WO2008068072A1 - Method for the production of an alternating multi-block copolymer with shape memory - Google Patents

Method for the production of an alternating multi-block copolymer with shape memory Download PDF

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WO2008068072A1
WO2008068072A1 PCT/EP2007/059583 EP2007059583W WO2008068072A1 WO 2008068072 A1 WO2008068072 A1 WO 2008068072A1 EP 2007059583 W EP2007059583 W EP 2007059583W WO 2008068072 A1 WO2008068072 A1 WO 2008068072A1
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macromonomer
characterized
pcl
ω
α
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PCT/EP2007/059583
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German (de)
French (fr)
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Andreas Lendlein
Günter Malsch
Hans-Jürgen KOSMELLA
Helmut Kamusewitz
Steffen Kelch
Nico Scharnagl
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Gkss-Forschungszentrum Geesthacht Gmbh
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    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/66Polyesters containing oxygen in the form of ether groups
    • C08G63/664Polyesters containing oxygen in the form of ether groups derived from hydroxy carboxylic acids
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/06Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
    • C08G63/08Lactones or lactides
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G81/00Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2261/00Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
    • C08G2261/10Definition of the polymer structure
    • C08G2261/12Copolymers
    • C08G2261/126Copolymers block
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2280/00Compositions for creating shape memory
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/78Preparation processes
    • C08G63/81Preparation processes using solvents

Abstract

The invention relates to a method for the production of an alternating multi-block copolymer with shape memory whose structure is composed of the macromonomers A and B alternating in succession, using the steps of (a) provision of the macromonomer A having bilateral functionalization using a nucleophilic end group and provision of the macromonomer B having bilateral functionalization using an electrophilic end group and (b) reaction of the nucelophilically end-group-functionalized macromonomer A with the electrophilically end-group-functionalized macromonomer B in solution, where a stoichiometric ratio of the nucleophilic end group with respect to the electrophilic end group is established, in such a way that any molar deviation from the stoichiometric ratio is at most ± 8 mol%. The invention further encompasses an alternating multi-block copolymer which can be prepared by the method claimed.

Description

A process for producing an alternating multiblock shape memory

The invention relates to a method for producing a shape memory polymer, which - in addition to a permanent shape - can store at least one temporary shape. The polymer is an alternating multi-block copolymer, which has a consisting of the alternately follow each other macromonomers A and B structure.

In the prior art are known so-called shape memory polymers or SMPs (shape memory polymers), which show when induced by an appropriate stimulus a transition in shape from a temporary shape into a permanent shape corresponding to a previous programming. Most commonly, this shape memory effect is thermally stimulated, that is, when heating the polymer material programmed over the defined transition temperature driven by entropic elasticity provision takes place. Shape memory polymers are usually polymer networks where chemical (covalent) or physical (non-covalent) crosslinks determine the permanent shape. Programming is carried out by the polymeric material is deformed and then cooled while maintaining the deformation forces below this temperature above the transition temperature of a switching segment in order to fix the temporary shape. Re-heating above the transition temperature leads to a phase transition of the switch segment determining phase and recovery of the original permanent shape.

Shape memory polymers are usually statistical multi-block copolymers, which are mostly of two thermodynamically incompatible segments (macromonomers A and B) are constructed. The blocks A and B must each have a minimum molecular weight and a minimum portion, so that a phase separation of the blocks is ensured in the polymer. Statistical multiblock form of physical crosslinks. The responsible for this phase is referred to as hard segment, and has the highest thermal transition temperature T tran s A in the system. The phase with the next lowest thermal transition temperature T tra ns B is the switch segment bestimmen- de phase and for switching the thermally induced shape memory effect with the switching temperature T SC hait

Figure imgf000004_0001
B) responsible.

Statistical multiblock copolymers are prepared by polyaddition or polycondensation of the macromonomers A and B. The chemical structure of these multi-block copolymers is generally characterized by a random sequence of the macromonomers A and B. This results in a different number of repeat units A and B within the multi-blocks, and thus a heterogeneous distribution of the coupled each blocks of the same type (or -AA- -BB-) or another type (-A-B-) (eg AABABBBAB). In contrast, (strictly) alternating multi-block copolymers can be distinguished, which are characterized by an alternating sequence of blocks A and B, and consequently the structure - (AB) n - have. Alternating multiblock shape memory have not yet been realized.

In US 6,388,043 B1 (EP 1062278 A) and US 6,160,084 B (EP 156,487 A) block will be described copolymers consisting of at least two different segments (blocks) are built and at least two temporary shapes can save "shape memory" in their , In the particular embodiment PDS macromonomers (copolymer of p-dioxane-2-one and ethylene glycol monomers) and poly (ε-caprolactone) - linked macromonomers (PCL). The Kijpplungsreaktion for the preparation of multi-block copolymers is carried out by reaction of macrodiols with a low molecular Diisicyanat, that is about Diurethanbrücken whereby statistical multi-block copolymers are formed.

Further statistical multi-block copolymers and their preparation methods are for example from Lendlein & Langer (Science 296 (2002), 1673-1676), Lendlein & Kelch (Angew. Chem. 1, 14 (2002), 2138-2162) and Cho et al. (J. Appl. Polym. Sci. 93 (2004) 2410-2415) are known.

Teng et al. (. J. Polymer Sci 42, 2004, 5045-53) discloses a multiblock copolymer of poly (ε-caprolactone) - (L-lactide) blocks and poly constructed. The polymer is made from the PCL Diisocynat (α, ω-macrodiisocyanate) and the PLLA-diol (α, ω-macrodiol). The coupling reaction of end-functionalized macromonomers takes place from the melt at variable mass ratios of the segments, so that statistical multi-block copolymers are to be expected. It examines the influence of the composition and molecular weight on the thermal behavior and the crystalline properties while not reported on the mechanical properties and shape memory behavior.

The known methods for the preparation of multiblock copolymers have the disadvantage that the incorporation of the macromonomers A and B are in the polymer chain always statistically, that is, result in random multiblock copolymers in the result. In the case of synthesis from the solution can not be excluded that the same varied copolymer due to differential solubility of the macromonomers in the solvent used or because of differences in reactivity, the rate of incorporation into the multiblock. The reason for this is probably a multi due to a different coil expansion or less good steric accessibility or differences in the activation of the competing reactive end groups of the macromonomer A and B. Thus, dipole component that is with increased solubility and reactivity, in particular at low conversions, amplified in the multiblock copolymer incorporated. The resulting Veruneinheitlichung the chemical composition contributes to the irregularities of the microstructure. In the case of carrying out the coupling reaction in the melt, however, not a homogeneous mixing of the two macromonomers A and B can be ensured, so that there are different concentration ratios of the components in the various sub-volumes of the melt.

A disadvantage of the known, leading to random multiblock manufacturing method is also their lack of reproducibility. Thus, random statistical sequence of the macromonomers A and B differ in the product even at identical reaction mixtures, with the result that the resulting thermomechanical properties of the polymer also vary widely, and the shape memory effect may be due to the non regularly formed microstructure is not programmed and activated. Further, it was observed that good mechanical properties and the shape memory behavior can only be achieved when the multi-block copolymer having relatively high molecular weights. Typically, number average molecular weights are in this context, M n of at least 30,000 g / mol and weight average molecular weights M w of at least 100,000 g / mol required. This required borrowed molecular weights can only be realized with considerable technical effort so far.

The invention is therefore based on the object to provide a method for producing a multi-block copolymer shape memory which results with high reliability to an alternating sequence of blocks A and B or to a homogeneous distribution of the sequence / nit narrow length distribution, thus producing polymer products which have an improved performance profile regarding the SM-effect and the mechanical properties. It is especially also important that the resulting multi-block copolymers - as well as their statistical comparison pattern - reach a required for forming the SM-effect minimum molecular weight.

This object is achieved by a process for producing an alternating multi-block copolymer with shape memory properties, which has a consisting of the alternately follow each other macromonomers A and B structure, comprising the steps of:

(A) providing the macromonomer A with a reversible functionalization with a nucleophilic end group of the macromonomer B and provision with a reversible functionalization with an electrophilic end group and

(B) reacting the nucleophilic end-functionalized macromonomer A with the electrophilic end-functionalized macromonomer B in solution, wherein a STOE chiometrisches ratio of nucleophilic end group is set to the electrophilic end group so as to minimize a molar deviation from the stoichiometric ratio, in particular at most ± 8 mol%.

In the first process stage, accordingly elec- trophile and nucleophilic reaction sites are created by end-group, so that achieved by their reaction in the second process stage, an alternating "crossover coupling". By careful selection of the two end groups and the preparation of the corresponding functionalized macromonomers A and B in step (a) in reactivity of the macromonomers can be minimized and disturbing influences on the homogeneity of the coupling steps in step (b) are excluded. The product resulting from the method Multiblockcopoly- mer has a substantially steady AB block structure in which the macromonomers A and B having the structure (AB) n successive alternately. To achieve this, has one hand proved to be essential, strict as possible stoichiometry of

- A - nucleophilic end group of the macromonomer A and comply with in step (b), that is, to set a molar ratio of nucleophilic end group to the electrophilic end group of 1 electrophilic end group of the macromonomer B, with a maximum molar deviation of ± 8 mol % has been shown to be tolerable. The reliability of the method can be further improved if the molar deviation from the stoichiometric ratio is at most ± 5 mol%, in particular within ± 3% by mole. Furthermore is important the coupling reaction in step (b) carried out in solution. Together with the strict stoichiometry ensures this measure - in contrast to the implementation in melt - a homogeneous mixing of the reactants, so that ideally each partial volume of the reaction mixture present matching concentrations of the macromonomers A and B.

According to a particularly advantageous embodiment of the inventive method, the number average molecular weights M n of the end-functionalized macromonomers A and B for its reaction in step (b) are matched to one another as far as possible. In this case, a difference between the degrees of polymerization of the macromonomers A and B is adjusted to not more than 15 -% by weight, based on the number-average degree of polymerization P n of the heavier macromonomer -%, in particular more than 10%, preferably at most. 5 This measure requires two beneficial effects. First, is achieved by the alignment of the molecular weights that both Endgruppenfunktionen have a similar steric accessibility during the reaction in solution in step (b) and the segment lengths in the product are largely the same. Thereby matching rates of incorporation of the macromonomers A and B in the chain of the resultant multiblock copolymer, and thus achieves a further support of the alternating structure. Second, the measure results in approximately matching chain segment lengths of blocks A and B in the product, which in turn promotes the formation of a homogeneous, phase-segregated morphology in the polymer product, which are the basis of particularly advantageous thermomechanical SM properties.

The resulting multi-block copolymer comprises thermally inducible shape memory properties, that is, it is capable of, in dependence on the temperature in addition to a permanent shape to take at least one temporary shape. Is one of the blocks A or B of the switch segment determining block with a defined thermal transition temperature and the other block of the hard segment determining block, this can save "shape memory" in a form. Alternatively, however, both A and B blocks for the construction of switching segment forming phases may contribute forming differing transition temperatures, so that in addition to the permanent shape two temporary shapes are programmable. In this case,, the term switch segment a phase understood in the solid polymer whose structure is defined by the used in the synthesis of the macromonomers A and B. The formation of a separate phase by phase separation in the solid state is thus the basis for the formation of the typical material properties of the corresponding compound. In this way it is achieved that the polymer system as a whole has material properties that can be assigned to the respective blocks. The switching temperatures for the thermally induced effect can be, glass transition or melting temperatures in particular.

In the context of the present invention has been found to be obtained by the homogeneous sequence of building blocks A and B materials, which, owing to their homogeneous microstructure very good mechanical properties and particularly good shape memory characteristics (shape-memory properties). Particularly surprising was the finding that compared to the corresponding statistical counterparts already relatively low molecular weights sufficient to achieve superior mechanical properties and defined shape transitions. According to an advantageous embodiment of the invention provides that the number average molecular weight M n of the alternating multiblock copolymer in the range of 10,000 to 50,000 g / mol, in particular in the range from 20,000 to 40,000 g / mol, is, while the preferred weight average molecular weight M alternating w of multiblock copolymer in the range of 40,000 to 80,000g / mol, in particular in the range of 50,000 to 70,000 g / mol. In contrast, higher molecular weights to achieve good mechanical properties and a highly reproducible SM effect are necessary in the described in the prior art multiblock. The number-average molecular weight M n defined by Equation 1, and the weight average molecular weight M w by Equation 2, where M is the molecular weight of the polymer grade is i, n, the number of all the polymers prepared with the molecular weight M, and n the total number of polymers.

Figure imgf000008_0001
As further has advantageously been found that the switching temperature of the alternating multi-block copolymers, that is, the transition temperatures of the phase transition, lie in a narrower temperature range compared to the statistical counterparts. This means a sharper and well defined transition. Also, polymers of the invention have an increased modulus of elasticity (E-modulus) compared to the random polymers. In particular, a modulus of elasticity is achieved in the middle which is larger by one order of magnitude than the corresponding random multiblock copolymers with comparable elongation at break (ε max ~ 1000%).

According to a further preferred embodiment of the invention, a hydroxyl group is used in step 1 of the process as a nucleophilic end group, ie the end-group nucleophilic macromonomer A is a α, ω-diol. This has the advantage that many macromonomers that can be potentially used as blocks in multiblock shape memory, ω-diol are commercially available as α.

As electrophilic end group is an isocyanate group can be used to advantage. In this case, the electrophilic end-functionalized macromonomer B nat a α, ω-diisocyanatobutane. Isocyanates govern the one hand well with hydroxyl groups and can be the other hand, a good yield from the commercially available α, ω-diols prepared. In addition, isocyanates have comparable reactivities such as hydroxyl groups, which - as already stated above - favors the establishment of an alternating and homogeneous product structure. the α, ω-diisocyanate of the macromonomer B in Step 1 by reacting the corresponding α, ω-diol of the macromonomer B is particularly preferably provided with a Isocyanatalkan. In particular, the reaction may be carried out with a Diisocyanatalkan, for example with 1, 6-diisocyanato-2,2,4-trimethylhexane or 1, 6-diisocyanato-2,4,4-trimethylhexane (TMDI), an isomer thereof, or 1, 6 - diisocyanatohexane (HDI). In order to achieve a quantitative conversion as possible of the hydroxyl groups with the isocyanate, an excess of isocyanate groups to Hydroxylguppen is submitted to advantage. In particular, a molar ratio of isocyanate groups to Hydroxylguppen of at least 20: 1, preferably of at least 50: 1. A specific embodiment of the invention provides that one of the macromonomers A or B is a polyester of the general formula I with n = 1 ... 14, or a co-polyesters having different n or a derivative thereof. In the context of the present invention include derivatives of the polyester of Formula I structures in which one or more of the hydrogen radicals of the methylene units (-CH 2 -) are replaced by straight or branched, saturated or unsaturated C1 to C14 radicals. is critical in the choice of substituents in the specified frame, that the formation of a separate phase of the switch segments is not prevented by crystallization. Particularly preferred is a poly (ε-caprolactone) (PCL) may be used, that is a polyester having the general formula I with n = 5, or a poly (pentadekalacton), that is a polyester having the general formula I with n = 14th

Figure imgf000010_0001

In a further advantageous embodiment of the invention one of the macromers A or B is a polyether of the formula II (poly (p-dioxanone), PPDO), of the formula III (Poly (ethylene oxide), PEO), of the formula III (Poly (tetrahydrofuran), are) by unbranched or branched, saturated or unsaturated C1 to C6 radicals exchanged - PTHF), of the formula V (poly (propylene oxide))) or a derivative thereof in which one or more of the hydrogen radicals of the methylene units (-CH 2 , However, an unsubstituted polymer of the formula Il is preferably used, that is, poly (p-dioxanone) (PPDO). The above macromers according to the formulas II to V act as switching segments in the rule ( "Weichsegemente") in the corresponding multiblock copolymers.

Figure imgf000010_0002
Figure imgf000011_0001

According to a particularly advantageous embodiment, a polyester of the formula I in particular PCL is used as a first macromonomer used, and as a second a polyether macromonomer of formula II, in particular PPDO. Here, the PCL with the electrophilic end group can be functionalized at both ends, in particular with isocyanate groups (α, ω-PCL-di-isocyanate), and the PPDO with the nucleophilic end group, in particular having hydroxyl groups (α, ω-diol PPDO). Likewise, however, ω-diisocyanate PPD0- ω-PCL diol can in the second process step α, with α, are reacted.

According to an alternative embodiment of a macromonomer of the formula I with n <5 and a macromonomer of formula I with n> 10 is converted to an alternating multiblock copolymer after functionalization. In this case, the macromonomer of formula I with n <5 preferably with an electrophilic end group (particularly diisocyanate) and macromonomer of formula I with n> 10 preferably with a nucleophilic end group (particularly diol) provided.

Another aspect of the present invention relates to a producible by the inventive process multiblock copolymer, which has the advantageous material properties described.

Further preferred embodiments of the invention emerge from the other, referred to in the subclaims.

The invention is described in embodiments with reference to the accompanying drawings. Show it:

1, the chemical process steps for producing an alternating multiblock copolymer according to a first embodiment in which the α, ω-PCL macrodiisocyanate of the α ω macrodiol is reacted PPDO of the invention; 2, the chemical process steps for producing an alternating

Multiblock copolymer according to a second embodiment in which the α, ω-macrodiisocyanate of PPDO with the α ω macrodiol is implemented by PCL of the invention;

FIG cyanatisierung 3 FTIR spectra of PCL after various reaction times of diisopropyl;

Figure 4 FTIR reference spectra of α, ω-diisocyanate functionalized PCL;

Figure 5 1 H-NMR spectra of PCL after various reaction times of the

Diisocyanatisierung;

6 shows 1 H-NMR spectrum of the alternating multiblock copolymer PCL-10K-bl-

PPDO-1.5K;

7 shows 1 H-NMR spectrum of the alternating multiblock copolymer PCL-2K-bl-

PPDO-1.5K;

8 shows voltage Dehunungsdiagramm an alternating poly (PCL-alt-

PPDO) -Multiblockcopolymers;

9 shows temporal variations of the temperature and the elongation of an alternating

Poly (PCL-alt-PPDO) -Multiblockcopolymers in a cyclic, thermomechanical experiment.

The principle of the inventive method for the preparation of alternating copolymers multiblock shape memory should follow the example of a polyether-ester multi-block copolymer of the macromonomer poly (ε-caprolactone) (PCL) and poly (p-dioxanone) (PPDO) will be explained. This selection PCL blocks determine the switching segment, the thermally induced phase transition (melting transition) is carried out, and PPDO blocks determine due to physical crosslinking the hard segment which has the highest thermal transition temperature in the polymer product. According to the invention, the synthesis is carried out in two steps, wherein in the first step the cyanatisierung diisopropyl one of the two macromonomer diols is carried out and in the second step the reaction of the thus prepared α, ω-Makrodiisocyanats with the α, ω-macrodiol of the macromonomer other through crossover Coupling. Here, the α, ω-PCL macrodiisocyanate of the α be implemented by PPDO, ω macrodiol (Example 1) or the α, ω-macrodiisocyanate of PPDO with the α, ω-PCL macrodiol (Example 2).

Generally, in the first process stage for the end group of the α, ω-macrodiols a α, ω-Diisocyanatalkan, preferably 1, 6-diisocyanato-2,4,4-trimethyl-hexane (TMDI), are used. high molar [NCO] / [OH] ratios of 50 mol / mol to minimize side reactions and to achieve the highest possible conversion and high functionalization with Diisocyanatendgruppen (50- fold molar excess of NCO, based on OH) to be carried out in solution submitted to reaction, and a solution of the macrodiol metered in with stirring. Thus, a stable high excess of NCO groups is ensured. The reaction may advantageously be catalytically supported by a suitable catalyst. The Diisocyanatisierungen the α, ω-PCL macrodiols and PPDO require due to the significantly different solubility adapting the reaction procedure to obtain the desired reaction products.

The crossover coupling in the second process stage of α, ω-PCL-diisocyanate and α, ω- PPDO-diol (Example 1) and α, ω-PPDO-diisocyanate and α ω-PCL-diol (Example 2), is under performed a stoichiometric (molar) ratio of the NCO and OH groups of the macromonomers used. The concentrations of the end groups are calculated assuming complete as possible α, ω-end functionalization of the to be coupled macro-diisocyanates from the number average molecular weight M n. Thereafter, an equimolar rate of incorporation of the macromonomers is given in the multiblock copolymer. In contrast, the incorporation rates are significantly different at greatly differing molecular weights M n of coupled, macromonomers, wherein the macromonomer having the lower molecular weight a lower rate of incorporation achieved with the consequence that the macromonomer with the higher molecular weight partially accumulated occurs in the product polymer. This results in a multiblock copolymer with random structure. In contrast, according to the invention for obtaining an alternating structure with a 1: 1 stoichiometry in the product, the number average molecular weights M n of the macromonomers as far as possible to each other aligned. The coupling reaction can be catalyzed by a suitable catalyst.

Example 1: Preparation of PCL-PPDO-multiblock copolymer of the α, ω-diisocyanate of macro- PCL and the α, ω-macrodiol of PPDO

Process Step 1:

The functionalization of the PCL-macrodiol having isocyanate end groups is carried out according to the in Figure 1 (step 1) reaction illustrated. For this purpose, a solution of 1, 6-diisocyanato-2,4,4-trimethylhexane (TMDI) (Sigma Aldrich) in anhydrous tetrahydrofuran (THF) is charged under argon atmosphere. To this initial charge with stirring a solution of the PCL macrodiol (PCL 3.3K: prepared from ε-caprolactone from Sigma Aldrich; PCL and PCL 2K 1 OK from Sigma Aldrich) was dropwise added in anhydrous THF. During the Zudo- tion of the reaction mixture, and the polymer solution is maintained at about 0 0 C. The concentration of TMDI in the template is set such that with respect to the completed reaction mixture is present, a 50-fold molar excess of TMDI with respect to the PCL macrodiol. After complete addition of the solution of PCL macrodiol the reaction mixture is heated to about 60 0 C and stirred under argon atmosphere at this temperature over a period of 24-72 h. This will - favored by good dissolution behavior of PCL in THF - enables temperature control, remains below the inlet during the reaction dosage suppressed at low temperature and a uniform reaction start is carried out by increasing the temperature. Then, the PCL-diisocyanate is precipitated from the solution, washed thoroughly, dried and stored under vacuum until constant weight cooled.

The above-described reaction was carried out in three different approaches in which PCL macrodiols having molecular weights con 2,000 g / mol (PCL 2K), 3,300 g / mol (PCL 3.3K) and 10,000 g / mol (PCL 10K) were used. The products were subjected to chromatography (GPC) and differential scanning calorimetry (DSC) of a comprehensive analysis of FTIR spectroscopy, 1 H-NMR spectroscopy, gel permeation chromatography.

The recorded as a function of the reaction time FTIR spectra are shown in Figure 3, while Figure 4 as a reference, the FTIR spectra of PCL macrodiol (PCL 1 R), and PCL macrodiisocyanate (PCL 1 R-NCO) and TMDI shows. FTIR recorded with intensities of the NCO stretching vibration at 2270 cm "1 (Figure 3) shows that the final conversion is reached after about 48 h.

To determine the degree of functionalization with isocyanate groups was 1 H-NMR-spectroscopically, the ratio of CH 3 signal of terminal units TMDI at chemical shifts of about 0.9 ppm and the characteristic CH 2 signals of the functionalized PCL blocks determined at about 2.3 ppm (Figure 5). In this determination, isocyanate-functionalization were obtained from 70 to 90%. By combined use of GPC and 1 H-NMR spectroscopy 5-3 coupling steps were as a side reaction coupling rates within a narrow range of 1, are determined based on a coupling of already formed isocyanate macromer with unreacted macrodiol despite the high [NCO ] / [OH] -Verhältnisses can be recycled. Taking into account the number of coupling steps in the evaluation of the signal intensity ratios in the 1 H NMR spectrum at the end group analysis leads to an almost complete Diisocyanatisierungsrate.

Process Step 2:

The "cross-coupling" of the two macromers in strict equimolarity terminal group concentration of the two reactants. Therefore, inevitably results - in contrast to the random multiblock - the n alternating defined by the number average molecular weight M of the multiblock copolymer composition. Therefore, an adjustment of the molecular weights M n of PPDO macrodiols to the molecular weights M n of the PCL macrodiisocyanates (here: 10 K, 3.3 K and 2 K) for the controlled adjustment of the molar composition of PCL and PPDO macromonomer according to Table 1 made with the present limits set by the commercial availability of the macromonomers. As the monomer having different molecular weights ([-PPDO-]: 102 g / mol; [-PCL-] 1 14 g / mol) are the molecular weights shown in the table M n of PPDO by a factor of 1 12 to 1 to multiply 14, to arrive at the corresponding molecular weights M n of PCL.

Table 1

Mole fraction adaptation M, n PPDO

XPCL XPPDO M n, PCL = 1 0 KM n, P C L = 3.3 km s, PCL - 2 K

0.9 0.1 1,050 380 250

Figure imgf000016_0001

In the second in Figure 1 (Step 2) reaction step of the cross-coupling of the α, ω-PCL-diisocyanate with the α, ω-diol PPDO is catalyzed with a suitable catalyst. Shown For this purpose the in dichloroethane (DCE) dissolved α, ω-PCL-diisocyanate under argon atmosphere and stirring to 70 0 C is heated. Subsequently, the dropwise addition of dissolved in DCE α, ω-diol PPDO occurs. As a rule, 20 wt% strength reach PCL and 10 wt .-% strength PPDO solutions used for this reaction. The reaction takes place at 70 0 C over a period of 24 h. Then the product is precipitated and dried to constant weight.

The reaction products were characterized chemically by means of 1 H-NMR spectroscopic analysis (Figures 6 and 7) thermally by means of the DSC (Table 2) and mechanically by means of Zugdehnungsmessung and shape memory properties by means of cyclic, thermodynamic examinations (Figures 8 and 9). The results are discussed below along with the results of Example 2. FIG.

Example 2: Preparation of PCL-PPDO-multiblock copolymer of the α, ω-macro diisocvanat of PPDO and the α, ω-PCL macrodiol

Process Step 1:

The functionalization of PPDO macrodiol having isocyanate end groups is carried out according to the in figure 2 (Step 1) reacting shown. Opposite the functionalisation of PCL (Example 1) the homogeneous reaction of the PPDO macrodiols is significantly more difficult due to their low solubility and limited to the use of DCE as the solvent at elevated temperatures. It is presented to a solution of TMDI in anhydrous DCE under an argon atmosphere. To this initial PPDO a solution of the macrodiol (prepared from p-dioxanone of from Boehringer-Ingelheim) was dropwise added in anhydrous DCE with stirring. During the metered addition of the reaction mixture, and the polymer solution is maintained at about 70 0 C, to keep the PPDO-diol in solution. The concentration of TMDI in the template is set such that with respect to the completed reaction mixture, a 50-fold molar excess of TMDI against the PPDO- macrodiol is present. After complete addition of the solution of PPDO macrodiol the reaction mixture is stirred at about 70 0 C under an argon atmosphere over a period of 48 h. Which adjusting turbidity of the solution is maintained over the entire reaction time. Subsequently, the PPDO diisocyanate is precipitated from the solution, washed thoroughly, dried and stored under vacuum until constant weight cooled. The products were subjected to chromatography (GPC) and differential scanning calorimetry (DSC) of a comprehensive analysis of FTIR spectroscopy, 1 H-NMR spectroscopy, gel permeation chromatography.

The determination of the degree of functionalization isocyanate was carried out analogously to Example first By combined use of GPC and 1 H-NMR-spectroscopy coupling rates coupling steps 5-3 could be determined for it within a narrow range of 1. Taking into account the number of coupling steps leading to an almost complete end group. Such running in the first reaction stage coupling can also be used selectively, especially in the case of PPDO-diols with low usually molecular weights of M n <3000 g / mol to realize higher levels of this component in alternating Multiblockco- polymer.

Process Step 2:

As in Example 1, the "crossover coupling" of the two macromers is under strict equidistant molarity of the terminal group concentration of the two reactants conducted and the molecular weights M n of the PCL macrodiisocyanates equalized.

The second in Figure 2 (Step 2) reaction step of the cross-coupling of the α, ω-PPDO-diisocyanate with the α, ω-PCL diol is catalyzed with a suitable catalyst. Shown For this purpose, the dissolved in DCE α, ω-PPDO diisocyanate is heated under an argon atmosphere and stirring to 70 ° C. Subsequently, the dropwise addition of dissolved in DCE α, ω-PCL diol is carried out. In general, strength PCL and 10 wt .-% strength PPDO solutions arrive for this reaction 20 wt .-% are used. The reaction takes place at 70 0 C over a period of 24 h. The product with anhydrous and cooled to -30 0 C di- ethyl ether is precipitated and dried to constant weight.

The reaction products were characterized chemically by means of 1 H-NMR spectroscopic analysis (Figures 6 and 7) thermally by means of the DSC (Table 2), mechanical means Zugdehnungsmessungen and the shape memory properties by means of cyclic, thermo-of mechanical tests (Figures 8 and 9) characterized.

1 H-NMR-spectroscopic characterization of the alternating Multiblockcopolvmere The 1 H-NMR spectrum of a multiblock copolymer PCL 10K-bl-PPDO-1.5K prepared according to Example 1 is shown in Figure 6, while Figure 7 shows the 1 H-NMR spectrum of a is also prepared in example 1 multiblock copolymer PCL-2-bl-PPDO-1.5K. The molar ratio of PCL in the multiblock copolymers was calculated from the integral intensities of the characteristic doublet doublet signals from PCL (PCL, dd) at about 4.05 ppm and PPDO (PPDO, dd) at about 3.8 ppm or 4:35 according to the equation

PCL (mol%) = PCL determined, dd / (PCL, dd + PPDO, dd). For PCL-1 OK-bl-PPDO-1.5K (Figure 6) a PCL content of 84.5 mol% and PCL-2-bl-PPDO-1.5K (Figure 7) of 53.5 mol was % determined.

Thermomechanical Characterization of alternating Multiblockcopolvmere Table 2 shows the in DSC measurements on the selected poly (PCL-alt-PPDO) -Multiblock- copolymers according to the present invention, different compositions specific enthalpies of fusion AH. It can be noted that a significant dependence of the enthalpy of fusion of the crystalline fractions of the PCL and the PPDO-block segment is present. In particular, can be observed as a reference sample with increasing PCL-share an approximation of the melting enthalpies of the PCL segment to the melting enthalpy of the pure PCL 10K macrodiol. The same applies for the enthalpies of fusion of this PPDO-1, 5K segment.

table 2

Figure imgf000018_0001
Figure imgf000019_0001

The stress-strain curve of a non-annealed sample of a poly (PCL-alt- PPDO) -Multiblockcopolymers (M n = 23,600 g / mol M w = 52.400 g / mol; C PCL = 68.0 wt .-%) is illustrated in Figure 8 with curve 1 and characterized by three regions. The elastically beginning, visco-elastic elongation range A shows a significant increase in voltage at low elongation up to 10%. In the following region B to an elongation of about 200% extends purely plastic elongation occurs (so-called "necking behavior"), wherein the material without voltage boost "flows". The subsequent third region C up to an elongation of about 1000% extends, is characterized by proportionality between stress and strain. In contrast, the 48 h at 55 ° C annealed sample (curve 2) shows the initial region to approximately 200% elongation, a visco-elastic deformation during the further course up to 1000% elongation, a similar behavior as the unannealed sample is observed.

The values for the maximum tensile strength σ max, the maximum elongation ε max, and the modulus of elasticity E were (PCL-alt-PPDO) for the inventive alternating poly - determined multiblock copolymers composed of stress-strain testing in accordance with Figure 8 and comparatively relied on mechanical properties of the corresponding statistical poly (PCL-old PPDO) -Multiblockcopolymere (from: Lendlein & chalice... Clin Hemorheol Microcirc 32 (2005), 105-1 16) compared. The mechanical properties are summarized in dependence on the temperature (T = 20 0 C, 37 ° C and 50 0 C) in Table 2 below. It is found that for the alternating as well as statistical multi-block copolymers, the maximum tensile strength σ max, the maximum elongation ε max, and the modulus decrease with increasing temperature. The comparison of the thermo-mechanical characteristics of the alternating poly according to the invention (PCL-alt-PPDO) -Multiblockcopolymere further shows the statistical variations comparable composition that the former have comparable values for σ max and ε max at lower molecular weights. However, compared to their statistical comparison samples the alternating multi-block copolymers possess significantly higher moduli, indicating an influence of the materials according to the invention by forming a molecular superstructure.

To characterize the shape memory properties (SM behavior) cyclic thermo-mechanical tests were performed on a tempered sample poly (PCL-alt-PPDO) - multiblock copolymer (M n = 23,600 g / mol M w = 52.400 g / mol; C PCL = 68, made 0 wt .-%). Figure 9 shows the time courses of the elongation (curve 1) and the temperature (curve 2) during the first three cycles. For this purpose, the sample was stretched 100% within one cycle T n = 52 ° C to ε max = T 1 and then cooled to = -5 ° C. The graph shows an increase in elongation of 110% during this cooling. After withdrawal of outer used to stretch tensile force at zero force = leads -5 ° CWhen fixing the sample to the slight relaxation of the sample at 105% T. 1 This designated as a temporary form of state can be maintained over a long period even at room temperature without spontaneous shape change. A subsequent heating of the sample to a temperature of T = 52 ° C n passes the thermally stimulated recovery of the sample - the so-called switching - a, which is identified in the first cycle by the provision of elongation below 20%. Proceeding from the sample in the second cycle is expanded again to the set already in the first cycle the sample length. The second and third cycle confirm the SM-behavior, which is evidenced by the recovery of the elongation of about 105% to about 20% in all three cycles. From these three cycles, the sizes for the quantification of SM behavior can be determined. Thus, the strain fixity rate f R from the ratio of elongation of the fixed sample and applied for fixing real maximum strain ε m is determined. The average value of the cycles in Figure 9 is R f (1-3) 96%. Furthermore, the elongation recovery ratio R r of the N-th cycle of ε m and the expansion can be calculated -th cycle after reset in the preceding (N-1). Thereafter, the R f values for the three be described cycles R r (1) 84%, R r (2) 98% R and r (3) 99%. Table 3:

Polymeric mechanical properties

CPCl molecular weights

T Omax £ max modulus

(Wt .-%) (kg / mol) (0 C) (MPa) 10 /. (MPa) M n M w old stat old stat old stat old stat old stat old stat

87.3 90.0 36.4 75.6 73.1 158.7 20 20 ± 3 16 ± 1 700 ± 50 1037 ± 100 275 ± 30 34 ± 8

20 22 ± 5 21 ± 1 805 ± 50 1100 ± 100 410 ± 50 39 ± 5 37 15 ± 3 11 ± 2 695 ± 105 1200 ± 70 77 ± 33 10 ± 3

68.4 70.0 18.7 62.8 64.6 134.4 50 3 ± 0.3 0.6 ± 0.1 340 ± 40 740 ± 60 4 ± 1 0.9 ± 0.1

20 32 ± 0.7 13 ± 2 815 ± 2 700 ± 50 214 ± 1 34 ± 5 ​​37 28 ± 0.2 10 ± 2 835 ± 25 800 ± 50 121 ± 29 15 ± 3

53.4 60.0 20.2 31.5 117 76.5 50 18 ± 3 4 ± 0.6 735 ± 120 560 ± 60 94 ± 19 2 ± 0.6

13.0 10.2 17.8 38.0 45.4 65.4 20 20 ± 5 25 ± 4 400 ± 50 730 ± 50 680 ± 65 90 ± 30

Claims

1. A process for producing an alternating multiblock shape memory, which has a consisting of the alternately follow each other macromonomers A and B structure, comprising the steps of
(A) providing the macromonomer A with a reversible functionalization with a nucleophilic end group of the macromonomer B and provision with a reversible functionalization with an electrophilic end group and
(B) reacting with a stoichiometric ratio of nucleophilic end group is set to the electrophilic end group such that a molar deviation from the stoichiometric ratio is at most ± 8% by mole of the nucleophilic end-functionalized macromonomer A to the macromonomer B electrophilic functional end-groups in solution.
2. The method according to claim 1, characterized in that the molar ratio of the deviation of the stoichiometric nucleophilic end group for electrophilic end group in step (b) is at most ± 5 mol%, preferably ± 3 mol%.
3. The method according to any one of the preceding claims, characterized in that the number average molecular weights n of the end-functionalized macromonomers A and B for its reaction in step (b) equalized M to each other so that a difference between the degrees of polymerization of the macromonomers at most 15%, in particular more than 10%, preferably at most 5% based on the number-average degree of polymerization P n of the heavier macromonomer is.
4. The method according to any one of the preceding claims, characterized in that the number average molecular weight M n of the alternating multiblock copolymer in the range of 10,000 to 50,000 g / mol, in particular in the range from 20,000 to 40,000 g / mol, is located.
5. The method according to any one of the preceding claims, characterized in that the weight average molecular weight M w of the alternating multiblock copolymer in the range from 40,000 to 80,000 g / mol, in particular in the range of 50,000 to 70,000 g / mol.
6. The method according to any one of the preceding claims, characterized in that the nucleophilic end group of a hydroxyl group and the nucleophile end-group functionalized macromonomer A α, ω-diol is a.
7. The method according to any one of the preceding claims, characterized in that the electrophilic end group is an isocyanate group and the electrophilic end-functionalized macromonomer B is an α, ω-diisocyanate.
8. The method according to claim 7, characterized in that the provision of the α, ω-diisocyanate by reaction of an α, ω-diol of the macromonomer B is performed with a Isocyanatalkan, in particular a Diisocyanatalkan, preferably with 1, 6- diisocyanato-2,2 , 4-trimethylhexane or 1, 6-diisocyanato-2,4,4-trimethylhexane (TMDI) or 1, 6-diisocyanatohexane.
9. The method according to claim 8, characterized in that the reaction of the α, ω-diol of the macromonomer B with the Isocyanatalkan an excess of isocyanate groups to hydroxyl groups is presented, in particular, a molar ratio of isocyanate groups to hydroxyl groups of at least 20: 1 , preferably of at least 50: is set. 1
10. The method according to any one of the preceding claims, characterized in that one of the macromonomers A or B is a polyester of the general formula I with n = 1 ... 14, or a co-polyesters having different n or a derivative thereof, in particular poly (ε-caprolactone) or with n = 5 poly (pentadekalacton) with n = 14
Figure imgf000023_0001
1 1. A method according to any one of the preceding claims, characterized in that one of the macromers A or B is a polyether according to one of the formulas II to V or a derivative thereof
Figure imgf000024_0001
Figure imgf000024_0002
12. Alternating multiblock copolymer prepared by the process according to any one of claims 1 to 1. 1
13. The use of an alternating multiblock copolymer according to claim 12 in biomedical applications.
PCT/EP2007/059583 2006-12-08 2007-09-12 Method for the production of an alternating multi-block copolymer with shape memory WO2008068072A1 (en)

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