Abstract
Polydimethylsiloxane (PDMS) is a silicone elastomer-based material that is used in various applications, including coatings, tubing, microfluidics, and medical implants. PDMS has been modified with hydrogel coatings to prevent fouling, which can be done through UV-mediated free radical polymerization using benzophenone. However, to the best of our knowledge, the properties of hydrogel coatings and their influence on the bulk properties of PDMS under various preparation conditions, such as the type and concentration of monomers, and UV treatment time, have never been investigated. Acrylate-based monomers were used to perform free radical polymerization on PDMS surfaces under various reaction conditions. This approach provides insights into the relationship between the hydrogel coating and bulk properties of PDMS. Altering the UV polymerization time and the monomer concentration resulted in different morphologies with different roughness and thickness of the hydrogel coating, as well as differences in the bulk material stiffness. The surface morphology of the coated PDMS was characterized by AFM. The cross section and thickness of the coatings were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The dependence of coating development on the monomer type and concentration used was evaluated by surface hydrophilicity, as measured by water contact angle. Elongation-until-break analysis revealed that specific reaction conditions affected the bulk properties and made the coated PDMS brittle. Therefore, boundary conditions have been identified to enable high quality hydrogel coating formation without affecting the bulk properties of the material.
Highlights
In recent years, silicone rubber has gained growing importance due to its beneficial properties in many promising applications including insulating coatings, microfluidics, optics, tubing in both food industry and biomedical devices, and implants [1,2,3,4,5,6,7,8]
In this study NIPAM, Hydroxyethyl methacrylate (HEMA), and AAm were selected as model monomers for the surface modification
Acrylamide monomer coatings on PDMS substrates via UV mediated free radical polymerization using benzophenone were successfully modulated by changing the acrylamide monomer concentration and controlling the UV irradiation time
Summary
Silicone rubber (polydimethylsiloxane, PDMS) has gained growing importance due to its beneficial properties in many promising applications including insulating coatings, microfluidics, optics, tubing in both food industry and biomedical devices (catheters), and implants [1,2,3,4,5,6,7,8]. PDMS lacks many of the desired characteristics for these applications because of its hydrophobic nature; for instance, PDMS shows undesirable fouling behavior by different organisms and wettability complications in microfluidic systems [2,11,12,13]. Polymers 2018, 10, 534 affects the function of the material [14,15,16]. To overcome these negative issues of PDMS, many different types of surface modification approaches have been developed. Polymer brushes have offered many fascinating possibilities to enhance the fouling resistance of PDMS, but so far, this method still requires complex synthetic approaches and the usage of undesired Fe or Cu catalysts [26,27,28,29]
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