Degradable dynamic crosslinking silicone rubber composition and preparation method thereof

Abstract

The invention discloses a degradable dynamic cross-linked silicone rubber composition and a preparation method thereof, and belongs to the technical field of organic silicon materials. The composition is prepared from the following components in parts by mass: 100 parts of methyl vinyl silicone rubber raw rubber, 10 to 30 parts of dynamic cross-linking agent (siloxane copolymer containing disulfide bonds), 10 to 30 parts of biodegradable block (polycaprolactone-siloxane copolymer), 3 to 10 parts of modified cellulose nanocrystal, 0.1 to 2 parts of photosensitizer (benzophenone derivative) and 0.05 to 0.5 part of platinum catalyst. The dynamic cross-linking agent is an addition product of tetra (3-mercaptopropyl) siloxane and diacrylate siloxane, and the disulfide bond density of the dynamic cross-linking agent is 2-5 mmol / g. According to the invention, through the synergistic effect of the dynamic disulfide bond and the polycaprolactone block, efficient self-repairing and controllable enzymatic / photopromoted degradation of the material at room temperature are realized. After the nanocrystalline of the modified cellulose is introduced, the tensile strength is greater than 8.5 MPa, and the elongation at break reaches 680%.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic silicon materials, and specifically relates to a silicone rubber composition with dynamic covalent bonds and biodegradable properties and a preparation method thereof, which is suitable for medical implants, environmentally friendly packaging, flexible electronic devices and other fields. Background Art

[0002] Silicone rubber is widely used in electronic packaging, medical devices, aerospace, and other fields due to its excellent heat resistance, weather resistance, electrical insulation, and flexibility. Traditional silicone rubber primarily achieves mechanical stability through a permanent covalent cross-linked network, resulting in an insoluble and infusible three-dimensional network structure upon curing. While this structure imparts high mechanical strength, it also has significant drawbacks such as non-recyclability, biological inertness, and a single function. Dynamic covalent bonds, a type of chemical bond that reversibly breaks and reconstructs under specific stimuli (heat, light, pH), offer new insights into balancing material stability and recyclability. Summary of the Invention

[0003] The purpose of the present invention is to solve the problems of insufficient degradability and poor functional compatibility of dynamic silicone rubber, and to provide a degradable dynamically cross-linked silicone rubber composition and a preparation method thereof.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows: A degradable dynamically cross-linked silicone rubber composition comprises the following components in parts by mass: 100 parts of methyl vinyl silicone rubber raw rubber, 10-30 parts of a dynamic cross-linking agent (a siloxane copolymer containing disulfide bonds), 10-30 parts of a biodegradable block (a polycaprolactone-siloxane copolymer), 3-10 parts of modified cellulose nanocrystals, 0.1-2 parts of a photosensitizer (a benzophenone derivative), and 0.05-0.5 parts of a platinum catalyst.

[0005] Among them: platinum-catalyzed hydrosilylation generates a stable permanent network, disulfide bonds provide reversible cross-linking points, forming a dynamic network. The dynamic network absorbs stress to prevent crack propagation, and the permanent network maintains overall strength to form a synergistic effect; cellulose nanocrystals are dispersed at the polycaprolactone-siloxane interface, enhancing the adhesion between polycaprolactone and the matrix and inhibiting phase separation. The hydrophilic surface of the nanocrystals guides enzyme / water intrusion and directionally degrades the PCL area (avoiding premature disintegration of the siloxane backbone); dibenzophenone derivatives are excited under ultraviolet light, catalyzing the homolytic cleavage and recombination of disulfide bonds, achieving room temperature self-repair (no heating required).

[0006] Furthermore, the dynamic crosslinking agent is an addition product of tetrakis(3-mercaptopropyl)siloxane and diacrylate siloxane, and its disulfide bond density is 2-5 mmol / g.

[0007] A method for preparing the above-mentioned degradable dynamically cross-linked silicone rubber composition, the method comprising the following steps: (1) Mix the methyl vinyl silicone rubber, dynamic crosslinking agent and biodegradable block in an internal mixer at 80-120°C for 10-30 minutes; (2) Add modified cellulose nanocrystals and continue mixing until uniform; (3) Add photosensitizer and continue mixing until uniform; (4) Add platinum catalyst and continue mixing until uniform; (5) Inject into the mold and cure at 60-80℃ and 0.5-2MPa pressure for 1-3 hours.

[0008] The silicone rubber composition is applied to degradable medical catheters or flexible electronic sensors.

[0009] The present invention provides a silicone rubber with both self-repairing and biodegradable functions. Through the synergistic effect of dynamic disulfide bonds and polycaprolactone blocks, the material achieves efficient self-repair and controllable enzymatic / photocatalytic degradation at room temperature. After the introduction of modified cellulose nanocrystals, the tensile strength exceeds 8.5 MPa, and the elongation at break reaches 680%. This material is suitable for short-term implantable medical devices (such as postoperative anti-adhesion membranes) and environmentally friendly electronic devices (degradable strain sensors), solving the problems of traditional silicone rubber's non-recyclability and poor biocompatibility. The present invention proposes a dual-network silicone rubber that integrates dynamic covalent bonds and biodegradable units. Through the synergistic crosslinking of dynamic siloxane bonds and biodegradable blocks, it achieves the dual functions of "recyclability and biodegradability." DETAILED DESCRIPTION

[0010] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0011] Example 1: 1. Raw material ratio: 100g methyl vinyl silicone rubber, vinyl content 0.8 mol%, dynamic crosslinker (containing disulfide bonds) 10g, disulfide bond density 3.2 mmol / g, polycaprolactone-siloxane copolymer 30g, polycaprolactone molecular weight 5000, siloxane proportion 40%, modified cellulose nanocrystals 10g, surface acetylation treatment, 2,4-dihydroxybenzophenone (photosensitizer) 0.5g, chloroplatinic acid isopropanol solution (platinum catalyst) 0.05g.

[0012] 2. The method comprises the following steps: mixing methyl vinyl silicone rubber, a dynamic crosslinking agent, and a biodegradable block in an internal mixer at 90-100° C. for 25 minutes; adding modified cellulose nanocrystals and continuing to mix until uniform; adding a photosensitizer and continuing to mix until uniform; adding a platinum catalyst and continuing to mix until uniform; injecting into a mold, and curing at 60-65° C. and 0.5-1 MPa pressure for 2 hours to form a catheter with a thickness of 0.5 mm.

[0013] 3. Function: Self-healing: Scratches (50μm depth) completely healed in 20 minutes at 25°C; Degradability: 82% weight loss in 30 days in phosphate buffer (containing lipase) at 75°C; Mechanical Properties: Tensile strength 6.8MPa, elongation at break 680%. Application: Postoperative anti-adhesion membrane (degradation takes 2-4 weeks), balancing intraoperative self-healing and rapid absorption requirements.

[0014] Example 2: 1. Raw material ratio: 100g methyl vinyl silicone rubber, vinyl content 1.2 mol%, dynamic crosslinker (containing disulfide bonds) 30g, disulfide bond density 4.8 mmol / g, polycaprolactone-siloxane copolymer 10g, polycaprolactone molecular weight 8000, siloxane proportion 60%, modified cellulose nanocrystals 3g, surface silanization treatment, 4-methoxybenzophenone (photosensitizer) 1.5g, platinum-vinyl complex (platinum catalyst) 0.3g.

[0015] 2. Process: The method comprises the following steps: mixing methyl vinyl silicone rubber, a dynamic crosslinker, and a biodegradable block in an internal mixer at 90-100°C for 25 minutes; adding modified cellulose nanocrystals and continuing to mix until uniform; adding a photosensitizer and continuing to mix until uniform; adding a platinum catalyst and continuing to mix until uniform; injecting into a mold, and curing at 60-65°C and 0.5-1MPa pressure for 2 hours to form a 0.5mm thick catheter, and additionally irradiating with 365nm ultraviolet light for 10 minutes (light intensity 50mW / cm²) to activate dynamic network reconstruction.

[0016] 3. Function: Self-repair cyclability: 92% strength retention after five repairs; Conductivity stability: <5% resistance change when stretched to 200% strain; Mechanical properties: Tensile strength 10.5 MPa; Controllable degradation trigger: Enzymatic degradation rate triples after 30 minutes of UV irradiation. Application: Degradable strain sensor, capable of multiple circuit self-repairs, with UV-triggered degradation upon expiration.

Claims

1. A degradable dynamically cross-linked silicone rubber composition, characterized in that: The composition comprises the following components by weight: 100 parts of methyl vinyl silicone rubber, 10-30 parts of a dynamic crosslinking agent (a siloxane copolymer containing disulfide bonds), 10-30 parts of a biodegradable block (a polycaprolactone-siloxane copolymer), 3-10 parts of modified cellulose nanocrystals, 0.1-2 parts of a photosensitizer (a benzophenone derivative), and 0.05-0.5 parts of a platinum catalyst.

2. The degradable dynamically cross-linked silicone rubber composition according to claim 1, characterized in that: The dynamic crosslinking agent is an addition product of tetrakis(3-mercaptopropyl)siloxane and diacrylate siloxane, and its disulfide bond density is 2-5 mmol / g.

3. A method for preparing the degradable dynamically cross-linked silicone rubber composition according to claim 1 or 2, characterized in that: The method comprises the following steps: (1) Mix the methyl vinyl silicone rubber, dynamic crosslinking agent and biodegradable block in an internal mixer at 80-120°C for 10-30 minutes; (2) Add modified cellulose nanocrystals and continue mixing until uniform; (3) Add photosensitizer and continue mixing until uniform; (4) Add platinum catalyst and continue mixing until uniform; (5) Inject into the mold and cure at 60-80℃ and 0.5-2MPa pressure for 1-3 hours.

4. The silicone rubber composition according to claim 1 is used in a degradable medical catheter or a flexible electronic sensor.