Prepolymers useful in biomedical devices

Details Prepolymers useful in biomedical devices Prepolymers useful in biomedical devices

2000-01-26

2001-11-06

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Implant or insert

C424S427000, C424S429000, C514S912000, C351S16000R, C351S16000R

Reexamination Certificate

active

06312706

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to specific prepolymers especially useful as monomers that can be formed into biomedical devices.
BACKGROUND OF THE INVENTION
Heretofore, biomedical materials especially useful commercially as contact lenses have been based upon polymers and/or copolymers of a select set of chemistries. Methylmethacrylic acid type chemistries form the oldest type, the polymers from which poly(methylmethacrylates) (PMMA) have been surpassed by hydrogel chemistries based upon poly(hydroxyethyl methacrylate) (pHEMA) or polyvinyl pyrrolidinone (pNVP), and copolymers of HEMA and NVP. These materials formed the basis for most soft contact lenses.
Silicone chemistries have played a lesser role in the marketplace, but have offered higher oxygen permeabilities than their hydrogel counterparts. They have, however, presented certain performance characteristics which limit their application—specifically surface wettability problems.
Copolymers employing PMMA types of chemistry have been employed in conjunction with silicone chemistry and hydrogel chemistry to produce a wide assortment of materials which have the common characteristics of high oxygen permeability and high modulus (rigidity). These materials have been characterized as hard gas permeable or rigid gas permeable materials.
Urethane chemistries have not been employed commercially in the contact lens market despite significant work in the area such as U.S. Pat. No. 3,786,034 issued to Blair et al relates to hard, hydrophilic polyurethane material formed from reacting a specific polyol with a polyfunctional isocyanate. U.S. Pat. No. 3,821,186 teaches similar materials as U.S. Pat. No. 3,786,034.
U.S. Pat. No. 4,136,250 teaches a polymer formed by reacting a high molecular weight polydimethyl siloxane diol with 2 mole equivalents isophorone diisocyanate and then reacting with excess hydroxy containing monomers. Essentially, this is a soft segment prepolymer endcapped with ethylenically reactive endcap. These materials are relatively weak and in their hydrated form show low degrees of elongation.
U.S. Pat. No. 4,309,526 teaches adhesive compositions which employ low molecular weight polyols reacted with diisocyanates and short chain cycloaliphatic or aromatic diols, endcapped with hydrophilic endcaps. Various characteristics such as oxygen permeability are not mentioned.
U.S. Pat. No. 4,359,553 teaches polyurethane diacrylate compositions useful as biomedical materials which are formed by reacting a diol mw 200 to 20,000 with 2 mole equivalents diisocyanate which is then reached with diethyleneglycol diacrylate to form the water soluble polyurethane. Specific applications taught in the patent are as controlled release matrices.
U.S. Pat. No. 4,454,309 teaches a hydrophilic random block copolymer with polyurethane linkage between randomly using high molecular weight polyols and low molecular weight ethylene mers. The materials absorbed 100-500% by weight additional water.
U.S. Pat. No. 4,740,533 teaches materials which are block copolymers of polyoxyalkylenes and polysiloxanes which have no hard segments.
U.S. Pat. No. 4,780,488 teaches a prepolymer with only a central soft segment endcapped with hydroxyethyl methacrylate endcaps or the like.
The art does not disclose polyurethane prepolymers useful as biomedical materials with the hard-soft-hard or the soft-hard-soft configurations disclosed herein which are oxygen permeable and still exhibit exemplary physical strength characteristics. Nor does the art teach that these prepolymers are useful as biomedical materials.
SUMMARY OF THE INVENTION
The present invention relates to prepolymers especially useful in biomedical copolymers of the general formula:
E(*D*A*D*G)
a
*D*A*D*E′
or
E(*D*G*D*A)
a
*D*G*D*E′
where
A denotes a divalent polymeric radical chosen from the group of
 wherein
R
P
denotes a straight or branched alkyl group with 1 to 6 carbon atoms and n provides for a moiety weight of the radical between 2000 and 10,000;
R
F
denotes a fluorinated straight or branched alkyl radical with 1 to 6 carbon atoms and m provides a moiety weight of between 400 and 10,000;
R
S
denotes an alkyl radical or a short chain fluorinated alkyl radical with 1 to 3 carbon atoms; and
p provides a moiety weight of 400 to 10,000;
D denotes an alkyl diradical, an alkyl cycloalkyl diradical, a cycloalkyl diradical, an alkylaryl diradical or an aryl diradical, with 6 to 30 carbon atoms;
G denotes an alkyl diradical, a cycloalkyl diradical, an alkyl cycloalkyl diradical, an aromatic diradical or an alkylaromatic diradical with 1 to 40 carbon atoms which may have ether, thio, or amine linkages in the main chain;
* denotes a urethane or ureido linkage; and
E and E′ denote polymerizable unsaturated organic radicals represented by the general chemical formula
 wherein
R
1
denotes a divalent alkylene radical with 1 to 10 carbon atoms;
R
2
denotes a —H or —CH
3
radical;
R
3
denotes a —H radical or an alkyl radical with 1 to 6 carbon atoms or a
 radical where Y is —O—, —S— or —NH— and R
4
denotes an alkyl radical with 1 to 12 carbon atoms;
Ar denotes an aromatic radical with 6 to 30 carbon atoms;
a is at least 1;
w is 0 to 6;
x is 0 or 1;
y is 0 or 1; and
z is 0 or 1.
These prepolymers are especially useful in forming copolymerizates with ethylenically unsaturated monomers which are known and used in the biomedical materials field. The resultant copolymers have a combination of oxygen permeability, surface wettability and physical strength in dry and/or hydrated forms otherwise unavailable.
DETAILED DESCRIPTION OF THE INVENTION
The prepolymers of the present invention are especially useful in making biomedical materials due to this combination of physical strength and high oxygen permeability when copolymerized with state of the art ethylenically unsaturated biomedical monomers. The combination of advantageous properties is achieved due to the specific chemistry inherent in the claimed prepolymer.
The prepolymers of the invention can be represented by the general formulae:
E(*D*A*D*G)
a
*D*A*D*E′
or
E(*D*G*D*A)
a
*D*G*D*E′
where
A denotes a divalent polymeric radical chosen from the group of
 wherein
R
P
denotes a straight or branched alkyl group with 1 to 6 carbon atoms and n provides for a moiety weight of the radical between 2000 and 10,000;
R
F
denotes a fluorinated straight or branched alkyl radical with 1 to 6 carbon atoms and m provides a moiety weight of between 400 and 10,000;
R
S
denotes an alkyl radical or a short chain fluorinated alkyl radical with 1 to 3 carbon atoms; and
p provides a moiety weight of 400 to 10,000;
D denotes an alkyl diradical, an alkyl cycloalkyl diradical, a cycloalkyl diradical, an alkylaryl diradical or an aryl diradical, with 6 to 30 carbon atoms;
G denotes an alkyl diradical, a cycloalkyl diradical, an alkyl cycloalkyl diradical, an aromatic diradical or an alkylaromatic diradical with 1 to 40 carbon atoms which may have ether, thio, or amine linkages in the main chain;
* denotes a urethane or ureido linkage; and
E and E′ denote polymerizable unsaturated organic radicals represented by the general chemical formula
 wherein
R
1
denotes a divalent alkylene radical with 1 to 10 carbon atoms;
R
2
denotes a —H or —CH
3
radical;
R
3
denotes a —H radical or an alkyl radical with 1 to 6 carbon atoms or a
 radical where Y is —O—, —S— or —NH— and R
4
denotes an alkyl radical with 1 to 12 carbon atoms;
Ar denotes an aromatic radical with 6 to 30 carbon atoms;
a is at least 1;
w is 0 to 6;
x is 0 or 1;
y is 0 or 1; and
z is 0 or 1.
The prepolymers upon polymerization form two domains which can be characterized as hard and soft domains, respectively. The soft domain generally have glass transition temperatures (Tg s) lower than room temperature whereas the hard domains have Tg s higher than room temperature. Upon polymerization, the hard segments of the prepolymer associate with one another and the soft segments form the soft domain which account for the oxygen permeabilit

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