Method for accurately regulating and controlling shape recovery rate of polyurethane porous skeleton

Abstract

The invention relates to the technical field of shape memory high-molecular polymers, and discloses a method for accurately regulating and controlling the shape recovery rate of a polyurethane porous framework, which comprises the following steps of: reacting polyether polyol with isocyanate to generate a blocked prepolymer, introducing a multi-branched monomer to construct a branched chain segment with a free tail end on a polyurethane molecular chain, and carrying out polymerization reaction to obtain the shape recovery rate of the polyurethane porous framework. The preparation method comprises the following steps: adding a diamine chain extender with steric hindrance characteristics to carry out foaming reaction, and setting a dissociation energy barrier of a hard segment micro-phase region by utilizing a side chain steric hindrance effect of the chain extender, so that a damping phase region formed by a branched chain segment on an interface of a hard segment and a soft segment is utilized, and accumulated elastic strain energy is dissipated through friction in the chain segment at the instant of dissociation of a physical cross-linking point; the stress kick in the shape recovery process is inhibited, so that the porous skeleton generates constant radial expansion force output, and the use safety of the vascular interventional instrument is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of shape memory polymer technology, and particularly relates to a method for precisely controlling the shape recovery rate of a polyurethane porous framework. Background Technology

[0002] Currently, porous polyurethane frameworks, due to their deformation recovery properties and microporous structure, are often introduced into predetermined locations in a compressed state via a delivery system. They recover their initial shape under thermal response or fluid wetting. This recovery kinetics is jointly determined by the dissociation resistance of the hard segment physical crosslinking points within the polymer and the relaxation kinetics of the soft segment chains. When external environmental excitation exceeds the glass transition temperature trigger threshold, the elastic strain energy stored within the porous framework is released. Due to the polarity difference between the hard and soft segments of polyurethane, discontinuous energy transitions easily occur in the hard segment aggregation region during dissociation, causing the porous framework to generate instantaneous rebound mechanical pulses in the early stages of shape recovery. This can easily cause mechanical damage to the intima of microvessels. Existing technologies typically use methods such as increasing material density or improving chemical crosslinking density to suppress the recovery rate. While reducing the recovery rate, this also reduces the effective permeability of the porous framework and fails to eliminate the stick-slip phenomenon during polymer chain relaxation. This results in nonlinear fluctuations in the radial pressure output during shape recovery, limiting the safety of the framework in complex biochemical fluid environments.

[0003] Besides the limitations of the overall morphology of the skeleton, the lack of a single means of dynamic control for the relaxation process of molecular chain segments is a key issue restricting the stable output of mechanics. For example, Chinese invention patent CN101033286A discloses a shape memory polyurethane yarn and fabric, which achieves shape memory function through a block structure composed of a fixed phase and a reversible phase. The design logic is anchored to the shape preservation of the fabric fiber morphology, without addressing the capture and dissipation of instantaneous local elastic potential energy during shape recovery. In the context of vascular intervention, the solution lacks precise definition of the hard segment dissociation energy barrier, and the interface between soft and hard segments lacks a molecular-level damping buffer mechanism, making the recovery trajectory highly sensitive to the polarity of the environmental fluid and causing unexpected fluctuations in the recovery rate. In addition, the internal physical microphase structure is at risk of instability during long-term compressed storage, and there is a lack of in-situ detection methods for recovery efficiency.

[0004] Therefore, the technical problem to be solved by this invention is how to construct a self-regulating molecular-level damping structure without changing the intrinsic strength of the material, and to achieve a platform-based output of the shape recovery rate of the porous skeleton. Summary of the Invention

[0005] This invention provides a method for precisely controlling the shape recovery rate of a polyurethane porous skeleton, comprising the following steps:

[0006] Step S1, the polyether polyol and isocyanate are heated at 60°C. Up to 80 The mixture is mixed at a certain temperature and undergoes a prepolymerization reaction to generate an isocyanate-terminated polyurethane prepolymer.

[0007] Step S2: In the polyurethane prepolymer, a branched monomer with a molar percentage of 0.4% to 0.9% is added to carry out an in-situ chain extension reaction to construct branched segments with free ends on the polyurethane molecular chain to 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.

[0008] Step S3: The modified prepolymer is mixed with a diamine chain extender with steric hindrance characteristics and a foaming agent to form a polyurethane porous skeleton with a microphase separation structure through an in-situ foaming reaction; the diamine chain extender is used to form a dissociation energy barrier defined by the side chain steric hindrance effect in the hard segment microphase region, and physical crosslinking points are established in the polyurethane porous skeleton by the hard segment microphase region.

[0009] Step S4 utilizes the damping phase region formed by the branched chain segments at the interface between the hard and soft segments. At the instant when the physical cross-linking point crosses the dissociation energy barrier and dissociates, the elastic strain energy accumulated inside the polyurethane porous skeleton is dissipated. The internal friction of the molecular chain segments in the damping phase region is used to suppress the fluctuation of the chain segment relaxation rate, so that the polyurethane porous skeleton generates a constant radial expansion force output.

[0010] Preferably, the amount of branched monomer added is determined based on the steric hindrance volume of the diamine chain extender, and the ratio of branched monomer to diamine chain extender satisfies the following quantitative rule: ,in, The molar percentage of branched monomers preset in step S2. The functionality of branched monomers, The molar percentage of the diamine chain extender added in step S3; the distribution density of branched segments in the damping phase region is limited by quantitative rules, so that the radial restoring force fluctuation amplitude of the polyurethane porous skeleton during the shape recovery process is less than 10%.

[0011] Preferably, the steric hindrance characteristic diamine chain extender is selected from 2,2'-dichloro-4,4'-dimethylenebisphenylamine and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0012] Preferably, step S3 includes: limiting the topological crosslinking density of the hard segment microphase region by adjusting the isocyanate index of the isocyanate and the hydroxyl groups in the modified prepolymer, so that the shape recovery trigger temperature of the polyurethane porous framework is 35°C. Up 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 mg KOH / g.

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

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

[0016] Preferably, the radial expansion force output is verified by the following steps: compressing the polyurethane porous skeleton to 20% of its original volume and releasing it at the shape recovery trigger temperature, and collecting the radial expansion force of the polyurethane porous skeleton as a function of displacement during the shape recovery process using a dynamic thermodynamic analyzer.

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

[0018] Preferably, the polyurethane porous framework for vascular interventional devices is at 37°C. The shape fully recovers in a saline environment in 30 to 120 seconds.

[0019] Compared with existing technologies, the method for precisely controlling the shape recovery rate of polyurethane porous skeletons in this invention has the following advantages: In the shape recovery rate of polyurethane porous skeletons, the diamine chain extender with steric hindrance characteristics constructs a diffusion barrier inside the hard segment microphase region, setting the dissociation resistance of the physical crosslinking points of the hard segments, so that the synergistic relaxation of polyurethane chain segments during the shape recovery process changes from an instantaneous burst to restricted diffusion, thereby generating a continuous and uniform expansion characteristic of the porous skeleton, eliminating the radial impact force generated at the moment of rebound; secondly, the branched ends of the branching dissipation factor and the side chains of the steric hindrance chain extender form physical entanglement, constructing a high-damping transition region at the interface between hard and soft segments, and using the molecular-level viscous chain pendulum effect to dissipate the local instantaneous elastic strain energy during the dissociation process of hard segments, suppressing high molecular weight loss. The stick-slip phenomenon during sub-segment relaxation enables the porous framework to exhibit a mechanical response characteristic of constant radial pressure output. During the in-situ foaming process of low surface energy segments and polarity regulating factors, they migrate directionally to the surface of the micropore walls, constructing a composite diffusion barrier. The low surface energy segments generate friction reduction when the micropore walls undergo relative displacement, while the hydrophobic micro-regions formed by the polarity regulating factors impede the penetration and diffusion of external fluid polar molecules into the soft segments, allowing the shape recovery rate to maintain a preset response trajectory in complex biochemical fluid environments. Furthermore, the supramolecular monomers with cyclic structures interspersed between polyurethane molecular chains lock the spatial arrangement of the hard segment microphase regions through physical entanglement and act as topological sliding tracks to maintain the stress stability of the porous framework under compressed storage conditions, eliminating the recovery rate drift caused by long-term stress. Attached Figure Description

[0020] Figure 1 This is a flowchart of the preparation process and implementation steps of the method for precisely controlling the shape recovery rate of polyurethane porous skeleton according to the present invention;

[0021] Figure 2 This is a block diagram illustrating the technical mechanism and full-cycle logic architecture of the method for precisely controlling the shape recovery rate of polyurethane porous skeletons according to the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0023] It should be noted that all directional and positional terms used in this invention, 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 and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0024] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication between two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0025] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0026] A method for precisely controlling the shape recovery rate of a porous polyurethane framework includes a synthesis stage of isocyanate-terminated prepolymer, an in-situ modification stage of branched segments, a foaming and locking stage for establishing physical crosslinking points, and a shape recovery stage regulated by a damping phase region. By introducing hard segments with steric hindrance characteristics and a damping phase region composed of branched segments into the polyurethane molecular chain, a dynamic mechanism constrained by the dissociation energy barrier defined by side chain steric hindrance and intra-segment friction is established, achieving a controlled and stable output of the porous framework's shape recovery rate. Step S1 involves mixing polyether polyol and isocyanate at 60°C. Up to 80 The mixture is mixed at a specific temperature and subjected to a prepolymerization reaction to generate an isocyanate-terminated polyurethane prepolymer. The polyether polyol has a molecular weight of 1000 to 4000 and a hydroxyl value of 28 to 56. During the reaction, the isocyanate index is maintained within the range of 1.15 to 1.25 to ensure that the prepolymer molecular chain segments have a preset segment length distribution. Due to the polarity difference between the hard and soft segments of polyurethane, the hard segment aggregation region is prone to discontinuous energy release during dissociation. To address this challenge, the system introduces branched dissipative structures into the molecular chain. In step S2, 0.4% to 0.9% of a branched monomer is added to the polyurethane prepolymer to carry out an 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. This branched monomer forms nonlinear branching points on the polyurethane molecular chain. Utilizing the wobbling effect of the branched ends, a damping phase region is constructed at the interface between the subsequently formed hard and soft segments.

[0027] To address potential mechanical pulse fluctuations during shape recovery, the system employs steric hindrance to set the dissociation resistance of the physical crosslinking points in the hard segments. In step S3, the modified prepolymer is mixed with a diamine chain extender exhibiting steric hindrance characteristics and a foaming agent. An in-situ foaming reaction forms a porous polyurethane framework with a microphase separation structure. The steric hindrance diamine chain extender is selected from 2,2'-dichloro-4,4'-dimethylenebisphenylamine or 3,3'-dichloro-4,4'-diaminodiphenylmethane. The diamine chain extender creates a dissociation energy barrier defined by the side-chain steric hindrance effect within the hard segment microphase region, and physical crosslinking points are established within the polyurethane porous framework from the hard segment microphase region. By adjusting the isocyanate index of the isocyanate and the hydroxyl groups in the modified prepolymer, the topological crosslinking density of the hard segment microphase region is limited, ensuring that the shape recovery trigger temperature of the polyurethane porous framework is maintained at 35°C. Up to 42 In the construction of the hard segment microphase region, differential scanning calorimetry was used to limit the dissociation energy barrier with a feedback adjustment program. Test samples were prepared using a reference isocyanate index of 1.20, and the peak temperature of the hard segment phase transition was measured. Characterizing the dissociation activity of physical crosslinking points, experimental measurement Below 35 At that time, the isocyanate dosage was increased in 0.02 step increments to achieve the peak temperature. At 35 Up to 42 To compensate for the deviation in isocyanate group consumption caused by trace residual moisture in raw materials, the dissociation energy barrier inside the hard segment microphase region is established to meet the preset kinetic threshold. In order to improve the stress stability of the polyurethane porous skeleton during long-term compression storage and prevent the shape recovery rate from drifting over time, cyclic supramolecular monomers with a mass percentage of 1.5% to 3.0% are introduced into the preparation process. Hydroxypropyl betacyclodextrin is selected as the cyclic supramolecular monomer. The cyclic molecular cavity forms a non-covalent physical interpenetration structure with the polyurethane chain segment. When the porous skeleton is in a compressed state, it acts as a topological sliding track to dissipate the rearrangement stress of the molecular chain segment, suppress the plastic deformation of the hard segment microphase region under long-term load, and ensure that the physical crosslinking point maintains the preset dissociation energy barrier before the shape recovery is triggered.

[0028] Step S4 utilizes the damping phase region formed by branched segments at the interface between hard and soft segments. At the instant the physical crosslinking point crosses the dissociation energy barrier and dissociates, the elastic strain energy accumulated within the porous polyurethane framework is dissipated. The friction within the molecular chain segments of the damping phase region suppresses fluctuations in the chain segment relaxation rate, resulting in a constant radial expansion force output from the porous polyurethane framework. The shape recovery process is controlled by the entropy increase generated by the friction within the chain segments, thereby converting the stored elastic potential energy into stable heat dissipation. In the adjustment of radial force fluctuations during shape recovery, a dynamic thermodynamic analysis damping factor calibration procedure is used. Determination of loss factor of polyurethane porous skeleton under certain conditions Based on the strain recovery path distribution curve, when the radial force fluctuation amplitude exceeds 10%, it is determined according to the quantization rule. Increase the molar percentage of branched monomers Increase the branching density at the ends of the damping phase region to improve the frictional dissipation power within the molecular chain segments. This makes the radial force output trajectory smoother and the fluctuation value return to within 10%, achieving programmed constraint on the elastic strain energy release rate; to achieve quantitative limitation on shape recovery stability, the amount of branched monomer added is determined based on the steric hindrance volume of the diamine chain extender, and the ratio of branched monomer to diamine chain extender satisfies the following quantitative rule: ,in, The molar percentage of branched monomers preset in step S2. The functionality of branched monomers, The molar percentage of the diamine chain extender added in step S3 is used to limit the distribution density of branched segments in the damping phase region through quantitative rules, so that the radial restoring force fluctuation of the polyurethane porous skeleton during the shape recovery process is less than 10%.

[0029] The in-situ foaming reaction is carried out under a negative pressure environment with a pressure value of -0.05MPa to -0.08MPa to adjust the open porosity of the polyurethane porous skeleton, so that the open porosity is not less than 90% and the average pore size is 100. Up to 300 In addition, in step S3, a fluorocarbon segment regulating monomer is added to form a bio-inert interface on the pore wall surface of the polyurethane porous framework. Simultaneously, a polar regulating factor of 2.5% to 5.0% by mass is added. This polar regulating factor is an end-capped polydimethylsiloxane oligomer. During foaming, the polar regulating factor segregates to the pore wall surface and forms a hydrophobic shielding region to reduce the interference of external environmental fluids on the polyurethane segment relaxation rate, allowing the porous framework to maintain a stable foaming rate at 37°C. The shape recovery time under physiological saline conditions ranged from 30 to 120 seconds. To verify the effectiveness of the radial expansion force output, the polyurethane porous skeleton was compressed to 20% of its original volume and released at the shape recovery trigger temperature. The radial expansion force of the polyurethane porous skeleton during the shape recovery process was collected using a dynamic thermodynamic analyzer. When preparing the prepolymer or carrying out the chain extension reaction, a stress-sensitive molecular probe with a mass percentage of 0.05% to 0.2% was added, specifically a spiropyran-type chromophore. The stress-sensitive molecular probe characterizes the structural integrity of the hard segment microphase region through color status. If a red shift of the characteristic absorption peak of the chromophore is detected, it indicates that stress relaxation or microcrack growth has occurred in the internal physical cross-linking network, thus providing a visual verification basis for the effectiveness of the shape recovery rate.

[0030] Example 1: In the vascular reconstruction scenario of intracranial aneurysm interventional embolization, the inner wall of microvessels is highly sensitive to radial force fluctuations generated during the expansion of the polyurethane porous framework. Furthermore, the elastic strain energy accumulated by the shape memory polymer after crossing the shape recovery trigger temperature tends to be released explosively. Using the aforementioned specific implementation method, a molecular weight of 2000 and a hydroxyl value of 56 were selected. Polyether polyols and isocyanates at 75 An isocyanate-terminated prepolymer is generated through a reaction under environmental conditions, and 0.5% of a functional group is added during the in-situ chain extension stage. The compound is 3% trimethylolpropane, with 0.8% 2,2'-dichloro-4,4'-dimethylenebisphenylamine as a steric hindrance chain extender. The steric hindrance effect of the side chains of the steric hindrance chain extender sets the dissociation energy barrier at the physical crosslinking points. Combined with branched segments generated by branched monomers, a damping phase region with intramolecular friction characteristics is constructed at the edge of the hard segment microphase region, resulting in the calculated characteristic ratio. The value is 1.875, falling within the quantization range of 1.2 to 2.5, when the porous framework is at 37... When shape recovery is triggered under physiological conditions, the damping phase region captures and dissipates the local elastic strain energy released instantaneously during hard segment dissociation, eliminates the stick-slip phenomenon during chain segment relaxation, and transforms the accumulated strain energy into a smooth expansion with constant radial pressure output.

[0031] During the continuous operation of the porous framework in contact with physiological fluids, the solvation and plasticization effect of saline molecules on the polyurethane soft segments can cause unexpected fluctuations in the recovery rate. To address this, a 3.5% (by mass) polarity modifier, specifically an end-capped polydimethylsiloxane oligomer, is introduced during the in-situ foaming stage. This modifier chemically anchors the isocyanate groups in the prepolymer and constructs a composite diffusion barrier on the micropore wall surface, composed of the polarity modifier and fluorocarbon segments. The low surface energy fluorocarbon segments reduce interfacial frictional resistance, while the hydrophobic microdomains formed by the polarity modifier impede the penetration path of external fluid molecules. This transforms the recovery kinetics of the porous framework from environmentally sensitive to structurally dependent. The shape recovery time is controlled to ensure that it remains stable within a window of 30s to 120s. After the porous skeleton completely fills the aneurysm cavity and enters a stable filling state, the integrity of the internal physical cross-linking network is verified by collecting the color development state of a spiropyran-type stress-sensitive molecular probe with a mass percentage of 0.1%. When the characteristic absorption peak of the chromogenic molecule is detected without redshift, it is determined that the dissociation energy barrier of the physical cross-linking point and the frictional dissipation mechanism of the branched chain segments support the safety of the porous skeleton under extreme constraint environment. In this embodiment, by introducing dissipation units at the molecular scale, the overall mechanical pulse is dissolved into the internal frictional work between chain segments, thereby completing the programmed control of the shape recovery rate of the polyurethane porous skeleton.

[0032] Example 2: In the mechanical response characteristics verification test of polyurethane porous skeleton for vascular interventional embolization, a dynamic thermodynamic analysis platform equipped with a load sensor with a resolution of 0.01N and a sampling frequency of 10Hz was selected. This platform has a sensing boundary sufficient to capture the strain energy release pattern during chain segment relaxation. The experimental data came from a physical experimental platform simulating a physiological environment. Phosphate buffer was injected into the test cell, and periodic pressure fluctuations generated by a circulating pump were introduced as background noise interference. The sampling period setting needed to balance the real-time performance of signal acquisition with the system load of data processing. The slope of the monitored radial force change was... Exceeding the preset fluctuation threshold At this time, the sampling frequency is increased to 50Hz to avoid signal aliasing. This represents the change in radial force, expressed in nanometers (N). The increment is time, measured in seconds (s). The fluctuation threshold is expressed in units of... The adjustment of the sampling frequency ensured a complete record of the transient release of local elastic strain energy. The test process was carried out by performing isothermal strain recovery tests on polyurethane porous skeletons with different components. Each group of samples was compressed to 20% of its original volume and locked, and placed at 37°C. In phosphate buffer.

[0033] Table 1: Comparison of Shape Recovery Performance of Polyurethane Porous Skeleton

[0034]

[0035] Refer to the test results in Table 1, the eigenvalues ​​of experimental groups 1 to 3. Within the quantization range of 1.2 to 2.5, the radial force fluctuation amplitude is less than 10%, and the complete shape recovery time is stable within a preset window of 30s to 120s. This represents the molar percentage of branched monomers. The functionality of branched monomers, The molar percentage of the diamine chain extender is shown in the figure. Comparing the data with control group 3, it can be found that under the condition of lacking branched monomers to construct the damping phase region, the radial force fluctuation amplitude increases to 35.4%, exhibiting transient strain energy burst characteristics. When the characteristic ratio is below 1.2, as shown in control group 1, the intra-segment frictional work provided by the branched segments is insufficient to completely dissipate the local elastic potential energy released instantaneously by the dissociation of hard segments, resulting in a jump-like mechanical response. When the characteristic ratio exceeds 2.5, as shown in control group 2, although the mechanical stability is better, the excessively high frictional energy barrier between chain segments leads to a sharp decrease in the recovery rate, with the recovery time extended to 186.7 s. This indicates that there is a performance inflection point in the ratio of the product of the functionality and content of the branched monomer to the content of the steric hindrance chain extender, which is particularly relevant for extreme... The plasticization interference caused by the infiltration of the polar fluid was analyzed by comparing the data of experimental group 2, control group 4, and control group 5. Experimental group 2, by adding a polarity regulating factor of 3.5% by mass, formed a hydrophobic shielding zone on the surface of the micropore wall, locking the recovery time at 75.3s. In control group 4, due to the addition of polarity regulating factor of less than 2.5%, the hydrophobic barrier coverage was incomplete, which led to the rapid infiltration and plasticization of polyurethane segments by external fluid molecules, shortening the recovery time to 28.5s and accompanied by rate fluctuations. When the addition exceeded the saturation limit of 5.0%, as shown in control group 5, the excessive polarity regulating factor component underwent phase separation in the system, which not only failed to maintain the stability of the recovery rate, but also weakened the physical cross-linking network strength, resulting in insufficient recovery motive force.

[0036] Example 3: This example combines Figures 1 to 2 A method for precisely controlling the shape recovery rate of a porous polyurethane framework is explained, such as... Figure 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 Figure 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 fully recovered in a simulated blood environment in 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, the fluctuations in the hydroxyl value and molecular weight distribution of the raw materials can cause a shift in the zero-shear viscosity of the foaming system and interfere with the correlation coefficient. The determined value is achieved by utilizing a measurement range covering 0.01 to 100. And the temperature control accuracy is better than A rotational rheometer was used to collect data on the material during the initial stage of foaming at a shear rate of 0.1. Complex viscosity under certain conditions And combined with the target aperture ratio Calculate the correlation coefficient Correction value, correlation coefficient The following mapping relationship is satisfied: ,in, The corrected correlation coefficient is expressed in units of 1000 ppm. , The baseline correlation coefficient for the standard sample is 0.20. , The base batch of raw materials is at 25 Reference viscosity under the given conditions, in units of , The measured complex viscosity of the current batch of raw material to be processed, in units of... By feeding back the measured rheological parameters to the negative pressure foaming control loop, the porous skeleton can adjust the foaming pressure during the production process. To compensate for the resistance to cell expansion caused by viscosity fluctuations and maintain the average pore size Stable at 100 Up to 300 Within the range.

[0041] When a polyurethane porous framework is deployed in a physiological fluid environment containing electrolyte ions, to eliminate interference from background components on the shape recovery rate monitoring signal, the system performs a signal reference locking procedure based on a zero-strain state before deployment, immersing the porous framework in an osmotic pressure of 280 to 320. The initial characteristic absorption peak intensity of the spiropyran-type stress-sensitive molecular probe was collected in an isotonic solution. With the initial color components , where subscript This represents the initial state before shape recovery begins, thus determining the baseline zero point for subsequent monitoring. During the process of the porous framework being introduced into the vascular lesion site via catheter, the controller calculates in real-time the changes in the color characteristics of the chromophore molecules in the current environment and the initial color components. The difference, when the difference remains within the preset static stability threshold. Within 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. An internally injected modified prepolymer system was used. By monitoring the dynamic viscosity of the reaction system, when the viscosity reached 15... When the molding threshold is reached, the discharge operation is performed and the material is introduced into the negative pressure molding mold at a temperature of [temperature value missing]. And the pressure value is -0.09. Perform 24 hours in a vacuum environment Heat setting and solvent removal processes were performed to obtain a finished skeleton with the target open-pore structure and rate response characteristics.

[0044] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for precisely controlling the shape recovery rate of a polyurethane porous skeleton, characterized in that, Includes the following steps: Step S1, the polyether polyol and isocyanate are heated at 60°C. Up to 80 The mixture is mixed at a certain temperature and undergoes a prepolymerization reaction to generate an isocyanate-terminated polyurethane prepolymer. Step S2: In the polyurethane prepolymer, a branched monomer with a molar percentage of 0.4% to 0.9% is added to carry out an in-situ chain extension reaction to construct branched segments with free ends on the polyurethane molecular chain and generate a modified prepolymer. The branched monomers are branched polyols with a functionality of 3 or more and a molecular weight of less than 500. Step S3: The modified prepolymer is mixed with a diamine chain extender with steric hindrance characteristics and a foaming agent to form a polyurethane porous skeleton with a microphase separation structure through an in-situ foaming reaction; the diamine chain extender is used to form a dissociation energy barrier defined by the side chain steric hindrance effect in the hard segment microphase region, and physical crosslinking points are established in the polyurethane porous skeleton by the hard segment microphase region. Step S4 utilizes the damping phase region formed by the branched chain segments at the interface between the hard and soft segments. At the instant when the physical cross-linking point crosses the dissociation energy barrier and dissociates, the elastic strain energy accumulated inside the polyurethane porous skeleton is dissipated. The internal friction of the molecular chain segments in the damping phase region is used to suppress the fluctuation of the chain segment relaxation rate, so that the polyurethane porous skeleton generates a constant radial expansion force output.

2. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, The amount of branched monomer added is determined based on the steric hindrance volume of the diamine chain extender, and the ratio of branched monomer to diamine chain extender satisfies the following quantitative rule: ,in, The molar percentage of branched monomers preset in step S2. The functionality of branched monomers, The molar percentage of the diamine chain extender added in step S3; the distribution density of branched segments in the damping phase region is limited by quantitative rules, so that the radial restoring force fluctuation amplitude of the polyurethane porous skeleton during the shape recovery process is less than 10%.

3. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, The steric hindrance characteristics of the diamine chain extender are selected from 2,2'-dichloro-4,4'-dimethylenebisphenylamine and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

4. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, Step S3 includes: limiting the topological crosslinking density of the hard segment microphase region by adjusting the isocyanate index of the isocyanate and the hydroxyl groups in the modified prepolymer, so that the shape recovery trigger temperature of the polyurethane porous framework is 35°C. Up to 42 .

5. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, In step S1, the polyether polyol has a molecular weight of 1000 to 4000 and a hydroxyl value of 28 to 56 mg KOH / g.

6. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, Step S3 further includes: adding fluorocarbon segment modulator monomers to form a bio-inert interface on the pore wall surface of the polyurethane porous framework using fluorocarbon segment modulator monomers.

7. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, In step S3, the in-situ foaming reaction is carried out under a negative pressure environment with a pressure value of -0.05MPa to -0.08MPa to adjust the open porosity of the polyurethane porous skeleton so that the open porosity is not less than 90% and the average pore size is 100μm to 300μm.

8. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, The radial expansion force output was verified through the following steps: the polyurethane porous skeleton was compressed to 20% of its original volume and released at the shape recovery trigger temperature. The radial expansion force of the polyurethane porous skeleton during the shape recovery process was collected using a dynamic thermodynamic analyzer.

9. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, 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 physical crosslinking points within the hard segment microphase region.

10. The method for precisely controlling the shape recovery rate of a polyurethane porous skeleton according to claim 1, characterized in that, Polyurethane porous framework for vascular interventional devices at 37 The shape fully recovers in a saline environment in 30 to 120 seconds.

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