Tailoring Dynamic Chains of Cross‐Linked PDMS to Hinder Oil Penetration

Abstract Polydimethylsiloxane (PDMS) is the most studied organosilicon polymer, finding broad applications in soft lithography of microfluidic devices, wearable electronics insulation, medical tubing, shielding coatings, and sealant elements. However, their cross‐linked forms swell severely in nonpolar oils due to the comparable solubility parameters. Here, an oil‐stable cross‐linked PDMS discovered by grafting flexible PDMS chains onto its polymeric networks is reported, which enables surface‐exposed chains with high dynamics. It is found that the synergetic effect of mobile nanopore filling and quasi‐liquid lubrication of PDMS brushes endows the cross‐linked matrix with a reduced oil absorption ratio of up to 91.7% without altering its surface composition. Moreover, stretching polymeric networks can be re‐arranged with an adequate grafting of PDMS chains, further enhancing the antipenetration performance. This discovery of the oil‐stable surface configuration of cross‐linked PDMS breaks the constraint of siloxane elastomers not being applicable in nonpolar soluble liquid, opening a new era of research in organosilicon chemistry.