Silanization of Plasma-Activated Hexamethyldisiloxane-Based Plasma Polymers for Substrate-Independent Deposition of Coatings with Controlled Surface Chemistry

Abstract

Plasma polymerization has emerged as an appealing technique for surface modification because of its advantages over a variety of conventional techniques, including ease-of-use and the possibility to modify nearly any substrate. One of the main challenges of plasma polymer-based surface modification, however, is having control over the coating chemistry, as plasma deposition generates a diversity of chemical structures. Therefore, this study presents an alternative plasma-based method for the fabrication of coatings that contain selective functionalities. In a first step, hexamethyldisiloxane (HMDSO) plasma polymerization is performed in a medium-pressure dielectric barrier discharge (DBD) to deposit polydimethylsiloxane (PDMS)-like coatings. In a second step, this coating is exposed to an air plasma in a similar DBD setup to introduce silanol groups on the surface. These groups are used in a third and final step as anchoring points for grafting of (3aminopropyl)triethoxysilane (APTES) and (3-bromopropyl)trichlorosilane (BrPTCS) to selectively introduce amino or bromo groups, respectively. X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) measurements indicated that the first two steps were successful. Moreover, the coating could be synthesized on three different surfaces, namely, glass, ultrahigh-molecularweight polyethylene, and polytetrafluoroethylene, indicating the wide applicability of the developed procedure. Afterward, XPS also proved that the APTES and BrPTCS grafting resulted in the formation of a coating containing primary amines and alkyl bromides, respectively, in combination with an organosilicon matrix containing silanol groups as remaining reactive groups, proving the successful synthesis of selective functional plasma-based coatings. The intermediate air-plasma-activation step was demonstrated to be necessary for successful and stable grafting of the final layer. In conclusion, this study established a general procedure for the development of coatings with selective functionality that can be applied on a wide variety of substrates for, e.g., biosensor applications, biomolecule, or polymer immobilization or for the synthesis of antibacterial coatings.

Bonding antimicrobial rhamnolipids onto medical grade PDMS: A strategy to overcome multispecies vascular catheter-related infections

“…The XPS spectrum of the PDMS exhibited a O1s/C1s photoemissions ratio of 1.09, while for the PDMS-RLs the ratio determined was 0.48, which indicates that the functionalization with RLs changed the PDMS surface chemical compositions by introducing more carbon. After curve-fitting, it can be observed that the high-resolution C1s XPS spectra of the PDMS exhibited four peaks, two well defined at 284.8 eV (C-Si/C-C/ C-H) and 285.5 eV (C-OH), and one small peak at 286.6 eV (C-O/C-N) [41,42]. However, in the C 1 s core-level spectrum of the PDMS-RLs surface (Fig.…”

Plasma Polymerized Coatings on Hollow Fiber Membranes-Applications and Their Aging Characteristics in Different Media

“…Coatings produced from the plasma polymerization of siloxanes and perfluoro monomers are the main focus of this study. Plasma polymerized silanes, siloxanes, and silazanes coatings have been of interest to plasma polymer chemists for many years [ 32 , 33 , 34 , 35 , 36 ]. They offer convenient thin-film alternatives to conventional polysiloxanes, such as silicone rubber, which are versatile polymers and find vast applications in biomedical engineering, electrical engineering, aerospace engineering, automotive applications, O-rings, and many other fields [ 37 ] but are difficult to deposit as thin films.…”

Comparison of the physicochemical properties and aging behavior of two different APTES-derived plasma polymer-based coatings

“…In the last decades, plasma polymerization emerged as an attractive technique for surface modification because of its advantages over a variety of conventional techniques. [1][2] Usually, plasma polymerization refers to the deposition of cross-linked, sub-micrometer coatings by introducing organic compounds (often called precursors or monomers) in a non-thermal plasma. [3][4] A variety of different types of plasma polymerization exist, among which plasma-enhanced chemical vapor deposition (PECVD) is the most investigated type.…”

“…3,7 In order to synthesize coatings with a specific chemical functionality, which were previously referred to as "selective functional plasma polymer coatings", multiple studies have employed a modification step after plasma polymer deposition. 2 This can be useful for certain applications like biosensors or antibacterial coatings. Friedrich et al, for example, developed a twostep method that was based on the deposition of bromine-based plasma polymer coatings, after which diamines, diols, dithiols or sodium azides can react with the C-Br bond to form coatings with a high density of amine, alcohol, thiol and azide functionalities, respectively.…”

“…[8][9][10] More recently, plasma polymerized hexamethyldisiloxane (ppHMDSO) coatings were silanized with (3aminopropyl)triethoxysilane (APTES) and (3-bromopropyl)trichlorosilane (BrPTCS) to obtain coatings with a high density of primary amines and alkyl bromides. 2 The main advantage of this method is that the ppHMDSO coating can be deposited on any surface to make them suitable for further silanization reactions. Additionally, other functionalities can be introduced by this technique due to the wide variety of available commercial silanization agents.…”