AU776330B2 - Shape memory polyurethane or polyurethane-urea polymers - Google Patents

Description

WO 01/07499 PCT/AU00/00863 1 SHAPE MEMORY POLYURETHANE OR POLYURETHANE-UREA POLYMERS The present invention relates to polyurethane and polyurethane-urea polymers which have shape memory characteristics. The polymers respond to their shape memory when heated in a temperature range of about 20 0 C to about 100°C and are suitable for manufacturing articles, devices and implants requiring shape memory properties. The polymers are particularly useful in biomedical applications.

A shape memory polymer as a cast, moulded, foamed or extruded shape is capable of remembering a basic shape such as plane configuration and dead folds and taking on a second shape when the basic shape is modified. The basic shape can be modified by changing the plane configuration and adding further folds, twists, kinks, bends and/or other three dimensional configurations at a temperature higher than the glass transition point of the polymer, but lower than the moulding temperature. The modified shape is typically set when the polymer is cooled in the modified state to a temperature lower than the glass transition temperature. The method of utilising the shape memory is by heating the modified shape to a temperature higher than the glass transition temperature thereby restoring the original shape. Polymers with such characteristics combined with biostability would find many applications in the fabrication of various medical devices. The device shape can be optimised depending on the location site, for example, the shape could be modified by coiling or collapsing and subsequent cooling to a temperature below the glass transition temperature to freeze the modified shape. Thermally triggered shape memory could then occur thereby returning the device to its original shape to enable fixing or anchoring to the location site. Medical devices which would benefit from such shape memory characteristics include bone suture anchors, vascular, esophageal and bilial stents and cochlear implantations.

WO 01/07499 PCT/AUOO/00863 2 Segmented copolymers such as thermoplastic polyurethanes usually exhibit shape memory characteristics if formulated such that the glass transition temperature of one segment falls within a useful temperature range of about 25°C to about 60 0 C. Such polyurethanes are generally prepared from polyester or polyether macrodiols, aromatic diisocyanates and chain extenders' 2 3 The shape memory polyurethane compositions disclosed in United States Patent Nos. 5,049,591 and 5,139,832 are formulated with conventional reagents used in the art of polyurethane manufacture and hence are prone to degradation, particularly under the oxidative and hydrolytic conditions present in biological environments.

The stability of such compositions in long term implant applications is expected to be very poor since commercial polyurethanes such as Estane are based on degradation-prone' 5 polytetramethylene oxide (PTMO), 4,4'diphenylmethane diisocyanate and 1,4 butanediol.

Similarly, polycarbonate macrodiol based shape memory polyurethanes are expected to have very poor hydrolytic resistance and be unsuitable for long term medical implants 6 These commercial polyurethanes often also contain small amounts of low molecular weight residues and additives that leach out of the polyurethane and cause undesirable biological responses.

United States Patent No. 5814705 discloses shape memory compositions based on blends of commercial polyurethanes such as Estane with other block copolymers.

The compatibility of the component polymers may not be sufficient to have a homogeneous shape memory polymer composition. Such compositions, particularly in long term use, may lead to poor performance due to a phase separation of the component polymers.

A range of biostable polyurethanes are disclosed in International Patent Publication Nos. W098/13405 and W099/03863 and United States Patent No. 5,393,858. We have found that by proper choice of components and the relative 3 amounts of the hard and soft segments that biostable polyurethanes can be formulated to have one glass transition temperature in a temperature range of about 20 0

C

to about 100 0 C. Such polyurethanes therefore possess both the properties of biostability, compatibility and shape memory which enable them to be used in the manufacture of medical articles, devices and implants.

According to the present invention there is provided a biostable shape memory polyurethane or polyurethane-urea polymer comprising a reaction product of and as set out under below or a reaction product of and as set out under below: a silicon-based macrodiol; a polyether of formula below; or a silicon-based macrodiol and a polyether of formula A- (CH) n(CH 2 )mn-(CH2)-A' (I) wherein 20 A and A' are endcapping groups; m is an integer of 6 or more; and n is an integer of 1 or greater, wherein the molecular weight range of the silicon-based macrodiol in component is 300 25 to 700; a diisocyanate; and .o a chain extender; or a diisocyanate; 60% by weight of a diol or diamine chain 30 extender based on the total weight of chain extender; and 40% by weight of a silicon-containing chain extender based on the total weight of chain extender, said polymer having a glass transition temperature which enables the polymer to be transformed from its original shape into a first shape at a temperature higher than the H:u7AnmetWXecp\SpecMY7974-0. I SPECIdoc 24AO04 4 glass transition temperature and maintained in said first shape when the polymer is cooled to a temperature lower than the glass transition temperature, said polymer then being capable of resuming its original shape on heating to a temperature higher than the glass transition temperature.

The term "endcapping group" is used herein in its broadest sense and includes reactive functional groups or groups containing reactive functional groups. Suitable examples of reactive functional groups are alcohols, carboxylic acids, aldehydes, ketones, esters, acid halides, acid anhydrides, amines, imines, thio, thioesters, sulphonic acid and expoxides. Preferably the reactive functional group is an alcohol or an amine, more preferably an alcohol.

Further according to the present invention there is provided a biostable shape memory composition which comprises: a blend of two or more biostable shape memory polymers comprising a reaction product of and 20 as set out under below or a reaction product i°-o of and as set out under below: a silicon-based macrodiol; the polyether of formula as defined above; or a silicon-based macrodiol and the 25 polyether of formula as defined above; a diisocyanate; and a chain extender; or a diisocyanate; and a chain extender, 30 said polymers having glass transition temperatures which enable the polymers to be transformed from their original shape into a first shape at a temperature higher than the glass transition temperature and maintained in said first shape when the polymers are cooled to a temperature lower than the glass transition temperature, said polymers then being capable of resuming their original shape on heating to a temperature higher H:\suanctU(mepLSp57974-.1 SPECIdoc I 67/04 5 than the glass transition temperature; or (ii) a blend of at least one biostable shape memory polymer as defined above in combination with a polymeric material.

Component preferably has greater than about silicon-based macrodiol, in particular greater than about 70% as such polymers possess good biostability.

The silicon-based macrodiol or macrodiamine may be a polysiloxane.

The polysiloxane may be represented by the formula (III):

HO-R

5 i- Si -R 6

-OH

R3 R4

P

(III)

wherein 15 A and A' are as defined above;

R

1

R

2

R

3 and R 4 are the same or different and selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; 20 R 5 and R 6 are the same or different and selected from a divalent optionally substituted straight chain, Sbranched or cyclic, saturated or unsaturated hydrocarbon radical; and p is an integer of 1 or greater.

25 The hydrocarbon radical for substituents R, R 1

R

2

R

3 and R 4 may include alkyl, alkenyl, alkynyl, aryl or heterocyclyl radicals. It will be appreciated that the equivalent radicals may be used for substituents Rs, R 6 and

R

7 except that the reference to alkyl, alkenyl and alkynyl should be to alkylene, alkenylene and alkynylene, respectively. In order to avoid repetition, only detailed H:\sutmnnetUep\SppecN7 7974-0I SPECIldoc 24A06A4 Sa definitions of alkyl, alkenyl and alkynyl are provided hereinafter.

The term "alkyl", denotes straight chain, branched or mono- or poly-cyclic alkyl, pref erably CI-.

12 alkyl or cycloalkyl. Examples of straight chain and branched alkyl include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, amiyl, isoamyl, sec-amyl, 1,2-dimethylpropyl, 1, l-dimethylpropyl, pentyl, hexyl, 4 -methylpentyl, 1-methylpentyl, 2 -methylpentyl, 3 -methylpentyl, 1, 1-dimethylbutyl, 2,2 -dimethylbutyl, 3,3 -dimethylbutyl, 1, 2-dimethylbutyl, 1, 3-dimethylbutyl, 1,2,2trimethylpropyl, 1,1, 2-trimethylpropyl, heptyl, 1-methylhexyl, 2, 2-dimethylpentyl, 3,3 -dimethylpentyl, 4, 4-dimethylpentyl, 1,2 -dimethylpentyl, 1, 3-dimethylpentyl, 1, 4-dimethylpentyl, 1,2, 3-trimethylbutyl, 1,1, 2-trimethylbutyl, 1,1, 3-trimethylbutyl, octyl, 6-methylheptyl, 1methylheptyl, 1,1,3,3-tetramethylbutyl, nonyl, 3-, 6- or 7-methyloctyl, 4- or 20 ethylheptyl, 2- or 3-propylhexyl, decyl, 3-, 7- and 8-methylnonyl, 5- or 6-ethyloctyl, 3- or 4-propylheptyl, undecyl, 1-, 8- or 9-methyldecyl, 3-, 6- or 7-ethylnonyl, 4- or 5-propyloctyl, 2- or 3-butylheptyl, 1-pentylhexyl, dodecyl, 9- or H:\sunrKccp\Spci\57974-). I SPECIdoc 24AW04 WO 01/07499 PCT/AUOO/00863 7- or 8-ethyldecyl, 5- or 6-propylnonyl, 2-, 3- or 4-butyloctyl, 1,2-pentyiheptyl and the like.

Examples of cyclic alkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl and the like.

The term "alkenyla denotes groups formed from straight chain, branched or mono- or poly-cyclic alkenes including ethylenically mono- or poly-unsaturated alkyl or cycloalkyl groups as defined above, preferably C 2 _1 alkenyl. Examples of alkenyl include vinyl, allyl, 1-methylvinyl, butenyl, iso-butenyl, 3 -methyl-2 -butenyl, 1-pentenyl, cyclopentenyl, 1-methyl-cyclopentenyl, 1-hexenyl, 3-hexenyl, cyclohexenyl, 1-heptenyl, 3-heptenyl, 1-octenyl, cyclooctenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl, 1-decenyl, 3-decenyl, 1, 3-butadienyl, 1,4-pentadienyl, 1,3cyclopentadienyl, 1, 3-hexadienyl, 1, 4-hexadienyl, 1, 3-cyclohexadienyl, 1,4-cyclohexadienyl, 1, 3-cycloheptadienyl, 1,3, 1,3,5,7-(cycloocta-tetraenyl) and the like.

The term "alkynyl" denotes groups formed from straight chain, branched, or mono- or poly-cyclic alkynes.

Examples of alkynyl include ethynyl, 1-propynyl, 1- and 2-butynyl, 2-methyl-2-propynyl, 2-pentynyl, 3-pezitynyl, 4-pentynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl, 1O-undecynyl, 4-ethyl-1-octyn-3-yl, 7-dodecynyl, 9-dodecynyl, lO-dodecynyl, 3-methyl-l-dodecyn-3-yl, 2-tridecynyl, 11-tridecynyl, 3-tetradecynyl, 7-hexadecynyl, 3-octadecynyl and the like.

The term "aryl" denotes single, polynuclear, conjugated and fused residues of aromatic hydrocarbons.

Examples of aryl include phenyl, biphenyl, terphenyl, quaterphenyl, phenoxyphenyl, naphthyl, tetrahydronaphthyl, anthracenyl, dihydroanthracenyl, benzanthracenyl, dibenzanthracenyl, phenanthrenyl and the like.

The term "heterocyclyl" denotes mono- or poly-cyclic heterocyclyl groups containing at least one WO 01/07499 PCT/AU0/00863 7 heteroatom selected from nitrogen, sulphur and oxygen.

Suitable heterocyclyl groups include N-containing heterocyclic groups, such as, unsaturated 3 to 6 membered heteromonocyclic groups containing 1 to 4 nitrogen atoms, for example, pyrrolyl, pyrrolinyl, imidazolyl, pyrazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazolyl or tetrazolyl; saturated 3 to 6 membered heteromonocyclic groups containing 1 to 4 nitrogen atoms, such as pyrrolidinyl, imidazolidinyl, piperidino or piperazinyl; unsaturated condensed heterocyclic groups containing 1 to nitrogen atoms, such as, indolyl, isoindolyl, indolizinyl, benzimidazolyl, quinolyl, isoquinolyl, indazolyl, benzotriazolyl or tetrazolopyridazinyl; unsaturated 3 to 6-membered heteromonocyclic group containing an oxygen atom, such as, pyranyl or furyl; unsaturated 3 to 6-membered heteromonocyclic group containing 1 to 2 sulphur atoms, such as, thienyl; unsaturated 3 to 6-membered heteromonocyclic group containing 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms, such as, oxazolyl, isoazolyl or oxadiazolyl; saturated 3 to 6-membered heteromonocyclic group containing 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms, such as, morpholinyl; unsaturated condensed heterocyclic group containing 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms, such as, benzoxazolyl or benzoxadiazolyl; unsaturated 3 to 6-membered heteromonocyclic group containing 1 to 2 sulphur atoms and 1 to 3 nitrogen atoms, such as thiazolyl or thiadiazolyl; saturated 3 to 6-membered heteromonocyclic group containing 1 to 2 sulphur atoms and 1 to 3 nitrogen atoms, such as, thiadiazolyl; and unsaturated condensed heterocyclic group containing 1 to 2 sulphur atoms and 1 to 3 nitrogen atoms, such as benzothiazolyl or benzothiadiazolyl.

In this specification, "optionally substituted" means that a group may or may not be further substituted with one or more groups selected from oxygen, nitrogen, sulphur, alkyl, alkenyl, alkynyl, aryl, halo, haloalkyl, haloalkenyl, haloalkynyl, haloaryl, hydroxy, alkoxy, 8alkenyloxy, alkynyloxy, aryloxy, carboxy, benzyloxy, haloalkoxy, haloalkenyloxy, haloalkynyloxy, haloaryloxy, nitro, nitroalkyl, nitroalkenyl, nitroalkynyl, nitroaryl, nitroheterocyclyl, azido, amino, alkylamino, alkenylamino, alkynylamino, arylamino, benzylamino, acyl, alkenylacyl, alkynylacyl, arylacyl, acylamino, acyloxy, aldehydo, alkylsuiphonyl, arylsuiphonyl, alkylsuiphonylamino, arylsuiphonylamino, alkylsuiphonyloxy, arylsuiphonyloxy, heterocyclyl, heterocycloxy, heterocyclylamino, haloheterocyclyl, alkylsuiphenyl, arylsuiphenyl, carboalkoxy, carboaryloxy, mercapto, alkylthio, arylthio, acylthio and the like.

A preferred polysiloxane is PDMS which is a compound of formula (III) wherein R, to R4 are methyl and R and R 6 are as def ined above. Preferably R 5 and R 6 are the same or different and selected from propylene, butylene, pentylene, hexylene, ethoxypropyl (-CH 2

CH

2

OCH

2

CH

2

CH

2 propoxypropyl and butoxypropyl.

The polysiloxane macrodiols may be obtained as commercially available products such as X-22-160AS from Shin Etsu in Japan or prepared according to known procedures. The preferred molecular weight range of the :polysiloxane macrodiol is 500 to about 700.

Suitable polyethers include polyether macrodiols represented by the formula H0 L(CH2)M-Oj -H

M

~.wherein m is as defined in formula above, preferably 6 to 18; and n is as defined in formula above, preferably 1 to Polyether macrodiols of formula wherein m is 6 or higher such as poly(hexamethyleneoxide) (PHNO), poly(heptamethyleneoxide), poly(octamethylene oxide) (POMO) fi:su7nneW~cp\r~m\5774-0I SPECIAdoc 24/(W04 9 and poly(decamethylene oxide) (PDMO) are preferred over the conventional PTMO. PHMO and PDMO are particularly preferred due to their relatively high glass transition temperatures.

The polyether macrodiols may be prepared by the procedure described by Gunatillake et a1 6 The molecular weight range of the polyether macrodiol is about 300 to about 2000, more preferably about 300 to about 700.

The diisocyanates may be aliphatic or aromatic diisocyanates such as, for example 4,4'-diphenylmethane diisocyanate (MDI), methylene biscyclohexyl diisocyanate

(H

12 MDI), p-phenylene diisocyanate (p-PDI), trans-cyclohexane-1,4-diisocyanate (CHDI), 1,6-diisocyanatohexane (DICH), (NDI), para-tetramethylxylenediisocyanate (p-TMXDI), meta-tetramethylxylene diisocyanate (m-TMXDI), 2,4-toluene diisocyanate (2,4-TDI) isomers or mixtures thereof or isophorone diisocyanate (IPDI). MDI is particularly preferred.

The chain extender may be selected from diol or diamine chain extenders. Examples of diol chain extenders include 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1, 10-decanediol, 1,12-dodecanediol,1,4cyclohexanediol, 1,4-cyclohexanedimethanol, p-xyleneglycol, 1,3-bis(4-hydroxybutyl) tetramethyldisiloxane, 25 1,3-bis(6-hydroxyethoxypropyl)tetramethyldisiloxane and 1,4-bis(2-hydroxyethoxy)benzene. Suitable diamine chain %6 6extenders include 1,2-ethylenediamine, 1,3-propanediamine,1,4-butanediamine, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4-aminobutyl)tetramethyldisiloxane and 1,6-hexanediamine.

The chain extender may also be a silicon-containing chain extender of the type described in our International Patent Publication No. W099/03863, the entire contents of which are incorporated herein by reference. Such chain extenders include a silicon-containing diol of the formula (VI): H:'6uiannetLKccpSpcdN37974-X). I SPECI.doc 24/0/(1

R

1 2

HO-R

5 -Si- -R 7 -Si- -R 6

-OH

R3 R4 q

(VI)

wherein

R

1

R

2

R

3

R

4 Rs and R 6 are as defined in formula (III) above;

R

7 is a divalent linking group or a divalent optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; and q is 0 or greater, preferably 2 or less.

Component of the polymer generally forms the soft segment of the polyurethane or polyurethane-urea and provides the low glass transition temperature. The high glass transition temperature is provided by the hard 0** segment components and 15 Preferably, the amount of hard segment in the polymer of the present invention is about 30 to about Gee 100 wt%, more preferably about 50 to about 80 wt%, most preferably about 60 to about 70 wt%. However, it will be appreciated that this amount is dependent on the type of *ee

G

a0 0 H:\urnnc\Kccp\Spc57974-X). I SPECIdoc 24A(W04 11 THIS AND THE FOLLOWING PAGE ARE INTENTIONALLY BLANK THE NEXT PAGE IS PAGE 13 HAsu72nwtiU,=p Spccil57974-SX) I SPECIAOc 24106104 13 soft segment polymer used, in particular the molecular weight of this polymer. For example, when the molecular weight of the soft segment polymer is about 500, then a to 60 wt% hard segment is preferred.

For most applications, it is preferred that the shore hardness of the polymer below the glass transition temperature is in the range of about 82D to about while the hardness above the glass transition temperature is in the range of about 20D to about 30D. The glass transition temperatures of the polymers and compositions of the present invention are generally in the range of about 0 C to about 100 0 C, preferably about 20 to about 60 0

C.

However, in some applications such as biotechnological applications, it may be advantageous for the glass transition temperature to be sub ambient below about 0

C.

It will be appreciated that the shape memory compositions of the present invention may include a blend of two or more of the shape memory polyurethane or polyurethane-urea polymers defined above or at least one shape memory polyurethane or polyurethane-urea polymer defined above in combination with another material. The o.o other material will preferably be of any suitable known S* type which does not substantially effect the shape memory and/or biostability properties of the polymers of the present invention and may include polymeric and nonpolymeric materials.

Examples of polymeric materials include S: conventional polyurethanes such as PELETHANE

TM

ESTANE

TM

CARBOTHANE

T

CORETHANE

T and CHRONOFLEX

T

m; shape memory polyurethanes such as those disclosed in United States Patent Nos. 5,145,935 and 5,135,786 and available from Mitsubishi Heavy Industries Ltd (distributed by Memry Corporation in the United States of America; polyolefins such as polyethylene, polypropylene, ethylene propylene H:suanrtccp SpciA57974-(X. I SPECIdoc I 1103/04 WO 01/07499 PCT/AU00/00863 14 copolymers, metallocene polymers, ethylene vinylacetate copolymers and polyvinyl chloride; polyamides; and liquid crystalline polymers such as those available from Eastman Kodak (XG7), Mitsubishi Chemical Industry (Novaculates) and Idemitsu Petrochemical Industry (Idemitsu LCP and Unitika (Lodrum LC). Such polymeric materials generally blend well with the shape memory polymers of the present invention which usually contain high levels of polysiloxane segments.

Each of the polymers forming the shape memory composition preferably have different glass transition temperatures and/or different amounts of hard segment component. Suitable compositions may include a first polymer with a low glass transition temperature, preferably below about ambient temperature and a second polymer with a glass transition temperature above the ambient temperature, more preferably above about 50 0 C. The two polymers can be blended in proportions such that the final blend will have a glass transition temperature in the preferred range of about 20 0 C to about 60 0 C. Generally the glass transition temperature of the composition is intermediate to those of the two polymers.

Alternatively, the composition may include a first polymer having a high percentage of hard segment component, for example, above about 70 wt%, more preferably above about 90%. Particularly preferred examples of such polymers are the non-elastomeric polyurethane or polyurethane-urea polymers disclosed in International Patent Application No. PCT/AU99/00236. This first polymer can be blended with a second polymer having a lower percentage of hard segment, for example, about 30 to about wt%, more preferably about 40 to about 50 wt%. Examples of suitable polymeric blends include a combination of an elastomeric and a non-elastomeric polyurethane or polyurethane-urea polymer. The term "non-elastomeric" refers to polyurethanes having a elongation of up to about 200% generally up to about 100%. This technique allows a composition having a softening temperature 15 appropriate for the application to be prepared.

The shape memory polymers and compositions of the present invention may be prepared by any technique familiar to those skilled in the manufacture of polyurethanes. These include one or two-step bulk or solution polymerisation procedures. The polymerisation can be carried out in conventional apparatus or within the confines of a reactive extruder continuous injection moulding or mixing machines.

In a one-step bulk polymerisation procedure the appropriate amount of component is mixed with the chain extender first at temperatures in the range of about 45 to about 100 0 C, more preferably about 60 to about 80 0 C. If desired a catalyst such as stanneous octoate or dibutyltin dilaurate at a level of about 0.001 to about 0.5 wt based on the weight of the total ingredients may be added to the initial mixture. Molten diisocyanate is then added and mixed thoroughly to give a homogeneous polymer liquid and cured by pouring the liquid polymer into Teflon-coated trays and heating in an oven to about 100°C.

20 The shape memory polymers can also be prepared by a two-step method where a prepolymer is prepared by reacting component with a diisocyanate. The prepolymer is then reacted with a suitable chain extender.

The polymers and compositions of the present invention are particularly useful in preparing materials having good mechanical properties, more specifically biomaterials as a consequence of their biostability or improved resistance to degradation and their shape memory properties.

According to another aspect of the present invention there is provided a material having improved mechanical properties, clarity, processability, biostability and/or degradation resistance comprising the polymer or composition defined above.

The present invention also provides use of the polymer or composition defined above as a material having improved mechanical properties, clarity, processability, H:uanncil\KeepSpccM79744 SPECIdoc I 1/0304 16 biostability and/or degradation resistance.

The present invention further provides the polymer or composition defined above when used as a biostable material having improved mechanical properties, clarity, processability, biostability and/or degradation resistance.

The mechanical properties which are improved include tensile strength, tear strength, flex fatigue resistance, abrasion resistance, Durometer hardness, flexural modulus and related measures of flexibility or elasticity.

The improved resistance to degradation includes resistance to free radical, oxidative, enzymatic and/or hydrolytic processes and to degradation when implanted as a biomaterial.

The improved processability includes ease of processing by casting such as solvent casting and by thermal means such as extrusion and injection molding, for example, low tackiness after extrusion and relative freedom 20 from gels.

The term "biostability" is used herein in its broadest sense and refers to a stability when in contact with cells and/or bodily fluids of living animals or humans.

There is further provided a degradation resistant material which comprises the polymer or composition defined *0 above.

The polymer or composition of the present invention should also have a good compatibility and 30 stability in biological environments, particularly when implanted in vivo for extended periods of time.

According to another aspect of the present invention there is provided an in vivo degradation resistant or biostable material which comprises the polymer or composition defined above.

The polymer or composition may also be used as a HsnuannclUWtcp spi7974-. I SPECIAdoc 1103/04 WO 01/07499 PCT/AU00/00863 17 biomaterial. The term "biomaterial" is used herein in its broadest sense and refers to a material which is used in situations where it comes into contact with the cells and/or bodily fluids of living animals or humans.

The polymer or composition is therefore useful in manufacturing medical devices, articles or implants.

Thus, the present invention still further provides medical devices, articles or implants which are composed wholly or partly of the polymer or composition defined above.

The medical devices, articles or implants may include catheters; stylets; bone suture anchors; vascular, oesophageal and bilial stents; cochlear implants; reconstructive facial surgery; controlled drug release devices; components in key hole surgery; biosensors; membranes for cell encapsulations; medical guidewires; medical guidepins; cannularizations; pacemakers, defibrillators and neurostimulators and their respective electrode leads; ventricular assist devices; orthopaedic joints or parts thereof including spinal discs and small joints; cranioplasty plates; intraoccular lenses; urological stents and other urological devices; stent/graft devices; device joining/extending/repair sleeves; heart valves; vein grafts; vascular access ports; vascular shunts; blood purification devices; casts for broken limbs; vein valve, angioplasty, electrophysiology and cardiac output catheters; and tools and accessories for insertion of medical devices, infusion and flow control devices.

As the polymers and compositions of the present invention may be designed so that they are rigid at ambient temperature but soften around the body temperature they have many applications in the construction of medical articles, devices and implants. For example, intravenous catheters made from such materials could be inserted initially in the vein due to the high flexural modulus of the material, but would then soften once inside the blood vessel. Furthermore, catheters may be modified to a WO 01/07499 PCT/AU00/00863 18 predetermined shape for ease of directing to a target area or modified in such a way to have sections with different softening temperatures, for ease of guidance of the device to a specific location.

It will be appreciated that polymers and compositions having properties optimised for use in the construction of various medical devices, articles or implants and possessing shape memory characteristics will also have other non-medical applications. Such applications may include toys and toy components, shape memory films, pipe couplings, electrical connectors, zero-insertion force connectors, Robotics, Aerospace actuators, dynamic displays, flow control devices, sporting goods and components thereof, body-conforming devices, temperature control devices, safety release devices and heat shrink insulation.

Thus, the present invention extends to the use of the polymer or composition defined above in the manufacture of devices or articles.

The present invention also provides devices or articles which are composed wholly or partly of the polymer or composition as defined above.

The invention will now be described with reference to the following non-limiting examples.

EXAMPLE 1 Poly(hexamethylene oxide) (PHMO) (MW 489.7) was prepared according to a method described by Gunatillake et a1 7 and United States Patent No. 5,403,912 and dried at 130°C under vacuum for 4 h. A shape memory polyurethane composition from PHMO was prepared according to a one-step bulk polymerisation as described below.

PHMO (35.00 g) and 1,4-butanediol (BDO) (12.06 g) were weighed in to a 500 mL polypropylene beaker and the contents warmed to 70 0 C. Molten MDI (52.93 g) was weighed into a 100 mL, wet-tared polypropylene beaker and added to the PHMO/BDO mixture quickly with stirring. The mixture was WO 01/07499 PCT/AU00/00863 19 stirred for about 30 sec and the contents poured onto a Teflon-coated metal pan. The polyurethane was cured at 100°C for 4 h under nitrogen. The resulting polyurethane was clear and transparent. The specimens for various tests were prepared by compression molding at a temperature of 200 0 C and injection moulding.

Dynamical Mechanical Thermal Analysis, DMTA (Rheometrics MkIIIe) was performed on 40 mm x 10 mm x 1 mm compression moulded samples in single cantilever bending mode at Htz over a temperature range of 30 0 C to 90 0 C at a ramp rate of 2 0 C/min. The onset of the change in the bending modulus was at 37 0 C (1100±50 MPa bending mod) and the endset of change in the bending modulus was 56 0 C (50±20 MPa bending modulus).

The shape memory characteristics of the polyurethane composition were demonstrated as follows. An injection moulded flat, 2.5 mm thick plaque of the polyurethane and a compression moulded flat thin film (0.1 mm thick) were folded 1800 at 55 0 C and cooled to 20 0 C so that the plaque and thin film were locked into a 1800 folded configuration. The folded plaque and the thin film were stored for 72 hours without any configurational change and then subsequently heated in water to 55 0 C at which point the folded thin film very quickly sec) returned to its original flat configuration and the thicker plaque returned also to its original flat configuration but more slowly (ca. 20 sees).

A reverse experiment was also performed whereby permanent 1800 folds were placed in the samples by compressing between flat plates heated to 150 0 C. The thick and thin samples were then heated to 55 0 C and the 1800 fold undone to 00, this unfolding being locked in by cooling to The samples were stored at ambient temperature for 72 hours in the modified (unfolded) shape with no observable configuration changes. The samples were subsequently heated in water at 55 0 C causing the original 1800 fold to reform in similar times to those observed in the previous WO 01/07499 PCT/AU00/00863 20 experiment.

EXAMPLE 2 A polyurethane based on PHMO with a molecular weight of 398.0 was prepared using a procedure similar to that described in Example 1. PHMO (32.00 g) and 1,4butanediol (12.67 g) was weighed into a 500 mL polypropylene beaker and the contents warmed to 70 0

C.

Molten MDI (55.33 g) was weighed into a 100 mL wet-tared polypropylene beaker and added to the PHMO quickly with stirring. The mixture was stirred for about 30 sec and the contents poured onto a Teflon-coated metal pan. The polyurethane was cured at 100 0 C for 4 h under nitrogen. The resulting polyurethane was clear and transparent. The test specimens for various tests were prepared by compression moulding at a temperature of 200 0 C and injection moulding.

The onset of the change in the bending modulus was at 46 0 C (1050±50 MPa bending mod) and the endset of change in the bending modulus was 60 0 C (50±20 MPa bending mod) as determined by DMTA analysis. The shape memory characteristics of the composition was similar to that of the composition of Example 1 EXAMPLE 3 This example illustrates the preparation of shape memory polyurethane compositions with desired glass transition temperatures in the 20 0 C to 100 0 C range by solvent blending of two polyurethane compositions, one with a low flexural modulus (approximately in the range of about 15 to about 100 MPa range) and the other with a high flexural modulus 500MPa).

The low modulus polyurethane composition was prepared by reacting bis(6-hydroxyethoxypropyl) polydimethylsiloxane (48.00 g, MW 940.3), poly(hexamethylene oxide) (12.00 g, MW 700.2), 1,4-butanediol (5.80 g) and MDI (34.19 g) according to a one-step polymerisation procedure. The flexural modulus of WO 01/07499 PCT/AUOO/00863 21 the polyurethane was 30 MPa.

The high modulus polyurethane composition was prepared by reacting 1,4-cyclohexanedimethanol (25.27g), 1, 3bis(4-hydroxybutyl)-1, ,3,3-tetramethyldisiloxane (16.27 g) and MDI (58.46 g) according to a one-step bulk polymerisation. The flexural modulus of the polyurethane was 1770 MPa.

Differential scanning calorimetry (at a ramp rate of 10°C/min) demonstrated the presence of glass transition change onset at 91.2°C and an endset at 106.7°C with a Cp of 0.28J.g- 1 .°C This high modulus composition exhibited shape memory characteristics. A compression moulded thin plaque (0.1 mm) was folded at 110°C and immediately cooled to ambient temperature to preserve the fold. It was subsequently heated to 110°C resulting in a reversal of the shape to the original.

The high modulus and low modulus polyurethanes were blended by mixing 7.5 g and 2.5 g, respectively and dissolving the blend in N,N-dimethylformamide to give a 20 wt% solution. A thin film of the blend was prepared by solvent casting. The polymer solution was poured onto a Petrie Dish to form a 5 mm thick layer and the solvent evaporated in a nitrogen circulating oven over a period of 48 h. DSC analysis of the dried film showed a glass transition onset temperature of 45.6°C and an end set at 49.5°C.

A thin film (0.3 mm) of the blend was folded by 180° by heating to a temperature above 50°C and the folded shape fixed by cooling to room temperature. The folded shape reverted to the original shape when it was heated to exhibiting the shape memory characteristics of the blended polyurethane.

EXAMPLE 4 A polyurethane composition based on 1, 3-bis(4-hydroxybutyl)tetramethyldisiloxane (BHTD) and MDI was prepared.

WO 01/07499 PCT/AU00/00863 22 BHTD (Silar Laboratories, 55.68 g) was added to molten (45 0 C) MDI (50.00g) and thoroughly mixed until a clear and homogenous solution was obtained. This required about 3 min of stirring. The viscous polymer was then poured onto a Teflon-coated metal tray and cured at 100 0

C

for 4 h in an oven under nitrogen. The resulting polymer was clear and transparent. The cured polyurethane was compression moulded at 200 0 C to a 1 mm thick plaque. The materials exhibited a shore hardness of 75D, ultimate tensile strength of 60 MPa, and flexural modulus of 1795 MPa.

The onset of glass transition temperature was 0 C and the polyurethane remained rigid below 30 0 C and softened at body temperature (37 0

C).

EXAMPLE This example illustrates the preparation of a polyurethane using a low molecular weight siloxane macrodiol such that the polyurethane composition has a glass transition temperature close to the body temperature.

The polyurethane was prepared by reacting 4,4'methylenediphenyl diisocyanate (MDI, Orica), a, 3-bis (6-hydroxyethoxypropyl)-polydimethylsiloxane (PDMS MW 595) and 1,4-cyclohexanedimethanol (Aldrich PDMS with a molecular weight of 595 was obtained by distilling Shin- Etsu product X-22-160AS (Lot No. 803037) using a wiped-film evaporator.

PDMS was degassed at ambient temperature under vacuum (0.1 torr) for 4 h prior to polymerisation and CHDM (Aldrich) was melted at 60 2 C and degassed under vacuum (0.1 torr) for 1 h.

Degassed PDMS (5.94g) was added to molten (50 0

C)

MDI (5.00g) in a polypropylene beaker and stirred rapidly until the solution turned clear followed by adding CHDM (1.44 After stirring the mixture for further 35 sec, the viscous polymer was poured onto a Teflon-coated pan and cured at 100eC for 6 h under nitrogen. Tensile properties WO 01/07499 PCT/AU00/00863 23 were measured on a compression moulded sheet. DSC analysis was carried out to determine the glass transition temperature of the polyurethane. The polyurethane exhibited an ultimate tensile strength of 23.3 MPa, elongation at break of 97 ±8 and a Young's modulus of 201±65. The DSC results showed the onset of glass transition to be 26 2

C,

mid point at 342C and end at 422C. The polyurethane showed shape memory properties when tested using the procedure described in Example 3.

EXAMPLE 6 This example illustrates the preparation of shape memory polyurethanes by blending commercial polyurethanes and a high modulus polyurethane with a glass transition temperature of about 1002C. PELLETHANEr 2363-80A and CORETHANE"M AW 80 were used as examples of commercial polyurethanes.

The high modulus polyurethane was prepared using the following procedure. Molten (50 2 C) MDI (500.00 g) was weighed into a 2 L polypropylene beaker. The chain extenders BHTD (139.11 g) and CHDM (216.08 g) were weighed separately into two wet-tared polypropylene beakers. BHTD was added to MDI and stirred for about 45 seconds followed by molten (80 2 C) CHDM. Stirring was continued for another to 25 sec and the viscous polymer was immediately stirred into a Teflon-coated tray. The tray containing the polymer was kept under nitrogen at ambient temperature for about 45 min and cured at 100 C for 4 h.

Two compositions were prepared by blending the high modulus polyurethane with CORETHANE T and PELLETHANE, respectively. Composition 1 was prepared by dissolving g of the high modulus polyurethane with 2.5 g of

CORETHANE

T

N in 40 mL of dimethyl acetamide. The mixture was cast into a thin film by pouring the solution into a Petrie dish and evaporating the solvent in a nitrogen circulating oven at 70 2C for 48 h. Similarly Composition-2 was 24 prepared by dissolving 2.5 g of PELLETHANE

T

N and 7.5 g of the high modulus polyurethane in dimethylacetamide and casting a thin film of the composition.

The tensile properties and glass transition temperature of the two compositions were determined and the results are summarised in Table 1 below. The two compositions showed shape memory properties when tested using the procedure described in Example 3.

TABLE 1. Tensile properties and glass transition temperatures of the polyurethane compositions prepared in Example 6.

Composition Elon. UTS YM Tg Mid Endpoint MPa MPa (°C)Onset point Composition 1 13 41.5 648 39.8 43.2 46.7 Composition 2 13 28.0 280 44.6 48.3 52.0 0%oo oooo 15 In the claims of this application and in the description of the invention, except where the context requires otherwise due to express language or necessary Soo implication, the words "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in •o various embodiments of the invention.

REFERENCES

1. J. R. Lin and L. W. Chen, J Appl. Polym. Sci., 69, 1563 (1998).

S. Hayashi, S. Kondo and K. Kawamura, 3 4 t h Annual Polyurethanes Technical Marketing Conf, p. 605 (1992).

3. T. Takahashi, N. Hayashi and S. Hayashi, J. Appl. Polym.

Sci., 60, 1061 (1996).

4. S. J. McCarthy, G. F. Meijs, N. Mitchell, P. A.

Gunatillake, G. Heath, A. Brandwood and K. Schindhelm, H:%annct\Kocp\Specj\57974-00.1I SPECI.doc I 1M3/04 24a Eiomaterials, 18, 1387 (1997).

L. Pinchuck, J. Eiomater. Sci. Edn. Vol 3 225 (1994).

6. Y. W. Tang, J. P. Santerre, R. S. Labow, I. Revenko and M. A. Sing, 25th Annual Meeting, Society for Biomaterials.

Rhode Island, USA, p 58 (1999).

7. P. A. Gunatillake, G. F. Mejs, R. C. Chatelier, D. M.

McIntosh, and E. Rizzardo Polya. Xnt. Vol 27, pp 275 (1992).

H:Nsu7znrLU~cepkSpc?\579744O I SPECIdoc I M0AM)

Claims (44)

1. A biostable shape memory polyurethane or polyurethane-urea polymer comprising a reaction product of and as set out under below or a reaction product of and as set out under below: a silicon-based macrodiol; a polyether of formula below; or a silicon-based macrodiol and a polyether of formula A- ECH2)m- O n-(CH 2 (I) wherein A and A' are endcapping groups; m is an integer of 6 or more; and n is an integer of 1 or greater, wherein the molecular weight range of the silicon-based macrodiol in component is 300 to 700; 20 a diisocyanate; and a chain extender; or a diisocyanate; S(c) 60% by weight of a diol or diamine chain extender based on the total weight of chain 25 extender; and 40% by weight of a silicon-containing chain extender based on the total weight of chain extender, said polymer having a glass transition temperature which 30 enables the polymer to be transformed from its original shape into a first shape at a temperature higher than the glass transition temperature and maintained in said first shape when the polymer is cooled to a temperature lower than the glass transition temperature, said polymer then being capable of resuming its original shape on heating to a temperature higher than the glass transition temperature. H:su/nnclUecpSpcciA579744)0 I SPECIdoc 24/06/04 26

2. A shape memory polymer according to claim 1, wherein component has greater than about 50% silicon- based macrodiol.

3. A shape memory polymer according to any one of the preceding claims, wherein component has greater than about 70% silicon based macrodiol.

4. A shape memory polymer according to any one of the preceding claims, wherein the silicon-based macrodiol is a polysiloxane. A shape memory polymer according to claim 4, wherein the polysiloxane is represented by the formula (III): R, R 2 HO-Rs-Si- 0--Si- -R 6 OH I I R3 R4 (III) wherein A and A' are as defined in claim 1: R 1 R 2 R 3 and R 4 are the same or different and 20 selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; R 5 and R 6 are the same or different and selected from a divalent optionally substituted straight chain, 25 branched or cyclic, saturated or unsaturated hydrocarbon radical; and p is an integer of 1 or greater.

6. A shape memory polymer according to claim wherein the macrodiol is PDMS which is a compound of formula (III) wherein R 1 to R 4 are methyl and Rs and R 6 are H:\sunnc\Kcp\SpccM7974(X). I SPECdoc 24/W4 27 as defined in claim

7. A shape memory polymer according to claim 5 or claim 6, wherein R 5 and R 6 are the same or different and selected from propylene, butylene, pentylene, hexylene, ethoxypropyl (-CH 2 CH 2 OCH 2 CH 2 CH 2 propoxypropyl and butoxypropyl.

8. A shape memory polymer according to any one of the preceding claims, wherein the polyether is a polyether macrodiol represented by the formula HO- [(CH 2 )m-O n-H (V) wherein m is as defined in formula in claim 1; and n is as defined in formula in claim 1.

9. A shape memory polymer according to claim 8, S 20 wherein the polyether macrodiol is poly(hexamethylene oxide) (PHMO), poly(heptamethylene oxide), poly(octamethylene oxide) (POMO) or poly(decamethylene oxide) (PDMO). 25 10. A shape memory polymer according to claim 9, wherein the polyether of the formula is PHMO.

11. A shape memory polymer according to any one of the preceding claims, wherein the diisocyanate is an 30 aliphatic or aromatic diisocyanate. 0

12. A shape memory polymer according to any of the preceding claims, wherein the diisocyanate is 4,4'- diphenylmethane diisocyanate (MDI), methylene biscyclohexyl diisocyanate (H 12 MDI), p-phenylene diisocyanate (p-PDI), trans-cyclohexane-l,4-diisocyanate (CHDI), 1,6- diisocyanatohexane (DICH), H:%su/nnclUCcep\SpcecM7974-0 I SPECidAc 24A)MM 28 (NDI), para-tetramethyixylenediisocyanate (p-TMXDI), meta- tetramethyixylene diisocyanate (m-TMXDI), 2,4-toluene diisocyanate (2,4-TDI) isomers or mixtures thereof or isophorone diisocyanate (IPDI).

13. A shape memory polymer according to any one of the preceding claims, wherein the diisocyanate is MDI.

14. A shape memory polymer according to any one of the preceding claims, wherein the diol chain extender is 1, 4-butanediol, 1, 6-hexanediol, 1, 8-octanediol, 1,9- nonanediol, 1, 10-decanediol, 1, 12-dodecanediol, 1,4- cyclohexanediol, 1, 4-cyclohexanedimethanol, p-xyleneglycol, 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane, 1, 3-bis(6- hydroxyethoxypropyl) tetramethyldisiloxane or 1, 4-bis (2- hydroxyethoxy) benzene. A shape memory polymer according to any one of the preceding claims, wherein the diamine chain extender is 20 1, 2-ethylenediamine, 1, 3-propanediamine, 1, 4-butanediaiine, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4- aminobutyl) tetramethyldisiloxane or 1, 6-hexanediamine.

16. A shape memory polymer according to any one of the preceding claims, wherein the silicon-containing chain extender includes a silicon-containing diol of the formula (VI): R, R2 HO-Rt-7iSi 7 6 -OH L Jq (VI) wherein R 1 R 2 R 3 R 4 R 5 and R 6 are as def ined in formula (III) in claim H: su/annctU~ccp .SpceMA7974-(X). I SPECIdoc 24/06/0)4 29 R 7 is a divalent linking group or a divalent optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; and q is 0 or greater.

17. A shape memory polymer according to any one of the preceding claims, wherein component polymer forms the soft segment of the polyurethane or polyurethane-urea polymer.

18. A shape memory polymer according to any one of the preceding claims, wherein components and of the polymer form the hard segment of the polyurethane or polyurethane-urea polymer.

19. A shape memory polymer according to claim 18, wherein the amount of hard segment in the polymer is about to 100 wt%. 20 20. A shape memory polymer according to claim 18 or claim 19, wherein the amount of hard segment in the polymer about 50 to about 80 wt%.

21. A shape memory polymer according to any one of 25 claims 18 to 20, wherein the amount of hard segment in the polymer is about 60 to about 70 wt%.

22. A shape memory polymer according to any one of Sthe preceding claims, wherein the shore hardness of the 30 polymer below the glass transition temperature is in the range of about 82D to about 50D, while the hardness above the glass transition temperature is in the range of about to about

23. A shape memory polymer according to any one of the preceding claims, wherein the glass transition temperature is in the range of about 20 0 C to about 100 0 C. II:Vu/rn.wAKcpSpcc579744). I SPECIdc 24/0604 30

24. A shape memory polymer according to any one of the preceding claims, wherein the glass transition temperature is in the range of about 20 to about 60 0 C. A biostable shape memory composition which comprises: a blend of two or more biostable shape memory polymers comprising a reaction product of and as set out under below or a reaction product of and as set out under below: a silicon-based macrodiol; the polyether of formula as defined in claim 1; or a silicon-based macrodiol and the polyether of formula as defined in claim 1; a diisocyanate; and a chain extender; or a diisocyanate; and a chain extender, said polymers having glass transition temperatures which enable the polymers to be transformed from their original shape into a first shape at a 25 temperature higher than the glass transition temperature and maintained in said first shape when the polymers are cooled to a temperature lower than the glass transition temperature, said polymers then being capable of resuming their original shape on heating to a temperature higher than the glass transition temperature; or (ii) a blend of at least one biostable shape memory polymer as defined above in combination with a polymeric material.

26. A shape memory composition according to claim wherein the polymeric material is a conventional polyurethane, shape memory polyurethane, polyolefin, H:\s2nr\Kecp\SpeeM79744)0 I SPECIdoc 16&07/04 31 polyamide or a liquid crystalline polymer.

27. A shape memory composition according to claim or claim 26, wherein each of the polymers forming the shape memory composition have different glass transition temperatures and/or different amounts of hard segment component.

28. A shape memory composition according to claim 27, which comprises a first polymer with a low glass transition temperature of below about ambient temperature and a second polymer with a glass transition temperature above the ambient temperature.

29. A shape memory composition according to claim 28, wherein the second polymer has a glass transition temperature of about 50 0 C.

30. A shape memory composition according to any one S 20 of claims 27 to 29, wherein the two polymers can be blended in proportions such that the final blend will have a glass transition temperature in the range of about 20 0 C to about 60 0 C. 25 31. A shape memory composition according to claim 27, which comprises a first polymer having a high percentage of hard segment component of above about 70 wts and a second *5 g. polymer having a lower percentage of hard segment of about 30 to about

32. A shape memory composition according to any one of claims 28 to 31 which comprises a first polymer having a high flexural modulus above 500 MPa and a second polymer having a low flexural modulus of about 15 to about 100 MPa.

33. A shape memory composition according to claim 32, wherein the composition includes a combination of an H:\su/znri\Kccp\SpccM7974-.o I SPECIdoc 24/0((M4 32 elastomeric and a non-elastomeric polyurethane or polyurethane-urea polymer.

34. A process for preparing a shape memory polymer as defined in any one of claims 1 to 24 which is a reaction product of and as set out under comprising the steps of: mixing component and the chain extender and (ii) reacting the mixture with the diisocyanate A process according to claim 34, wherein step (i) is performed at a temperature in the range of about 45 0 C to about 100 0 C.

36. A process according to claim 34 or claim wherein step occurs in the presence of a catalyst.

37. A process for preparing a shape memory polymer as 20 defined in any one of claims 1 to 24 which is a reaction product of and as set out under comprising S• the steps of: reacting component with a diisocyanate to form a prepolymer; and (ii) reacting the prepolymer with the chain extender S38. A process for preparing a shape memory polymer as defined in any one of claims 1 to 24 which is a reaction *oo product of and as set out under comprising the step of reacting the diisocyanate with the chain extenders and

39. A biostable material having improved mechanical properties, clarity, processability, biostability and/or degradation resistance which comprises the shape memory polymer as defined in any one of claims 1 to 24 and/or the H:\sulannetKcp\Spcc579744X).1 SPECI.doc 24/0610 33 composition as defined in any one of claims 25 to 33. A material according to claim 39, wherein the improved mechanical properties are tensile strength, tear strength, flex fatigue resistance, abrasion resistance, Durometer hardness, flexural modulus and/or related measures of flexibility or elasticity.

41. A material according to claim 39 or claim wherein the improved resistance to degradation is resistance to free radical, oxidative, enzymatic and/or hydrolytic processes and/or to degradation when implanted as a biomaterial.

42. A material according to any one of claims 38 to wherein the improved processability is ease of processing by casting and/or thermal means.

43. A material according to any one of claims 38 to Si 20 42, which is a degradation resistant material.

44. A material according to any one of claims 38 to 43, which is an in vivo degradation resistant or biostable material.

45. A material according to any one of claims 38 to 44, which is a biomaterial.

46. Use of the shape memory polymer as defined in any one of claims 1 to 24 and/or composition as defined in any one of claims 25 to 33 as a material having improved mechanical properties, clarity, processability, biostability and/or degradation resistance.

47. The shape memory polymer as defined in any one of claims 1 to 24 and/or composition as defined in any one of claims 25 to 33 when used as a material having improved H:\suannciUrcepXSpcci'.57974-(X) I SPECISO 24106/04 34 mechanical properties, clarity, processability, biostability and for degradation resistance.

48. A device or article which is composed wholly or partly of the shape memory polymer as defined in any one of claims 1 to 24 and/or composition as defined in any one of claims 25 to 33.

49. A device or article according to claim 48, which is a medical device, article or implant. A device or article according to claim 49, which is a stylet; bone suture anchor; vascular, oesophageal or bilial stent; cochlear implant; reconstructive facial surgery; controlled drug release device; component in key- hole surgery; biosensor; membrane for cell encapsulation; medical guidewire; medical guidepin; cannularization; pacemaker, defibrillator or neurostimulator and their respective electrode leads; ventricular assist device; 20 orthopaedic joint or parts thereof; intraoccular lens; urological device; stent/graft device; device joining/extending/repair sleeves; heart valve; vein graft; vascular access port; vascular shunt; blood purification device; cast for a broken limb; vein valve, angioplasty, electrophysiology or cardiac output catheter; or tools for insertion of medical devices, infusion and flow control o*o devices.

51. A device or article according to claim 48, which 30 is a toy or component thereof, shape memory film, pipe coupling, electrical connector, zero-insertion force connector, robotic, aerospace actuator, dynamic display, flow control device, sporting goods and components thereof, body-conforming device, temperature control device, safety release device or heat shrink insulation.

52. Use of the shape memory polymer as defined in any H:suannc\Xecp)pcc\57974-0. I SPECIdoc 24A)M) 35 one of claims 1 to 24 and/or composition as defined in any one of claims 25 to 33 in the manufacture of a device or article.

53. A shape memory polymer as defined in any one of claims 1 to 24 and/or a composition as defined in any one of claims 25 to 33 when used in manufacture of a device or article.

54. Shape memory polymers or compositions, processes for their preparation, biostable materials, devices or articles containing them or uses involving them, substantially as hereinbefore described with reference to any one of examples 1 to 3, 5 and 6. Dated this 24th day of June 2004 AORTECH BIOMATERIALS PTY LTD By their Patent Attorneys 20 GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia S.o H:\sutannic\Kccp\Spece?57974-(X). I SPECIduc 24AW04