Tuning the Bulk and Surface Properties of PDMS Networks through Cross-Linker and Surfactant Concentration

Litwinowicz, Matthew; Rogers, Sarah; Caruana, Andrew; Kinane, Christy; Tellam, James; Thompson, Richard

Abstract

The elastic modulus and hydrophilicity of cross-linked poly(dimethylsiloxane) (PDMS) are tunable via cross-linker concentration and the addition of a simple surfactant, C12E4, before curing. However, the surfactant concentration, [C12E4], reduces the elastic modulus (73% lower for 6.3% w/w) because it reduces the extent of curing. This is likely because the hygroscopic surfactant results in water poisoning of the catalyst. Three distinct time-dependent hydrophilicity profiles were identified using water contact angle analysis with [C12E4] determining which profile was observed. This indicates the concentration-dependent phase behavior of C12E4 within PDMS films. Changes in phase behavior were identified using small-angle neutron scattering (SANS) and a compatibility study. No surface excess or surface segregation of surfactant was observed at the PDMS–air interface. However, a surface excess revealed by neutron reflectivity against a D2O interface indicates that the increase in hydrophilicity results from the migration of C12E4 to the film interface when exposed to water.

Citation

Litwinowicz, M., Rogers, S., Caruana, A., Kinane, C., Tellam, J., & Thompson, R. (2021). Tuning the Bulk and Surface Properties of PDMS Networks through Cross-Linker and Surfactant Concentration. Macromolecules, 54(20), https://doi.org/10.1021/acs.macromol.1c01600

• Journal Article Type: Article
• Online Publication Date: Oct 6, 2021
• Publication Date: 2021
• Deposit Date: Jan 11, 2022
• Publicly Available Date: Jan 11, 2022
• Journal: Macromolecules
• Print ISSN: 0024-9297
• Electronic ISSN: 1520-5835
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 54
• Issue: 20
• DOI: https://doi.org/10.1021/acs.macromol.1c01600
• Public URL: https://durham-repository.worktribe.com/output/1220868