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Published on: January 7, 2019
Tuning the Surface Properties and Biofouling Resistance of Fluorinated Siloxane Copolymers
Taysha B L Telenar1,2, Amanda Godar3, Jae Sang Lee1
1Department of Chemical Engineering, School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85281, United States.
Abstract:
This study explores the suitability of fluorinated polysiloxanes in medical applications through biofouling studies with Escherichia coli MG1655 (E. coli) and Pseudomonas aeruginosa PAO1 (P. aeruginosa). Commercially available fluorinated poly(dimethylsiloxane) poly(trifluoropropyl methylsiloxane) (PTFPMS) exhibits a significantly higher resistance to biofouling compared to traditional poly(dimethylsiloxanes) (PDMS), such as Sylgard 184. The enhanced resistance is likely due to the reduction in surface energy and friction coefficients due to the incorporation of fluorine groups. Varying the fluorination content from 0 to 35 mol % trifluoropropylmethylsiloxane (TFPMS) in cross-linked PDMS exhibits consistent patterns in tribological and surface data: increased fluorination decreases friction and surface energy while increasing roughness. Profilometry reveals the formation of circular domains as fluorine groups are introduced, which increase in size with higher fluorine content. Corresponding roughness measurements show a significant rise in three dimensional (3D) root-mean-square roughness (Sq) from 0.07 ± 0.06 μm for PDMS to 1.89 ± 0.02 μm for 22.7 mol % TFPMS. Tribological data mirror the roughness trend: the friction coefficients decrease as roughness increases. Contact angle measurements for water increase from 100° to a plateau of 110°, while those for diiodomethane increase from 65° to a plateau of 90°. Contact angle hysteresis indicates that the minimum fluorination needed to impact hydrophobicity is 22.7 mol %. Lap shear tests confirm bulk adhesion of 35 mol % TFPMS to glass (0.45 ± 0.23 MPa) and to PDMS (0.10 ± 0.04 MPa). 35 mol % TFPMS exhibits 2.7 (rough) to 10 (smooth) times lower cell adhesion for E. coli and 1.7 (smooth) to 43 (rough) times lower cell adhesion for P. aeruginosa compared to PDMS. These findings highlight how a mechanistic understanding of how polymer structure and chemistry influence fouling resistance, with implications extending beyond the medical field to many industries requiring antifouling surfaces.
Insights
Fluorinated polysiloxanes show superior resistance to biofouling by bacteria like Escherichia coli and Pseudomonas aeruginosa compared to traditional materials. Increased fluorine content reduces surface energy and friction, enhancing antifouling properties for medical and industrial applications.
Area of Science:
- Materials Science
- Biomaterials Engineering
- Surface Chemistry
Background:
- Poly(dimethylsiloxane) (PDMS) is widely used but susceptible to biofouling.
- Fluorinated polymers offer potential for improved surface properties.
- Understanding the relationship between polymer structure and biofouling is crucial.
Purpose of the Study:
- To evaluate the biofouling resistance of fluorinated polysiloxanes for medical applications.
- To investigate the effect of varying fluorination content on surface properties and bacterial adhesion.
- To compare the performance of fluorinated poly(dimethylsiloxane) (PTFPMS) with traditional PDMS.
Main Methods:
- Biofouling studies using Escherichia coli and Pseudomonas aeruginosa.
- Surface characterization including profilometry and contact angle measurements.
- Tribological testing to assess friction coefficients.
- Lap shear tests to evaluate adhesion properties.
Main Results:
- PTFPMS demonstrated significantly higher resistance to biofouling than PDMS.
- Increased fluorination decreased surface energy and friction coefficients.
- Roughness increased with fluorination, forming distinct circular domains.
- Fluorination content of 22.7 mol % TFPMS was the minimum to impact hydrophobicity.
- 35 mol % TFPMS showed substantially lower bacterial cell adhesion compared to PDMS.
Conclusions:
- Fluorinated polysiloxanes, particularly PTFPMS, offer excellent antifouling properties.
- Surface energy reduction and altered surface topography due to fluorine incorporation are key to enhanced resistance.
- These findings have broad implications for developing antifouling surfaces in various industries.
