CN114634608B

CN114634608B - Shape memory polyurethane and self-reinforced regular pore polymer film prepared from same

Info

Publication number: CN114634608B
Application number: CN202210335238.4A
Authority: CN
Inventors: 罗彦凤; 王远亮; 杨伟
Original assignee: Chongqing University
Current assignee: Chongqing University
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2023-03-31
Anticipated expiration: 2042-03-31
Also published as: CN114634608A

Abstract

The invention belongs to the technical field of polymer materials, and particularly relates to a shape memory polyurethane material and a self-reinforced regular-pore polymer film prepared from the shape memory polyurethane material. The shape memory polyurethane of the present invention is prepared from diisocyanate, soft block polymer and

polymerized; the soft segment polymer is polylactic acid, polyglycolic acid, polycaprolactone, polylol or a copolymer of at least two of the polylactic acid, the polyglycolic acid, the polycaprolactone and the polylol. Combining this shape memory polyurethane material with a water droplet templating method enables the formation of porous polymer films comprising crystalline structures. The porous film material has excellent mechanical properties, can meet the performance requirements of application scenes such as artificial periosteum, anti-adhesion membranes and the like, and has good application prospects.

Description

Shape memory polyurethane and self-reinforced regular pore polymer film prepared from same

Technical Field

The invention belongs to the technical field of polymer materials, and particularly relates to a shape memory polyurethane material and a self-reinforced regular pore polymer film prepared from the shape memory polyurethane material.

Background

Shape Memory Polymer (SMP), also called Shape Memory Polymer, refers to a Polymer material that can restore its original Shape after a product with the original Shape is fixed after its original condition is changed under certain conditions, and is stimulated by external conditions (such as heat, electricity, light, chemical induction, etc.). Shape memory polymers have been widely used in biomedical, aerospace, optical and textile fields due to their shape recovery properties.

Shape memory polymers include thermotropic, electric, photo, chemical, etc. according to their recovery principle. The thermotropic shape memory polymer can be adjusted to be consistent with the body temperature by controlling the glass transition temperature of the thermotropic shape memory polymer, thereby realizing the application in the medicine. For example: the membrane made of the thermotropic shape memory polymer material or the device with a specific shape can be miniaturized and deformed, and then is implanted into the body through a micro-catheter, and the original set shape is recovered after the membrane reaches the correct position.

Thermotropic shape memory polymers include various classes of polyurethane, ethylene/vinyl acetate copolymers, and crosslinked polyethylene. When the materials are used for preparing films or devices implanted into human bodies, a series of performance requirements such as permeability, biocompatibility, mechanical property and the like need to be met according to the implanted positions and purposes. The conventional thermotropic shape memory polymer materials made into common compact films can not meet the requirements of permeability and biocompatibility. To ameliorate this problem, porous polymer membranes with regular pores have the potential to be membranes for implantation into the human body due to their unique performance characteristics (e.g., permeability to molecules/ions, biocompatibility, extensibility, etc.).

However, the existing thermotropic shape memory polymer material can cause the problem of insufficient mechanical properties in the process of introducing a large number of pores to prepare a porous membrane. For example, "CN201110224930.1 a method for forming a polyurethane porous film" provides a method for producing a polyurethane porous film by a water droplet template method. However, due to the limitation of mechanical properties, the porous polymer films made of these polyurethane materials are still difficult to be applied in the fields of bionics, tissue engineering, etc. with high requirements on the mechanical properties of the materials. The method has great limitation on the development and application of the porous polymer film, and the design and preparation of the polymer film with good mechanical property and a regular porous structure are beneficial to expanding the application of the material. The ordered arrangement, crystal or microphase separation of polymer molecules are all helpful for enhancing the mechanical properties of materials, however, the ideal type and structure of shape memory polymer materials cannot be deduced according to the existing theory, which is a problem to be solved at present.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a shape memory polyurethane material and a self-reinforced regular pore polymer film prepared from the shape memory polyurethane material, and aims to provide a porous polymer film with mechanical properties and regular pores.

A shape memory polyurethane is an amorphous polymer with 37-45 deg.C of glass transition temperature or a semi-crystalline polymer with 37-45 deg.C of melting point, and is prepared from diisocyanate, soft-segment polymer and

according to the molar ratio of 1.2-8:1:0.2-7, having a molecular weight of 30000-150000; />

The soft segment polymer is polylactic acid, polyglycolic acid, polycaprolactone, polyol or copolymer of two or more of them.

Preferably, diisocyanates, soft block polymers and

the molar ratio of (1).

Preferably, it has the formula shown in formula I:

wherein x is selected from 1 to 10, y is selected from 1 to 10;

is a repeating unit of the soft segment polymer;

being repeat units of diisocyanates or diisocyanates with

Repeating units of the copolymer of (1).

Preferably, the soft segment polymer is a polymer of lactic acid and a polyol.

Preferably, the soft segment polymer has a structural formula shown in formula II:

wherein m and n are respectively and independently selected from 4 to 50, r is selected from 1 to 20.

Preferably, the diisocyanate is selected from aliphatic diisocyanate or aromatic diisocyanate, the aliphatic diisocyanate is selected from hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate or a mixture of two or more of the hexamethylene diisocyanate, and the aromatic diisocyanate is selected from toluene diisocyanate, diphenylmethane diisocyanate or a mixture of two or more of the toluene diisocyanate and the diphenylmethane diisocyanate.

The invention also provides a high-mechanical-property porous polymer film with regular pores, which is prepared by taking the shape memory polyurethane as a raw material and adopting a water drop template method.

Preferably, the parameters of the water drop template method are selected as follows: the environmental temperature is 4-50 deg.C, the humidity is 25-80%, and the volatilization rate of the solvent is 5-50 μ L/min.

The invention also provides a preparation method of the porous polymer film, which comprises the following steps:

step 1, dissolving the shape memory polyurethane in a volatile solvent to obtain a polyurethane solution;

and 2, coating the polyurethane solution on the surface of a substrate, and volatilizing in humid air to obtain the polyurethane coating.

Preferably, in step 1, the volatile solvent is selected from chloroform, dichloromethane, tetrahydrofuran, carbon disulfide or a mixture of two or more of the above;

and/or the concentration of the polyurethane solution is 5-200mg/mL;

and/or, in the step 2, the substrate coated with the polyurethane solution is dried under the conditions of the ambient temperature of 4-50 ℃ and the humidity of 25-80%, and the volatilization rate of the solvent is 5-50 mu L/min.

The invention also provides application of the shape memory polyurethane in preparing a porous polymer film with high mechanical property and regular pores, wherein the method for preparing the porous polymer film by the shape memory polyurethane is a water drop template method.

The invention designs a new shape memory polyurethane material, and after the shape memory polyurethane material is prepared into a porous polymer film with regular pores by a water drop template method, the microstructure of the film material shows certain crystal characteristics. This indicates that the molecular chains in the porous polymer film are arranged more orderly and the hard segments are assembled better, which makes the prepared porous polymer film have good mechanical properties. Compared with similar porous polymer films, the high-mechanical-property porous polymer film provided by the invention has a good application prospect in the fields of artificial periosteum, anti-adhesion membrane and the like which have higher requirements on the mechanical property of the film.

Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.

The present invention will be described in further detail with reference to the following examples. This should not be understood as limiting the scope of the above-described subject matter of the present invention to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Drawings

FIG. 1 shows two coupling agents of example 1 ¹ H NMR spectrum;

FIG. 2is an FT-IR spectrum of two coupling agents of example 1;

FIG. 3 is a FT-IR spectrum of PDLLA-PEG400-PDLLA macrodiol and ISO-PUs of example 1 (right spectrum is an enlargement of the rectangular marked part of the left spectrum);

FIG. 4 is a graph of PDLLA-PEG400-PDLLA and ISO-PUs in example 1 ¹ H NMR spectrum;

FIG. 5 is a GPC curve of ISO-PUs in example 1;

FIG. 6 is a macroscopic topography (thickness = 0.032. + -. 0.011 mm) of ISO-PUs porous film (a) and non-porous control film (b);

FIG. 7 is an optical microscope image of condensation of water droplets on the surface of an ISO-PUs solution during the formation of a porous film;

FIG. 8 is an SEM image of ISO-PUs porous membrane after drying, (b) is an enlargement of the red phase region in (a);

FIG. 9 is an optical microscope image of ISO-PUs porous membrane (a) and under crossed polarizers (b-d), (c) and (d) are enlargements of the red region in (b);

FIG. 10 is an optical microscope image and a microscope image under cross-polarizer of an ISO-PUs porous film prepared at rates of 10. Mu.l/min ((a) and (b)) and 40. Mu.l/min ((d) and (e)) ((c) and (f) are enlarged images of red regions in (b) and (e), respectively);

FIG. 11 is the microscopic morphology under optical microscope and cross-polarizer of porous membranes of PPZ-PU (a and b), upy-PU (c and d), and PDLLA (e and f);

FIG. 12 is a DSC plot of an ISO-PUs non-porous control film and an ISO-PUs porous film (where (a) is the first heat cycle plot and (b) is the cool down and second heat curves);

FIG. 13 is a 2D-WAXD diffraction pattern of ISO-PUs non-porous control film (a) and ISO-PUs porous film (b), and a 1D-WAXD curve of ISO-PUs non-porous control film (c) and ISO-PUs porous film (D);

FIG. 14 shows FT-IR spectra (a) and 3260-3460cm of ISO-PUs control thin and porous films ^-1 Fitting a peak separating curve (b) of the region;

FIG. 15 is a tensile stress-strain curve (a) and mechanical properties (b) at 25 ℃ for ISO-PUs porous and nonporous transparent control films;

FIG. 16 is the cell morphology of rMSCs after 24h incubation on ISO-PUS nonporous control membranes (a and c) and porous membranes (b and d);

FIG. 17 is a plot of the spread area and aspect ratio of cells after 24h incubation of rMSCs on ISO-PUS nonporous control and porous membranes;

FIG. 18 shows the results of alkaline phosphatase (ALP) staining experiments after 14 days of culturing rMSCs on ISO-PUS nonporous control membranes and porous membranes;

FIG. 19 is a morphological observation result of a cell compatibility experiment performed on an ISO-PUs porous anti-adhesion film and a nonporous control film;

FIG. 20 shows the absorbance values of NIH 3T3 cells (p <0.05, p < 0.01) measured by CCK-8 method for different culture times in cell compatibility experiments of ISO-PUs porous anti-blocking films and non-porous control films.

Detailed Description

Reagents and materials not specifically described in the following examples and experimental examples are commercially available.

Example 1 shape memory polyurethane

The present embodiment provides a shape memory polyurethane material. The preparation method comprises the following steps:

1. synthesis and purification of PDLLA-PEG400-PDLLA macrodiol

Mixing D, L-Lactide (D, L-Lactide, melting point: 118 ℃, purity: 99.9%), PEG400 (Aladdin, CAS No. 25322-68-3, cat No. P103723), sn (Oct) ₂ (Sigma-Aldrich, CAS number: 301-10-0, cat number: S3252) in a molar ratio of 5000; putting the single-mouth bottle into an oil bath kettle at 140 ℃, starting magnetic stirring after the mixture is completely melted to uniformly stir the reaction system, and continuously reacting for 24 hours; after the reaction is finished, a dichloromethane/ice absolute ethyl alcohol (-15 ℃) coprecipitation system is adopted to repeatedly purify the product for three times, and then the dichloromethane/ice normal hexane (-15 ℃) coprecipitation system is used to purify the product for one time; vacuum drying at room temperature for 72h to obtain target product PDLLA-PEG400-PDLLA macrodiol (m =46, n =46 and r =10 in the structural formula) for later use.

2. Synthesis and purification of HDI blocked ISO novel diisocyanate

HDI (Aladdin, CAS number: 822-06-0, cat number: H106723) and ISO (

Sigma-Aldrich, CAS number: 652-67-5, cargo number: i157515 In a molar ratio of 4:1, respectively, into different round-bottom single-neck flasks while a magnetic stirrer was placed, in m (ISO, g): v (DMF, mL) =1:6 the proportion is added into two single-mouth bottles and anhydrous DMF is added, and the ISO is completely dissolved by magnetic stirring; then using ISO and Sn (Oct) ₂ Adding Sn (Oct) according to the proportion of 500 ₂ After three times of nitrogen replacement, reacting for 1h at 75 ℃ under the protection of nitrogen; and after the reaction is finished, cooling to room temperature, using normal hexane dried by a molecular sieve to remove unreacted HDI, drying the obtained white powder to a constant weight to obtain the novel diisocyanate coupling agent (the value of z in the structural formula in the embodiment is z = 0) of the HDI blocking ISO, and reserving for later use.

3. Synthesis and purification of ISO-PUs

Wherein, OCN-DI' -NCO is the novel diisocyanate synthesized in the step 2. Wherein y is given a value of y =5.

OCN-DI' -NCO and PDLLA-PEG400-PDLLA (macrodiol) were added in a molar ratio of 1.5: adding anhydrous DMF into V (DMF, mL) =1.0, and mechanically stirring to completely dissolve the macrodiol; then, the macrodiol is mixed with Sn (Oct) ₂ Adding Sn (Oct) according to the proportion of 500 ₂ Reacting for 6h at 75 ℃ under the protection of nitrogen (20 vol% of anhydrous DMF is added into the reaction system in every 2h to reduce the viscosity of the system); adding ISO according to the molar ratio of ISO to macroglycol of 0.5,to reduce system viscosity). And cooling to room temperature after the reaction is finished, pouring the reaction system into normal-temperature absolute ethyl alcohol for precipitation, and separating out white solid, namely ISO-PUs. And finally, purifying the ISO-PUs twice by using a dichloromethane/absolute ethyl alcohol coprecipitation system, and drying for later use. The glass transition temperature of ISO-Pus was determined to be 42 ℃.

4. Structural characterization

4.1 structural characterization of the coupling agent

FIGS. 1 (a) and (b) new diisocyanate nuclear magnetic hydrogen spectra of sample HDI-terminated ISO obtained by reacting HDI and ISO at 4:1 and 2:1, respectively (( ¹ H NMR) spectrum, the proton absorption peaks on the two lines are consistent in position, but the intensities are greatly different. Wherein peaks at σ =3.98 to 4.29 (H-1, H-6), σ =4.78 (H-3), σ =5.12 (H-4), and σ =5.28 to 5.32 (H-2,H-5) are proton absorption peaks in ISO; peaks at σ = 1.30-1.48 (H-c ', H-c), σ = 1.58-1.72 (H-b ', H-b) and σ = 3.14-3.29 (H-a ', H-a) belong to methylene proton absorption peaks in HDI; of two products ¹ No proton absorption peak on the unreacted ISO ring was present in the H NMR spectrum, indicating complete capping of the ISO by HDI. According to the theoretical formula (HDI-ISO (-HDI-ISO) _z HDI) it can be seen that the molar ratio of HDI to ISO in the two coupling agents can be calculated from the integrated areas of H-a', a and peak H-3, as shown in equation (4-1):

HDI/ISO＝I _H-a′+a /(I _H-3 ×4) (4-1)

for FIG. 1 (a), HDI/ISO is close to 2 (7.74/(1.00X 4) ≈ 2), indicating that HDI and ISO reacted at 4:1 to give HDI-ISO-HDI. While FIG. 1 (b) shows that HDI/ISO is close to 1.5 (6.37/(1.00X 4) ≈ 1.5), indicating that HDI and ISO reflected 2:1 is HDI-ISO-HDI-ISO-HDI.

Furthermore, in the FT-IR spectra of the two coupling agents (FIG. 2) a peak at 2273cm was clearly observed ^-1 An absorption peak of-NCO group appeared, and at 1698cm ^-1 An absorption peak of the-C = O group in the urethane bond appeared. And 1698cm in HDI-ISO-HDI-ISO-HDI spectrogram ^-1 And 2273cm ^-1 The peak area at (A) is significantly larger than the ratio of the two peak areas in the HDI-ISO-HDI spectrum. These all further demonstrate the novel diisocyanates HDI-ISO-HDI andsuccessful synthesis of HDI-ISO-HDI-ISO-HDI.

4.2ISO-PUs structural characterization

The samples synthesized with HDI as a coupling agent were designated ISO1-PU, while the samples synthesized with HDI-ISO-HDI and HDI-ISO-HDI-ISO-HDI as coupling agents were designated ISO2-PU and ISO3-PU, respectively. The FT-IR spectra of PDLLA-PEG400-PDLLA and ISO-PUs are shown in FIG. 3. 1751cm in the PDLLA-PEG400-PDLLA curve ^-1 The absorption peak at (A) is the ester-C = O absorption peak in PDLLA-PEG 400-PDLLA. No observation at 2273cm was made in all ISO-PUs spectra ^-1 The peak of-NCO absorption appeared, and some new peaks appeared compared with the spectrum of PDLLA-PEG 400-PDLLA. I.e. 3300-3400cm ^-1 、～1621cm ^-1 And 1529cm ^-1 The peaks respectively belong to the stretching vibration absorption peaks of-NH, amide I band (-C = O) and amide II band (-NH) in the carbamate bond. In conclusion, the occurrence of these absorption peaks proves that ISO-PUs have been successfully synthesized.

To further explore the molecular structure of ISO-PUs, PDLLA-PEG400-PDLLA and ISO-PUs were also performed ¹ H NMR measurement, the obtained spectrum is shown in FIG. 4. In PDLLA-PEG400-PDLLA ¹ In the spectrum in H NMR, peaks at σ =1.57ppm (H-B) and σ =1.48ppm (H-B') respectively belong to-CH of lactoyl unit in macrodiol ₃ and-CH in the terminal lactic acid residue of the macroalcohol ₃ A proton absorption peak; the peak at σ =3.64ppm (H-D) comes from-CH within PEG400 ₂ A proton absorption peak; peak σ =5.16ppm (H-a) is the-CH proton absorption peak on the lactoyl unit of the macrodiol; the peaks at σ =4.23 to 4.46ppm (H-A', H-C) are-CH attached to-OH on the terminal lactic acid residue of the macrogol and-CH adjacent to the PDLLA block in PEG400 ₂ The proton absorption peak of (1). Using peak σ =5.16ppm (I) _H-A = 17.08) and σ =4.23 to 4.36ppm (I) _H-A'+C (4-2) and the integral value of = 1.00), and the molecular weight (M) of PDLLA-PEG400-PDLLA used was calculated _n ) Is 7700.

Three ISO-Pus their ¹ Proton absorption peaks of-CH and-CH 3 (H-a ', H-B ') attached to-OH at the PDLLA-PEG400-PDLLA terminal lactic acid residue at spectrum σ =4.36 to 4.46ppm and σ =1.48ppm in H NMR almost completely disappeared, and proton absorption peaks belonging to H-a ', H-B ', and H-c ' of HDI appeared at σ =3.14ppm, σ =1.38ppm, and σ =1.28 ppm. Furthermore, the proton characteristic peaks on the ISO ring (H-1 to H-6) are evident in the spectra of ISO2-PU and ISO3-PU, whereas they cannot be observed in the spectrum of ISO1-PU due to the low ISO content. Proton absorption peak at σ =3.64ppm assigned to H-D in PDLLA-PEG400-PDLLA as internal standard (I) _H-D = 1.00) while taking the integrated area (I) of the H-3 peak _H-3 ) Or the integrated area of the H-4 peak (I) _H-4 ) Represents the ISO content, in terms of the integral value (I) of the H-a' peak _H-a' ) Representing the HDI content, the actual ratio of PDLLA-PEG400-PDLLA/ISO/HDI in ISO-PUs can be calculated, and the calculation results are shown in Table 1. M of ISO-PUs at the same time from GPC measurement (FIG. 5) _w And PDI are also listed in table 1. As the molecular length of the coupling agent increases, the difference between the actual ratio of PDLLA-PEG400-PDLLA/ISO/HDI and the theoretical ratio is larger, and the molecular weight of PU is lower, which is caused by the difference of the reactivity of the coupling agent.

TABLE 1 composition ratio and molecular weight data for three ISO-PUs

The above test results show that ISO-PUs have been successfully synthesized and that their molecular and theoretical structures have been consistent.

Example 2 high mechanical Property porous Polymer film with regular porosity

This example prepares the shape memory polyurethane material of example 1 into a porous polymer film with high mechanical properties and regular pores by the following method:

the ISO-PUs prepared in example 1 (ISO 2-PU, M) were weighed out _w =61kda,pdi = 1.57), and the volume was determined by volumetric flask after completely dissolving chloroform in a beaker, and a solution of 50mg/mL was prepared. And (5) washing the cover glass with twice-distilled water for three times, washing with twice absolute ethyl alcohol, and drying in the air. Will be provided withThe coverslip was placed on a horizontal laboratory bench in a fume hood at an ambient temperature of 28 ℃ and a humidity of 70%, and about 200. Mu.L of ISO-PUs solution was applied uniformly to the surface of the coverslip using a pipette gun while adjusting the air flow rate to give a volatilization rate of about 20. Mu.L/min. And after the solvent is completely volatilized, the porous film with the regular hexagonal pore structure can be obtained. The pore diameter of the porous film can be adjusted by controlling the volatilization rate, and the pore diameter is smaller when the volatilization rate of the solution is faster, and is larger when the volatilization rate of the solution is faster. By utilizing the principle, porous films with different pore diameters are prepared at 10 mu L/min and 40 mu L/min respectively.

Comparative examples 1PPZ-PU, upy-PU and PDLLA cellular porous films

Comparative example PPZ-PU (M) was prepared by the method of example 2 _w ＝80kDa,PDI＝1.66)、Upy-PU(M _w =25kDa, PDI = 2.12) and PDLLA (M) _w =75kda, pdi = 1.35) was prepared as a honeycomb-shaped porous film. Wherein, the synthetic process of PPZ-PU and Upy-PU is as follows:

wherein the R group of PPZ-PU is:

the R group of Upy-PU is:

HDI and PDLLA-PEG400-PDLLA (macrodiol) were added in a molar ratio of 1.5: adding anhydrous toluene (Tol) into V (DMF, mL) =1.0, and mechanically stirring to completely dissolve the macrodiol; then, the macrodiol is mixed with Sn (Oct) ₂ Adding Sn (Oct) according to the molar ratio of 500 ₂ Reacting for 3 hours at 75 ℃ under the protection of nitrogen; then PPZ or Upy is added according to the molar ratio of PPZ or Upy to the macroglycol of 0.5, and the reaction is continued for 6h at 75 ℃ under the protection of nitrogen gas. Cooling to room temperature after the reaction is finished, and reactingThe system is poured into absolute ethyl alcohol at normal temperature for precipitation, and white solid which is PPZ-PU or Upy-PU is separated out. And finally, purifying the PPZ-PU or Upy-PU twice by using a dichloromethane/absolute ethyl alcohol coprecipitation system, and drying for later use.

The synthesis of PDLLA is as follows:

mixing D, L-Lactide (D, L-Lactide, melting point: 118 ℃, purity: 99.9%), sn (Oct) ₂ (Sigma-Aldrich, CAS No. 301-10-0, cat No. S3252) in a molar ratio of 5000; putting the single-mouth bottle into an oil bath kettle at 140 ℃, starting magnetic stirring after the mixture is completely melted to uniformly stir the reaction system, and continuously reacting for 14 hours; and after the reaction is finished, repeatedly purifying the product for three times by adopting a dichloromethane/normal temperature absolute ethyl alcohol coprecipitation system, and carrying out vacuum drying for 72 hours at room temperature to obtain a target product PDLLA for later use.

COMPARATIVE EXAMPLE 2ISO-PUs NON-POROUS CONTROL FILM

This comparative example, which was prepared using a similar procedure to example 2 for the preparation of an ISO-PUs nonporous control film, differs from example 2 in that: the humidity was set at 30%, and the air flow rate was adjusted to give a volatilization rate of 20. Mu.L/min.

The advantageous effects of the present invention will be further described below by experiments.

Experimental example 1 structural characterization

The samples used in this experimental example were the ISO-PUs porous polymer film prepared in example 2, the PPZ-PU, upy-PU and PDLLA cellular porous films prepared in comparative example 1 and the ISO-PUs non-porous control film prepared in comparative example 2.

1. Experimental methods

(1) Testing by a polarizing microscope: after the porous film on the cover glass is completely dried, the glass slide is placed on an MP41 type polarizing microscope (Mingmu photoelectric microscope) objective table, the appearance of the porous film under normal transmission light and orthogonal polarization at a corresponding position is respectively observed in a high power lens (20-50 times) transmission mode, and is recorded by a digital camera.

(2) Scanning Electron Microscope (SEM) testing: the completely dried porous film sample was removed from the cover glass, and SEM test was performed on the film surface using a JSM-7800F scanning electron microscope (Nippon electronics Co., ltd.). Before testing, the sample is sprayed with gold, the thickness is about 0.5nm, and the testing voltage is 8KV. The C, O and the N element of the sample were imaged simultaneously using x-ray electron spectroscopy (EDS).

(3) One-dimensional wide-angle X-ray diffraction (1D-WAXD) test: thin film samples were subjected to a 1D-WAXD test using a panalyticic-Empyrean high resolution X-ray diffractometer (marvens parnaraceae, netherlands), cu target, scan rate 2 θ =1 °/min, scan range 5 ° -35 °.

(4) Two-dimensional wide-angle X-ray diffraction (2D-WAXD) test: two-dimensional wide-angle x-ray diffraction (2D-WAXD) analysis of the film was performed on the BL16B1 beam line station of the Shanghai synchrotron radiation apparatus (SSRF). The sample was at a distance of 30mm from the detector and the diffraction pattern was acquired by a Pilatus300K detector with a resolution of 487 × 619 pixels with a test time of 45s.

(5) FT-IR test: fourier transform infrared (FT-IR) spectra of film samples were collected using an IRTracer-100 attenuated reflectance FT-IR spectrometer (Shimadzu, japan). Each sample was scanned 16 times with a resolution of 4cm ^-1 Recording the sample at 4000-700 cm ^-1 In-range spectra. The spectra were peaked and integrated using OriginPro 9.0 software after the test was completed.

(6) DSC test: using a DSC 200F3 type (Netzsch, germany) Differential Scanning Calorimeter (DSC) at N ₂ In the atmosphere, the temperature rise (decrease) rate is 10 ℃/min. The sample was first heated from-10 ℃ to 150 ℃, then cooled to-10 ℃ and finally heated again to 150 ℃. Data for the first temperature rise, temperature fall, and second temperature rise cycles are recorded.

2. Results of the experiment

1. Macroscopic morphology of ISO-PUs porous film

FIG. 1 is a photograph comparing the macro-topography of ISO-PUs porous films and non-porous control films. The porous membrane (fig. 6 (a)) is translucent without forming a complete porous structure visually except for the edge region where the solution is volatilized too fast, and most of the region is white and opaque. All subsequent porous films were tested for visually white opaque areas. While the ISO-PUs non-porous film as a control (fig. 6 (b)) appeared colorless and transparent, indicating that no phase separation structure existed or did not exceed the nano-scale in the non-porous control film.

2. Micro-morphology of ISO-PUs porous film

FIG. 7 is a photograph showing the condensed water droplets accumulated on the surface of the solution during the various film manufacturing processes of ISO-PUs (solvent evaporation rate of about 20. Mu.L/min). It can be observed that the coalesced water droplets (like white particles) are regularly arranged in most areas, the water droplets are in the shape of regular hexagons and there are distinct boundaries between individual water droplets. This region appears as a single layer of regular hexagonal pore region in the SEM test (fig. 8 (a)) after complete evaporation of the solvent and water. While in a small fraction of the area, the droplets are interconnected and overlap, and eventually complete evaporation of solvent and water appears as a multi-layered pore area (fig. 8 (a)). Fig. 3 is a photograph of the morphology obtained by SEM test after the honeycomb-shaped porous film was completely dried, the size of the pores was very uniform, and each of the regular hexagonal pores had a diameter of about 4.0 μm (fig. 8 (b)).

When the porous film was observed in the transmission mode using a microscope, the single-layer hole was visually white, and the multi-layer hole was visually red due to the difference in light transmittance (fig. 9 (a)). When further viewed under crossed polarisers (fig. 9 (b)), an odd image can be observed in the single layer region, with the four edges symmetrically disposed on either side of the hexagon showing crystal-like characteristics, and the two remaining edges lying between the four edges showing no crystal characteristics, i.e. being visually completely dark. At the same time, the edges with crystalline character have a regio-orientation, and the boundaries of these differently oriented regions are the multi-layer pore regions. Further magnification of these regions revealed that each edge having a crystalline character was "Z" shaped, and that two adjacent crystalline edges in the same orientation region were not closely connected, and that a space of about 0.3 to 0.5 μm existed between them (FIGS. 9 (c) and (d)).

Further, example 2 obtained ISO-PUs porous films having pore diameters of 1.5 μm and 7.0 μm by adjusting the air flow rate so that the solvent volatilization rates were 10 μ l/min and 40 μ l/min, respectively, and the optical microscopic morphologies of these two films and the microscopic morphology under crossed polarizers are shown in FIG. 10. When the optical microscope morphologies in FIGS. 10 (a) and (d) are compared with the morphology of the porous film having a pore size of about 4.0 μm in FIG. 9 (a), it can be seen that the pore size is proportional to the size of the multi-layer pore-forming region, i.e., the film having a larger pore size exhibits a larger multi-layer pore region area. The two hexagonal holes with diameters of 1.5 μm and 7.0 μm (FIGS. 10 (b) and (e)) under crossed polarizers showed similar crystal morphologies to the hexagonal holes in FIG. 9 (b). However, due to the resolution of the optical microscope, "zigzag" crystal morphology at the edges of hexagonal holes with diameters of 1.5 μm became less pronounced (FIG. 10 (c)), while "zigzag" crystal morphology at the edges of hexagonal holes with diameters of 7.0 μm became more pronounced (FIG. 10 (f)).

Comparative example 1PPZ-PU, upy-PU and PDLLA porous membranes were also prepared separately by BF method, wherein PPZ-PU and Upy-PU have the same PDLLA-PEG400-PDLLA soft segment molecular chain as ISO-PUs. FIG. 11 shows the microscopic morphology of these porous films under optical microscopy and crossed polarizers, and the porous films PPZ-PU (FIG. 11 (a)) and UPy-PU (FIG. 11 (c)) are also honeycomb-shaped, i.e., the surface pores are all regular hexagons and the diameter of the pores is similar to that of the ISO-PUs porous film in FIG. 9 (a). The pores on the surface of the PDLLA porous membrane are irregular, and the pore diameter is obviously smaller than that of PPZ-PU and Upy-PU. Importantly, the porous films of these three materials did not exhibit crystalline characteristics when viewed under a polarizer (fig. 11 (b), (d) and (f)), i.e., were completely dark in the field of view. Since ISO-PUs differs from PPZ-PU (and Upy-PU) only in the presence of the repeating units of the bicyclic ISO small molecule, it can be speculated that the bicyclic ISO small molecule plays a crucial role in the formation of similar crystal structures in fig. 9 and 10.

3. Thermal performance of ISO-PUs porous films

To further confirm the presence of crystals on the edges of the ISO-PUs porous membranes, DSC tests were performed on ISO-PUs porous membranes and ISO-PUs non-porous control films having a diameter of 4.0 μm. The first thermal scan curve is shown in FIG. 12 (a), and the DSC curve of the porous film has a typical crystal melting peak, a melting range of 46.5-55.7 ℃, a melting point of 51.7 ℃, and a melting enthalpy of 9.97J/g, while the DSC curve of the control film has no similar melting peak. In addition, the glass transition temperature of the porous film was 43.1 ℃ which is much higher than 31.4 ℃ of the control film, probably due to the restriction of the molecular chains in the amorphous region by the crystals, indicating that there is a difference in the degree and structure of separation between the soft and hard phases in the two films.

The cooling curve and the reheating curve of both films were not significantly different (FIG. 12 (b)), and neither of them exhibited a crystallization peak in the cooling curve nor a crystal melting peak in the reheating curve. In addition, the glass transition temperatures of the two films on the cooling curve and the secondary heating curve are substantially the same. It is stated that ISO-PUs are indeed an amorphous polymer, the crystals in the porous film being formed by the BF process.

4. WAXD analysis of ISO-PUs porous membranes

In order to further detect the crystal structure in the ISO-PUs porous film, a porous film with a pore size of 4.0 μm was subjected to two-dimensional wide-angle X-ray diffraction (2D-WAXD) and one-dimensional wide-angle X-ray diffraction (1D-WAXD) tests. The 2D-WAXD diffraction pattern and 1D-WAXD curve obtained using ISO-PUs non-porous clear films as control samples were also tested as shown in FIG. 13. In the 2D-WAXD diffraction pattern (fig. 13 (a)) of the ISO-PUs control film, only a strong diffraction spot appears on the equator, and in the corresponding 1D-WAXD diffraction curve (fig. 13 (c)), there is a sharp diffraction peak evident at 2 θ =9.8 ° in addition to a broad diffraction peak of the amorphous phase. These results show that the molecular chains in the ISO-PUs control films spontaneously assemble to form structures on the nanometer scale and with an ultrahigh degree of orientation. However, the content of such ordered nanostructures was too small to observe a distinct melting peak in the DSC curve thereof (fig. 12 (a)). The 2D-WAXD diffraction pattern of the ISO-PUs porous film (FIG. 13 (b)) is significantly different from the control film, with 5 typical elliptical diffraction rings in the pattern, corresponding exactly to 5 crystalline diffraction peaks in the 1D-WAXD diffraction curve (FIG. 13 (D)). These phenomena further verify that typical crystal structures exist in the porous film and that the crystal structures have a certain orientation.

5. FT-IR analysis of ISO-PUs porous films

The total reflection FT-IR spectrum of ISO-PUs bulk transparent control film and honeycomb porous film with 4.0 μm pore size is shown in FIG. 14 (a). At 1528cm ^-1 The band (-NH group) of amide II in amide bond is found at 1590-1870 cm ^-1 Absorption peaks for ester-C = O group in the macrodiol and-C = O group in the amide bond can be observed in the region. 3260-3460cm due to partial overlap of the two types of-C = O groups ^-1 the-NH group at (A) is more suitable for characterizing the formation of hydrogen bonds. 3260-3460cm ^-1 The results of fitting the FT-IR spectrum of the region were shown in FIG. 14 (b), and the free-NH groups in both films appeared at 3408cm ^-1 The positions at which they form ordered and disordered hydrogen bond-NH groups are different. In the spectrum of the control film, an absorption peak at which disordered hydrogen bond-NH groups were formed appeared at 3357cm ^-1 The absorption peak forming the ordered hydrogen bond-NH group appears at 3323cm ^-1 To (3). However, the absorption peaks of disordered and ordered hydrogen bond-NH groups formed in the porous film appeared at a lower wave number than the corresponding-NH groups in the control film, which were shifted to 3350cm, respectively ^-1 And 3315cm ^-1 To (3). The integral areas of peaks corresponding to-NH groups of different states in two sample curves obtained by peak splitting fitting are shown in table 2, the integral areas of peaks corresponding to ordered and unordered hydrogen bond-NH groups in the porous membrane are far larger than those of a control film, and the peak areas corresponding to free-NH groups are far smaller than those of the control film. This indicates that the molecular chains in the ISO-PUs porous films are significantly more oriented than the control films.

TABLE 2 fitting peak and integral calculations of-NH groups in ISO-PUs control and porous membranes

In summary, the characterization results of the experimental examples show that the shape memory polyurethane material provided by the invention can be combined with a water drop template method to prepare a porous polymer film containing an ordered crystal structure.

Experimental example 2 characterization of mechanical Properties

The samples used in this experimental example were the ISO-PUs porous polymer film prepared in example 2 and the ISO-PUs non-porous control film prepared in comparative example 2.

1. Experimental methods

Mechanical Properties of the samples measured in ElectroPuls equipped with an optical extensometer ^TM Tensile mechanical testing was performed on an E1000 test instrument (Instron, USA) at a loading rate of 5.0 mm/min. The sample was a thin strip film (thickness about 32 μm, width 10mm, total length 50mm, gauge length 25 mm). The final result is the average of 5 replicates.

2. Results of the experiment

The phase structure of the polymer has an important influence on its mechanical properties. Thus, the tensile mechanical properties of ISO-PUs cellular porous membranes having pore diameters of 4.0 μm were evaluated in this chapter and, likewise, using a nonporous, transparent ISO-PUs film as a control, the thicknesses of the two films were very close. The obtained stress-strain curve and the mechanical property calculated according to the stress-strain curve are shown in fig. 15 (a) and (b), the porous film obviously has better mechanical property than the comparison film, and the tensile strength of the porous film and the tensile strength of the comparison film are calculated to be 21.5 +/-4.1 MPa and 16.3 +/-1.8 MPa respectively; the Young modulus is 942.9 +/-111.7 MPa and 759.9 +/-99.7 MPa respectively; the elongation at break was 31.6. + -. 3.2% and 11.4. + -. 2.7%, respectively.

Therefore, compared with a control film with the thickness close to that of the polymer raw material, the porous polymer film prepared by the method has obviously improved mechanical properties. And according to the above characterization results of mechanical properties, the porous polymer film of the present invention has achieved mechanical property requirements that satisfy artificial periosteum (tensile strength 3-4 MPa, elongation at break 19.6-34.8%, ex biomech, 2003,18, 760-764) and anti-adhesion membrane (young's modulus 131.4MPa, tensile strength 9.5MPa, elongation at break 630%, materials Science and Engineering: C,2020,117, 111283).

Experimental example 3 Effect of porous Structure on morphology and osteogenic differentiation of rMSCs

The samples used in this example were the ISO-PUs porous polymer film prepared in example 2 and the ISO-PUs non-porous control film prepared in comparative example 2.

1. Experimental method

The ISO-PUs porous and non-porous control films were vacuum dried at 40 ℃ for 7 days to completely remove the chloroform. After ultraviolet irradiation for 30min on both sides of the sample, the sample was placed in a 24-well plate (material film side up), and rat bone marrow mesenchymal stem cells (rMSCs) were seeded at a cell density of 0.6X 104 cells/cm 2. After co-culturing for 24h in high-sugar medium supplemented with 10% fetal bovine serum and 1% penicillin-streptomycin, the medium was aspirated from the 24-well plate and washed 3 times with PBS. Then fixing the rMSCs by using an immunostaining fixing solution at room temperature for 2H, respectively staining cell nuclei and skeletons by using H33258 and phalloidin, and observing the forms of the rMSCs by using a TCS SP8 laser confocal microscope. Aspect ratio and spread area of rMSCs were statistically analyzed using ImageJ software. After 14 days of co-culture, the medium was aspirated from the 24-well plate and washed 3 times with PBS; then fixing for 2 hours at room temperature by using an immunostaining fixing liquid; then staining the kit with alkaline phosphatase (ALP) for 2h at room temperature; finally, the staining of the sample was observed and recorded by an optical microscope (MP 41, mingmei light) with a camera.

2. Results of the experiment

The cell morphology of rMSCs after 24h culture on ISO-PUS nonporous control membranes and cellular porous membranes with pore size of 4.0 μm is shown in FIG. 16. The cell morphology of the two film surfaces is significantly different, the rMSCs on the surface of the ISO-PUs nonporous control film are mostly triangular or quadrangular, and the small part is circular (FIGS. 16 (a) and (c)), while the rMSCs on the surface of the ISO-PUs porous film are almost elongated quadrangles (FIGS. 16 (b) and (d)), and the cell pseudopodia can be clearly seen to adhere to the edges of the hexagonal hole. The present study also counted the spread area and aspect ratio distribution of the rMSCs on both films, and the resulting distribution is shown in fig. 17. On the graph, the rMSCs on the surfaces of 116 ISO-PUs porous films and 105 ISO-PUs nonporous control films are counted respectively, the spreading areas of the rMSCs on the two films are similar overall, and the rMSCs on the surfaces of only a few porous films have the spreading areas which are far larger than those of the rMSCs on the surfaces of the control films. Meanwhile, the distribution of the length-diameter ratios of the rMSCs on the surface of the comparison film is concentrated, the distribution of the length-diameter ratios of the rMSCs on the surface of the porous film is dispersed, and the length-diameter ratios of the rMSCs on the surface of the porous film are generally larger than the length-diameter ratios of the rMSCs on the surface of the comparison film. ALP is an early osteogenic marker that directly reflects the activity or functional status of osteoblasts. It can be seen from fig. 18 that the cells on both the control film and the cellular porous film after staining are dark blue, and the cells on the cellular porous film are darker in color, i.e., higher in ALP content. The results show that the rMSCs are subjected to osteogenic differentiation on the two films, but the rMSCs on the cellular porous film are more obviously osteogenic differentiation, and the osteogenic activity is higher after the rMSCs are differentiated into osteoblasts.

The above results show that ISO-PUs porous membranes have a better promoting effect on osteogenic differentiation of rMSCs than non-porous control membranes. The porous polymer film provided by the invention has application potential as an artificial periosteum.

Experimental example 4 characterization of anti-adhesion Membrane cell compatibility

The samples used in this experimental example were the ISO-PUs porous polymer film prepared in example 2 and the ISO-PUs non-porous control film prepared in comparative example 2. And (3) taking mouse embryo fibroblasts (NIH 3T 3) as model cells, and evaluating the cell compatibility of the ISO-PUs porous anti-adhesion film and the non-porous control film.

1. Experimental method

Before cell experiments, the porous film and the nonporous control film are placed in a vacuum oven to evaporate and remove the organic solvent, the temperature of the oven is set to be 45 ℃, and the drying time is 72 hours until the weight content of the organic solvent is less than 0.01 percent.

Placing the dried porous anti-adhesion film and the nonporous control film into a 24-hole cell culture plate after ultraviolet sterilization, then adding NIH 3T3 cell suspension into the 24-hole plate with the density of about 1 plate, ⁴ per well. Finally, the 24-well plate is put into an incubator for cell culture, and the culture solution is replaced every two days. After culturing for 1 day and 3 days, taking out samples, and observing cells under an inverted fluorescence microscope and photographing and recording the shapes of the cells after the steps of cleaning, fixing, dyeing, mounting and the like. Samples were taken at 4 time points (1 day, 3 days, 5 days, 7 days) after inoculation, and the absorbance of each group was measured by the CCK-8 method to evaluate the proliferation activity of the cells.

2. Results of the experiment

FIG. 19 is a morphological observation of the two films seeded with NIH 3T3 cells 1 day and 3 days later. There was no major difference in cell morphology and number between the two films after 1 day of culture. After 3 days, the number of cells on the porous membrane was significantly greater than the control membrane. In terms of cell morphology, more cells on the porous membrane protrude from the pseudopodium to form a contact point with the polymer surface, spread out, and form a long fusiform or triangular shape. FIG. 20 is the absorbance values of the NIH 3T3 cells on the surface of the porous membrane and the control membrane measured by the CCK-8 method at different culture times, and the magnitude of the absorbance value represents the level of the proliferation activity. From day 1 to day 7 of inoculation, NIH 3T3 cells were clearly proliferating on both groups of material, during which there was a significant difference in cell proliferation activity of both groups of material at different time points, with very significant differences (p < 0.01) after 1, 5, and 7 days.

The morphology and proliferation experimental results of NIH 3T3 cells show that the surface of the porous membrane is more favorable for cell adhesion and spreading, thereby promoting cell proliferation. This preliminarily demonstrates that ISO-PUs porous membranes have good cellular compatibility and are suitable for supporting tissue repair after implantation of an anti-adhesion membrane.

It can be seen from the above examples and experimental examples that the present invention designs a new shape memory polyurethane material and combines the shape memory polyurethane material with a water drop templating method, which can comprise a porous polymer film of a crystalline structure. The porous film material has excellent mechanical properties, can meet the performance requirements of application scenes such as artificial periosteum, anti-adhesion membranes and the like, and has good application prospects.

Claims

1. A high mechanical property porous polymer film with regular pores is characterized in that: the shape memory polyurethane is prepared by a water drop template method by taking shape memory polyurethane as a raw material;

the shape memory polyurethane is an amorphous polymer with a glass transition temperature of 37-45 ℃ or a semi-crystalline polymer with a melting point of 37-45 ℃, and is prepared from diisocyanate, a soft segment polymer and

according to the molar ratio of 1.2-8:1:0.2-7, having a molecular weight of 30000-150000;

the soft segment polymer is polylactic acid, polyglycolic acid, polycaprolactone, polyol or a copolymer of two or more of the polylactic acid, the polyglycolic acid, the polycaprolactone and the polyol;

the parameters of the water drop template method are selected as follows: the environment temperature is 4-50 deg.C, humidity is 25-80%, and solvent is chloroform, so that the volatilization rate of solvent is 10-40 μ L/min.

2. The porous polymeric membrane of claim 1, wherein: the structural formula of the shape memory polyurethane is shown as the formula I:

formula I

Wherein x is selected from 1 to 10, y is selected from 1 to 10;

is a repeating unit of the soft segment polymer;

being repeat units of diisocyanates, or diisocyanates and

repeating units of the copolymer of (1).

3. The porous polymeric film according to claim 1 or 2, wherein: the soft segment polymer is a polymer of lactic acid and polyalcohol.

4. The porous polymeric membrane of claim 3, wherein: the structural formula of the soft segment polymer is shown as the formula II:

formula II

5. The porous polymeric film according to claim 1 or 2, wherein: the diisocyanate is selected from aliphatic diisocyanate or aromatic diisocyanate, the aliphatic diisocyanate is selected from hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate or a mixture of two or more of the hexamethylene diisocyanate, and the aromatic diisocyanate is selected from toluene diisocyanate, diphenylmethane diisocyanate or a mixture of two or more of the diphenylmethane diisocyanate.

6. A method of making a porous polymeric membrane according to any of claims 1 to 5, comprising the steps of:

step 2, coating the polyurethane solution on the surface of a substrate, and volatilizing in humid air to obtain the polyurethane solution;

in step 1, the volatile solvent is selected from chloroform;

in step 2, the substrate coated with the polyurethane solution is dried under the conditions of the ambient temperature of 4-50 ℃ and the humidity of 25-80%, and the volatilization rate of the solvent is 10-40 mu L/min.

7. The method of claim 6, wherein: the concentration of the polyurethane solution is 5-200 mg/mL.

8. Use of the shape memory polyurethane according to claim 1 for the preparation of high mechanical properties, porous, regularly porous polymer films, characterized in that: the method for preparing the porous polymer film by the shape memory polyurethane is a water drop template method;