ES2359631T3 - POLYMERS WITH FORM MEMORY BASED ON SEMI-CRYSTAL THERMOPLASTIC POLYURETHANS CONTAINING NANO-STRUCTURED HARD SEGMENTS. - Google Patents

Abstract

A method for producing a shape memory polymer based on thermoplastic polyurethane, which comprises reacting in one step: (A) a polyol, (B) a polyhedral diol oligosylesquioxane, and (C) a diisocyanate, where the memory polymer It has a thermal activation temperature of 30 to 60ºC.

Description

Reference related to related requests

This application claims priority of provisional applications Nos. series 60 / 418,023 filed on October 11, 2002, 60 / 466,401 filed on April 29, 2003; 60 / 419,506 filed on October 18, 2002; 60 / 488,590 filed on July 18, 2003 and 60 / 488,323 filed on July 18, 2003.

Technical field

The present invention relates to polymers with shape memory and more specifically to thermoplastic polyurethanes with an alternating sequence of hard and soft segments in which a nanostructured polyhedral oligomeric silosquioxane diol is used as a chain extender to form a crystalline hard segment, and also refers to methods for the preparation of these thermoplastic polyurethanes and their applications.

Background of the invention

Shape memory materials are characterized by the ability to transform from a provisional frozen form to a permanent form when there is a triggering environmental stimulus, such as heat, light or steam. Used creatively, this phenomenon can be exploited for a wide range of applications. Although shape memory alloys (SMA) and shape memory polymers (SPM) have similar memory properties by thermal stimulation, their mechanisms of action are quite different. The advantages of SMA include rapid recovery of deformation (over the course of 1 second), potential bimodal reversible memory training and apparent super-elasticity due within the low temperature austenite phase. Instead, polymers intrinsically exhibit shape memory effects derived from their considerably wound constituent chains that are collectively extensible by mechanical work and this energy can be stored indefinitely, which is known as "shape fixation," cooling below Tg. or Tm. Polymeric samples can later perform mechanical work and return to a stress-free state when they are heated above the critical temperature, mobilizing frozen chains to recover the entropy of their rolled state. Compared to SMAs, thermally stimulated SMPs have the following advantages:

(i) large recoverable deformations above several hundred percent deformation; (ii) easy adjustment of the transition temperature through the variation of polymer chemistry; and (iii) low cost processing facility.

Thermally stimulated SMPs with different thermomechanical properties have previously been synthesized and characterized to function in various applications, for example, as medical devices and mechanical actuators. The materials cover a wide range of ambient temperature modules, from rigid vitreous materials with multi-GPa storage modules to compatible rubbers with modules as low as tens of MPa. On the other hand, the contraction (elastic) modules have been adjusted in the range 0.5 <E <10 MPa, as prescribed by the final application. An example of this is chemically crosslinked polycyclooctene (PCO), a rigid semicrystalline rubber that is elastically deformed above Tm to a temporary shape that is fixed by crystallization. Fast and complete recovery of serious deformations is achieved by immersion in hot water. These SMPs have been described in US provisional patent application serial number 60 / 419,506 filed on October 18, 2002 entitled "Chemically Crosslinked Polycyclooctene", whose priority is claimed. In WO 03/093341, entitled "Castable Shape Memory Polymers", more rigid SMPs are described that offer critical temperatures and adjustable elastic modulus using a random thermosetting copolymer made of two vinyl monomers that provide controlled Tg and empty-type processing. These copolymers were crosslinked with a difunctional vinyl monomer (crosslinking agent), so that the concentration of crosslinking agent controlled the elastic modulus and thereby the working potential during recovery. In addition to their shape memory effects, these materials are also empty, which allows emptying more complex shapes. In addition, they are optically transparent, which makes them useful for additional applications.

The use of chemical crosslinking in both cases limits the types of processing possible and forever establishes the form of equilibrium at the point of network formation. Therefore, combinations of a semicrystalline polymer with amorphous polymers have also been intensively investigated due to their attractive crystalline and mechanical properties. For combinations that are miscible at the molecular level, a single glass transition occurs, without extending, an important aspect for shape memory. Additionally, in such miscible combinations the crystallinity in equilibrium (which controls the plateau modulus between Tg and Tm when the shape fixation is made) also dramatically and systematically changes with the composition of the combinations. This provides a simple route to alternative memory plastics; i.e. SMP with relatively high modulus in the state set at room temperature, which have an adjustable and sharp transition, and the permanent shape can be repeatedly re-molded above certain softening temperatures. These SMP combinations have been described in the US provisional patent application. Serial No. 60 / 466,401 filed on April 29, 2003 and entitled "Blends of Amorphous and Semicrystalline Polymers with Shape Memory Properties" of which priority is claimed.

Semi-crystalline thermoplastic polymers separated by microfases that have two acute softening transitions Tm2> Tm1> ambient temperature, where the difference between the two softening points is at least 20 ° C, are also good candidates for shape memory, offering the advantage of be processed in a molten state above Tm2, and repeatedly recover the equilibrium form by relaxing the tension in a fluid state. Representative old examples of these polymers in this class of SMP are conventional polyurethanes whose soft domains are vitreous or semi-crystalline with low softening point (but above Tcrit) and whose hard domains have a higher softening point, only exceeded during the processing

Another system separated by microfases is one described by Fu et al, in Polymer, vol. 42 (2001), pages 599-611. However, the incorporation of a polyhedral oligomeric silsesquioxane (POSS) in only one of the two phases in this system will not have altered the thermal activation temperature of the composite material in general, which will have remained essentially as that of the phase without POSS.

Objects of the invention

An object of the present invention is to provide shape memory polymers comprising hybrid polyurethanes.

It is another object of the invention to provide memory polymers so that they have a medium and adjustable module in the state set at room temperature, with an adjustable and sharp transition, whose permanent form can be repeatedly remodeled above a certain temperature of softening.

It is another object of the invention to provide SMP polyurethane hybrids that accredit acute and adjustable transition temperatures, adjustable stiffness above their transition temperatures and thermal processing capacity above the softening point of the POSS domains.

It is another object of the invention to provide SMP polyurethane hybrids that possess excellent shape recovery effect at the recovery temperature and where the retraction force is adjustable according to the composition of the POSS.

Still another object of the invention is to provide hybrid polyurethanes that are biocompatible and can be used as medical devices and implants.

Another object of the invention is a method for the synthesis of such hybrid polyurethanes.

Compendium

In general terms the invention provides a method for producing SMP of hybrid polyurethanes by reacting (A) a polyol, (b) a chain extender that is a dihydroxy-terminated POSS and (C) a diisocyanate, where POSS represents a polysesric diol silsesquioxane and wherein the shape memory polymer has a thermal activation of 30 to 60 ° C. The polyol (A) can be polyethylene glycol (PEG), polycaprolactone (PCL), polycyclooctene (PCO), trans-1,4-butadiene, trans-isoprene, polynorbornene diol and polymethacrylate copolymer, the chain extender (B) can be TMP cyclopentyldiol-POSS, TMP cyclohexyldiol-POSS, TMP isobutyldiol-POSS, trans-cyclohexanediolcyclohexane POSS, or trans-cyclohexanediolisobutyl POSS, and the diisocyanate (C) may be selected from a large number of diisocyanates and preferably 4-diisocyanate -diphenylmethane (MDI). Other diisocyanates (C) that are suitable for use in the synthesis of SMP based on hybrid polyurethanes include: toluene 2,4-diisocyanate (TDI), toluene 2,6-diisocyanate, hexamethylene 1,6-diisocyanate (HDI ), isophorone diisocyanate (IPDI), and hydrogenated 4,4'-diphenylmethane diisocyanate (H12MDI).

The polyol can be semi-crystalline and is preferably selected from polyethylene glycol (PEG), polycaprolactone (PCL), polycyclooctene (PCO), trans-1,4-butadiene, trans-isoprene or can be amorphous, for example with a Tg in the range of 20 ° C-80 ° C, in which case it may be a copolymer of polynorbornene diol and / or polymethacrylate.

The method for producing SMP from hybrid polyurethanes and the new hybrid polyurethanes prepared in this way are illustrated by the following non-limiting reaction schemes.

image 1

This scheme shows an example of TPU synthesis using polyethylene glycol as a polyol, trans-cyclohexanediol isobutyl POSS as a chain extender to react with 4,4'-diphenyl methylene diisocyanate in toluene.

image2

This scheme shows an example of TPU synthesis using polycaprolactone diol as a polyol, TMP Isobutyldiol-POSS as a chain extender to react with 4,4'-diphenyl methylene diisocyanate.

image3

This scheme shows an example of TPU synthesis using polycyclooctene diol as a polyol, TMP Isobutyldiol-POSS as a chain extender to react with 4,4'-diphenyl methylene diisocyanate.

The following is a general formula for POSS-based TPUs incorporating PEG diol, prepared analogously to Scheme 1 but using a different Isobutyldiol-POSS. The polymers allow a systematic variation in the ratio X / Y (1 to 20), the polymeric degree of polymerization (1 <n <1000), and the total degree of polymerization, 2 <m <100.

image4

The hybrid polyurethanes of the invention demonstrate sharp and adjustable transition temperatures, adjustable stiffness above their transition temperatures, and thermal processability above the softening point of the POSS domains. Hybrid polyurethanes also have an excellent recovery effect at the temperature of recovery and a retraction force that is adjustable according to the composition of the POSS. They also have a unique property that is different from that of other shape memory polymers and it is now found (in the PEG embodiment) that recovery can be activated with moisture (liquid or vapor) in addition to heat. For the thermal activation mechanism, the interval of 30 ° C to 60 ° C is important depending on the proportion of the components used and (very important) of the heat treatment to produce crystallinity in the steady state (equilibrium). Recovery may end in a matter of seconds when it is heated 20 ° C above the transition temperature. Additional advantages of the materials include that the materials are rigid at room temperature, the polymers are generally biocompatible and in some cases biodegradable and can be used as medical devices and implants. The

15 products can also be dyed in any color or made radiopaque to X-ray radiographs according to the requirements of the application.

Any of the above-mentioned hybrid polyurethane polymers can be charged, for example, with nanoparticles of boron nitride, silica, titanium dioxide, montmorillonite clay, Kevlar, staple fibers, aluminum nitride, barium subcarbonate and bismuth subcarbonate. For example, clay and silica can be used to increase the plastic modulus. For example, dispersing agents and / or compatibilizing agents can be used to improve mixing between polymers and mixing of polymers with fillers. Dispersing and / or compatibilizing agents include, for example, ACRAWAX® (ethylene bis-stearamide), polyurethanes and ELVALOY® (polyethylene with acrylic functionality). The polymers can be crosslinked by application of radiation such as e-rays, UV, gamma, x-rays or by heat activated chemical cross-linking techniques. The techniques of

Radiation has the advantage that the polymer does not normally have to be heated too much to produce crosslinking. If e-rays are used, an exposure of approximately 200-300, for example 250 kGy, usually provides sufficient cross-linking.

Brief description of the drawings

FIGURE 1 graphically illustrates the DMA curve for thermoplastic polyurethane based on TMP BOSS (TPU) 30 with PEG: POSS molar ratio 1: 6, 1: 4 respectively;

FIGURE 2 graphically illustrates the DSC results for the TPU based on TMP POSS with different PEG molar ratios: POSS;

FIGURE 3 illustrates the equipment used to measure stress-strain; Y

FIGURE 4 graphically illustrates the stress-strain curve of the TPU based on TMP POSS (PEG: POSS = 35 1.6).

Detailed description

Thermoplastic polyurethanes of different compositions were synthesized by the one stage condensation polymerization technique, using the scheme indicated above. Toluene was used as solvent and dibutyl tin dilaurate as catalyst. The reaction was maintained at 90 ° C under nitrogen for 2 hours and then cooled to room temperature and precipitated in hexane. The product was thoroughly dried and dissolved in toluene to make a 10% solution by weight. The molecular weights and molecular weight distributions of this series of samples obtained by size exclusion chromatography are summarized in Table 1.

Table 1. Molecular weights and molecular weight distributions of POS-based polyurethanes having polyol blocks (PEG) with a length of 10,000 g / mol

Sample Mn (g / mol) Mw / Mn

PEG: POSS = 1: 3 47,400 1.42

PEG: POSS = 1: 4 48,800 1.44

PEG: POSS = 1: 6 54,000 1.54

PEG: POSS = 1: 8 49.200 1.30

Polyurethane samples with different compositions were characterized by differential scanning calorimetry (TA Instruments DSC2920). All samples were characterized under the same conditions: Two 10 scans were performed for each sample with heating and cooling rates of 10 ° C / min (Figure 2). It was observed that this series of polyurethanes have two softening points, one in the range 45 <Tm1 <50 ° C corresponding to a softening temperature of the "soft" PEG block. The other softening transition appears in the interval 110 <Tm2 <130 ° C, which corresponds to the softening of a hard segment phase reinforced with POSS. It is observed that the softening temperature of the soft segment shifts to lower values with a broadening of the softening peak while the softening temperature of the hard segment shifts to higher values with a sharpening of the softening peak when the ratio in moles of polyol / chain extender decreases. This result can be explained because as the PEG: POSS ratio decreases, the resulting block copolymer will have less PEG content as a whole, which will directly affect the size and perfection of crystallization of the

20 blocks of PEG. Therefore, the softening temperature moves towards lower values and the peak widens. On the contrary, the content of POSS will increase in block copolymers, which provides a clearer aggregation of hard segments to form larger and more perfect crystals. Therefore, the softening temperature of the hard segment shifts towards higher values while the peak sharpens (Figure 2).

The dried films of the formed polyurethanes were cut into thin strips for provisional fixation tests and subsequent recovery, or shape memory. For example, a sample was first heated in the hot phase at 65 ° C, which is well above the first transition temperature but is a temperature low enough to prevent softening of the elastic network of the POSS-rich phase. It was then stretched to a certain degree of elongation and cooled to room temperature. The deformed shape was set to

30 room temperature Finally, the deformed form was heated again in hot plate at 65 ° C and it was observed that the sample recovered its original length completely and in a few seconds. A similar phenomenon was observed when water was used as a stimulus for shape recovery, except that the sample experienced secondary swelling to form a strong hydrogel.

The hybrid polyurethanes of the invention can be used for the following applications.

35 a. Stents, patches and other implants for human health care.

b.

Surgical instruments that require adjustable forms but high rigidity.

C.

Structural instruments arbitrarily adjustable, including personal care items (dishes, brushes, etc.) and tool handles.

d.

Plastics that repair themselves.

40 e. Medical devices (a serrated panel is repaired by heating or plasticizing with solvent).

F.

Matrices for drug administration.

g.

High-strength thermoplastic (non-crosslinked) superabsorbent hydrogels.

h.

Aqueous rheological modifiers for paints, detergents and personal care products.

i.

Printing material for molding, duplicates, rapid prototyping, dentistry and figure printing.

j.

 Toys.

k.

Reversible enhancements to store information.

l.

Temperature and humidity sensors.

m.

Safety valves.

n.

Heat shrink tapes or seals.

or.

Couplings and fixing elements controlled by heat.

p.

Large force actuators, large deformation.

q.

Coatings, adhesives.

r.

 Textiles, clothes.

Shape memory polymers of the invention are particularly suitable as biomaterials due to their low thrombogenicity, high biocompatibility, as well as unique mechanical properties. According to the invention, shape memory polyurethanes were formulated so that the softening temperature of a segment decreased within a useful temperature range for biomedical applications: 37 ° C-50 ° C.

The present invention provides a memory polymer advantageously that includes thermoplastic polyurethane based memory polymers formed by reacting, in one step, a polyol, a POSS chain extender and a diisocyanate, which has a medium and adjustable module in the state set at room temperature, it has an adjustable acute transition, whose permanent form can be repeatedly remodeled above a certain softening temperature.

Although the polymers and processing methodologies of the present invention have been described with reference to specific illustrative embodiments thereof, the present invention is not limited to such illustrative embodiments. Instead, as will be apparent to those skilled in the art, the descriptions of the present description are susceptible to many embodiments and / or applications, without departing from the scope of the present invention. Actually, modifications and / or changes in the selection of specific polymers, polymer ratios, processing conditions and end-use applications are contemplated, and such modifications and / or changes are included within the scope of the present invention set forth in the following claims.

Claims (16)

1. A method for producing a shape memory polymer based on thermoplastic polyurethane, comprising reacting in one step: (A) a polyol, (B) a polyhedral diol oligosylesquioxane, and (C) a diisocyanate, where the polymer With shape memory it has a thermal activation temperature of 30 to 60ºC. The method of claim 1, wherein the polyol is a member selected from the group consisting of polyethylene glycol (PEG), polycaprolactone (PCL), polycyclooctene (PCO), polynorbornene diol and polymethacrylate copolymer. 3. The method of claim 1, wherein the polyol is a member selected from the group consisting of polyethylene glycol, polycaprolactone and polycyclooctene and is semi-crystalline. 4. The method of claim 1, wherein the polyol is an amorphous diol having a Tg in the range of 20-80 10 ° C, and is a member selected from the group consisting of polynorbornene diol and polymethacrylate copolymer.

5.

The method of claim 1, wherein the polyhedral oligosylesquioxane diol is a member selected from the group consisting of TMP cyclopentyldiol-POSS, TMP cyclohexyldiol-POSS, TMP isobutyldiol-POSS, transcyclohexanediolcyclohexane-POSS, or transcyclohexanediolisobutyl.

6.

The method of claim 1, wherein the diisocyanate is a member selected from the group consisting of

15,4'-diphenyl methylene diisocyanate (MDI), toluene 2,4-diisocyanate (TDI), toluene 2,6-diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and Hydrogenated 4,4'-diphenylmethane diisocyanate (H12MDI).

7.

The method of claim 1, wherein the diisocyanate is 4,4'-diphenyl methylene diisocyanate.

8.

The method of claim 1, wherein the polyol is a member selected from the group consisting of

20 polyethylene glycol, polycaprolactone and polycyclooctene; wherein the polyigos oligosylsquioxane diol is a member selected from the group consisting of TMP cyclopentyldiol-POSS, TMP cyclohexyldiol-POSS, TMP isobutyldiol-POSS, transcyclohexanediolcyclohexane-POSS, and transcyclohexanediol-isobutyl-POSS; and, wherein the diisocyanate is 4,4'-diphenyl methylene diisocyanate.

9.

The method of claim 8, wherein said reaction is carried out in the presence of dibutyl tin dilaurate as a catalyst.

10. The method of claim 1, wherein the reaction is carried out according to the following reaction scheme

eleven.

The method of claim 1, wherein the reaction is carried out according to the following reaction scheme

image 1 image 1

12.

The method of claim 1, wherein the reaction is carried out according to the following reaction scheme

13.

A shape memory polymer based on thermoplastic polyurethane obtainable by the method of claim 1, wherein the shape memory polymer has a thermal activation temperature of 30 to 60 ° C.

image 1 5 14. A shape memory polymer based on thermoplastic polyurethane according to claim 13 obtainable by the method of claim 8.

fifteen.

A thermoplastic polyurethane based memory polymer according to claim 13 obtainable by the method of claim 9.

16.

A thermoplastic polyurethane based memory polymer according to claim 13 obtainable by the method of claim 10.

A shape memory polymer based on thermoplastic polyurethane according to claim 13 obtainable by the method of claim 11. 18. A thermoplastic polyurethane based memory polymer according to claim 13 containing a filler that is a member selected from the group consisting of boron nitride, silica, titanium dioxide, montmorillonite, clay, staple fibers, nitride aluminum, barium subcarbonate, and bismuth subcarbonate. A shape memory polymer based on thermoplastic polyurethane according to claim 13 having the formula -