The Relationship between Oxygen Permeability and Phase Separation Morphology of the Multicomponent Silicone Hydrogels

Abstract

In this article, the multicomponent copolymers were prepared by the copolymerization of two hydrophobic silicon-containing monomers bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate (SiMA) and tris(trimethylsiloxy)-3-methacryloxypropylsilane (TRIS) with three hydrophilic monomers 2-hydroxyethyl methacrylate, N-vinylpyrrolidone, and N,N-dimethyl acrylamide. The copolymers were hydrated to form transparent silicone hydrogels. The oxygen permeability coefficients (Dk) of hydrogels were measured, and their relationships with the equilibrium water contents (EWC) and the types and contents of silicon containing monomers as well as the phase separation structures of silicone hydrogels were analyzed in detail. The results showed that the EWC decreased as the increase of SiMA content. The relationship between Dk and SiMA content, as well as that between Dk and EWC, showed inverted bell curve distributions, which meant two main factors, i.e., silicon-oxygen bond in silicone and water in hydrogel, contributed to oxygen permeation and followed a mutual inhibition competition mechanism. The internal morphologies of the hydrogels were observed by transmission electron microscope, and the results showed that the hydrogels presented two different phase separation structures depending on the types of the silicon-containing monomers. The silicone phase in SiMA containing hydrogel presented to be a granular texture, while the silicone phase in TRIS containing hydrogel formed a fibrous texture which resulted in a higher Dk value. These results could help to design a silicone hydrogel with better properties and wider application.

Multifunctional sensors based on silicone hydrogel and their responses to solvents, pH and solution composition

“…Ying et al proposed a multiphase‐transition mechanism to explain this abnormal response in which there is an interaction between the soft and hard segments and the responsiveness of one affects the responsiveness of the other . As discussed in our previous report, the silicone phases and hydrogel phases are generated and aggregated during the copolymerization of hydrophilic and hydrophobic monomers . The silicone phase is the hard segment and the hydrogel phase is the soft segment in our prepared hydrogels.…”

“…The silicone hydrogels were prepared using the following method . The photoinitiator D‐1173 and crosslinker EGDMA were combined in a flask.…”

“…A great deal of research has focused on the preparation and properties of multifunctional silicone hydrogels . Some silicone hydrogels display an obvious change in volume in response to pH and solvent stimuli which can be observed by the naked eye .…”

The Relationship between the Hydrophilicity and Surface Chemical Composition Microphase Separation Structure of Multicomponent Silicone Hydrogels

“…49 The results showed that the internal compositions were also not homogeneous, and the content of silicon element in bulk hydrogel is obviously less than that on the surface. The surface of silicone hydrogel became hydrophobic mainly due to the enrichment of silicon group.…”

“…So the dark areas were hydrophobic SiMA phase and the size of this phase region was about 100 nm, which was consistent with the result observed using TEM. 49 These phase separation structures made the surface of the hydrogel uneven, meanwhile, many tiny holes formed on the surface of SiMA hydrogel as shown in Figure 7A. Figure 2C showed the SEM image of the same SiMA hydrogel.…”