Surface active segmented block copolymers

This application claims the benefit of Provisional Patent Application No. 61/016,844 filed Dec. 27, 2007; Provisional Patent Application No. 61/016,845 filed Dec. 27, 2007; Provisional Patent Application No. 61/016,841 filed Dec. 27, 2007; and Provisional Patent Application No. 61/016,843 filed Dec. 27, 2007.

This invention relates to a new class of tailored polymers useful as surface coatings for ophthalmic devices. These polymers can be specifically tailored using controlled radical polymerization processes and contain functional domains. Controlled radical polymerization allows the facile synthesis of segmented block copolymers with tunable chemical composition that, as a result, show different chemical properties than those prepared via conventional free radical polymerization. Surface active segmented block copolymers with hydrophobic domain(s) and hydrophilic domain(s) show good surface properties when applied to substrates.

Medical devices such as ophthalmic lenses are made from a wide variety of materials. In the contact lens field materials are broadly categorized into conventional hydrogels or silicone hydrogels. Recently, the use of silicone-containing materials (silicone hydrogels) has been preferred. These materials can vary greatly in water content. However, regardless of their water content, silicone materials tend to be relatively hydrophobic, non-wettable, and have a high affinity for lipids. Methods to modify the surface of silicone devices by increasing their hydrophilicity and improving their biocompatibility are of great importance.

A number of copolymers for surface coatings have been investigated. U.S. Pat. No. 6,958,169 discloses providing a medical device formed from a monomer mixture comprising a hydrophilic device-forming monomer including a copolymerizable group and an electron donating moiety, and a second device-forming monomer including a copolymerizable group and a surface active functional group; and, contacting a surface of the medical device with a wetting agent including a proton donating moiety reactive with the functional group provided by the second lens-forming monomer and that complexes with the electron donating moiety provided by the hydrophilic lens-forming monomer.

U.S. Pat. No. 6,858,310 discloses a method of modifying the surface of a medical device to increase its biocompatibility or hydrophilicity by coating the device with a removable hydrophilic polymer by means of reaction between reactive functionalities on the hydrophilic polymer with functionalities that are complementary on or near the surface of the medical device.

U.S. Pat. No. 6,599,559 discloses a method of modifying the surface of a medical device to increase its biocompatibility or hydrophilicity by coating the device with a removable hydrophilic polymer by means of reaction between reactive functionalities on the hydrophilic polymer which functionalities are complementary to reactive functionalities on or near the surface of the medical device.

U.S. Pat. No. 6,428,839 discloses a method for improving the wettability of a medical device, comprising the steps of: (a) providing a medical device formed from a monomer mixture comprising a hydrophilic monomer and a silicone-containing monomer, wherein said medical device has not been subjected to a surface oxidation treatment; (b) contacting a surface of the medical device with a solution comprising a proton-donating wetting agent, whereby the wetting agent forms a complex with the hydrophilic monomer on the surface of the medical device in the absence of a surface oxidation treatment step and without the addition of a coupling agent.

Many copolymers are currently made using conventional free radical polymerization techniques with the structure of the polymer being completely random or controlled by the reactivity ratios of the respective monomers. By using controlled free radical polymerization techniques one is able to assemble copolymers in a controlled fashion and, in turn, they show completely different solution and coating properties than copolymers prepared using conventional free radical polymerization techniques. Controlled free radical polymerization can be conducted by a variety of methods, such as ATRP (atom transfer radical polymerization) and RAFT (Reversible addition-fragmentation chain transfer polymerization).

There are a number of commercially available block copolymer surfactants that can function as antifoaming agents, wetting agents, dispersants, thickeners, and emulsifiers. One such surfactant class is the Pluronic® and Tetronic® block copolymers based on ethylene oxide and propylene oxide, available from BASF. Another class of surfactants is the Silwet® and Silsoft® block copolymers based on ethylene oxide and siloxane blocks, available from GE silicones. These block copolymers and a variety of others rely on ring opening polymerization methods to produce the blocks.

With the advent and rapid growth of RAFT polymerization in the late 1990\'s, block copolymers can now be prepared from a wide variety of vinyl based monomers. This opens up the toolbox for polymer chemists to synthesize countless number of block copolymer compositions. In addition, for the construction of surfactants there is a lot of chemical diversity in the selection of both the hydrophobic moieties and the hydrophilic moieties.

Surfactants or “surface active agents” lower the surface tension of water or other liquids and concentrate at the surface of the liquid. Surfactants have a common structural feature in which one portion of the surfactant molecule is highly polar or even ionic (hydrophilic or water loving) and the other portion is largely non-polar (hydrophobic or water fearing). The relationship of these two structural parts of the molecule with respect to each other controls the properties of the surfactant.

This particular invention is related to the synthesis and preparation of specifically tailored block copolymer surfactants where both the lengths of the individual blocks, the chemical composition, and the sequence distribution are carefully controlled and the affinity of these surfactants for specific substrates can be guided by the “like prefers like” principle. For example, fluorocarbons interact with higher affinity to other fluorine-containing materials, as well as silicone containing blocks will interact with higher affinity to silicone containing materials. Therefore in one embodiment of this invention, a block copolymer surfactant is prepared via RAFT polymerization that contains a hydrophilic block (NVP or DMA), and a fluorine containing hydrophobic block (perfluoroacrylate), where the surfactant is used to treat a fluorine containing substrate (i.e. Teflon or a fluoroelastomer). In another embodiment, a block copolymer surfactant is prepared via RAFT polymerization that contains a hydrophilic block (NVP or DMA), and a silicone containing hydrophobic block (TRIS-VC or M1-MCR-C12), where the surfactant is used to treat a silicone containing substrate (i.e. silicone hydrogel or a silicone elastomer).

In still another embodiment of this invention, a block copolymer surfactant is prepared via RAFT polymerization that contains a hydrophilic block (NVP or DMA), and a hydrocarbon containing hydrophobic block (Hexyl methacrylate or lauryl methacrylate), where the surfactant is used to treat a hydrocarbon based substrate (i.e. polyethylene or polypropylene).