Engineering the Surface Properties of Poly(dimethylsiloxane) Utilizing Aqueous RAFT Photografting of Acrylate/Methacrylate Monomers Cary C. Kuliasha,* ,† Rebecca L. Fedderwitz, † Patricia R. Calvo, ‡ Brent S. Sumerlin, ‡ and Anthony B. Brennan* ,†,§ † Department of Materials Science and Engineering, § J. Crayton M. Pruitt Family Department of Biomedical Engineering, and ‡ George & Josephine Butler Polymer Research Laboratory, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States *S Supporting Information ABSTRACT: Polymeric surface grafting offers a tunable way to control the interfacial interactions between a material’s surface and its environment. The ability to tailor the surface properties of poly(dimethylsiloxane) elastomer (PDMSe) substrates with functional chemistry, wettability, and roughness can enhance the fields of biofouling, microfluidics, and medical implants. We developed a reversible addition−fragmentation chain transfer (RAFT) polymerization technique to synthesize a host of copolymers composed of acrylamide, acrylic acid, hydroxyethyl methacrylate, and (3-acrylamidopropyl)trimethylammonium chloride with targetable molecular weight from ∼5 to 80 kg/mol and low dispersity of Đ ≤ 1.13. This RAFT strategy was used in conjunction with photografting to chemically engineer the surface of PDMSe with hydrophilic, hydrophobic, and anionic groups. Varying grafting time and copolymer composition allowed for targetable molecular weight, chemical functionality, and water contact angles ranging from 112° to 14°. These new material surfaces will be evaluated for their antifouling and fouling release potential. ■ INTRODUCTION Poly(dimethylsiloxane) elastomer (PDMSe) is a ubiquitous polymeric material that is utilized in microfluidics, electro- phoretic separation, and medical devices due to its optical transparency, oxygen permeability, and low cost, in addition to its relative biocompatibility and chemical stability in biological environments. 1−4 PDMSe is easy to physically emboss with a variety of microtopographies for soft lithography, 5 biofouling research, 6 and microfluidic designs, 7 and it is commonly used as a fouling release standard due to its low modulus combined with low surface free energy (SFE), i.e., hydrophobicity, which limits the bioadhesion of some organisms to its surface. 1,8,9 However, there are several drawbacks that can limit its applicability in these areas such as its high susceptibility to nonspecific protein adhesion, 10 fouling by diverse marine organisms, such as diatoms, barnacles, and tube worms, 11 and wetting/adhesion difficulties in microfluidics. 3,12 Modifying PDMSe to reduce these negative factors is a thriving research area, and several techniques have been developed to control its surface properties including high energy discharge, 13 UV/ozone, 14 acid/base reactions, 15 silane coupling, 16,17 and surface grafting. 18−22 Unfortunately, several of the modifications that make PDMSe more hydrophilic are only temporary due, in part, to the diffusion of nonpolar low molecular weight (MW) constituents to the surface and/or reorientation of Si−O−Si bonds leading to hydrophobic recovery. 23−25 Covalently grafting polymeric chains with charged, hydrophilic, or hydrophobic groups offers a versatile and more permanent strategy to control the surface properties of PDMSe while maintaining its advantageous bulk properties, i.e., low modulus. The ideal grafting strategy should allow for precise control of graft chemistry, structure, molecular weight, and grafting density in order to tailor the surface properties for friction/ tribology, 26 colloidal stability, 27 cell adhesion, 28 protein fouling, 29−31 and marine fouling 32 applications. A bevy of traditional multistep grafting strategies have been developed for organic or inorganic substrates that utilize surface-anchored initiators such as azo compounds 33,34 or silane agents; 35,36 however, they can suffer from imprecise graft MW control and low grafting densities that limit their applicability. 33,37,38 Researchers have turned to living polymerization to provide controllable molecular weight and high graft density surfaces due in part to the low MW dispersity (Đ) that reduces steric blocking of growing graft sites. 39−42 Living chain-growth polymerization strategies employ a transiently fast and reversible propagation/termination reaction Received: December 4, 2017 Article Cite This: Macromolecules XXXX, XXX, XXX-XXX © XXXX American Chemical Society A DOI: 10.1021/acs.macromol.7b02575 Macromolecules XXXX, XXX, XXX−XXX