A Facile Method for Permanent and Functional Surface Modification of Poly(dimethylsiloxane)

Abstract

Poly(dimethylsiloxane) (PDMS) is the choice of material for a wide range of applications, 1-3 because PDMS has many advantageous properties such as chemical inertness, nontoxicity, ease of handling, and commercial availability. It is impossible, however, to have one material that meets all the individual needs of microfluidic systems, 1 micro-electromechanical systems (MEMS), 2 and cellular study. 3 New materials have been developed to replace PDMS. For example, a photocurable perfluoropolyether (PFPE) was synthesized to fabricate microfludic devices that were organic solvent compatible. 4,5 In a consensus, it is costly to develop a new elastomer for each individual need. And we believe surface modification of PDMS will be a cost-effective and time-saving strategy, if a facile method for surface modification can be developed, since surface modification retains the desired bulk properties of PDMS and reveals the need for new material development.A number of strategies have been developed for PDMS surface modification, which can be divided into two categories, namely physisorption and chemical coupling. Physisorption of materials to PDMS surface, such as surfactants 6 and polyelectrolytes 7 are driven by hydrophobic force and electrostatic force, respectively. This simple method ensures PDMS based devices after modification perform well in situations that only require moderate density and thickness of coatings, and only to sustain low shear force.Chemical coupling is stable but is difficult to achieve because PDMS is chemically inert, which is ironically one of its merits. Common for this approach, the first step is to apply high-energy bombardment (i.e., plasma) to PDMS surface, which results in a silicate layer with functional groups on the surface, such as -OH and -NH 2 . Those functional groups not only render the surface hydrophilicity but also allow further modification via chemical coupling. 8 Chemical coupling has two problems: (1) Plasma treatment is easy but not sustainable; recovery of hydrophobicity of treated PDMS is well documented. 9 High-energy bombardment also has the tendency to damage PDMS. Furthermore, this strategy is only applicable to planar structure because of its limited penetration depth. (2) Concentration gradient in "grafting to" strategy prevents the preparation of thick and dense films. 10 We reported herein a facile method for permanent and functional surface modification of PDMS based on a commercial material. First, a vinyl-terminated initiator (v-initiator, part C in Scheme 1) was mixed with the viscous base and curing agent of Sylgard 184, resulting in an initiator integrated PDMS (iPDMS). The base is a poly(dimethyl-methylvinylsiloxane) prepolymer with small amount of platinum (Pt) catalyst (part A in Scheme 1) and the curing agent is a mixture of vinyl-endcapped PDMS precursors and poly-(dimethyl-methylhydrogenosiloxane) precursors as cross-linkers (part B in Scheme 1). Upon mixing together (the so-called curing process), the vinyl groups and the hydrosilane hydrogens undergo ...

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

“…As described in the literature, 5 we thoroughly mixed component A and component B consisting of Sylgard 184 and undec-10-enyl-2-bromo-2-methylpropanoate at a desired mass ratio (10/1/0.13). The mixture was then cured at 80 C for 2.5 h. The substrates were cut into small discs (0.6 cm diameter) and rinsed in hexane for 24 hours to extract any physisorbed and entrapped undec-10-enyl-2-bromo-2-methylpropanoate.…”

Molecular Aggregation State of Surface-grafted Poly{2-(perfluorooctyl)ethyl acrylate} Thin Film Analyzed by Grazing Incidence X-ray Diffraction

“…Ma et al have prepared poly{2-(perfluorooctyl)ethyl methacrylate} brush on cross-linked polydimethylsiloxane containing the alkylbromide moiety to give a stable hydrophobic surface. 16 Diblock copolymer consisting of poly(methyl acrylate)-block-poly(pentafluoro acrylate) has also been prepared by surface-initiated ATRP from porous silica immobilized with alkyl bromide. 17 The solvent repellency of the porous silica surface was improved by grafting of fluoropolymers.…”

Functionalization of Silicone Rubber Surfaces towards Biomedical Applications

“…Since the graft ing density and thickness of polymer brushes play an important role in preventing microbial adhesion, the most suitable procedure to grow polymer brushes from a surface ("graft ing from") is atom transfer radical polymerization (ATRP) [6,128,129]. Atom transfer radical polymerization is a catalyzed reversible redox process that belongs to the category of controlled/living radical polymerization as it obeys four major criteria: polymerization exhibits a fi rstorder kinetic behavior, the degree of polymerization (DP) can be predetermined, a pre-defi ned and (usually) narrow molecular mass distribution can be achieved, and fi nally it allows for long-lived polymer chains with preserved endfunctionalities (this means that new and diff erent monomers can be added later to continue another polymerization reaction; also, other molecules-including biomoleculescan be coupled to these dormant terminals as well) [130,131].…”