Facile Functionalization of PDMS Elastomer Surfaces Using Thiol–Ene Click Chemistry

Abstract

A variety of methods have been developed for polydimethylsiloxane (PDMS) elastomer surface functionalization, particularly for the improvement of hydrophilicity. However, in addition to difficulties in avoiding undesired physical changes to the modified surface, including surface cracking, "hydrophobic recovery" frequently leads hydrophilically modified surfaces to completely return over time to their hydrophobic nature, with accompanying loss of accessible functional groups. Thiol-ene chemistry provides a mild and robust technology for synthetic elaboration. We demonstrate the introduction of thiol groups onto the PDMS surface via base-catalyzed equilibration of MTS ((MeO)3Si(CH2)3SH). Thiols in the product elastomer were shown to be located primarily at the air interface using EDX, XPS, and fluorescence labeling initially, and after extended periods of time: total thiol concentrations at the surface and in the bulk were established by complementary chemical titrations with DTDP (4,4'-dithiodipyridine) and iodine titrations in different solvents. The surface density of thiols was readily controlled by reaction conditions: the rate of hydrophobic recovery, which led to incomplete loss of accessible functional groups, was determined. Thiol-ene click chemistry was then used to introduce a variety of hydrophilic moieties onto the surface including a silicone surfactant and maleic anhydride, respectively. In the latter case, molecular functionalization with both small (fluorescent labels) and polymeric nucleophiles (poly(ethylene glycol), chitosan) could be subsequently induced by simple ring-opening nucleophilic attack leading to permanently functional surfaces.

Making Silicone Rubber Highly Resistant to Bacterial Attachment Using Thiol-ene Grafting

“…35 Briefly, (3-mercaptopropyl)trimethoxysilane (10% v/v) and KOH (1% w/v) were dissolved in methanol. PDMS catheters and sheets were sectioned into areas 2 × 0.5 cm and placed into the reaction solution.…”

“…35 In this study, nontoxic polymeric materials have been covalently attached to medical-grade silicone using thiol-ene chemistry to generate novel, hybrid biomaterials. The methodology offers an advance over dip coating for durability and is sufficiently versatile to allow the grafting of acrylate-based monomers of varying functionalities.…”

A facile approach to modify poly(dimethylsiloxane) surfaces via visible light-induced grafting polymerization

“…Consequently, a preliminary step that uses high-energy treatments or chemical etching to introduce functional groups such as -OH and -NH 2 on the PDMS surface, is usually needed. 19 However, these high-energy treatments and chemical etching methods have a tendency to damage PDMS. 20,21 In addition, the process of immobilizing an initiator on the PDMS surface is usually complex and timeconsuming, which hinders their industrial applications, making the production of commercial products difficult.…”

An excellent ozone-resistant polymethylvinylsiloxane coating on natural rubber by thiol-ene click chemistry

“…In addition, thiol functional groups were successfully introduced on polydimethylsiloxane (PDMS) elastomer, and the thiol-functionalized PDMS was modified with hydrophilic molecules containing enes by using the thiol-ene click reaction [14].…”