint Funds of National Natural Science Fund Committee - China National Petroleum Corporation (U1362108) and China Postdoctoral Science Foundation (2014T70217).

References (49)

  • X. Wei et al.

    CF4 plasma surface modification of asymmetric hydrophilic polyethersulfone membranes for direct contact membrane distillation

    J. Membr. Sci.

    (2012)
  • H. Watanabe et al.

    Surface chemical modification of carbon nanowalls for wide-range control of surface wettability

    Plasma Processes Polym.

    (2013)
  • Z.-P. Zhao et al.

    Controllable modification of polymer membranes by long-distance and dynamic low-temperature plasma flow: AA grafting penetrated through electrospun PP fibrous membranes

    J. Membr. Sci.

    (2013)
  • H. Savoji et al.

    Development of plasma and/or chemically induced graft co-polymerized electrospun poly(vinylidene fluoride) membranes for solute separation

    Sep. Purif. Technol.

    (2013)
  • A. Khoddami et al.

    Improvement in poly(lactic acid) fabric performance via hydrophilic coating

    Prog. Org. Coat.

    (2011)
  • C. Chaiwong et al.

    Effect of plasma treatment on hydrophobicity and barrier property of polylactic acid

    Surf. Coat. Technol.

    (2010)
  • P. Chen et al.

    Effects of oxygen plasma treatment power on surface properties of poly(p-phenylene benzobisoxazole) fibers

    Appl. Surf. Sci.

    (2008)
  • F. Rombaldoni et al.

    Adhesion enhancement of electrospun nanofiber mats to polypropylene nonwoven fabric by low-temperature oxygen plasma treatment

    Surf. Coat. Technol.

    (2013)
  • V. Švorčík et al.

    Modification of surface properties of high and low density polyethylene by Ar plasma discharge

    Polym. Degrad. Stab.

    (2006)
  • C. Wang et al.

    Studies on surface modification of poly(tetrafluoroethylene) film by remote and direct Ar plasma

    Appl. Surf. Sci.

    (2008)
  • N. Slepickova Kasalkova et al.

    Biocompatibility of plasma nanostructured biopolymers

    Nucl. Instrum. Methods Phys. Res. Section B (Beam Interact. Mater. Atoms)

    (2013)
  • P. Slepicka et al.

    Surface ablation of PLLA induced by KrF excimer laser

    Appl. Surf. Sci.

    (2013)
  • Z.Q. Yao et al.

    Structural, mechanical and hydrophobic properties of fluorine-doped diamond-like carbon films synthesized by plasma immersion ion implantation and deposition (PIII-D)

    Appl. Surf. Sci.

    (2004)
  • F. Rossi et al.

    Polymer functionalization as a powerful tool to improve scaffold performances

    Tissue Eng. Part A

    (2013)
  • Cited by (0)

    View full text