Crosslinked polycyclooctene

This application applies to the following provisional patent applications: Application No. 60 / 418,023 (filed October 11, 2002), Application No. 60 / 419,506 (filed October 18, 2002), and Application No. 60 / 488,323 (filed October 18, 2002). Claim priority based on (filed July 18, 2003). Each of the provisional patent applications is incorporated herein by reference to the extent consistent with the present disclosure.

The present disclosure can be fixed in a temporary or dormant shape under specific temperature and stress conditions, after which the associated elastic deformation is almost completely relieved under thermal, electrical and / or environmental stimuli to relieve stress. It relates to a shape memory polymer material that can be removed and returned to its original state. More specifically, the present disclosure relates to crosslinked polycyclooctene (PCO) and blends thereof, which have excellent shape recovery properties and particularly rapid strain recovery rates. The present disclosure also relates to a method for producing the crosslinked polycyclooctene and its use.

Polymers originally exhibit a shape memory effect based on, for example, rubber elasticity, but have various characteristics such as strain recovery speed, work ability during recovery, and stability in a contracted state. The first reported shape memory polymers (SMPs) were cross-linked polyethylene, discovered and patented by Radiation Applications, Inc. in 1971, and Vernon- It was a methacrylic acid ester reported by Benshoff Co.) and used as a prosthesis material. However, it was quickly confirmed that the strain recovery mechanism of such materials was very different from that of shape memory alloys (SMAs), which are mainly based on nickel-titanium alloys.

Shape memory polymers are actually superelastic rubbers. When the polymer is heated to a rubber state, it can be deformed under a resistance of elastic modulus of ~ 1 MPa, and when the temperature is lowered to less than either the crystallization temperature or the glass transition temperature, the deformed shape is fixed by low temperature rigidity, but at the same time. The mechanical energy spent on the material during deformation is stored. Transition temperature (T)_mOr T_g) Higher, the polymer returns to its original form, driven by the restoration of the conformational entropy of the network chain. The advantages of SMP are closely related to their network architecture and the sharpness of the transition that separates the rigid and rubber states. Compared to SMA, SMP has the advantage of high strain (up to hundreds of percent) due to its large rubbery compliance, while the maximum strain of SMA is less than 8%. An additional advantage of SMP is that the transition temperature can be tailored to the requirements of the application. For example, the transition temperature can be adjusted as a thermal sensor, or strain recovery can be triggered above a predetermined temperature for biomedical applications, such as 37 ° C.

Numerous polymers have been found with particularly attractive shape memory effects. The most famous are polyurethanes, polynorbornene, styrene-butadiene copolymers, and cross-linked polyethylene.

<p> Polystyrene (PS) and trans-polybutadiene (TPB) block copolymas with low PS content have a unique mechanism for triggering strain fixation and recovery, providing another option for shape memory. are doing. The domain of the PS block separated into microphases is T_gAmorphous with ~ 93 ° C, but continuous TPB phase is T_g= -90 ° C and T_mSemi-crystalline with = 68 ° C. Since the PS and TPB blocks are immiscible below 120 ° C, the copolyma forms a microdomain structure with elastic flow properties at temperatures above the melting point of the TPB, with the PS phase acting as a physical bridge. I'm playing. Therefore, reversible deformation can be fixed by crystallizing the TPB phase below about T = 40 ° C, but heating above 80 ° C melts the TPB phase, freeing the elastically deformed material to strain. When it is restored, it can be restored to the state in which the stress is removed (shape memory).</p><p> Another known semi-crystalline shape memory polymer is T_mTrans-polyisoprene (TPI) with = 67 ° C and about 40% crystallinity, which is easily crosslinked with peroxide. T_mBelow, the crosslinked TPI has a three-dimensional network, which is linked by both chemical crosslinks and crystalline regions. T_mIf it exceeds, the crystalline phase melts and becomes amorphous, so that only the chemical cross-linking remains and the primary shape having a rubber-like elastic modulus is maintained. This primary shape is the form of the material during chemical cross-linking by peroxide curing. Peroxide curing usually occurs at about T = 145 ° C for 30 minutes. Crystallization then occurs while cooling to room temperature. Similar to the PS-TPB block copolyma, elastic deformation of the crosslinked TPI can be performed by heating the polymer above T = 80 ° C, and this deformed secondary shape can be fixed by crystallization by cooling. The deformed shape returns to the primary shape when heated above 80 ° C.</p><p> In addition to the above, semi-crystalline polycaprolactone (PCL) copolimas have also been studied for their SMP properties. In particular, since polycaprolactone diols are bifunctionalized with a methacrylate-terminated group, they are subsequently copolymerized with n-butyl acrylate. The polycaprolactone segment forms a crystalline phase that can fix the secondary shape, but T_mThermosetting at temperatures above will result in an elastic network that allows for large reversible deformations. It was found that the molecular weight of PCL controls the shape recovery temperature. It is believed that this is because the molecular weight affects the melt transition. On the other hand, the n-butyl acrylate comonomer formulation has a low glass transition temperature of poly (n-butyl acrylate) (T)._g= -55 ° C), providing a softening effect. SMPs based on polycaprolactone segments have been shown to recover their primary shape at 70 ° C within 20 seconds, a relatively slow recovery.</p>

<p> According to the present disclosure, chemically crosslinked polycyclooctenes (PCOs) synthesized from cis-cyclooctene are found to have a high content of trans double bonds. This polymer can be chemically crosslinked at various crosslink densities to form novel semi-crystalline thermosetting SMPs. Polymer synthesis is carried out by ring-opening metathesis polymerization of cyclooctene using a dihydroimidazolidene-modified Grubbs catalyst. The formed PCO is cured by adding dicumyl peroxide to the PCO. The mixture is compression molded onto a film and further cured through chemical cross-linking by heating. The effect of synthetic products on the thermal, mechanical and microstructural properties depends on the degree of cross-linking.</p><p> The beneficial polymers of the present disclosure exhibit excellent shape recovery properties and particularly rapid strain recovery rates. The transition temperature of PCO can be adjusted by changing the trans / cis ratio of the vinylene group and blending the miscible rubber. Soft shape memory behavior is observed, primary stress-free The shape) recovered within 1 second when immersed in hot water exceeding the melting point of the PCO crystal phase. In contrast to vitreous shape-remembering polymers, chemically cross-linked PCOs behave as elastomers that allow free shaping at temperatures above the sharp melting point of the PCO crystal phase and shape fixation during subsequent crystallization. The shape memory polymers of the present disclosure exhibit excellent shape recovery effects, where the recovery temperature and shrinkage force depend on the ratio of tacticity used, the degree of cure, and the thermal properties of the blended components. It can be adjusted from 20 ° C to 60 ° C accordingly. Recovery can be achieved within 1 second when heated to a temperature 20 ° C above the transition temperature. An additional advantage of SMP is that the material is flexible at room temperature and its flexibility is tailored to the requirements of the application by blending either a hard particle filler or a soft polymer rubber, the application requirements. Depending on the color, it can be dyed in any color, and the strain recovery initiated by the trigger can be accompanied by an optical clearing transition.</p><p> The present disclosure discloses the disclosed PCO and other exemplary polymer materials such as styrene-Butadiene Rubber, ethylene propylene-diene (EPDM) rubber, natural rubber (cis-polyisoprene), poly (ethylene). -Includes shape memory polymers formed by blending with poly (ethylene-co vinyl acetate), polydimethylsiloxane (silicone), and polyurethane polymers.</p><p> The PCOs and blends of the present disclosure can be successfully used in combination with a variety of applications. For example, the following uses, but are not limited to these. Flexible catheters and guide wires b. Properly colored and embossed artificial leather (the properties that make this possible are proper stiffness, luster, and ease of embossing). c. Impression material for molding, duplication, rapid prototyping (stereolithography, high-speed modeling technology), dentistry, and inkless fingerprint imprinting d. Toys, such as, but not limited to, freely deformable action figures and hot water-initiated plastic boats with propellers. e. Reversible embossing (surface structuring) for information storage f. Reversible embossing (surface structuring) for pumps and valves in microfluidic devices g. Mirror lining to adjust wave surface distortion h. Temperature sensor i. Safety valve j. Heat shrink tape or seal k. Flexible custom fittings and fasteners l. Gap filler, exploiting rubber, surface wetting and vacuum sealing m. Actuator n. Medical impression material for dentistry, orthopedics (eg cast fitting), and podiatry (customized orthodontic appliances).</p>

The following unrestricted examples are provided to illustrate the beneficial features, functions and uses of the exemplary polymers according to the present disclosure. As will be readily apparent to those skilled in the art, the following examples should not be considered absolute as they are merely for illustration of aspects of the present disclosure, and thus potential polymer materials that may be conveniently used in accordance with the present disclosure. , Processing conditions (eg relative percentages, temperature and time) and / or should not be considered limiting with respect to end use. The physical properties and processing conditions described in the examples below are merely descriptions of such properties / conditions and should not be considered limiting the scope or usefulness of the present disclosure.

(Material and synthesis) Ruthenium Catalyzed Bis (Tricyclohexylphosphine) Benzylidene Ruthenium (IV) Dichloride (1, Grabs Catalyzed) and Tricyclohexylphosphine [1,3-bis (2,4,6-trimethylphenyl) -4,5-dihydroimidazol-2 -Ilidene] [Benzylidene] Ruthenium (IV) dichloride (2) was purchased from Strem Chemical. Other reagents were procured from Aldrich and used as is unless otherwise noted. Sith-Cyclooctene is CaH before use₂Vacuum vapor from distillation City, methylene chloride was passed through a column of basic activated alumina prior to use.

&lt;Example&gt; CH of ruthenium catalyst 2 (5.1 mg, 6.0 μmol)₂Cl₂6.60 g (60 mmol) of cis-cyclooctene was added to the solution in (50 mL). The resulting reaction mixture was stirred under air at room temperature for 30 minutes. During this time the mixture gelled. 50 mL CH containing trace amounts of ethyl vinyl ether₂Cl₂Was injected to stop the reaction. The polymer was precipitated with methanol, recovered by filtration and dried under vacuum at room temperature overnight. The yield of the isolate was 5.0 g (75%). sample¹³C NMR spectra were recorded in chloroform-d on a Bruker DPX-300 FT NMR spectrometer (running at 75 Hz). Quantitative spectra were obtained using standard inversegated proton decoupling pulse sequences and a relaxation time of 2 seconds to obtain trans / cis ratios. Gel permeation chromatography was performed using a Polymer Lab LC1120 HPLC pump equipped with a Waters differential refractometer detector. The mobile phase was tetrahydrofuran (THF) with a flow rate of 1 mL / min. Separation is 10⁵Å, 10⁴Å and 10³It was performed using a Å Polymalab column set. The molecular weight was calibrated against a polystyrene standard with a narrow molecular weight distribution.

PCO Peroxide Hardening CHCl PCO and Dicumyl Peroxide₃It was carried out by dissolving in and forming a clear solution. The solution was dried in a ventilation hood at room temperature for 12 hours and vacuum dried in an oven at 40 ° C. for 12 hours. The dry PCO containing the DCP was transferred to a mold having dimensions of 1 x 3 x 0.05 cm. The mold was placed between two hot plates and compressed at 140 ° C. under a pressure of 1000 psi for 30 minutes to obtain a sheet sample. After curing, the specimen was cooled to room temperature in a mold.

Polymer blending was achieved by melt blending within a biaxial screw Brabender. A bravender with a 30 ml chamber is first placed at 80 ° C (T)._mIt was heated to + 20 ° C) and the speed was adjusted to 25 RPM. The feed (blended polymer) was premixed and fed to the chamber within 2 minutes, where it was mixed at 25 RPM for 10 minutes. The resulting mixture was removed and cooled to room temperature under air. The mixture was then introduced between two plates preheated to 180 ° C and pressed into film and cured for 30 minutes. Two Mylar films were used to separate the polymer from the stainless steel plate to prevent the film from adhering to the plate after curing. The sample thickness was adjusted with spacers. It also served as a sealer.

The thermal properties (melting point and crystallization temperature) of the cured PCO were measured using a differential scanning calorimetry device (DSC-7) manufactured by Perkin-Elmer. First heating rate from -50 ° C to 100 ° C 10 ° C / min, first cooling rate from 100 ° C to -50 ° C -10 ° C / min, and -50 ° C to 100 A second heating rate of 10 ° C / min up to ° C was used.

Wide-angle X-ray scattering (WAXS) analysis was performed using a Bruker GADDS-4 instrument with Cr source radiation (λ = 2.291 Å) and the transmission mode was selected. The voltage and current used were 40 kV and 40 mA, respectively, and the exposure time was 30 minutes. Scatter patterns were collected on a HiStar area detector with a distance between the sample and the detector set to 6.0 cm. The intensity profile (I vs. 2θ) was determined by azimuth averaging at each 2θ position in the isotropic pattern. The data were then analyzed with Peakfit® software (SPSS Science) to obtain peak locations and relative intensities for each peak.

Dynamic mechanical analysis was performed on the DMA 2980 from TA Instruments. It was operated in tensile mode with a frequency of 1 Hz, a static force of 10 mN, an amplitude of 5.0 μm (~ 0.1% strain), and an automatic tension setting of 125%. The temperature gradient was performed at 4 ° C / min over the range of -100 &lt;T &lt;100 ° C.

Next, the shape memory effect was measured. PCO samples with varying degrees of cross-linking were cut into rectangular strips of 0.5 x 2.0 x 30.0 mm and colored with red dye for optical contrast. The PCO strip was bent into a semicircle with an inner diameter of 0.737 cm in a warm water bath at 70 ° C (the sample was transparent and flexible at this temperature) and then transferred into an ice water bath to fix the curved secondary shape by crystallization. did. The curved PCO sample was then quickly immersed in a warm water bath at 70 ° C. During this time, a video camera was used to record a shape recovery image at a speed of 20 frames per second. Curved samples of various radii of curvature were analyzed using non-linear regression (Sigmplot®).

Polycyclooctene (PCO) is RuCl₂(= CHPh) (PCy₃)₂It can be synthesized using either 1 (Grabs catalyst) or dihydroimidazolidene-modified Grabs catalyst 2, but catalyst 2 has higher reactivity than catalyst 1 using the above-mentioned synthesis technique. Further established. A unique feature of PCO as a shape memory material is the adjustable transition temperature (PCO T)._m). The transition temperature is achievable in the temperature range of 19-61 ° C, as the melting point of PCO depends on the trans content of the double bond along the polymer backbone. The synthetic method of the present invention has the ability to control not only the molecular weight but also the trans / cis ratio by changing the conditions, that is, the reaction time, the type of catalyst, and the catalyst concentration. Table 1 below shows typical examples of various PCOs achieved in this way.

<tables num="1"><img file="JP4530989B2_D0001.tif" /></tables>

As can be seen from Table 1, the higher the catalyst concentration, the higher the trans concentration and the lower the molecular weight (compare samples 2 and 3 with 1). In addition, longer reaction times (compare Samples 4 and 2) or use of the highly reactive catalyst 2 (Sample 5) yield high melting point products. This is probably because more cross-metathesis occurs between the polymer chains, resulting in a more thermodynamically favorable trans product.

Since the melt transition temperature and molecular weight of sample 5 (PCO5 above) are desirable, they were selected for detailed property analysis.

(Thermal analysis) Curing made with various concentrations (wt%) of peroxide, (i) DCP 0%, (ii) DCP 1%, (iii) DCP 2.5%, (iv) DCP 5%, and (v) DCP 10% DSC analysis was performed on the first heating and cooling of PCO to clarify its melting and crystallization behavior. The raw PCO was also compression-molded with a hot-pressure press using the same conditions as the cross-linked PCO to give the same thermal history. During the first heating cycle, the raw PCO showed a melting point of 60.3 ° C, but no glass transition of the raw PCO was detected over -50 &lt;T &lt;100 ° C. According to J. Polym.Sci., Polym.Phys.Ed.1967,5,1283-1292 of Calderon and Morris, the crystal melting point of PCO is the percentage of trans-vinylene content in the polymer. Is linearly dependent on. Specifically, T_m= 60 ° C was reported as a trans-vinylene content of 78% in PCO. For the raw PCO samples described here, the trans-vinylene content is 80.6%, so the measured melt transition temperature at 60.3 ° C is in good agreement with the Calderon and Morris priors. During the first cooling cycle, the raw PCO exhibits crystallization heat at 37 ° C. The second heating cycle shows the same results as the first heating cycle.

Cross-linking PCO with dicumyl peroxide has a dramatic effect on its crystallization and melting behavior. Melting point T_m, Crystallization point T_c, And melting enthalpy (related to crystallinity) ΔH are plotted in Figure 1 and summarized in Table 2 below.

<tables num="2"><img file="JP4530989B2_D0002.tif" /></tables>

A significant effect of the degree of cross-linking is observed. PCO T_mAnd T_cBoth decrease as the amount of DCP increases, and the former has a difference of more than 40 ° C in the case of cross-linking with 10% DCP. The molten enthalpy also decreases as the number of crosslinks increases, indicating a decrease in crystallinity. Temperature is T_cWhen lowered below, the component PCO chains begin to crystallize and the crystals grow to a certain final size and shape. In the case of raw PCO (without cross-linking points), the high mobility of the polymer chain is expected to result in relatively low restrictions on the crystal growth of PCO. However, for samples with high crosslink density, crystallization is increasingly restricted because the polymer chains are constrained by diffusion and conformational rearrangement. As a result, if the amount of peroxide loaded is large, the crystallinity decreases, and the crystal size also decreases accordingly. The latter is inferred from the observed decrease in melting point. It can also be seen from Table 2 that the melting point of the cured PCO can be made as required by controlling the amount of peroxide loaded before curing. Furthermore, when the amount of peroxide exceeds 10%, T_mAnd T_cBoth become below room temperature, the melt transition spreads excessively, and the shape memory behavior of the cured PCO is lost.

(Crystal microstructure) The basic microstructure of PCO affected by cross-linking was investigated using wide-angle X-ray scattering (WAXS). From the intensity profiles of all PCO samples except PCO5-10, the microstructure has one amorphous halo pattern and the d-spacing is almost constant but the intensity decreases with increasing degree of cross-linking. It was found to be characterized by superposition with two crystal diffraction rings. For example, PCO cured with 1 wt% dicumyl peroxide shows two strong scattering peaks at 2θ = 30.02 ° (4.42 Å) and 34.81 ° (3.83 Å). This corresponds to the 010 and 100/110 reflections of the PCO triclinic crystal structure, respectively. In addition, there are two weak peaks corresponding to the 110 and 201 reflections of the PCO monoclinic crystal structure, 2θ = 31.94 ° (4.16 Å) and 2θ = 36.97 ° (3.61 Å), respectively.

WAXS patterns were analyzed using Peakfit® software to analyze component reflections. The data obtained are summarized in Table 3 below, along with an overview of the DMA below.

<tables num="3"><img file="JP4530989B2_D0003.tif" /></tables>

From the fitted data, it was found that the crystallinity of PCO was 25.5% at room temperature. This is close to the DSC results (28.8%) using the pure crystal enthalpy data (216 J / g) of the Schneider and Muller Journal of Molecular Catalysis 1988,46,395-403. In addition, crystallinity shows a monotonous decrease with increasing cross-linking, which is the same tendency observed by DSC, which is also explained by the constraining effect of cross-linking points that limit crystal growth. In fact, the sample's PCO5-10 (crosslinked with 10% DCP) did not show significant crystallinity at room temperature, but this does not mean that the sample cannot crystallize. DSC data conclude that the crystalline phase of PCO5-10 melts over the range -15 &lt;T &lt;30 °, but WAXS analysis was performed at room temperature (28 ° C). At this temperature, the melting was almost complete, so the measured crystallinity was only 2.6%.

When the scattering pattern was analyzed for the area% of each peak, it was found that the effect of cross-linking constraint on crystallinity depends on the related crystal structure. The triclinic 30.02 and 34.8 degree 2θ peaks decrease linearly with cross-linking, while the monoclinic 31.9 and 36.97 degree 2θ peaks appear to be largely unaffected by cross-linking. Therefore, the triclinic crystal structure is more sensitive to the constraining effects of cross-linking, while the monoclinic crystal structure is tougher, albeit with fewer components.

(Dynamic mechanical properties) Chemical cross-linking of PCO also directly affects thermomechanical properties such as modulus vs. temperature through the establishment of a permanent network and indirectly through the aforementioned morphological transitions. To clarify such effects by using DMA, a plot of tensile modulus (E') vs. temperature of cured PCOs made with varying amounts of DCP is shown in Figure 2. All PCO samples are characterized by a solid-like storage modulus (approximately 1.7 GPa) at temperatures below T = -70 ° C, the modulus of which is constant regardless of crosslink density. T in PCO sample_gAt temperatures above T = -70 ° C, which is the apparent onset of, E'begins to gradually decrease to a certain level depending on the crosslink density, but in the range of 0.05 to 0.5 GPa. The decrease in elastic modulus with cross-linking in this temperature range can be understood from the results of DSC and WAXS showing that cross-linking reduces the crystallinity of PCO. The crystalline phase is considered to function as a fixing mechanism for shape memory and as a means for controlling the room temperature elastic modulus over a general range. At temperatures near T = 62 ° C, which is close to the melting point as measured by DSC, the storage modulus of raw PCO begins to sharply decrease to about 2 MPa at 71 ° C when melting is complete. As can be seen from the DSC, this transition temperature is mechanically observed to decrease with increasing degree of cross-linking. T_mAt temperatures above, the modulus of raw PCO represented by trace (i) continues to decrease to the point where the material flows like a viscous liquid, showing no permanent rubbery plateau (Fig. 2). This feature hampers the applicability of raw PCO for use as a shape memory polymer. Because T_mThis is because it cannot be deformed as rubber at temperatures above the above without rapid stress relaxation. In contrast, cured PCO has a pronounced shape memory, as a permanent rubbery plateau is seen at temperatures above 72 ° C when it contains exactly 1% of the peroxide represented by trace (ii). The effect is possible. As the amount of peroxide increases, the elastic modulus of the rubber-like plateau increases, so that the storage of mechanical energy is enhanced, but the transition temperature and the sharpness of the transition decrease. Figure<u style="single">2</u>For PCOs or PCOs 5-10 with 10% DCP as shown in trace (v), the observed thermomechanical response is useless for the shape memory effect. This is because the fixing (crystallization) temperature is lower than room temperature, so cooling below the ambient temperature is required to fix the shape, and it is thought that the temporary shape will drift due to partial melting. Moreover, the melt transition is too broad to cause dramatic strain recovery.

From each curve in Fig. 2, the start temperature of the melt transition (T)₁) And end temperature (T₂) Is determined, T for shape memory behavior₁And T₂It was confirmed that the smaller the difference with, would be beneficial. Figure 3 (a) shows T₁() and T₂The effect of peroxide content on (Δ) is shown. Starting temperature from the figure (T₁) Corresponds closely with the melting point measured by DSC (Table 2). T₁Also T₂Also T in Table 2_mAnd T_cSimilarly, it decreases as the amount of peroxide increases, but T₂Is even more so. Figure 3 (b) shows the difference between the start and end transition temperatures, ΔT = T.₂-T₁() The amount of added peroxide is shown, but as the amount of peroxide increases, ΔT also increases, indicating that the sharpness of the transition is lost. The sharpness of this transition can be quantified by measuring the maximum slope of the E'-temperature trace in the melt region of FIG. 2, and these results are shown in FIG. Clearly, there is a compromise between the sharpness of the transition (high at raw PCO) and rubber elasticity (low at raw PCO), which influences the design of optimal shape memory polymers.

It was observed that the tendency of thermomechanical behavior was in good agreement with the above-mentioned observation with WAXS. In particular, the room temperature elastic modulus was found to decrease with increasing cross-linking. It was just like the decrease in crystallinity reported in Table 3.

(Shape memory effect) Figure 4 shows a typical example of the shape memory effect of PCO (PCO5-2.5) cured with 2.5 wt% DCP. The stress-free primary shape of the sample under study was set on a linear rectangular bar at this cross-linking step (see t = 0.7s in Figure 4). On the other hand, the secondary (temporary) shape was a semi-circular film curved along the semimajor axis, with an inner diameter of 0.737 cm (see t = 0s in FIG. 4). Such a shape heats the sample to a clear state at T = 70 ° C and pipettes. It was achieved by transforming it into a semicircle using a mandrel) and finally quenching the curved film with ice water to make the sample milky and leathery. Shape recovery was investigated by rapidly immersing the curved sample in a water bath heated to T = 70 ° C. As shown in FIG. 4, the transition from the secondary shape to the primary shape is completed within t = 0.7 seconds. In contrast, non-crosslinked sample PCO5-0 does not show such a noticeable shape-fixing and restoring effect. This is a finding predicted from the results of DMA, which revealed poor elasticity at temperatures above the melt transition. Therefore, the tensile stress applied to the sample at temperatures above the melt transition is somewhat relaxed so that it is not completely stored during crystallization and the primary shape cannot be restored at elevated temperatures for a reasonable observation time. Note that the polymer must combat buoyancy during strain recovery in the selected shape, as the density of PCO is lower than that of hot water. Very recently, Landlein et al. Reported shape memory properties of oligo (ε-caprolactone) / (n-butyl acrylate) copolimas (Proc. Natl. Acad. Sci. 2001, 98, 842-847). The authors showed that shape recovery of the copolima took 20 seconds to complete at 70 ° C. Compared to their results, the cured PCO samples of the present disclosure show extremely rapid shape recovery, but direct comparison is not appropriate because the tests were performed using a unique protocol.

In order to quantitatively evaluate the transfer rate, the time course of the curvature of the recovering sample (κ = 1 / r, r = radius of the circle overlaid on the curved film) was measured by image processing, and the time was measured. Plotted. This is shown in Fig. 5. Comparing the curvature relaxation plots for different samples, it is clear that the raw PCO does not restore the original form of κ = 0. Not within at least 5 seconds (data beyond the shown plot range). Cross-linked PCO samples, on the other hand, exhibit faster and more complete shape memory behavior with increasing cross-linking density. Of the samples tested, 5% peroxide shows the best shape memory behavior at 70 ° C. Since the transformation of the chosen shape is arbitrary, any other transformation is possible within the limits of tensile strain set by the material strength. To name a few, coiled to flat, flat to coiled, concave to flat, matte to glossy, glossy to matte, and so on. Considering the WAXS presentation data summarized in Table 3, the recovery rate (maximum slope of the plot in Figure 5) is of crystallinity as long as the sample is cross-linked.<u style="single">Decrease</u>It increases with. In addition, the degree of recovery increases with crystallinity up to 2.5% DCP. Beyond this cross-linking level, cross-linking has little effect on the degree of recovery, suggesting that the optimal DCP composition is around 5 wt%.

According to the present invention, PCO polymers are produced by controlling the composition and molecular weight of cis / trans double bonds, which was possible by the use of ruthenium catalysts. Samples of polymer were cured using dicumyl peroxides of various concentrations and the effect of cross-linking on thermal, microstructural, and thermomechanical properties was measured. We also investigated the dependence of desirable shape memory properties on the degree of cross-linking, and found that shape-fixing had a competitive effect on crystallinity (it was seen to decrease with cross-linking), and T_mRubber elasticity at temperatures above (observed to increase with cross-linking was observed as expected) was revealed. Raw linear PCO does not show shape memory effect due to lack of rubber plateau at temperatures above the melt transition temperature, but even a small amount of peroxide cross-linking (~ 1%) imparts shape memory effect to PCO. Ru. A quick shape memory effect was observed with crosslinked PCO. It is obtained when a modified sample fixed by crystallization is immersed in a warm water bath. For PCO containing either 2.5% or 5% peroxide, curvature κ = 0.14 mm^-1Complete shape recovery from to zero curvature occurs at 70 ° C within 0.7 seconds.

Various blends of PCO and other polymers such as styrene butadiene, EVA and polyurethane are produced with varying proportions of polymers in the blends, isothermal characterization of the stiffness, thermomechanical. Melt and other properties were evaluated on their own and in comparison to non-blended PCO, EVA, SBR and polyurethane.

(Modification of isothermal rigidity during blending with styrene-butadiene soft rubber) The storage modulus of PCO blends with different ratios of SBR was measured and compared using the temperature gradient method and the isothermal method. The results are shown in Figures 6 and 7. As shown in Figure 6, at temperatures below the glass transition temperature, all blends have the same level of stiffness of about 2 GPa, and all blends except pure SBR have the same glass transition around -50 ° C. Has a temperature. When PCO is the dominant component, the transition is like a glass transition of PCO, as PCO represents a continuous phase in the blend. At temperatures above the glass transition, it is clear that the blends exhibit different stiffness values. Rigidity decreases as the amount of SBR component increases. Figure 7 shows the storage modulus of the blend at 37 ° C. The result is that the stiffness decreases linearly with increasing proportions of SBR components. That is, SBR softens PCO. PCO appears to be completely immiscible with SBR as it retains the same melting point in the blends examined. This conclusion reached is that when PCO and SBR are blended at temperatures above the melting point of PCO, the blend becomes white rather than transparent. In this case, the critical temperature and rigidity of the rubber can be adjusted independently. The mode in which SBR denatures PCO at a temperature of 37 ° C (body temperature) was also confirmed by isothermal characterization. The tendency seems to be linearly related to the weight fraction of PCO in the range examined.

(Denaturation of body temperature rigidity and transition temperature by blending with compatible components) PCO was blended with other ingredients. For example, PCO Vestenamer with different tacticity 6213 (which lowers the melting point below that of Vestenamer due to its low transformer content) and EVA. Both components were compatible with PCO-8012 and had the effect of significantly lowering the melting point. Both were found from the DMTA results (Fig. 8) and the DSC results. It was considered that this was because the combined PCO and its structure were almost the same except for the trans-cis content. However, EVA's compatibility with PCO was surprising. This miscibility is derived from the similarity of the ethylene moiety, and it is considered that this miscibility can change if the ethylene content in EVA fluctuates. The DSC results obtained for PCO / EVA indicate that there are two melting stages. One is that of PCO and the other is that of EVA. The DMTA results also show two melting stages, as they show two melting transition stages and two height plateaus. This would indicate that a dual network could be present in the blend and that EVA could act as a cross-linking agent.

In addition to SBR, EVA and other PCO starting materials, shape memory polymers have been produced using a variety of rubberic polyurethanes as the second material in the blend with similar results.

Further, according to the present disclosure, the body temperature elastic modulus of the crosslinked PCO material can be substantially increased by adding an inorganic or organic filler powder. As an example, PCO (Vestenamer 8012®) was blended with different amounts of boron nitride (Advanced Ceramics, PT-140). Blending was performed using a twin-screw Brabender® mixer with a chamber with a volume of 30 ml at T = 80 ° C for 10 minutes to ensure sufficient mixing. The rotation speed of the screw was set to 25 rpm. The material was also very easily blended with a 30 wt% solid filler. This is a discovery derived from the low viscosity of PCO, which is itself a processing aid. It is believed that even higher filler content (up to 50%) will be feasible in this system. The cross-linking agent used is dicumyl peroxide, the amount of which is 1 wt-PHR based on the amount of PCO added (not PCO + BN (boron nitride)). The compound material was pressed under a load of 8 metric tons for 10 minutes in a hot pressure press at 180 ° C and was thermoset. The resulting film is smooth and eggshell white (egg-shell) white in I was doing color). Shape memory tests in hot water (~ 80 ° C) show quick and complete recovery. FIG. 9 shows the tendency of the tensile storage elastic modulus with respect to the body temperature (37 ° C) and the temperature of the rubber region (T = 60 ° C). It is clear that the filler allows a controlled increase in modulus. An increase in elastic modulus at body temperature may make it possible to meet biomedical applications, especially stent stiffness requirements. The increase in rubber modulus increases the mechanical work capacity obtained during deployment from a temporary shape to a permanent shape or during shape memory recovery. Many other fillers can also meet (user's) requirements for tensile storage modulus (of the product), tensile loss modulus, and linear strain (strain that loses elasticity beyond that). For example, but not limited to silica, titanium dioxide, montmorillonite clay, Kevlar® staples, aluminum nitride, barium, and bismuth oxycarbonate. Some of these fillers (barium and bismuth oxycarbonate) can also make (the product) radiation opaque at the same time. The addition of titanium dioxide also allows for strong UV absorption, which is beneficial for laser cutting of delicate shape memory products.

Fillers with extremely high thermal conductivity, such as boron nitride, are expected to improve the shape recovery rate in shape memory effects by reducing the time it takes for the product to become thermally homogeneous.

Thus, the present disclosure provides a beneficial shape memory polymer containing chemically crosslinked polycyclooctene synthesized from cis-cyclooctene with a high trans double bond content. The present disclosure further describes that ring-opening metathesis polymerization of cis-cyclooctene is carried out in the presence of a grabs catalyst and the formed polycyclooctene is reacted with dicumyl peroxide at an increased temperature to cure the polycyclooctene. It also provides a useful method of forming the including shape memory polymer.

Although the polymers and processing methods of the present disclosure have been described with reference to their particular exemplary embodiments, the present disclosure is not limited to such exemplary embodiments. On the contrary, as will be readily apparent to those skilled in the art, the teachings of this disclosure are applicable to many practices and / or uses without the spirit or scope of this disclosure. In fact, modifications and / or changes are conceivable thereby in the selection of specific polymers, polymer ratios, processing conditions, and end applications, and such modifications and / or changes are also within the scope of the invention as described in the claims. included.

<figref num="1">It is a figure which shows the dependency relationship of the melt transition temperature () and the crystallization temperature () of PCO hardened with various wt% dicumyl peroxides.</figref><figref num="2">Tensile storage modulus (E) of cured PCO cured with various wt% dicumyl peroxides (DCP) in linear stress oscillation mode with a frequency of 1 Hz and a gradient velocity of 4 ° C / min. ') It is a figure which shows the temperature | temperature. The wt% level of DCP is as follows. (i) DCP 0%, (ii) DCP 1%, (iii) DCP 2.5%, (iv) DCP 5%, and (v) DCP 10%.</figref><figref num="3">(a) Figure<u style="single">2</u>Determined from the curve of, T₁() and T₂Dependency of peroxide addition amount to () (the start and end temperatures of the transition, respectively), (b) ΔT () vs. peroxide addition amount (ΔT is T)₁And T₂It is a figure which shows (the difference).</figref><figref num="4">It is a figure which shows the shape memory behavior after rapid immersion in water of T = 70 ° C of PCO of DCP 2.5%. The exemplary sample undergoes a transition from a temporary shape (circular) to a permanent shape (linear) within 0.7 seconds.</figref><figref num="5">It is a graph which shows the curvature κ vs. the passage of time at T = 70 ° C. The peroxide wt% of PCO5 is as follows. (i) PCO5-0% (), (ii) PCO5-1% (), (iii) PCO5-2.5% (), and (iv) PCO5-5% ().</figref><figref num="6">It is a figure which shows the thermomechanical property of PCO: SBR of various compositions.</figref><figref num="7">It is a graph which shows the control or variation of the tensile modulus at T = 37 ° C (body temperature) possible through various compositions of PCO: SBR blend.</figref><figref num="8">It is a graph which shows the thermomechanical property of PCO blended with various other polymers.</figref><figref num="9">It is a figure which shows the increase of the tensile storage elastic modulus of PCO with the amount of added boron nitride (BN) filler at 37 ° C (white circle) and 60 ° C (black circle).</figref>