Silicone-containing prepolymers

Details Silicone-containing prepolymers Silicone-containing prepolymers

2000-02-25

2001-04-17

Truong, Duc (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From carboxylic acid or derivative thereof

C528S310000, C528S312000, C528S424000, C525S088000, C525S157000, C525S265000, C525S218000, C525S025000, C525S326900, C525S327100, C525S329400, C525S393000

Reexamination Certificate

active

06218503

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention generally relates to prepolymers based on block copolymers of a silicone-containing material and a hydrophilic material. The prepolymers are useful as a hydrogel lens material, such as a hydrogel contact lens or intraocular lens material.
Hydrogels represent a desirable class of materials for many biomedical applications, including contact lenses and intraocular lenses. Hydrogels are hydrated, cross-linked polymeric systems that contain water in an equilibrium state. Silicone hydrogels are a known class of hydrogels and are characterized by the inclusion of a silicone-containing material. Typically, a silicone-containing monomer is copolymerized by free radical polymerization with a hydrophilic monomer, with either the silicone-containing monomer or the hydrophilic monomer functioning as a crosslinking agent (a crosslinker being defined as a monomer having multiple polymerizable functionalities) or a separate crosslinker may be employed. An advantage of silicone hydrogels over non-silicone hydrogels is that the silicone hydrogels typically have higher oxygen permeability due to the inclusion of the silicone-containing monomer. Because such hydrogels are based on monomers polymerizable by free radical, these materials are thermosetting polymers.
U.S. Pat. No. 5,034,461 (Lai et al.) discloses polyurethane-containing prepolymers. These prepolymers may be copolymerized with a hydrophilic comonomer to form a silicone hydrogel copolymer that is useful as a contact lens material and other biomedical device applications. The prepolymers exemplified in U.S. Pat. No. 5,034,461 do not include any major hydrophilic portion, and therefore, these prepolymers are copolymerized with a hydrophilic monomer to form a hydrogel copolymer.
This invention provides a prepolymer useful as a hydrogel material, represented by the formula (I):
wherein
M is a hydrophilic radical derived from at least one hydrophilic ethylenically unsaturated monomer and having a molecular weight of about 500 to 5000;
each R is independently selected from an alkylene group having 1 to 10 carbon atoms wherein the carbon atoms may include ether, urethane or ureido linkages therebetween;
each R′ is independently selected from hydrogen, monovalent hydrocarbon radicals or halogen substituted monovalent hydrocarbon radicals wherein the hydrocarbon radicals have 1 to 18 carbon atoms which may include ether linkages therebetween;
a is an integer equal to or greater than 1;
each Z is independently a divalent urethane or ureido segment;
x is greater than or equal to 1, y is greater than or equal to 1; and z is greater than or equal to 1; and
each E is independently a polymerizable, ethylenically unsaturated radical.
The thermosetting polymers and copolymers formed from the prepolymers of this invention are useful in forming thermally stable biomedical devices and lenses.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The prepolymers of this invention include units of the general formula (I), represented above. The prepolymers include at least one silicone-containing block. More particularly, this silicone-containing block is derived from polysiloxanes endcapped with hydroxyl or amino radicals:
The prepolymers include at least one silicone-containing block. More particularly, this silicone-containing block is derived from polysiloxanes endcapped with hydroxyl or amino radicals:
wherein each A is an hydroxyl or amino radical;
each R is independently selected from an alkylene group having 1 to 10 carbon atoms wherein the carbon atoms may include ether, urethane or ureido linkages therebetween;
each R′ is independently selected from hydrogen, monovalent hydrocarbon radicals or halogen substituted monovalent hydrocarbon radicals wherein the hydrocarbon radicals have 1 to 18 carbon atoms which may include ether linkages therebetween, and
a is an integer equal to or greater than 1.
Preferred R′ radicals include: alkyl groups, phenyl groups, fluoro-substituted alkyl groups and alkenyl groups. Preferred R′ radicals are alkylene, preferably butylene. Preferably, a is about 10 to about 100, more preferably about 15 to about 60.
The prepolymers also include at least one highly hydrophilic block, represented by the “M” moiety in Formula (I). More particularly, this hydrophilic block can be prepared from at least one ethylenically unsaturated hydrophilic monomer, preferably an amino-substituted (meth)acrylamidc or an N-vinyl lactam. Most preferred hydrophilic monomers are N,N-dimethylacrylamide (DMA), N-vinyl pyrrolidone (NVP) and n-octylacrylamide (NOA). The “M” moiety in Formula (I) is conveniently derived from prepolymers of the aforementioned hydrophilic monomers, such prepolymers being endcapped with hydroxyl or amino radicals as in Formula (II):
A′—(M′)
n
—(A″)
m
wherein:
A′ is derived from a chain transfer agent and includes a terminal hydroxyl or amino radical;
A″ is derived from an ethylenically unsaturated monomer that includes a terminal hydroxyl or amino radical;
cach M′ is derived from at least one hydrophilic ethylenically unsaturated monomer, such as the preferred DMA, NOA and/or NVP;
m is an integer of 1 or greater, and preferably 1; and
n is about 5 to 50.
A′ in Formula (II) is derived from a chain transfer agent. More specifically, the hydrophilic ethylenically unsaturated monomer M′ is polymerized in the presence of the chain transfer agent which serves to control the molecular weight of the resultant polymer and provides hydroxy- or amino- functionality to the resultant polymer. Suitable chain transfer agents include mercapto alcohols (also referred to as hydroxymercaptans) and aminomercaptans. Preferred chain transfer agents include 2-mercaptoethanol and 2-aminoethanethiol. Accordingly, the chain transfer agent forms a terminal end of the hydrophilic polymer, with the hydroxy radical (in the case of a mercapto alcohol) providing the resultant polymer with terminal hydroxyl functionality, and the amino radical (in the case of a aminomercaptan) providing the resultant polymer with terminal amino functionality. Generally, the molar ratio of chain transfer agent to this hydrophilic monomer precursor will be about 1:5 to about 1:100.
The ethylenically unsaturated hydrophilic monomer and the chain transfer agent are copolymerized with another monomer having ethylenic unsaturation and a hydroxy-or amino- radical (A″ in Formula (II)). Accordingly, this additional monomer is also copolymerized with the hydrophilic monomer and also provides terminal hydroxy- or amino- functionality to the resultant polymer. Suitable monomers include alcohol esters of (meth)acrylic acid such as 2-hydroxyethylmethacrylate (Hema), allyl alcohol, amino esters of (meth)acrylic acid such as 2-t-butyl-aminoethylmethacrylate, and allylamine. Generally, this hydroxy- or amino-containing ethylenically unsaturated monomer will be at a 1:1 molar ratio to the chain transfer agent.
In the case where the “M” moiety of the hydrophilic block is based on more than one type of hydrophilic monomer, the “M” moiety is conveniently derived from prepolymers of the following Formula (IIa):
A′-((M
1
)
n1
(M
2
)
n2
-(A″)
m
wherein:
A′, A″ and m are as previously defined;
M
1
is derived from a first hydrophilic ethylenically unsaturated monomer;
M
2
is derived from a second hydrophilic ethylenically unsaturated monomer;
each of n1 and n2 is at least one, and n1+n2 is about 5 to 50.
Representative reaction schemes for these hydrophilic precursors of Formula (II) are illustrated as follows:
Representative reaction schemes are illustrated as follows in the case the hydrophilic precursors are based on two different hydrophilic monomers as in Formula (IIa):
In the above representative schemes, (DMA) is
(NVP) is
and (NOA) is
Such synthesis methods for the hydrophilic precursors will typically involve thermal polymerization by methods generally known in the art. Representative detailed syntheses of preferred precursors of F

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