Method for accurate control of shape recovery rate of polyurethane porous framework

Abstract

The present application relates to the shape memory polymer technical field, disclose a kind of shape recovery rate accurate control method of polyurethane porous framework, comprising: polyether polyol is reacted with isocyanate to generate end-capped prepolymer, introduce multi-branched monomer in polyurethane molecular chain Construction branched chain segment with free end, add the diamin of space steric hindrance characteristics Chain extender executes foaming reaction, the dissociation energy barrier of hard segment microphase region is set using chain extender side chain steric hindrance effect, the damping phase region formed by branched chain segment at the interface of hard segment and soft segment, through the internal friction of chain segment in the dissociation transient of physical crosslinking point, elastic strain energy accumulated is dissipated, stress snap in shape recovery process is inhibited, so that porous framework produces constant radial expansion force output, effectively improve the use safety of vascular interventional instrument.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of shape memory polymer polymers, and particularly relates to a shape recovery rate precise control method of a polyurethane porous framework. BACKGROUND

[0002] At present, polyurethane porous frameworks are often introduced into predetermined positions in a compressed state through a delivery system due to their shape recovery characteristics and microporous structure, and recover the initial shape under the action of thermal response or fluid immersion. The recovery dynamics behavior is jointly determined by the dissociation resistance of the hard segment physical crosslinking points in the polymer and the relaxation dynamics of the soft segment chain segments. When the external environmental excitation exceeds the trigger threshold of the glass transition temperature, the elastic strain energy stored in the porous framework is released. Due to the polarity difference between the hard segment and the soft segment of the polyurethane, the hard segment aggregation zone is prone to discontinuous energy transition in the dissociation process, resulting in a transient rebound mechanical pulse of the porous framework in the initial stage of shape recovery, which is easy to cause mechanical damage to the inner membrane of the microvessel. The existing technology usually uses the means of increasing the material density or improving the chemical crosslinking density to inhibit the recovery rate, which reduces the effective permeability of the porous framework while reducing the recovery rate, and cannot eliminate the stick-slip phenomenon in the relaxation process of the polymer chain segment, resulting in nonlinear fluctuation characteristics of the radial pressure output in the shape recovery process, which limits the application safety of the framework in the complex biochemical fluid environment.

[0003] In addition to the limitation of the overall appearance of the framework, the single means of dynamic regulation of the relaxation process of the molecular chain segment is the key to the smooth output of the mechanics. For example, the Chinese invention patent with the publication number CN101033286A discloses a shape memory polyurethane yarn and fabric. The block structure composed of fixed phase and reversible phase realizes the shape memory function. The design logic is anchored in the shape retention of the fabric fiber form, and does not involve the capture and dissipation of the instantaneous local elastic potential of the shape recovery. In the vascular intervention scene, the scheme lacks precise definition of the dissociation energy barrier of the hard segment, and the soft segment interface lacks a molecular level damping buffer mechanism, so that the recovery trajectory shows high sensitivity to the polarity of the environment fluid, resulting in unexpected fluctuations in the recovery rate. In addition, there is a risk of instability in the long-term compression storage of the internal physical microstructure, and there is a lack of in-situ detection means for recovery efficiency.

[0004] Therefore, how to construct a molecular level damping structure with self-regulating ability without changing the intrinsic strength of the material, and realize the platform output of the shape recovery rate of the porous framework, has become a technical problem to be solved by the present application. SUMMARY

[0005] The present application provides a shape recovery rate precise control method of a polyurethane porous framework, comprising the following steps:

[0006] Step S1, polyether polyol and isocyanate are mixed at 60 to 80 mixing and pre-polymerization at a temperature to form an isocyanate-terminated polyurethane prepolymer;

[0007] Step S2, adding a branched monomer with a mole percentage of 0.4% to 0.9% in the polyurethane prepolymer to perform an in-situ chain extension reaction, to build branched segments with free ends on the polyurethane molecular chain, to form a modified prepolymer; the branched monomer is a branched polyol with a functionality greater than or equal to 3 and a molecular weight less than 500;

[0008] Step S3, mixing the modified prepolymer with a diamine chain extender with steric hindrance characteristics and a foaming aid to form a polyurethane porous framework with a micro-phase separation structure through an in-situ foaming reaction; using the diamine chain extender to form a dissociation energy barrier defined by the side chain steric effect inside the hard segment micro-phase region, and to establish a physical crosslinking point inside the polyurethane porous framework by the hard segment micro-phase region;

[0009] Step S4, using the damping phase region formed by the branched segments at the interface between the hard segment and the soft segment to dissipate the elastic strain energy accumulated inside the polyurethane porous framework when the physical crosslinking point crosses the dissociation energy barrier, and using the internal friction of the molecular chain segments in the damping phase region to suppress the fluctuation of the chain relaxation rate, to make the polyurethane porous framework produce a constant radial expansion force output.

[0010] Preferably, the amount of branched monomer is determined according to the side chain steric volume of the diamine chain extender, and the ratio of the branched monomer to the diamine chain extender satisfies the following quantitative rule: wherein, is the pre-set mole percentage of the branched monomer in step S2, is the functionality of the branched monomer, is the mole percentage of the diamine chain extender put in step S3; the arrangement density of the branched segments in the damping phase region is limited by the quantitative rule, so that the radial recovery force fluctuation amplitude of the polyurethane porous framework during shape recovery is less than 10%.

[0011] Preferably, the diamine chain extender with steric hindrance characteristics is selected from 2,2'-dichloro-4,4'-dimethylene bisbenzene amine and 3,3'-dichloro-4,4'-diamino diphenyl methane.

[0012] Preferably, step S3 includes: by adjusting the isocyanate index of isocyanate and hydroxyl in the modified prepolymer, limiting the topological crosslinking density of the hard segment micro-phase region, so that the shape recovery trigger temperature of the polyurethane porous framework is 35 to 42 .

[0013] Preferably, in step S1, the molecular weight of the polyether polyol is 1000 to 4000, and the hydroxyl value is 28 to 56 mgKOH / g.

[0014] Preferably, step S3 further comprises adding fluorocarbon segment regulating monomers to form a bio-inert interface on the pore wall surface of the polyurethane porous framework.

[0015] Preferably, in step S3, the in-situ foaming reaction is carried out under a negative pressure environment with a pressure value of -0.05 MPa to -0.08 MPa to adjust the open porosity of the polyurethane porous framework, so that the open porosity is not less than 90% and the average pore size is 100 μm to 300 μm.

[0016] Preferably, the radial expansion force is verified by the following steps: compressing the polyurethane porous framework to 20% of the original volume and releasing at the shape recovery trigger temperature, and collecting the change curve of the radial expansion force of the polyurethane porous framework with displacement in the shape recovery process by a dynamic thermodynamic analyzer.

[0017] Preferably, in step S3, the diamine chain extender is selected to be an aromatic diamine with a symmetrical side group structure to improve the uniformity of the distribution of the physical cross-linking points in the hard segment microphase region.

[0018] Preferably, the polyurethane porous framework for the vascular interventional instrument has a shape recovery rate of 90% to 100% in 30 s to 120 s in a physiological saline environment at 37 The shape complete recovery time in a physiological saline environment is 30 s to 120 s.

[0019] Compared with the prior art, the shape recovery rate precise control method of the polyurethane porous framework has the following advantages: in the shape recovery rate of the polyurethane porous framework, the binary amine chain extender with a steric hindrance characteristic constructs a diffusion barrier inside the hard segment microphase region, sets the dissociation resistance of the hard segment physical crosslinking point, and changes the synergistic relaxation of the polyurethane segment in the shape recovery process from instantaneous burst to limited diffusion, so that the porous framework has a sustained and uniform expansion characteristic, and the radial impact force generated in the rebounding instant is eliminated; secondly, the branched ends of the branched dissipation factor and the steric chain extender produce physical entanglement, construct a high-damping transition zone at the interface between the hard segment and the soft segment, dissipate the local instantaneous elastic strain energy in the hard segment dissociation process by using the molecular-level viscous chain swing effect, inhibit the stick-slip phenomenon in the relaxation of the polymer chain segment, and make the porous framework have a mechanical response characteristic of constant radial pressure output; the low surface energy chain segment and the polar adjusting factor are directionally migrated to the micro-pore wall surface in the in-situ foaming process, and a composite diffusion barrier is constructed, wherein the low surface energy chain segment produces a friction reduction effect when the micro-pore wall is relatively displaced, and the hydrophobic micro-area formed by the polar adjusting factor blocks the penetration and diffusion of the external fluid polar molecules to the soft segment, so that the shape recovery rate maintains a preset response trajectory in a complex biochemical fluid environment; and the supramolecular monomer with a ring structure is inserted between the polyurethane molecular chains, locks the spatial arrangement of the hard segment microphase region through physical entanglement, and maintains the stress stability of the porous framework in the compressed storage state as a topological sliding track, thereby eliminating the recovery rate drift caused by long-term stress. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 is the preparation process and implementation step flow chart of the shape recovery rate precise control method of the polyurethane porous framework of the present application;

[0021] Fig. 2 is the technical mechanism and full-cycle logic architecture block diagram of the shape recovery rate precise control method of the polyurethane porous framework of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0023] It should be noted that all the terms indicating directionality and positionality in the present application, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship, connection condition, etc. between components in a certain specific state (as shown in the drawings), only for the convenience of describing the present application, and are not required to be constructed and operated in a specific orientation, therefore cannot be understood as a limitation on the present application, in addition, the description of first, second, etc. in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of indicated technical features.

[0024] In the description of the present application, unless otherwise explicitly specified and limited, the terms installation, connection, and connection should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection; can be directly connected, or indirectly connected through an intermediate medium; can be the communication inside two elements, and those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0025] In the description of the present application, the description of the terms one embodiment, some embodiments, illustrative embodiment, example, specific example, or some examples, etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application, in the present description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example, and the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0026] A shape recovery rate precise control method of a polyurethane porous framework, comprising a synthesis stage of isocyanate group terminated prepolymer, an in-situ modification stage of branched chain segment, a foaming locking stage of physical crosslinking point establishment, and a shape recovery stage adjusted by a damping phase region, by introducing a damping phase region composed of hard segment structure with steric hindrance characteristics and branched chain segment in the polyurethane molecular chain, a kinetic mechanism jointly restricted by dissociation energy barrier defined by side chain steric hindrance and chain segment internal friction is established, and the controlled smooth output of the shape recovery rate of the porous framework is realized; S1, polyether polyol and isocyanate are mixed and pre-polymerized at 60 to 80 temperature, to generate isocyanate group terminated polyurethane prepolymer, the molecular weight of the polyether polyol is 1000 to 4000 and the hydroxyl value is 28 to 56 , the reaction process by maintaining the isocyanate index in the range of 1.15 to 1.25, to ensure that the molecular chain segments of the prepolymer have a preset segment length distribution; due to the polarity difference between the hard segment and the soft segment of the polyurethane, the hard segment aggregation zone is prone to discontinuous energy release during dissociation. To address this challenge, the system introduces a branched dissipative structure into the molecular chain, step S2, adds a branched monomer with a molar percentage of 0.4% to 0.9% to the polyurethane prepolymer for in-situ chain extension reaction, to construct branched segments with free ends on the polyurethane molecular chain, generating a modified prepolymer, the branched monomer is a branched polyol with a functionality greater than or equal to 3 and a molecular weight less than 500. The branched monomer forms a nonlinear branched point on the polyurethane molecular chain, and uses the swing effect of the branched end to construct a damping phase region at the interface between the hard segment and the soft segment formed subsequently.

[0027] To address the mechanical pulse fluctuations that may occur during shape recovery, the system uses steric hindrance to set the dissociation resistance of the hard segment physical crosslinking point, step S3, mixes the modified prepolymer with a binary amine chain extender with steric hindrance characteristics and a foaming aid to form a polyurethane porous framework with a microphase separation structure through in-situ foaming reaction, the binary amine chain extender with steric hindrance characteristics is selected from 2,2'-dichloro-4,4'-dimethylene bisphenylamine or 3,3'-dichloro-4,4'-diamino diphenyl methane. The binary amine chain extender forms a dissociation energy barrier defined by the side chain steric hindrance effect inside the hard segment microphase region, and the hard segment microphase region establishes a physical crosslinking point inside the polyurethane porous framework. By adjusting the isocyanate index of isocyanate and hydroxyl in the modified prepolymer, the topological crosslinking density of the hard segment microphase region is limited, so that the shape recovery trigger temperature of the polyurethane porous framework is in the range of 35 to 42 ; In the construction of the hard segment microphase region, the differential scanning calorimetry feedback adjustment program is used to limit the dissociation energy barrier, and a reference isocyanate index of 1.20 is selected to prepare a test strip, and the hard segment phase transition peak temperature is measured to characterize the dissociation activity of the physical crosslinking point. The actual value is lower than 35 , and the isocyanate input is increased by 0.02 step gradient, so that the peak temperature is in the range of 35 to 42 The interval compensates for the deviation of isocyanate group consumption caused by trace residual moisture of raw materials, and establishes that the internal dissociation energy barrier of the hard segment microphase meets the preset kinetic threshold. To improve the stress stability of the polyurethane porous framework during long-term compression storage and prevent the shape recovery rate from drifting over time, 1.5% to 3.0% of the mass percentage of the cyclic supramolecular monomer is introduced into the preparation process. The cyclic supramolecular monomer is selected as hydroxypropyl betadex. The non-covalent physical interpenetrating structure is formed by the cavity of the cyclic molecule and the polyurethane segment. When the porous framework is in a compressed state, it acts as a topological sliding track to dissipate the rearrangement stress of the molecular segment, inhibits the plastic deformation of the hard segment microphase under long-term load, and ensures that the physical crosslinking point maintains a preset dissociation energy barrier before shape recovery is triggered.

[0028] Step S4, using the damping phase zone formed by the branched segment at the interface between the hard segment and the soft segment, dissipating the accumulated elastic strain energy inside the polyurethane porous framework when the physical crosslinking point crosses the dissociation energy barrier and dissociates, using the internal friction of the molecular segment in the damping phase zone to inhibit the fluctuation of the chain segment relaxation rate, making the polyurethane porous framework produce constant radial expansion force output, and the shape recovery process is controlled by the entropy increase generated by the internal friction of the chain segment, so as to convert the stored elastic potential energy into smooth heat dissipation; in the radial force fluctuation adjustment of shape recovery, the dynamic thermodynamic analysis damping factor calibration program is adopted, 37 Determination of the loss factor of the polyurethane porous framework under the condition With the strain recovery path distribution curve, when the radial force fluctuation amplitude exceeds 10%, according to the quantitative rule Adjust the molar percentage of branched monomers , increase the arrangement density of branched ends in the damping phase zone, and improve the internal friction dissipation power of the molecular segment , so that the radial force output trajectory tends to be smooth and the fluctuation value returns to within 10%, achieving programmed constraint on the release rate of elastic strain energy; to realize the quantitative limitation of shape recovery stability, the amount of branched monomers is determined according to the side chain steric volume of the diamine chain extender, and the ratio of branched monomers to diamine chain extender meets the following quantitative rule: , wherein, is the molar percentage of branched monomers preset in step S2, is the functionality of the branched monomer, is the molar percentage of the diamine chain extender put in step S3, by limiting the arrangement density of branched segments in the damping phase zone through the quantitative rule, the radial recovery force fluctuation amplitude of the polyurethane porous framework during shape recovery is less than 10%.

[0029] The in-situ foaming reaction is carried out under a negative pressure environment with a pressure value of -0.05 MPa to -0.08 MPa to adjust the opening rate of the polyurethane porous framework, so that the opening rate is not less than 90% and the average pore size is 100 Up to 300 In addition, the fluorocarbon chain segment adjusting monomer is added in step S3 to form a biologically inert interface on the pore wall surface of the polyurethane porous framework, and 2.5% to 5.0% by mass of a polar adjusting factor is added at the same time, the polar adjusting factor being a terminal-capped polydimethylsiloxane oligomer, the polar adjusting factor segregating to the pore wall surface during foaming and forming a hydrophobic shielding area, so as to reduce the interference of the external environment fluid on the relaxation rate of the polyurethane segment, so that the porous framework can restore the shape in 37 The shape recovery time in a physiological saline environment is maintained at 30 s to 120 s; to verify the effectiveness of the radial expansion force output, the polyurethane porous framework is compressed to 20% of the original volume and released at the shape recovery trigger temperature, and the change curve of the radial expansion force of the polyurethane porous framework with displacement during the shape recovery process is collected by a dynamic thermodynamic analyzer, and 0.05% to 0.2% by mass of a stress-sensitive molecular probe is added when preparing the prepolymer or carrying out the chain extension reaction, and a spiropyran type chromogenic molecule is specifically selected, the stress-sensitive molecular probe characterizing the structural integrity of the hard segment microphase area through color state, if the characteristic absorption peak of the chromogenic molecule is red-shifted, it indicates that the internal physical crosslinking network has stress relaxation or micro-crack growth, thereby providing a visual check basis for the effectiveness of the shape recovery rate.

[0030] Example 1: In the vascular reconstruction scene of intracranial aneurysm interventional embolization, due to the high sensitivity of the inner wall of the microvessel to the radial force fluctuation generated during the expansion of the polyurethane porous framework, and the tendency of the accumulated elastic strain energy of the shape memory polymer to release explosively after crossing the shape recovery trigger temperature, the foregoing specific implementation regulation method is used, a polyether polyol with a molecular weight of 2000 and a hydroxyl value of 56 is reacted with isocyanate at 75 to generate an isocyanate group terminated prepolymer, and 0.5% by mole and a functionality of 3 of trimethylolpropane are added as a steric chain extender in the in-situ chain extension stage, and 0.8% by mole of 2,2'-dichloro-4,4'-dimethylene benzidine is used as a steric chain extender, the steric chain extender generates a steric hindrance effect to set the dissociation energy barrier of the physical crosslinking point, and the branched chain segment generated by the branched monomer constructs a damping phase area with intramolecular friction characteristics at the edge of the hard segment microphase area, so that the calculated characteristic ratio is 1.875, which is within the quantification interval of 1.2 to 2.5, when the porous framework is triggered to recover the shape in a 37 physiological environment, the damping phase area captures and dissipates the local elastic strain energy released instantaneously when the hard segment is dissociated, eliminates the stick-slip phenomenon in the chain segment relaxation process, and converts the accumulated strain energy into a smooth expansion of the constant output of the radial pressure.

[0031] During the sustained operation of the porous framework in contact with physiological fluids, the solvation plasticization effect of physiological saline molecules on the soft segment of the polyurethane can cause unexpected fluctuations in the recovery rate. To address this issue, a polar modifier with a mass percentage of 3.5% is introduced during the in-situ foaming stage of the system. This polar modifier is a terminal-capped polydimethylsiloxane oligomer that chemically anchors with the isocyanate groups in the prepolymer. The resulting composite diffusion barrier on the surface of the microporous walls is composed of polar modifiers and fluorocarbon segments. The low surface energy fluorocarbon segments reduce the interfacial frictional resistance, while the hydrophobic microdomains formed by the polar modifier obstruct the penetration path of external fluid molecules. This transformation of the porous framework's recovery kinetics from environment-sensitive to structure-controlled ensures that the complete shape recovery time is stable within a window of 30s to 120s. When the porous framework is fully filled with the aneurysm cavity and enters a stable filling state, the internal physical crosslinking network integrity is verified by collecting a mass percentage of 0.1% of the spiropyran stress-sensitive molecular probe in the color state. When the characteristic absorption peak of the chromogenic molecule does not exhibit a red shift, it is determined that the dissociation energy barrier of the physical crosslinking points and the frictional dissipation mechanism of the branched segments support the safety of the porous framework in extreme constraint environments. This embodiment introduces dissipation units at the molecular scale to dissipate the overall mechanical pulse into the internal friction work between chain segments, achieving programmed regulation of the shape recovery rate of the polyurethane porous framework.

[0032] In the mechanical response characteristic verification test of the polyurethane porous framework for vascular intervention embolization, a load sensor with a resolution of 0.01N and a dynamic thermodynamic analysis platform with a sampling frequency of 10Hz are selected, which has a sensing boundary sufficient to capture the strain energy release pattern during chain relaxation. The test data is derived from a physical experiment platform simulating a physiological environment by injecting phosphate buffer into the test cell and introducing periodic pressure fluctuations generated by a circulating pump as background noise interference. The sampling period is set to balance the real-time signal capture and system load of data processing. When the monitored radial force change slope exceeds the preset fluctuation threshold , the sampling frequency is increased to 50Hz to avoid signal aliasing. Here is the radial force change, with units of N, is the time increment, with units of s, is the fluctuation threshold, with units of . The adjustment of the sampling frequency ensures the complete recording of the local elastic strain energy release transient. The test process is carried out by performing isothermal strain recovery tests on different components of the polyurethane porous framework. Each sample is compressed to 20% of the original volume and locked, then placed in a 37 phosphate buffer.

[0033] Table 1: Shape recovery performance comparison table of polyurethane porous framework

[0034]

[0035] Referring to the test results in Table 1, the characteristic ratio of Test Group 1 to Test Group 3 in the quantitative interval of 1.2 to 2.5, the radial force fluctuation amplitude is less than 10% and the shape complete recovery time is stable in the preset window of 30s to 120s, wherein is the mole percentage of branched monomers, is the functionality of branched monomers, is the mole percentage of diamine chain extenders, and by comparing the data of Control Group 3, it can be found that under the condition of lacking branched monomers to construct damping phase region, the radial force fluctuation amplitude increases to 35.4%, showing the characteristics of transient strain energy burst, and when the characteristic ratio is less than 1.2, as shown in Control Group 1, the intra-chain friction work provided by the branched segment is not enough to completely dissipate the local elastic potential energy released instantaneously by the hard segment dissociation, resulting in a jump characteristic of mechanical response, and when the characteristic ratio exceeds 2.5, as shown in Control Group 2, although the mechanical stability is good, the friction energy barrier between the segments is too high, resulting in a sharp decrease in recovery rate and an extension of recovery time to 186.7s, indicating that there is a performance inflection point between the product of the functionality and content of branched monomers and the ratio of the content of steric chain extenders, and for the plasticization disturbance caused by the penetration of polar fluid, by comparing and analyzing the data of Test Group 2, Control Group 4 and Control Group 5, Test Group 2 forms a hydrophobic barrier region on the surface of the microporous wall by adding 3.5% of the mass percentage of the polar adjusting factor, so that the recovery time is locked at 75.3s, Control Group 4 has an incomplete hydrophobic barrier coverage due to the addition of less than 2.5% of the polar adjusting factor, resulting in rapid penetration and plasticization of the polyurethane segment by the external fluid molecules, and the recovery time is shortened to 28.5s with fluctuation in rate, and when the addition amount exceeds the saturated upper limit of 5.0%, as shown in Control Group 5, the excess polar adjusting factor component in the system undergoes phase separation, which not only fails to maintain the stability of the recovery rate, but also results in insufficient recovery power due to the weakening of the physical crosslinking network strength.

[0036] Example 3: This example combines Figs. 1-2 , the shape recovery rate of the polyurethane porous framework is precisely controlled, and the method is as follows: Fig. 1As shown, the precise control process of the shape recovery rate of the polyurethane porous framework begins in step S1, where polyether polyol and isocyanate are mixed at 60°C to 80°C and subjected to a prepolymerization reaction to generate an isocyanate-terminated polyurethane prepolymer. In step S2, 0.4% to 0.9% of branched monomers are added to carry out an in-situ chain extension reaction, constructing branched segments with free ends on the polyurethane molecular chain and generating a modified prepolymer. Then, in step S3, the modified prepolymer is mixed with a diamine chain extender with steric hindrance characteristics and a foaming agent, and in-situ foaming is performed to form a polyurethane porous framework with a microphase separation structure and a dissociation energy barrier. Finally, in step S4, the damping phase region dissipates elastic strain energy at the moment of dissociation, and the friction within the molecular chain segments is used to suppress the fluctuation of the relaxation rate, so that the porous framework generates a constant radial expansion force output.

[0037] like Fig. 2 As shown, in the raw material preparation and prepolymerization node, polyether polyol and isocyanate undergo a prepolymerization reaction at 60 to 80 degrees to generate a capped prepolymer. Through in-situ chain extension reaction and synergistic action of the functional modification input node, the functional modification input node constructs a damping structure through branched monomers, sets a dissociation energy barrier through sterically hindered diamines, and introduces dissipation factors according to the control strategy of quantitative correlation rules. It enters the microstructure construction environment and performs negative pressure foaming molding. In this process, the hard segment microphase region and physical cross-linking points construct a damping phase region at the interface of soft and hard segments through steric hindrance effect and generate internal friction dissipation. The damping dissipates strain energy and suppresses stress jumps. At the same time, fluorocarbon segments and polarity regulation are introduced into the surface layer of the pore wall. Finally, in the vascular intervention clinical deployment environment and 37-degree physiological environment, when shape memory is triggered and elastic strain energy is released, the system uses the hydrophobic shielding region to block fluid penetration for environmental interaction. Safety monitoring is performed through stress-sensitive molecular probes and colorimetric status feedback, thereby achieving the core functional output of constant radial expansion force and smooth recovery without pulses.

[0038] Example 4: In the process calibration of large-scale continuous fabrication of vascular embolization stents, to address the foaming pressure fluctuations caused by differences in the volume of the production equipment chambers, the system executes a pore structure determination procedure based on negative pressure compensation, according to the target average pore size. and target aperture ratio Establish an initial pressure setting model and determine the pressure values ​​during the foaming process. According to the regulations It is confirmed that, among them, The foaming pressure is expressed in units of... , Standard ambient atmospheric pressure, unit: , The target open area ratio is expressed as a decimal. The target average aperture, in units of , This is the correlation coefficient, and its value ranges from 0.15 to 0.25. Furthermore, online calibration is performed based on the zero-shear viscosity of the foaming system; in the production process of the polyurethane porous skeleton, the controller adjusts the pressure value. At -0.05 to -0.08 The temperature range is adjusted to compensate for changes in cell wall strength caused by fluctuations in the isocyanate index, maintaining an open porosity above 90%. When the sensor detects that the temperature rise rate of the foaming system exceeds the preset slope, the controller reduces the vacuum level to suppress cell coalescence and control the average pore size at 100 mm. Up to 300 Within the window, the pressure gradient is used to compensate for the phase separation kinetics, eliminating the interference of equipment size effect on the skeleton morphology.

[0039] To address the sudden jump in local strain energy caused by hard segment dissociation during shape recovery, this embodiment determines the amount of branched monomer to be added by quantifying the energy dissipation power in the damping phase region. The intramolecular frictional work generated when the branched segments dissociate at the physical crosslinking points is also considered. Satisfy mapping relationship ,in, Intramolecular frictional work, unit: , This represents the molar percentage of branched monomers. The product represents the functionality of the branched monomer. The branching point density within the damping phase region is determined. In step S2, the molar percentage of branched monomers is determined based on the change in the kinetic viscosity of the prepolymer. It is 0.65% and has a functionality The damping volume fraction formed by the branched segments at the edge of the hard segment aggregation region dissipates more than 85% of the transient elastic potential energy within the initial 10 seconds of shape recovery, suppressing the fluctuation amplitude of the radial restoring force to below 5%. This allows the stent to maintain a stable rate in physiological fluids of different polarities. The amount of polarity adjustment factor added is adapted according to the polarity index of the external fluid, and the mass fraction of the polarity adjustment factor... Following the decision logic, when the wetting pressure of the external fluid exceeds a preset safety threshold, the content of the polydimethylsiloxane oligomer at the end caps is increased to 4.5%, utilizing the hydrophobic microregions on the microporous wall surface to generate... Additional resistance hinders the penetration of polar water molecules into the polyurethane hard segment aggregation region, ultimately resulting in a porous polyurethane framework at 37°C. The shape recovery time under simulated blood conditions was 82.4 s, and the relative deviation of the recovery rate was less than 3% in five consecutive batches of repeatability validation.

[0040] Example 5: In the production calibration scenario for different batches of polyether polyol raw materials, due to the fluctuations in the hydroxyl value and molecular weight distribution of the raw materials, the zero shear viscosity of the foaming system will deviate and interfere with the determination of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient

[0041] When the polyurethane porous scaffold is deployed in a physiological fluid environment containing electrolyte ions, in order to exclude the interference of environmental background components on the shape recovery rate monitoring signal, the system performs a signal reference locking procedure based on the zero strain state before intervention deployment, immerses the porous scaffold in an isotonic solution with an osmotic pressure of 280 to 320 The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficient The determination value of the correlation coefficientWithin the specified range, it is determined that the internal physical cross-linked network has not been damaged by the axial friction force generated during the introduction process. Using a pre-locking signal reference, the porous framework is within 37... Under physiological conditions, the intramolecular frictional energy dissipates elastic strain energy generated by branched chain segments, producing a constant radial expansion force output.

[0042] Example 6: In a cross-batch isocyanate index stability verification scenario, to establish the aforementioned correlation coefficient To establish a quantitative benchmark and eliminate uncertainties in the initial state of the material, the system executes an offline standard sample calibration procedure, selecting a molecular weight distribution index of [missing value]. Using standard polyether polyols as reference materials, the mixture was subjected to constant temperature of 25°C. The reference viscosity was measured in a controlled environment with relative humidity below 5%. A standard-shaped test skeleton was prepared and placed on a negative pressure foaming platform. The foaming pressure was changed. The evolution of the bubble structure was observed, and linear regression analysis was performed on multiple sets of measured data using the least squares method. When the sum of squared residuals was less than 0.05, the slope of the regression curve was determined to be the benchmark correlation coefficient. This is used as a constant input in the production control loop to achieve different batches of raw material viscosity. Foaming pressure Logic lock for adjusting sensitivity.

[0043] When the system is applied to the online quality monitoring process of interventional devices, it is necessary to determine the static stability threshold of stress-sensitive molecular probes. To eliminate interference from non-destructive deformation of the import path, the system executes a preset stress gradient cyclic calibration procedure. Using an electronic tensile testing machine with a resolution better than 0.01 N, an axial cyclic load of 0.1 to 0.5 N is applied to a sample containing 0.1% by mass of spiropyran-type chromophores to simulate the frictional contact conditions of the duct's inner wall. Color components are acquired in real time. The curves showing the change with the number of cycles were analyzed to identify the elastic range of the color development response. A threshold of 1.2 times the maximum color component deviation within this range was selected as the static stability threshold. During the process of introducing the porous skeleton into the vascular lesion site, the controller calculates the difference between the measured color component and the initial color component in real time and compares it with the static stability threshold. Comparison: If the difference remains within the static stability threshold Within the specified range, the controller determines that the internal physical cross-linked network has not been damaged by the introduced frictional force; in the molding process of the polyurethane porous skeleton, the system sets the speed range of the stirring device to 500 to 800. The mixed components containing sterically hindered chain extenders were added dropwise at a uniform rate over a period of 5 minutes. The inner injection modified prepolymer system, by monitoring the dynamic viscosity value of the reaction system, when the viscosity reaches 15 The molding threshold value, the discharge operation is performed and introduced into the negative pressure molding mold, the heat setting and solvent removal treatment is performed for 24 hours in a vacuum environment with a temperature of and a pressure value of -0.09 , to obtain the finished product framework with the target open hole structure and rate response characteristics.

[0044] The embodiments of the present application are described above in combination with the drawings, the embodiments in the present application and the features in the embodiments can be combined with each other without conflict, the present application is not limited to the above specific embodiments, the above specific embodiments are only illustrative, but not limited, the ordinary skilled in the art can make many forms without departing from the purpose of the present application and the scope protected by the claims under the inspiration of the present application, all of which belong to the protection of the present application.

Claims

1. A method for precisely controlling the shape recovery rate of a polyurethane porous framework, characterized in that, The method comprises the following steps: Step S1, mixing and pre-polymerizing a polyether polyol with an isocyanate at 60 to 80 temperature to produce an isocyanate group-terminated urethane prepolymer; Step S2, adding a branched monomer with a mole percentage of 0.4% to 0.9% in the polyurethane prepolymer to perform an in-situ chain extension reaction, so as to construct a branched segment with a free end on the polyurethane molecular chain, and generate a modified prepolymer; The branched monomer is a branched polyol with a functionality greater than or equal to 3 and a molecular weight less than 500; Step S3, mixing the modified prepolymer with a diamine chain extender with a steric hindrance characteristic and a foaming aid to form a polyurethane porous framework with a microphase separation structure through an in-situ foaming reaction; the diamine chain extender forms a dissociation energy barrier defined by a side chain steric hindrance effect inside the hard segment microphase region, and a physical crosslinking point is established by the hard segment microphase region inside the polyurethane porous framework; Step S4, using the damping phase region formed by the branched segment at the interface between the hard segment and the soft segment to dissipate the elastic strain energy accumulated inside the polyurethane porous framework when the physical crosslinking point crosses the dissociation energy barrier, and using the internal friction of the molecular segment of the damping phase region to inhibit the fluctuation of the chain relaxation rate, so that the polyurethane porous framework generates a constant radial expansion force output; The addition amount of the branching monomer is determined according to the side chain steric hindrance volume of the diamine chain extender, and the ratio of the branching monomer to the diamine chain extender satisfies the following quantitative rule: wherein, is the preset mole percentage of the branching monomer in step S2, is the functionality of the branching monomer, is the mole percentage of the diamine chain extender put in step S3; the arrangement density of the branched chain segment in the damping phase region is limited by the quantitative rule, so that the fluctuation amplitude of the radial recovery force of the polyurethane porous skeleton in the shape recovery process is less than 10%. In step S3, the diamine chain extender is an aromatic diamine with a symmetrical side group structure to improve the uniformity of the distribution of the physical crosslinking point inside the hard segment microphase region; the aromatic diamine with a symmetrical side group structure is 3,3'-dichloro-4,4'-diamino diphenyl methane; In addition, a fluorocarbon chain segment adjusting monomer is added in step S3 to form a biologically inert interface on the pore wall surface of the polyurethane porous framework, and a polar adjusting factor with a mass percentage of 2.5% to 5.0% is added, and the polar adjusting factor is a terminal blocked polydimethylsiloxane oligomer.

2. The method of claim 1, wherein the shape recovery rate of the polyurethane porous framework is precisely controlled. In step S1, the molecular weight of the polyether polyol is 1000 to 4000, and the hydroxyl value is 28 to 56 mgKOH / g.

3. The method of claim 1, wherein the shape recovery rate of the polyurethane porous framework is precisely controlled. In step S3, the in-situ foaming reaction is performed in a negative pressure environment with a pressure value of -0.05 MPa to -0.08 MPa to adjust the open porosity of the polyurethane porous framework, so that the open porosity is not less than 90% and the average pore size is 100 μm to 300 μm.

4. The method of claim 1, wherein the shape recovery rate of the polyurethane porous framework is precisely controlled. The radial expansion force output is verified by the following steps: compressing the polyurethane porous framework to 20% of the original volume and releasing at the shape recovery trigger temperature, and collecting the change curve of the radial expansion force of the polyurethane porous framework with displacement in the shape recovery process by a dynamic thermodynamic analyzer.

5. The method of claim 1, wherein the shape recovery rate of the polyurethane porous framework is precisely controlled. Polyurethane porous scaffolds for vascular interventional instruments at 37 The shape fully recovery time in a physiological saline environment is 30 s to 120 s.

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