DE102006058755A1 - Process for the preparation of an alternating multiblock copolymer with shape memory - Google Patents

Abstract

The invention relates to a process for the preparation of an alternating multiblock copolymer having a shape consisting of the alternating successive macromonomers A and B, comprising the steps of (a) providing the macromonomer A with a bilateral functionalization with a nucleophilic end group and providing the macromonomer M with bilateral functionalization with an electrophilic end group and (b) reacting the nucleophile endgroup-functionalized macromonomer A with the electrophile-endgroup-functionalized macromonomer B in solution, setting a stoichiometric ratio of the nucleophilic end group to the electrophilic end group such that a molar deviation from the stoichiometric ratio not more than ± 8 mol%. The invention further comprises an alternating multiblock copolymer preparable by the claimed process.

Description

The Invention relates to a method for producing a shape memory polymer, that - beside a permanent form - at least a temporary one Can save shape. The polymer is an alternating multiblock copolymer, one of the alternating successive macromonomers A and B has existing structure.

in the State of the art are so-called shape memory polymers or SMPs (shape memory polymer) known in induction by a suitable Stimulus a shape transition from a temporary shape in a permanent form according to a previous programming demonstrate. Most frequently is this shape memory effect thermally stimulated, that is, when heated of the programmed polymer material over the defined transition temperature the provision driven by entropy elasticity takes place. Shape memory polymers are usually polymer networks where chemical (covalent) or physical (non-covalent) crosslinks the permanent ones Determine shape. Programming is done by passing above the transition temperature a switching segment deforms the polymer material and then under Maintaining the deformation forces below this temperature chilled is going to be the temporary one To fix the shape. Reheating above the transition temperature leads to a phase transition the switching phase determining phase and restore the original permanent form.

Shape memory polymers are usually random multiblock copolymers, which are mostly composed of two thermodynamically incompatible segments (macromonomers A and B). The blocks A and B must each have a minimum molecular weight and a minimum proportion, so that a phase separation of the blocks in the polymer is ensured. Statistical multiblock copolymers form physical crosslinks. The responsible phase is called hard segment and has the highest thermal transition temperature T _transA in the system. The phase with the next lowest thermal transition temperature T _TRANSb is the segment determine the switching de phase and for switching the thermally induced shape memory effect with the switching temperature T _switching (≈ T _TRANSb) responsible.

Statistical multiblock copolymers are prepared by polyaddition or polycondensation of the macromonomers A and B. The chemical structure of these multiblock copolymers is generally characterized by a statistical sequence of the macromonomers A and B. This results in a different number of repeat units A and B within the multiblocks and thus a heterogeneous distribution of each coupled blocks of the same type (-AA- or -BB-) or other type (-AB-) (eg AABABBBAB). On the other hand, a distinction is made between (strictly) alternating multiblock copolymers, which are characterized by an alternating sequence of blocks A and B and accordingly have the structure - (AB) _n -. Alternating multiblock copolymers with shape memory have not been realized so far.

In US 6,388,043 B1 ( EP 1 062 278 A ) and US 6,160,084 B ( EP 156 487 A ) block copolymers are described, which are composed of at least two different segments (blocks) and can store at least two temporary forms in their "shape memory". In the specific embodiment, PDS macromonomers (copolymer of p-dioxan-2-one and ethylene glycol monomers) and poly (ε-caprolactone) macromonomers (PCL) are linked together. The coupling reaction for the preparation of the multiblock copolymers is carried out by reaction of the macrodiols with a low molecular weight diisocyanate, that is, via diurethane bridges, resulting in random multiblock copolymers.

Further statistical multiblock copolymers and their production processes are approximately off Lendlein & Langer (Science 296 (2002), 1673-1676) . Lendlein & Kelch (Angew Chem. 114 (2002), 2138-2162) and Cho et al. (J. Appl. Polym. Sci. 93 (2004), 2410-2415) known.

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

The known processes for the preparation of multiblock copolymers have the disadvantage that the incorporation of the macromonomers A and B into the polymer chain always takes place statistically, that is to say as a result lead statistical multiblock copolymers. In the case of a synthesis from the solution can not be ruled out that due to a different solubility of the macromonomers used in the solvent used or due to reactivity differences, the incorporation rate of the same varies in the multiblock copolymer. The reason for this is presumably a more or less good steric accessibility or differences in the activation of the competing reactive end groups of the two macromonomers A and B, as a result of different widening of the wedge. Thus, the dipole component with increased solubility and reactivity, in particular at low conversions, is intensified incorporated the multiblock copolymer. The resulting non-uniformity of the chemical composition contributes to irregularities of the microstructure. In the case of carrying out the coupling reaction in the melt, however, no homogeneous mixing of the two macromonomers A and B can be ensured, so that there are different concentration ratios of the components in the different partial volumes of the melt.

Another disadvantage of the known production methods leading to random multiblock copolymers is their lack of reproducibility. Thus, randomly the statistical sequence of the macromonomers A and B in the product may differ even with identical reaction mixtures, with the result that the resulting thermomechanical properties of the polymer also vary widely and the shape memory effect due to the not regularly formed microstructure can not be programmed and triggered. Further, it has been observed that good mechanical properties and shape memory performance are achieved only when the multiblock copolymer has comparatively high molecular weights. Typically, number-average molecular weights M _n of at least 30,000 g / mol and weight-average molecular weights M _w of at least 100,000 g / mol are required in this connection. These required molecular weights can be realized so far only with considerable process engineering effort.

Of the The invention is therefore based on the object, a process for the preparation a multi-block copolymer with shape memory to create with high reliability to an alternating sequence of blocks A and B or to a homogeneous one Distribution of the sequence with narrow length distribution leads and thus produces polymer products that have an improved performance profile in terms of SM effect and mechanical properties have. It is also important that the resulting Multiblock copolymers - as well like their statistical comparison patterns - one for the formation of the SM effect reach required minimum molecular weight.

• (a) Bereitstellung des Makromonomers A mit einer beidseitigen Funktionalisierung mit einer nukleophilen Endgruppe und Bereitstellung des Makromonomers B mit einer beidseitigen Funktionalisierung mit einer elektrophilen Endgruppe und
• (b) Umsetzung des nukleophil endgruppenfunktionalisierten Makromonomers A mit dem elektrophil endgruppenfunktionalisierten Makromonomer B in Lösung, wobei ein stöchiometrisches Verhältnis der nukleophilen Endgruppe zu der elektrophilen Endgruppe eingestellt wird derart, dass eine molare Abweichung vom stöchiometrischen Verhältnis minimiert wird, insbesondere höchstens ± 8 mol-% beträgt.

This object is achieved by a method for producing an alternating multiblock copolymer with shape memory properties, which has a structure consisting of the alternately successive macromonomers A and B, with the following steps:

• (A) providing the macromonomer A with a two-sided functionalization with a nucleophilic end group and providing the macromonomer B with a bilateral functionalization with an electrophilic end group and
• (b) reacting the nucleophile end-group-functionalized macromonomer A with the electrophilic end group-functionalized macromonomer B in solution, setting a stoichiometric ratio of the nucleophilic end group to the electrophilic end group such that a molar deviation from the stoichiometric ratio is minimized, in particular at most ± 8 mol% is.

In the first stage of the process, electrophilic and nucleophilic reaction centers are thus created by end-group functionalization, so that an alternating "crossover coupling" is achieved by their reaction in the second process stage. Targeted selection of the two end groups and the preparation of the correspondingly functionalized macromonomers A and B in step (a) can minimize reactivity differences of the macromonomers and eliminate interfering influences on the homogeneity of the coupling steps in step (b). The multiblock copolymer resulting from the process has a largely regular AB block structure in which the macromonomers A and B according to the structure (AB) _n alternate in succession. In order to achieve this, it has proved essential on the one hand to observe the strictest possible stoichiometry of the nucleophilic end group of the macromonomer A and the electrophilic end group of the macromonomer B in step (b), ie a molar ratio of the nucleophilic end group to the electrophilic end group of 1, wherein a maximum molar deviation of ± 8 mol% has been found to be tolerable. The reliability of the process can be further increased if the molar deviation from the stoichiometric ratio is at most ± 5 mol%, in particular at most ± 3 mol%.

Furthermore, it is important to carry out the coupling reaction in step (b) in solution. Together with the strict stoichiometry this measure ensures - unlike the implementation in melt - a homogeneous mixing of the reactants so that ideally in each subvolume of the reaction mixture corresponding concentrations of the macromonomers A and B are present.

According to a particularly advantageous embodiment of the method according to the invention, the number-average molecular weights M _{n of} the end group-functionalized macromonomers A and B are matched as far as possible for their reaction in step (b). In this case, a difference between the degrees of polymerization of the macromonomers A and B is set, which is at most 15%, in particular at most 10%, preferably at most 5%, based on the number-average degree of polymerization P _{n of} the heavier macromonomer. This measure requires two advantageous effects. First, by aligning the molecular weights, it is achieved that both end group functions have similar steric accessibility during the reaction in solution in step (b) and the segment lengths in the product are broadly consistent. This results in consistent rates of incorporation of the macromonomers A and B into the chain of the resulting multiblock copolymer and thus further support for the alternate construction. Second, the approach results in approximately consistent chain segment lengths of blocks A and B in the product, which in turn favors the formation of a homogeneous, phase-segregated morphology in the polymer product that forms the basis for particularly advantageous SM thermomechanical properties.

The resulting multiblock copolymer has thermally inducible shape memory properties this means, it is capable of being dependent from the temperature next to a permanent form at least one temporary Take shape. Is one of the blocks A or B, the switching segment determining block with defined thermal transition temperature and the another block of the hard segment determining block can be to save a shape in "shape memory". alternative can but also both blocks A and B contribute to the construction of switching segment-forming phases, the different transition temperatures form so that in addition to the permanent form two temporary forms are programmable. It is under the term switching segment understood a phase in the solid polymer whose structure by defines the macromonomers A and B used in the synthesis is. The formation of a separate phase by Phasenentmischung in the solid state is thus the basis for the training of the typical material properties the corresponding connection. In this way it is achieved that the polymer system as a whole has material properties which the respective blocks can be assigned. At the switching temperatures for the thermally induced effect may be, in particular, glass transition or Act melting temperatures.

In the context of the present invention, it has been found that, due to the homogeneous sequence of the components A and B, materials are obtained which, owing to their homogeneous microstructure, have very good mechanical properties and particularly good shape memory properties (shape memory properties). Particularly surprising was the finding that, compared with the corresponding statistical counterparts, relatively low molecular weights are already sufficient to realize superior mechanical properties and defined shape transitions. Accordingly, 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 of 20,000 to 40,000 g / mol, while the preferred weight average molecular weight M _{w of} the alternating Multiblockcopolymers in the range of 40,000 to 80,000 g / mol, in particular in the range of 50,000 to 70,000 g / mol. In contrast, in the multiblock copolymers described in the prior art, higher molecular weights are necessary for achieving good mechanical properties and a highly reproducible SM effect. Here, the number average molecular weight M _{n is} defined by Equation 1 and the weight average molecular weight M _w by Equation 2, where M _{i is} the molar mass of the polymer type i, n _{i is} the number of polymers produced with the molecular weight M _i and n is the total number of polymers.

As further advantageous, it has been found that the switching temperatures of the alternating multiblock copolymers, that is, the transition temperatures of the phase transition, lie in a narrower temperature range than the statistical counterparts. This means a sharper and well-defined transition. The polymers according to the invention also have an increased modulus of elasticity (modulus of elasticity) on the random polymers. In particular, on average, an E-modulus is achieved that is an order of magnitude greater than that of the corresponding random multiblock copolymers with comparable elongation at break (ε _max ≈ 1000%).

To Another preferred embodiment of the invention is in step 1 of the process used as the nucleophilic end group of a hydroxyl group, this means the nucleophile end-group functionalized macromonomer A is an α, ω-diol. This has the advantage of having many macromonomers, potentially as blocks in multiblock copolymers with shape memory can be used are commercially available as α, ω-diol.

When electrophilic end group can be used with advantage an isocyanate group become. In this case, the electrophile is end-group functionalized Macromonomer B is an α, ω-diisocyanate. Isocyanates, on the one hand, react well with hydroxyl groups and leave on the other hand, in good yield from the commercially available α, ω-diols produce. In addition, isocyanates have comparable reactivities like hydroxyl groups, what - like already stated above was - the Building an alternating and homogeneous product structure favors. Particularly preferred is the α, ω-diisocyanate of the macromonomer B in step 1 by reacting the corresponding α, ω-diol of the Makromonomers B provided with an isocyanate alkane. Especially For example, the reaction can be with a diisocyanate alkane with 1,6-diisocyanato-2,2,4-trimethylhexane or 1,6-diisocyanato-2,4,4-trimethylhexane (TMDI), an isomeric mixture of these or 1,6-diisocyanatohexane (HDI). To one as possible quantitative reaction of the hydroxyl groups with the isocyanate achieve, will advantageously be a surplus of isocyanate groups Submitted hydroxyl groups. In particular, a molar ratio of Isocyanate groups to hydroxyl groups of at least 20: 1, preferably set by 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 where n = 1 ... 14 or a co-polyester with different n or a derivative of these. In the context of the present invention, derivatives of the polyester according to formula I include structures in which one or more of the hydrogen radicals of the methylene units (-CH ₂ -) are replaced by unbranched or branched, saturated or unsaturated C 1 to C 14 radicals. Crucial in the selection of the substituents in the specified framework is that the formation of a separate phase of the switching segments is not prevented by crystallization. Particular preference is given to using a poly (ε-caprolactone) (PCL), ie a polyester of the general formula I where n = 5, or a poly (pentadecactone), ie a polyester of the general formula I where n = 14.

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), the formula III (poly (ethylene oxide), PEO), the formula III (poly (tetrahydrofuran), PTHF), the formula V (poly (propylene oxide))) or a derivative of these, in which one or more of the hydrogen radicals of the methylene units (-CH ₂ -) are replaced by unbranched or branched, saturated or unsaturated C 1 to C 6 radicals , However, preference is given to using an unsubstituted polymer of the formula II, that is to say poly (p-dioxanone) (PPDO). The abovementioned macromers according to the formulas II to V generally function as switching segments ("soft segments") in the corresponding multiblock copolymers.

To a particularly advantageous embodiment is as a first Macromonomer used a polyester of formula I, in particular PCL, and as a second macromonomer a polyether of formula II, in particular PPDO. In this case, the PCL with the electrophilic end group on both sides be functionalized, especially with isocyanate groups (α, ω-PCL diisocyanate), and the PPDO with the nucleophilic end group, especially with hydroxyl groups (Α, ω-diol PPDO). Likewise, however, in the second process step α, ω-PPDO diisocyanate can be reacted with α, ω-PCL diol.

To an alternative embodiment is a macromonomer of the formula I with n ≤ 5 and a macromonomer of formula I with n ≥ 10 to an alternating multiblock copolymer implemented after functionalization. This is the macromonomer of formula I with n ≤ 5 preferably with an electrophilic end group (especially diisocyanate) and macromonomer of formula I with n ≥ 10, preferably with a nucleophilic End group (especially diol) provided.

One Another aspect of the present invention relates to a with inventive method producible multiblock copolymer containing the described advantageous Has material properties.

Further preferred embodiments of the invention will become apparent from the others, in the subclaims mentioned features.

The Invention will be described below in embodiments with reference to FIG associated Drawings explained. Show it:

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

2 the chemical process steps for the preparation of an alternating multiblock copolymer according to a second embodiment of the invention, wherein the α, ω-macrodiisocyanate of PPDO is reacted with the α, ω-macrodiol of PCL;

3 FTIR spectra of PCL after different reaction times of the diisocyanation;

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

5 ¹ H-NMR spectra of PCL after different reaction times of the diisocyanation;

6 ¹ H-NMR spectrum of the alternating multiblock copolymer PCL-10K-bl-PPDO-1.5K;

7 ¹ H-NMR spectrum of the alternating multiblock copolymer PCL-2K-bl-PPDO-1.5K;

8th Stress-strain plot of an alternating poly (PCL-old-PPDO) multiblock copolymer;

9 Temporal plots of the temperature and elongation of an alternating poly (PCL-old-PPDO) multiblock copolymer in a cyclic, thermomechanical experiment.

The Principle of the method according to the invention for the production of alternating multi-block copolymers with shape memory below using the example of a polyether ester multiblock copolymer from the macromonomers poly (ε-caprolactone) (PCL) and poly (p-dioxanone) (PPDO) explained will. In this selection, PCL blocks determine the switching segment, the thermally induces a phase transition (Melting transition) performs, and PPDO blocks determine the hard segment due to physical crosslinking the highest thermal transition temperature in the polymer product.

According to the invention the synthesis in two steps, wherein in the first step, the diisocyanation one of the two macromonomer diols takes place and in the second step the reaction of the thus prepared α, ω-macrodiisocyanate with the α, ω-macrodiol of the other macromonomer through crossover coupling. In this case, the α, ω-macrodiisocyanate of PCL with the α, ω-macrodiol of PPDO (Example 1) or the α, ω-macrodiisocyanate of PPDO with the α, ω-macrodiol from PCL (Example 2).

in the Generally, in the first stage of the process for end-group functionalization the α, ω macrodiols an α, ω-diisocyanate alkane, preferably 1,6-diisocyanato-2,4,4-trimethylhexane (TMDI) used. To minimize side reactions and to achieve a possible high conversion and high degrees of functionalization with Diisocyanatendgruppen be high molar [NCO] / [OH] ratios of 50 mol / mol (50-fold molar excess of NCO based on OH) for the in solution to be performed Reaction submitted and a solution of the macrodiol with stirring added. Thus, a stable high excess of NCO groups is ensured. The reaction may be advantageous by a suitable catalyst catalytically supported become. The diisocyanatizations of the α, ω macrodiols of PCL and PPDO require due to the significantly different solubility an adaptation of the reaction procedure to the desired To obtain reaction products.

The crossover coupling in the second process stage of α, ω-PCL diisocyanate and α, ω-PPDO diol (Example 1) or α, ω-PPDO diisocyanate and α, ω-PCL diol (Example 2) is under a stoichiometric (molar) ratio of the NCO and OH groups of the macromonomers used. The concentrations of the end groups are calculated assuming the fullest possible α, ω-end functionalization of the macro-diisocyanates to be coupled from the number average molecular weight M _n . Thereafter, an equimolar incorporation rate of the macromonomers is given in the multiblock copolymer. In contrast, with widely differing molecular weights M _{n of} the coupling macromonomers, incorporation rates differ significantly, with the lower molecular weight macromonomer achieving a lower incorporation rate, with the result that the higher molecular weight macromonomer appears partially cumulated in the product polymer. This leads to a multiblock copolymer with a statistical structure. In contrast, according to the invention, to achieve an alternating construction with a 1: 1 stoichiometry in the product, the number average molecular weights M _{n of} the macromonomers are aligned as far as possible. The coupling reaction can be catalyzed by a suitable catalyst.

Example 1: Preparation of a PCL-PPDO Multiblock Copolymer from the α, ω-macrodiisocyanate of PCL and the α, ω-macrodiol from PPDO

Process stage 1:

The functionalization of PCL-macrodiol with isocyanate end groups is carried out according to the in 1 (1st step) reaction shown. For this purpose, a solution of 1,6-diisocyanato-2,4,4-trimethylhexane (TMDI) (Sigma Aldrich) in anhydrous tetrahydrofuran (THF) is placed under an argon atmosphere. A solution of the PCL macrodiol (PCL 3.3 K: prepared from ε-caprolactone from Sigma Aldrich, PCL 2K and PCL 10K from Sigma Aldrich) in anhydrous THF is added dropwise to this template while stirring. During Zudo tion, the reaction mixture and the polymer solution is maintained at about 0 ° C. The concentration of TMDI in the template is adjusted so that there is a 50-fold molar excess of TMDI over the PCL macrodiol with respect to the completed reaction mixture. After complete addition of the solution of the PCL macrodiol, the reaction mixture is heated to about 60 ° C and stirred under argon atmosphere at this temperature over a period of 24-72 h. This is - favored by the good dissolution behavior of PCL in THF - a temperature control allows under which during the addition at low temperature, the reaction is suppressed and after increasing the temperature, a uniform reaction start. Subsequently, the PCL diisocyanate is precipitated from the solution, washed extensively, dried under vacuum to constant weight and stored cooled.

The reaction described above 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) relationship 10,000 g / mol (PCL 10K) were used. The products were subjected to a comprehensive analysis of FTIR spectroscopy, ¹ H NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC).

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

To determine the degree of functionalization with isocyanate groups, the ratio of the CH ₃ signal of terminal TMDI units at chemical shifts of about 0.9 ppm and the characteristic CH ₂ signals of the functionalized PCL blocks was determined by ¹ H NMR spectroscopy at ca. 2.3 ppm determined ( 5 ). In this determination, isocyanate end group functionalization levels of 70 to 90% were determined. By combined application of GPC and ¹ H NMR spectroscopy, as a side reaction coupling rates within a narrow range of 1.5 to 3 coupling steps could be determined, which are based on coupling of already formed NCO macromer with unreacted macrodiol despite the high [NCO ] / [OH] ratio can be attributed. The consideration of the number of coupling steps on the evaluation of the signal intensity ratios in the ¹ H-NMR spectrum in the end group analysis leads to a nearly complete Diisocyanatisierungsrate.

Process level 2:

The "crossover coupling" of the two macromers occurs under strict equimolarity of the end group concentration of the two reactants. Therefore, unlike the random multiblock copolymers, the alternating composition of the multiblock copolymer as defined by the number average molecular weight M _n inevitably results. For the targeted adjustment of the molar composition of PCL and PPDO macromonomer units therefore an adaptation of the molecular weights M _n of PPDO macrodiols to the molecular weights M _{n of} the PCL macro diisocyanates used (here: 10 K, 3.3 K and 2 K) according to Table 1, where present limits are set by the commercial availability of macromonomers. Since the monomer units have different molar masses ([-PPDO-]: 102 g / mol; [-PCL-]: 114 g / mol), the molecular weights M _n of PPDO listed in the table are by a factor of 1.12 to 1, 14 to arrive at the corresponding molecular weights M _n of PCL. Table 1: mole fraction Adaptation M _{n, PPDO} X _PCL X _PPDO Mn _{, PCL} = 10K Mn _{, PCL} = 3.3K Mn _{, PCL} = 2K 0.9 0.1 1050 380 250 0.8 0.2 2250 770 480 0.7 0.3 3850 1280 780 0.6 0.4 5950 1950 1200 0.5 0.5 8900 2900 1750 0.4 0.6 13,300 4300 2600 0.3 0.7 20,700 6700 4000 0.2 0.8 35400 11,400 6800 0.1 0.9 79,600 25,600 15,200

In the second in 1 (2nd step) reaction step of the crossover coupling of the α, ω-PCL diisocyanate with the α, ω-PPDO diol is catalyzed with a suitable catalyst. For this purpose, the dissolved in dichloroethane (DCE) α, ω-PCL diisocyanate is heated to 70 ° C under argon atmosphere and stirring. This is followed by the dropwise addition of dissolved in DCE α, ω-PPDO-diol. As a rule, 20% by weight PCL and 10% by weight PPDO solutions are used for this reaction. The reaction is carried out at 70 ° C over a period of 24 h. The product is then precipitated and dried to constant weight.

The reaction products were chemically analyzed by ¹ H NMR spectroscopic analysis ( 6 and 7 ) thermally by means of DSC (Table 2) and mechanically by means of tensile strain measurement and shape memory properties by means of cyclic, thermodynamic investigations ( 8th and 9 Characterized. The results are discussed below together with the results of Example 2.

Example 2: Preparation of a PCL-PPDO Multiblock Copolymer from the α, ω-macrodiisocyanate of PPDO and the α, ω-macrodiol from PCL

Process stage 1:

The functionalization of isocyanate-terminated PPDO macrodiol is carried out according to the method described in US Pat 2 (1st step) reaction shown. Compared with the functionalization of PCL (Example 1), the homogeneous reaction of the PPDO macrodiols is considerably more difficult due to their low solubility and limited to the use of DCE as a solvent under elevated temperatures. A solution of TMDI in anhydrous DCE is placed under an argon atmosphere. A solution of the PPDO macrodiol (prepared from p-dioxanone from Boehringer-Ingelheim) in anhydrous DCE is added dropwise to this template while stirring. During the metered addition, the reaction mixture and the polymer solution are kept at about 70 ° C to keep the PPDO-diol in solution. The concentration of TMDI in the template is adjusted so that there is a 50-fold molar excess of TMDI over the PPDO macrodiol with respect to the completed reaction mixture. After complete addition of the solution of PPDO macrodiol, the reaction mixture is stirred at about 70 ° C under an argon atmosphere over a period of 48 h. The self-adjusting turbidity of the solution persists throughout the reaction time. Subsequently, the PPDO diisocyanate is precipitated from the solution, washed extensively, dried under vacuum to constant weight and stored refrigerated.

The products were subjected to a comprehensive analysis of FTIR spectroscopy, ¹ H NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC).

The determination of the degree of functionalization with isocyanate end groups was carried out analogously to Example 1. By combined application of GPC and ¹ H NMR spectroscopy, coupling rates within a narrow range of 1.5 to 3 coupling steps could be determined. The consideration of the number of coupling steps leads to an almost complete end-group functionalization. However, such a coupling occurring in the first reaction stage can also be used selectively, especially in the case of PPDO diols with generally low molecular weights of M _n <3,000 g / mol, in order to realize higher proportions of this component in the alternating multiblock copolymer.

Process level 2:

As in Example 1, the "crossover coupling" of the two macromers is carried out under strict equimolarity of the end group concentration of the two reactants and the molecular weights M _{n of} the PCL macrodiisocyanates used are adjusted.

The second in 2 (2nd step) reaction step of the crossover coupling of the α, ω-PPDO diisocyanate with the α, ω-PCL diol is catalyzed with a suitable catalyst. For this purpose, the dissolved in DCE α, ω-PPDO diisocyanate is heated to 70 ° C under argon atmosphere and stirring. This is followed by the dropwise addition of dissolved in DCE α, ω-PCL diol. As a rule, 20% by weight PCL and 10% by weight PPDO solutions are used for this reaction. The reaction is carried out at 70 ° C over a period of 24 h. The product is then precipitated with anhydrous and cooled to -30 ° C diethyl ether and dried to constant weight.

The reaction products were chemically characterized by ¹ H-NMR spectroscopic analysis ( 6 and 7 ), thermally by means of DSC (Table 2), mechanically by means of tensile strain measurements and the shape memory properties by means of cyclic, thermo-mechanical investigations ( 8th and 9 Characterized.

¹ H NMR spectroscopic characterization of the alternating multiblock copolymers

The ¹ H-NMR spectrum of a multiblock copolymer PCL-10K-bl-PPDO-1.5K prepared according to Example 1 is described in FIG 6 shown while 7 ¹ H-NMR spectrum of a also prepared according to Example 1 multiblock copolymer PCL-2K-bl-PPDO-1.5K. The molar fraction of PCL in the multiblock copolymers was determined by the integral intensities of the characteristic doublet doublet signals of PCL (PCL, dd) at about 4.05 ppm and PPDO (PPDO, dd) at about 3.8 or 4.35 ppm according to the equation PCL (mol%) = PCL, dd / (PCL, dd + PPDO, dd) certainly. For PCL-10K-bl-PPDO-1.5K ( 6 ) was a PCL fraction of 84.5 mol% and for PCL-2K-bl-PPDO-1.5K ( 7 ) of 53.5 mol%.

Thermomechanical characterization the alternating multiblock copolymers

Table 2 shows the enthalpies ΔH determined in DSC measurements on selected poly (PCL-old-PPDO) multiblock copolymers according to the present invention of different composition. It can be stated that there is a significant dependence of the enthalpy of fusion on the crystalline fractions of the PCL and PPDO block segments. In particular, an approach of the enthalpies of fusion of the PCL segment to the enthalpy of fusion of the pure PCL-10K macrodiol can be observed as a reference sample with increasing PCL content. Analogously, this applies to the enthalpies of fusion of the PPDO 1.5K segment. Table 2 block components C _PCL (wt%) ΔH _PCL (J * g ^-1 ) ΔH _PPDO (J · g ^-1 ) PCL 10K 100 78.7 PCL 10K NCO / PPDO-1.5K 87.3 64.0 4.3 PCL 2K NCO / PPDO-1.5K 68.4 49.0 24.5 PPDO-1.5C NCO / PCL 10K 53.4 45.9 42.4 PPDO-1.5K-NC-1.5K / 2K PCL 13.0 33.4 48.2 PPDO-1.5K 0 105.1

The stress-strain diagram of an unannealed sample of a poly (PCL-old PPDO) multiblock copolymer (M _n = 23,600 g / mol; M _w = 52,400 g / mol; c _PCL = 68.0 wt%) in 8th with curve 1 represented and characterized by three areas. The elastically beginning, visco-elastic stretching region A shows a significant increase in stress at low elongation of up to 10%. In the following area B, which extends to an elongation of about 200%, occurs purely plastic strain (so-called "necking behavior"), wherein the material "flows" without voltage increase. The subsequent third region C, which extends to an elongation of about 1000%, is characterized by the proportionality between stress and strain. In contrast, the sample annealed at 55 ° C. for 48 h (curve 2 ) in the initial range to about 200% elongation a visco-elastic deformation, while in the course up to 1000% elongation an analogous behavior as the untempered sample is observed.

The values for the maximum tensile strength σ _max , the maximum elongation ε _max and the modulus of elasticity E were determined for the inventive alternating poly (PCL-old-PPDO) multiblock copolymers from stress-strain studies according to 8th determined and comparatively used mechanical properties of the corresponding random poly (PCL-old-PPDO) multiblock copolymers (from: Lendlein & Kelch: Clin. Hemorheol. Microcirc. 32 (2005), 105-116 ). The mechanical properties are summarized in Table 2 as a function of the temperature (T = 20 ° C, 37 ° C and 50 ° C). It can be seen that for the alternating as well as for the statistical multiblock copolymers the maximum tensile strength σ _max , the maximum elongation ε _max and the modulus of elasticity decrease with increasing temperature. The comparison of the thermomechanical characteristics of the alternating poly (PCL-old-PPDO) multiblock copolymers prepared according to the invention with the statistical variants of comparable composition further shows that the former have comparable values for σ _max and ε _max at lower molecular weights. However, the alternating multiblock copolymers have significantly higher moduli of elasticity compared to their statistical comparison patterns, which indicates an influence on the materials produced according to the invention by formation of a molecular superstructure.

Cyclic thermomechanical investigations on a tempered sample of poly (PCL-old-PPDO) multiblock copolymers (M _n = 23,600 g / mol; M _w = 52,400 g / mol; c _PCL = 68) were used to characterize the shape memory properties (SM behavior). 0% by weight). 9 shows the time course of the strain (curve 1 ) and the temperature (curve 2 ) during the first three cycles. For this purpose, the sample was stretched within a cycle at T _h = 52 ° C to ε _max = 100% and then cooled to T _t = -5 ° C. The graph shows an increase in elongation to 110% during this cooling. After retraction of the outer tensile force used to stretch to zero force at T _t = -5 ° C leads to the sample for easy relaxation of the sample to 105% when fixing the sample. This state, referred to as a temporary shape, can be maintained over a longer period even at room temperature without spontaneous change in shape. Subsequent heating of the sample to a temperature of T _h = 52 ° C initiates the thermally-stimulated recovery of the sample - the so-called switching - which is indicated by the recovery of elongation to less than 20% in the first cycle. On this basis, the sample is stretched again in the second cycle to the sample length already set in the first cycle. The second and third cycles confirm the SM behavior, which is evidenced by the recovery of the strain from about 105% to about 20% in all three cycles. From these three cycles, the quantities for quantifying the SM behavior can be determined. Thus, the elongation fixing ratio R _{f is determined} from the ratio of the elongation of the fixed sample and the real maximum strain ε _m applied for fixing. The mean of the cycles in 9 R _f (1-3) is 96%. Furthermore, the strain recovery ratio R _{r of} the Nth cycle can be calculated from ε _m and the strain after recovery in the previous (N-1) th cycle. Thereafter, the R _r values for the three described cycles R _r (1) are 84%, R _r (2) 98% and R _r (3) 99%.

Claims (13)

Process for making an alternating Multiblock copolymers with shape memory, one of the alternating successive macromonomers A and B has existing structure, with the steps (a) Provision of the macromonomer A with a two-sided functionalization with a nucleophilic end group and providing the macromonomer B with a bilateral functionalization with an electrophilic End group and (b) Reaction of the nucleophile end-group-functionalized Macromonomer A with the electrophilic endgruppenfunktionalisierten Macromonomer B in solution, being a stoichiometric relationship the nucleophilic end group to the electrophilic end group set becomes such that a molar deviation from the stoichiometric ratio is at most ± 8 mol% is. Method according to claim 1, characterized in that that the molar deviation of the stoichiometric ratio of the nucleophilic end group to the electrophilic end group in step (b) not more than ± 5 mol%, preferably ± 3 mol%. Method according to one of the preceding claims, characterized in that the number-average molecular weights Mn of the end-group functionalized macromonomers A and B for their implementation in step (b) are adjusted to each other such that a difference between the degrees of polymerization of the macromonomers at most 15%, especially at most 10% , preferably at most 5%, based on the number-average degree of polymerization P _{n of} the heavier macromonomer. Method according to 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 of 20,000 to 40,000 g / mol. Method according to one of the preceding claims, characterized in that the weight average molecular weight M _{w of} the alternating multiblock copolymer in the range of 40,000 to 80,000 g / mol, in particular in the range of 50,000 to 70,000 g / mol. Method according to one of the preceding claims, characterized characterized in that the nucleophilic end group is a hydroxyl group and the nucleophile end-group functionalized macromonomer A is an α, ω-diol. Method according to one of the preceding claims, characterized characterized in that the electrophilic end group is an isocyanate group and the electrophilic end group-functionalized macromonomer B is an α, ω-diisocyanate is. Method according to claim 7, characterized in that that the provision of the α, ω-diisocyanate by Reaction of an α, ω-diol of Macromonomer B with an isocyanate alkane, in particular a diisocyanate alkane takes place, preferably with 1,6-diisocyanato-2,2,4-trimethylhexane or 1,6-diisocyanato-2,4,4-trimethylhexane (TMDI) or 1,6-diisocyanatohexane. Method according to claim 8, characterized in that that in the implementation of the α, ω-diol of Makromonomers B with the isocyanatoalkane an excess of isocyanate groups across from 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: 1 is set. Method according to one of the preceding claims, characterized in that one of the macromonomers A or B is a polyester of general formula I with n = 1 ... 14 or a co-polyester with different n or a derivative thereof, in particular poly (ε caprolactone) with n = 5 or poly (pentadekalactone) with n = 14

Method according to 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

Alternating multiblock copolymer, preparable according to the method of any one of claims 1 to 11. Use of an alternating multiblock copolymer according to claim 12 for biomedical applications.