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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

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


Authors

Matthew Litwinowicz

Sarah Rogers

Andrew Caruana

Christy Kinane

James Tellam



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.

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

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