NL8100975A - POLYMERIC SURFACES FOR BLOOD-CONTACTING SURFACES OF A BIOMEDICAL DEVICE AND METHODS FOR FORMING THEREOF. - Google Patents

Description

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Subject: Polymeric surfaces for blood-contacting surfaces of a biomedical device and methods of forming it.

A generally accepted hypothesis of blood compatibility is that it should be maximal within a narrow range of free surface energies that yield favorable interactions with plasma protein. A common measure of the free surface 5 energies is Zismanr's critical surface tension). The optimal value has been found empirically within the range of a Y at 20-30 dynes / cm (Ann. N.Y. AcafL. Sci. 17, 283 (1977)).

Conventional polymers (e.g., polyurethane) that provide the desired physical properties for blood-contacting surfaces of biomedical devices often fall outside this range of critical surface stresses.

Polysiloxanes are known for their particularly low critical surface tension and have been proposed for use in polyurethanes to improve the surface properties of these materials.

However, polys iloxan itself is known for its tendency to sweat out of a polyurethane polymer, see US Patent 3,2U3.U75.

Polysilcan polyurethane block copolymers have been proposed to modify the surface properties of blood-contacting surfaces for biomedical devices, see U.S. Patent 3,562,352. In addition, the entire blood-contacting device is made of this type of bleaching polymer or coated with this type of copolymer. The block copolymers themselves have poor structural properties due to the high polysiloxane content. On the other hand, the coated materials are particularly expensive to process because they cannot be processed by conventional thermoplastic methods such as injection molding and extrusion. The manufacture of tubes, catheters and other blood-contacting devices from this type of material is particularly expensive due to the need to employ solution techniques.

There are some publications regarding the blending of blck-30 copolymers of polydimethylsiloxane with hemopolymers of higher critical surface tension. These materials produce films with high silicone surface acacities, see e.g. Polym. Honorary. 11, kk2 (1970), ibidem 20 (1), 702 (1979) and ibidem 18 (1977). All of these articles describe the polymeric blends in terms of scientific experiments without any suggestion that the material has any biomedical properties. will find application.

The invention relates to new forms of low free surface energy polymers for use as surfaces for blood contacting devices; these are inexpensive, easy to obtain and have good processing properties.

For this purpose, the invention relates to a new technique for forming the blood-contacting surface of a biomedical device or component. In one embodiment, a minor amount of a polymeric additive is dispersed throughout the base polymer, while both are liquid to form a polymer blend. The polymeric additive comprises at least two different homopolymer chains, preferably in a graft or block copolymer form. One of the chains has a low free surface energy (e.g., polysiloxane), while the other chain is characterized by the ability to reduce the tendency of this material to diffuse away from the base polymer. Preferably, the base polymer and the second component of the polymeric additive are of the same material (e.g. polyurethaa). The polymeric additive must reduce the critical surface tension of the base polymer to make it suitable for blood.

A major facet of the invention is a technique for decreasing the free surface energy of a well structured polymer to convert a surface of such a material of incompatible blood into a blood compatible material. The term "base polymer" here refers to a polymer whose surface has been so modified. Typical hash polymers whose surfaces can be improved by the present technique include polyurethanes, polysulfones, polycarbonates, polyesters, polyethylene, polypropylene, polystyrene, poly (acrylonitrile-butadiene-sturene), polybutadiene, polyisoprene, styrene-butadiene-styrene block copolymers, styrene-polystyrene block copolymers methyl pentene, polyisobutylene, polymethyl methacrylate, polyvinyl acetate, polyacrylonitrile, polyvinyl chloride, polyethylene terephthalate, cellulose 35 and its esters, and derivatives, etc.

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The base polymer is of a type which can be molded into a self-supporting body, a self-supporting film, or applied as a coating to a self-supporting body. The final use of the final product is as a surface for a biomedical device or component.

Another property of the base polymer is that it has a critical surface tension higher than desired for a blood-contacting surface and is used in a greater amount than the polymeric additive, which is intended to reduce the value. The present measurements were performed by the direct method using a cantern angle meter of Kernco or Eame-Hart and a series of seven solvents according to the Zisman method described in Physical Chemistry for Surfaces of Adamson, biz. 339-357, bet particular 351 (3rd edition). The measurements were performed at room temperature using angles qp of solution cast films that had been annealed at 60 ° C for 4 hours. Mean contact angles were plotted on a Zisman chart using a linear regression calculator program.

According to the invention, a base polymer of the type described is mixed with a polymeric additive to reduce its free surface energy. The polymeric additive having a significantly lower value than that of the base polymer is well dispersed in the base polymer while in a liquid form to obtain a smooth polymer blend. This polymer mixture is then allowed to solidify and formed into a blood-contacting surface for a biomedical device or part. A suitable, wide range of free surface energies for the polymeric mixture is between 10 and 35 dynes / cm, while a preferred range is between 20-30 dynes / cm, most preferably 20-25 dynes / cm.

The polymeric additive comprises at least two different homopolymeric chain components with different functional properties. A hemopolymer chain (referred to here as the first component) has a relatively low value, less than that of both the base polymer and the second component, and lowers the polymer mixture. However, such a material typically has a tendency to sweat out of the 8100975 k -k base polymer.

To prevent this, at least a second hamopolymer chain (here the second component) is chemically bonded to the first component of the polymeric additive to reduce the tendency to exudate. The second component can be selected from the group of hard block polymer segments used in the preparation of thermoplastic block copolymers as described by Noshay and McGrath, Block Copolymers Overview and Critical Survey (Academic Press 1977). For biomedical applications, the hard blocks are characterized 10 also has a crystalline melting point above 37 ° C and / or a glass transition temperature also above 37 ° C. This second component has a higher free surface energy than the first. For good compatibility, the second component is preferably formed from a polymer of the same type as the base polymer.

It has been found that the homopolymer component of the adjuvant with the lowest waarde value controls the waarde value of the entire additive. the first component has a Yc value of 25 and the second one of 35, then the total c value of the tempered additive will be approximately 25.

Appropriate hamopolymers for the first component are those with a Y value in the desired range to lower the value of the base polymer to that desired for blood compatibility.

It is therefore favorable that such a first component is characterized by a value of less than 30 dynes / cm. A particularly effective '25. homopolymer for this purpose is a polydimethylsiloxane with an dec on the order of 22 dynes / cm. Techniques for forming silicone copolymers for use in the invention are known, e.g., from Noll:

Chemistry and Technology of Silicones (Academic Press, 1968). Appropriate first component polymers include, in addition to polydialkylsiloxanes, polyfluoroalkylalkylsiloxanes, polyalkylene oxides, polyolefins, poly; dienes and polyfluorocarbons. '

If the polymeric blend according to the invention is wound. by blending a preformed polymeric additive of the type shown above with a base polymer, such an additive is most preferably formed of block copolymers with alternating first and second.

81 ff 0 9 7 5 '-5- compound bonded by chemical bonds according to current techniques. E.g. such block copolymers can be formed according to the Eoshay and McGrath publication. An appropriate number of repeating units of each copolymer of a first component is sufficient to maintain the value of this copolymer, as evidenced by maintaining substantially the same glass transition temperature as the pure copolymer. Usually this figure is in the order of 5 to 10 units or more. Also, a sufficient number of repeating units of the second component must be in a segment so that the polymeric additive is solid at room temperature.

The preparation of block copolymers or multipolymers can be carried out by various methods which differ in the degree to which the structure of the resulting product can be defined.

One procedure involves coupling two or more preformed blocks prepared in the coupling reaction in separate reactions. This procedure includes a very clearly defined structure if the coupling reaction prevents these types of blocks from reacting with each other but only coupling several blocks together.

A slightly less well-defined structure arises if the two preformed blocks have the ability (via the coupling reaction) to react with each other as well as with different blocks.

An even less well-defined structure arises when a single (or more) preformed bleach is coupled to a second block, created during the coupling reaction. In this case, the initial length of the preformed bleach is known (from the individual reactions for its preparation), but the sequence distribution of the copolymer is not precisely known * because both coupling and chain growth in the reaction to form the second block is possible.

Appropriate methods of forming these and other such copolymers for use in the invention are set forth in the aforementioned Hoshay and McGrath publication.

A specific mixture according to the invention comprises a blk or graft polymer of poly (dialkylsilaxane), especially poly (dimethylsiloxane) as the first component and polyurethane as the second component. The term "polyurethane" includes polyether urethanurea-polyether urethanes, polyester urethanes or other known polyurethanes as shown in U.S. 8100975-6 patent No. 3,562,352 column 2, lines 66 et seq. This copolymer may be mixed with any base polymer having the desired physical properties. It is particularly effective with the same type of base polymer as the second component for good compatibility. If desired, three or more types of polymer chains can be used consecutively as long as at least one type has a low% c value. An excellent terpolymer additive comprises a block copolymer segment of the first and second components. The second component is attached to a segment formed of either polyethylene oxide or polyethylene oxide copolypropylene oxide, referred to below as hydrophilic components. In this case, the second component is a hard bleach with a crystalline melting point above 3T ° C or. a glass transition temperature above 37 ° C. In a terpolymer of this type, the second component bonds the first component and the hydrophilic component together. In a good terpolymer, the first component is a polydialkylsiloxane, the second component one of a broad group, such as polyurethane or polyurea urethane, and the hydrophilic component is polyethylene oxide or polyethylene oxide-propylene oxide. This terpolymer unexpectedly provides favorable improvements in blood compatibility to a base polymer having the desired structural properties such as a hard polymer of the same type as the second component.

Other forms of bonded first and second homopolymers are of the graft copolymer type. Either the. first or the second component. can act as a substrate on which the chains of a different type of hemopolymer are grafted. The method of grafting is known, see e.g. pp. 13-23 25 of the Noshay and McGrath publication. The third mechanism of Table 2-1 illustrates a basic structure suitable for opening a hydroxyalkyl terminated polydimethylsiloxane (e.g., through a urethane bond using a diisocyanate).

The ratio of first to second components in the polymer additive can vary widely as long as a sufficient amount of first component is present to decrease the value and a sufficient amount of second component to prevent sweating out of the additive. Preferably, the polymeric additive comprises at least 20% by volume of the first component. A suitable ratio is 20 to 80 vol. Of the first component and about 20 to 80 vol. Of the second type of polymer component. ·· '81 00 9 75 ..... ...........- -7-

The total amount of polymeric additive required to lower the value of the base polymer to the desired value of the

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polymeric mixture, it is without layer. E.g. it has been found that less than 5 vol., and preferably less than 1 to 2 vol. 3, total polymer additive 5 for silicone if the first component is already sufficient, even if the first component does not contain more than half or less of the additive. An appropriate polymeric additive to base polymer ratio is on the order of 0.00002 to 2% by volume of polymeric additive based on the total polymeric blend. Experimental results have shown that even if the polymeric adjuvant is initially mixed in bulk with the base polymer, it migrates to the surface to form a thin film without thin (monocolecular) film which provides the desired surface properties. Sufficient polymer measurement additive must be used to form this uniform layer The presence of an appropriate amount of polymeric additive is evidenced by a strong drop in the value of the polymer blend to approximately that of the first component. amount varies from system to system, it is usually less than 1 vol. # of the first component based on the total mixture. It is advantageous to use small amounts of polymer additive since large amounts of the first component reduce the physical properties of the polymer. can adversely affect the mixture.

It has been found that the required minimum amount of polymeric additive can be approximated by an understanding of the film thickness of a monolayer of the polymeric additive and the area to bulk volume ratio of the material produced. This is based on the simplified assumption that before the surface is saturated, virtually all polymeric adjuvant migrates to the surface.

On the basis of this insight, the minimum quantity can be calculated by a simple calculation.

A number of techniques can be used to mix the additive with the base polymer of the invention. In one method, both hasis polymer and additive, both of which are thermoplastic, are melted at elevated temperatures and thus the mixture is obtained. The polymer is then solidified by cooling. If desired, 8100975 -8-, the bulk polymer can be simultaneously processed into the final shape. The material can also be solidified and later attempted in the desired shape by thermoplastic methods, such as injection molding and extrusion.

A further mixing technique for additive and base polymer is to both dissolve in a solvent and then evaporate this solvent. A product thus remains, which can subsequently be processed "* according to thermoplastic techniques.

A third technique for forming the mixture is on-site polymerization with a generous excess (e.g., at least 95 vol. #) Of base polymer and a minor amount, e.g. less than 5 vol. #) homopolymer additive of the first component type. E.g. a low molecular weight polydimethylsiloxane with hydroxypropyl end groups can be replaced with a small amount of polyether glycol in the synthesis of a typical polyether urethane. Here, the reaction product must contain sufficient silicone / polyurethane copolymer to provide the desired surface properties. The concentration of the polymeric additive must be so low that the great majority (eg, at least 95 vol. #) Of a base polymer is attached to the additive polymer.

The additive polymer according to the invention must be accurately dispersed in the base polymer. For this purpose it is advantageous that the additive polymer is thermoplastic, soluble in organic solvents and virtually non-cross-linked.

For most biomedical applications, the base polymers of the invention must be thermoplastic so that they can easily. are processed. However, there are certain applications where the polymers can be processed in fluid form and then solidified in the form of the finished part, which can then no longer be made fluid. Such a basic polymer can e.g. thermosetting systems which are cured or vulcanized immediately after dispersion of the polymeric additive. Such systems may include two-component polyurethanes or epoxy resin systems.

A favorable system according to the invention comprises a mixture of a polymeric additive formed from a poly (dialkylsilèxan) segment, 8 1 0 0 9 7 5 ................... ...............

Chemically bonded to a polyurethane segment (e.g., a block or graft copolymer) and blended with an appropriate base polymer, e.g. of the same type of polyurethane as in the copolymer. A particularly effective system includes a polymeric additive having a block copolymer of about 50 parts by weight polydimethylsiloxane and 50% by weight polyurethane (polyester urethane) in a base polymer of polyurethane (polyester urethane). A suitable ratio is 99% polyester urethane base polymer and 0.1 # block copolymer.

A method of pretreating a base polymer to reduce its free surface energy is believed to be particularly effective in a base polymer containing high energy end groups, especially end groups that can form hydrogen bonds or react with proteins. In this case, the base polymer is first fractionated to remove the low molecular weight fraction thereby reducing the hydrogen bonding property of the remaining base polymer. Appropriate techniques for this are disclosed in Kantow, PQlymer Fractionation, Academy Press (New York-London 1967). Such techniques are liquid chromatography, especially gel permeation chromatography.

It has been found that variations in processing conditions that can otherwise strongly influence free surface energy can be reduced as a factor in systems of the invention by using a short heat treatment after surface formation. E.g. with a polyurethane base polymer and a polyether urethane / polyalkylsilixane base copolymer, it is annealed at 75 ° C for hours, giving a 25 µf value approximately equal to that of pure v polysiloxane, while taking significantly longer achieve your goal at room temperature. '

Vender has found that the polarity of the environment upon formation influences the <5 ^ value of the surface. For example, an air equilibrated surface provides a lower surface than a water equilibrated surface.

The polymeric blend of the invention is particularly effective for use as a blood-contacting surface for a biomedical device component. Such devices include auxiliary blood vessels, intra-aortic bulbs and various types of blood pumps.

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The following examples further illustrate the invention but do not limit the scope thereof.

Example I:

A characteristic synthesis of polydimethylsiloxane-polyurethane-5 block copolymer.

3

To a 500 cm four necked flask with a stirrer, a Dean and

Stark collector, a dropping funnel, a drying tube, a thermometer 3.

and an inert gas inlet became a mixture of 50 cm dimethyl-

O

Formamide and 100 cm Tetrahydrofuran were added. The mixture was heated under reflux and approximately 50 cm Tetrahydrofuran was distilled off. ;

The reaction mixture was cooled and 12.513 gm (0.05 mole) methylene bis (k-phenyl) isocyanate (MDI) added to give a clear solution. 15 g (0.015 mole) 3-hydroxypropyl was terminated from the dropping funnel poly dime thylsilox added dropwise with mol. wt. 1000. The reaction mixture was heated at 105-110 ° C for 1 hour, followed by dropwise addition of 3.15 g (0.035 mol). 1, k-butanediol in the course of if 5 minutes The polymerization lasted an additional 15 minutes, then it was cooled and precipitated by pouring into water in a mixer. The light yellow polymer was washed with water and then with ethanol and dried in a vacuum oven at 50 ° C until approx.

30-31 g of polymer (98-100 $ yield). (^) in tetrahydrofuran at. 25 ° C is 0.19.

Example II:

By replacing part of the dimethylsiloxane with hydroxypropyl end groups with polyethylene glycol, a polydimethylsiloxane / polyethyleneaxyde / polyurethanter polymer was obtained.

Example III; '

By replacing the DMF solvent with dimethylacetamide and instead of using butadiolethylene diamine, a poly-30 dimethylsiloxane / polyethylene oxide / polyurea urethanter polymer was obtained.

Example IV:

This example illustrates a solution manufacture. A food solution was prepared containing about 10% by weight mixed in a solution system of 90% tetrahydrofuran and 10% dimethylformamide. The 810 0 9 75 "........................" -11-mixture "consisted of 99.9% by weight of purified polyester urethane and for 0.1% by weight of silicone / polyurethane block copolymer. This "block copolymer" consisted of about 50 parts by weight of polydimethylsiloxane and 50% by weight polyurethane of diphenylmethane diisocyanate and "butanediol.

5 Apply this solution to stainless steel stamps by dipping several times. The solvent was allowed to evaporate and the film was removed from the stamp. The resulting material is applied to a pretreated catheter and is useful as a cardiac device when placed in the descending aorta and inflated and deflated with 10 COg against the heart beat.

The # of this film was 20-22 dynes / cm.

w

Example V;

Small test tubes were coated on their inner surface with two different polymer solutions in THF with a 10% w / w ratio. A solution resistant from polyether urethane in the solvent.

The second solution consisted of 90 parts by weight of solvent, 9 * 9 parts by weight of polyether urethane and 0.1% by weight of cc polymeric additive. This copolymer was comprised of about 50% polydimethylsiloxane and 50% polyethylene oxide-propylene glycol from Petrarch Systems with the trade designation PS 072.

Ka evaporate the solvent and equilibrate in distilled water for about 16 hours. Fresh fresh blood is placed in three tubes of this type.

The tubes coated with unmodified polyether urethane provided a blood clotting time of 39 minutes. Tubes coated with polyether-urethane containing the bldk copolymer additive provided clotting times of more than 70 minutes.

The value of the unmodified polyurethane polyurethane is approx.

28 dynes / cm. The polyether urethane containing the block copolymer 30 was about 20 dynes / cm.

Example VIi

This example illustrates thermoplastic machining.

A thermoplastic polyurethane mixed in a single screw extruder at approx. 200 ° C with a copolymer polymer additive consisting of approx. 50% by weight of polydimethylsiloxane and 50% by weight of 81 0 0 9 75 ...... ................

____.X,. ......... \ .........

Polyether urethane, such that the total silicone concentration of the mixture is 0.01% by weight. The mixture was extruded in the form of tubes suitable for the transport of blood. These tubes had a size of about 21 dynes / cm after annealing at 60 ° C for 6 hours. c3 Example VII:

This example illustrates a two-component vulcanization.

DuPont Adiprene L-167, a prepolymer with polyether urethanic cyanate end groups, was prepared for polyol treatment according to the manufacturer's instructions using a light stoichiometric 10 metric base on a butanediol / trimethylol propane mixture.

While still liquid, 0.1% by weight of the block copolymer additive of Example I was mixed with the reactants and an amine catalyst.

The resulting mixture was coated on a pre-primed titanium tube and cured in an oven at 100 ° C.

The coated connector had one of about 20 dynes / cm and was used in contact with blood to connect a blood vessel to a left ventricle auxiliary device used to treat low cardiac output.

Example VIII: ".

A Λ mm tubular prosthesis was formed by coating a stainless steel jacket with a polymer mixture of 99.9 wt.% Polyether urethanurea and 0.2% by weight of polydimethylsiloxane / polyurethane block copolymer with 50% polydimethylsiloxane, 50% polyurethane, in a dimethyl acetamide · . .

25 solution. After evaporation of the solvent, the resulting tube was removed from the jacket, extracted with distilled water at 60 ° C for 16 hours, dried and annealed at 60 ° C for 1 hour. After sterilization with ethylene oxide, this tube was applied to a goat's earotis artery. _________________-_______________—------------- When using a radiolabeled platelet technique, no increase in platelet deposition was measured compared to a hlanco experiment. A similar experiment readily demonstrates differences in platelet conversion using polyvinyl chloride tubes, which are otherwise known for their poor blood compatibility.

81 0 0 9 7 5 ............................................ ..................... ~.

Claims (35)

Method for forming a "blood-contacting surface for a" biomedical device or parts thereof ", characterized in that a) no more than 5 vol. # Of a polymeric additive is added by at least 5> 95 vol. # of a "base polymer" disperses thoroughly, while the additive and this "base polymer have a fluid form to yield a polymer blend, the polymeric additive comprising a first homopolymeric chain component chemically bonded to at least a second homopolymeric chain component of a different type 10 than the first component, which polymeric additive is characterized by one which is lower than that of the base polymer and the polymeric blend has a c between about 10 and 35 dynes / cm; and b) allows this polymeric mixture to solidify and form into a blood contact surface of a biomedical device or an on-its-part. Method according to claim 1, characterized in that the first component is characterized by a Ϋ c of less than 30 dynes / cm and a tendency to sweat, and the second component reduces this tendency to exudate. 3. Process according to claim 1, characterized in that the first coupon is a shark polymer from the group consisting of the polydialkylsiloxanes, 9 polyfluoroalkylalkylsiloxanes, polyalkylene oxides, polyolefins, polyadiene and polyfluorocarbons. i *. The method of claim 3, wherein the first component is poly-25-dimethylsilaxsn. The method of claim 1, wherein the first component is a polydialkylsiloxane and the second component is a polyurethane. The method of claim 1, wherein the second component and the base polymer are formed from the same type of copolymer. The method of claim 1, wherein the base polymer comprises end groups that have hydrogen bonding and protein reacting properties, and said base polymer is treated to remove the low molecular weight fractions and thereby reduce the hydrogen bonding properties of the base polymer before dispersion. 8100975 -3Λ- A method according to claim 1, characterized in that the polymeric mixture is also tempered. 9. Process according to claim 1, characterized in that about 0.00002 to 2 vol. Of polymeric additive is added to the base polymer, calculated per total polymer mixture. A method according to claim 1, characterized in that the polymeric additive contains at least about 20 vol. # Of the first component. The method of claim 1, wherein the polymeric additive contains 20-80 vol. # Of first component and 80-20 vol. # Of second component. The method of claim 1, wherein the polymeric mixture is deposited as a film on a biomedical device or part thereof. The method of claim 1, wherein adjuvant and base polymer 15 are in a molten form during dispersion and solidify. .. be by cooling. iH. The method of claim 1, wherein the polymeric mixture is dissolved in a solvent during mixing and this solvent is solidified before solidifying the mixture. The method of claim 1, wherein the base polymer comprises a curable thermosetting liquid polymer that solidifies upon curing. The method of claim 1, wherein the polymeric additive comprises a linear multi-block copolymer having blocks of at least the first 25 and the second components. The method of claim 1, wherein the polymeric additive comprises a graft polymer having a substrate formed from the first component and chains of the second component mounted thereon. The method of claim 1, wherein the polymeric adjuvant 30 comprises a graft polymer having a substrate consisting of the second component and chains of the first component attached thereto. 19 · Process for forming a polymer with a low free surface energy, characterized in that a) about 0.0002: -to 2 vol. # Of a copolymer additive is converted by at least 98 vol. # Of a base polymer, while the hcmc polymeric additive and the base polymer are in liquid form, whereby a liquid polymer mixture containing at least 95 vol. # pure base polymer and no more than 5 vol. # of a cc polymer of this base polymer and the copolymeric additive is formed, and b) allows this polymeric mixture to solidify, the additive polymer being characterized by a & less than that of the base polymer and the polymer blend is characterized by between about 10 and 35 dynes / cm. The method of claim 19, wherein the polymeric mixture 10 is formed into a blood-contacting surface of a biomedical device or part thereof. 21. A biomedical device or part thereof with a blood-compatible blood-contacting surface formed of a polymeric mixture containing at least 95 vol. # Of a base polymer 15 and at most 5 vol. # Of a polymeric adjuvant consisting of from a first hcopolymeric chain component that is chemically bonded to at least a second hcopolymeric chain component of a different type from the first component, which polymeric additive is dispersed throughout the base polymer, and one which is less than that of the base polymer, and wherein the polymeric mixture has a $ Q between 10 and 35 dynes / cm. Biomedical device according to claim 21, characterized in that the first component has a van of less than 30 dynes / cm and a tendency to sweat and a second component reduces this tendency. The biomedical device of claim 21, wherein the first component is a copolymer from the group of the polydialkylsiloxanes, polyfluoroalkylalkylsiloxanes, polyalkylene oxides, polyolefins, poly dienes and polyfluorocarbons. Biomedical device according to claim 21. wherein the first 30 component is polydimethylsiloxane. The biomedical device of claim 21, wherein the first component is a polydialkylsiloxane and the second component is a polyurethane. The biomedical device of claim 21 having a blood compatibility in the form of a blood contacting device 8100975-16 or part thereof. The biomedical device of claim 21, which contacts "blood in the toot of a blood-contacting layer adhered to the surface of a blood-contacting device. The biomedical device of claim 21, wherein a portion of the polymeric adjuvant is in the form of a continuous layer on the surface of a blood-contacting device. ïv The biomedical device of claim 21, wherein a portion of the polymeric adjuvant is a linear multiblock copolymer cravat with y '10 blocks of at least the first and second components on the surface. f'S V. of a device that comes into contact with blood. : '··· 30. The biomedical device of claim 21, wherein a portion of the polymeric adjuvant comprises a graft copolymer having a substrate of the first component and chains of the second component adhered thereto on the surface of a blood contacting device. The biomedical device of claim 21, wherein a portion of the polymeric adjuvant comprises a graft copolymer having a substrate of the second component and adhered chain of the first component ♦ on the surface of a blood-contacting device. 32. A process for forming a low free surface energy polymer blend from a base polymer and an adjuvant, wherein the base polymer contains graft groups capable of binding hydrogen and reacting with protein, by a) a fractionate the base polymer to remove the low molecular weight fraction and reduction. of the basis of the remaining base polymer, b) no more than about 5 vol. # of a polymeric additive by properly dispersing at least 95 vol. # of a base polymer, while additive and base polymer are in the fluid form, and a polymer blend is formed, wherein the additive comprises a first homopolymeric chain component which is chemically bonded to at least a second hcopolymeric chain component of a different type from the first component, which additive is characterized by one lower than that of the base polymer and the polymer blend has 35. between 10 and 35 dynes / cm as well as '81 0 0 9 75' ~ ·· -17- c) to solidify this polymeric mixture. 33. A blood-compatible polymer blend of at least 95 vol. # Of a base polymer and no more than 5 vol. # Of a polymeric additive from a polydialkylsiloxane segment chemically bonded to a polyurethane segment dispersed throughout the base polymer. and characterized by a Q Q lower than that of the base polymer, and wherein the polymer blend has a tussen between 10 and 35 dynes / cm. 3¾. Polymer mixture according to claim 30 in the form of a blood-contacting surface of a biomedical device or part thereof. 35. The polymer blend of claim 33 wherein the polymeric additive is a graft copolymer. 36. The polymer blend of claim 33, wherein the polymeric additive is a copolymer polymer. 37. The polymer blend of claim 33 wherein the base polymer is a polyurethane. 38. A method of forming a blood-compatible polymer mixture by a) dispersing no more than 5 vol. # Of a polymeric additive by well dispersing at least 95 vol. # Of a base polymer »while the polymeric additive and the base polymer flow the fluid form to form a polymer blend, wherein the additive has a polydialkylsiloxane-% segment component cravat chemically bonded to a polyurethane segment, which polymeric additive has a lower than that of the base polymer and the polymeric blend is comprised between 10 and 35 dynes / cm, as well as b) solidifying this polymeric mixture. 39 · A blood compatible polymer at 37 ° C consisting of a bldk polymer from a series of block segments of the formula (A) (B) (C), wherein A is a polyalkylsilcocan), B a hard block polymer segment having a crystalline melting point 37 ° C or a glass transition temperature above 37 ° C and C is a hydrophilic polymer from the group of the polyethylene oxides and polyethylene oxide propylene oxides. Polymer according to claim 39, admixed with a blood incompatible 8100975 base polymer in the ratio of at least 95% by volume base polymer and no more than 5% by volume polymeric additive. 81 0 0 9 7 5 "" "" ................. ''