CN102093586A - Method for physical and chemical combined modification of surface of polydimethylsiloxane - Google Patents

Abstract

The invention relates to a method for casting polydimethylsiloxane on an anodized aluminum template and modifying polyvinyl alcohol on the polydimethylsiloxane substrate with a nanostructure, which is a combination of physical and chemical methods combined surface modification methods. The anodized aluminum film is prepared by electrolytic aluminum sheet method, polydimethylsiloxane is poured on the anodized aluminum template, after curing and stripping, the surface nanostructure of the polymer is produced, and then, it is irradiated by plasma Activate the polymer surface and soak to realize the modification of polyvinyl alcohol, thereby introducing hydrophilic groups. The present invention combines physical modification and chemical modification, and designs a method that can increase the hydrophilicity of the PDMS surface and maintain it for a long time. Compared with unmodified PDMS, the modified PDMS has better biocompatibility , which is more conducive to cell growth.

Description

Combined Physical and Chemical Modification of Polydimethylsiloxane Surface

technical field

The invention relates to a method of casting polydimethylsiloxane on an anodized aluminum template and modifying polyvinyl alcohol on the polydimethylsiloxane substrate with nanostructures, which is a combination of physical and chemical methods combined surface modification methods.

Background technique

Polydimethylsiloxane (PDMS) has good plasticity, non-toxicity and light transmittance, and is widely used in microfluidic research and biochemistry, but the hydrophobicity of PDMS itself hinders its application in many fields. At present, there are two main methods for surface modification of PDMS: physical modification and chemical modification.

Chemical modification mainly includes plasma irradiation and the introduction of functional groups into grafted polymers. Although plasma irradiation is very simple, its durability is poor, and the surface hydrophobicity of PDMS will recover shortly after irradiation. In order to solve this problem, functional groups such as –OH, –COOH, –NH ₂ have been successfully introduced and grafted Used for surface modification in PDMS.

Physical modification mainly uses template method, vacuum pressure method or precise photolithography to form micron-scale structures on the surface of PDMS. These structures can be applied to drug screening, cell culture, enrichment of small molecules, etc.

The surface modification of PDMS can be successfully achieved by combining chemical modification and physical methods, and it has good stability.

Contents of the invention

The invention provides a method for chemically modifying polyvinyl alcohol (PVA) on the surface of a polymer with a nanostructure. Polydimethylsiloxane is cast on an anodized aluminum template, and polydimethylsiloxane is cast on the polydimethylsiloxane with a nanostructure A surface modification method that combines physical and chemical methods for modifying polyvinyl alcohol on a silyl substrate.

Concrete technical scheme of the present invention is as follows:

The present invention is a combined physical and chemical modification method for the surface of polydimethylsiloxane. The anodized aluminum film is prepared by electrolytic aluminum sheet method, and the polydimethylsiloxane is poured onto the anodized aluminum template. After curing and stripping, the surface nanostructure of the polymer is produced, and then the surface of the polymer is activated by plasma irradiation, and the polyvinyl alcohol (PVA) is modified by soaking to introduce hydrophilic groups.

The present invention makes the concrete steps of anodic aluminum oxide film by the method for electrolytic aluminum flake as follows:

(1) Ultrasonic cleaning of the aluminum sheet in ethanol solution and deionized water for 5 minutes each, and burning in a temperature-programmed furnace at 500°C for 3 hours to eliminate internal stress;

(2) In the mixed acid solution of sulfuric acid, phosphoric acid and nitric acid with a volume ratio of 2:2:1, keep at 40°C for 20 minutes to remove the grease on the aluminum surface, and clean it with deionized water;

(3) Perform electrochemical polishing in sulfuric acid, phosphoric acid, and aqueous solution with a volume ratio of 2:2:1 for 15 minutes, keep the current below 2A, use a carbon rod as a reference electrode, take it out and wash it with deionized water;

(4) Carry out primary oxidation in 6% phosphoric acid for 1 hour, the voltage is 55V, and the temperature is kept below 15°C by water bath method;

(5) Soak the above-mentioned aluminum sheet in a solution of phosphoric acid with a mass percentage concentration of 6% and chromic acid with a mass percentage concentration of 1.8% in a volume ratio of 1:1, and soak it at 60°C for 1 hour to remove primary oxidation. layer;

(6) Carry out secondary oxidation in 6% phosphoric acid solution for 1 hour, the voltage is 55V, and the temperature of the electrolyte is kept below 15°C by water bath method to prepare anodized aluminum template.

The present invention is in the step of making the polydimethylsiloxane surface modification PVA of nanostructure as follows:

(1) To prepare polydimethylsiloxane polymer, the precursor polydimethylsiloxane and curing agent are mixed evenly in a mass ratio of 10:1;

(2) Vacuum in a vacuum drying oven for half an hour to remove the bubbles generated during stirring;

(3) After cleaning the surface of the anodized aluminum template with deionized water, pour the prepared polydimethylsiloxane onto the anodized aluminum template, and heat it in a vacuum oven at 75°C for 1 hour to cure;

(4) Soak the anodized aluminum template cured by polydimethylsiloxane polymer in ethanol solution for half an hour, peel off the aluminum oxide film, and form a layer of nanostructure on the surface of the polymer;

(5) Irradiate the prepared polymer in the plasma irradiation apparatus for 3 minutes;

(6) Soak the irradiated polydimethylsiloxane polymer in 1% polyvinyl alcohol solution for 20 minutes, take it out and dry it with a hair dryer.

The aluminum flakes adopted in the present invention have a purity of 99.9%, a thickness of 0.2mm, and an area of 18mm ² ; the acids used are all concentrated acids, and the ethanol concentration is 95%;

The experimental environment of the present invention is indoors under one atmospheric pressure.

In the present invention, when the alumina template is prepared, the connection between the aluminum sheet and the wire is kept on the electrolytic solution, and is wound and protected with an insulating tape.

The electrolytic solution phosphoric acid and chromic acid adopted in the present invention are mass percentages. When the present invention prepares the alumina template, because the sulfuric acid solution is highly corrosive, the connection between the aluminum flake and the wire is kept on the electrolyte, and an insulating tape is used to Wind protection.

The present invention combines physical modification and chemical modification, and designs a method that can increase the hydrophilicity of the PDMS surface and maintain it for a long time. Compared with unmodified PDMS, the modified PDMS has better biocompatibility , which is more conducive to cell growth.

Description of drawings

Figure 1 is a height map of flat PDMS measured by an atomic force microscope;

Figure 2 is a height map of PDMS with nanostructures measured by an atomic force microscope;

Fig. 3 is the ATR-FTIR figure of the differently modified PDMS;

Fig. 4 is the change of surface hydrophilicity of differently modified PDMS with nanostructure after plasma irradiation for 1 minute;

Figure 5 is the change of surface hydrophilicity of differently modified flat PDMS after plasma irradiation for 1 minute;

Figure 6 is the growth morphology of C6 cells on the flat PDMS observed under an inverted microscope after 3 days;

Figure 7 is the growth morphology of C6 cells on the PVA-modified flat plate PDMS observed under an inverted microscope after 3 days;

Figure 8 is the growth morphology of C6 cells on PDMS with nanostructures observed under an inverted microscope after 3 days;

Figure 9 is the growth morphology of C6 cells on PVA-modified PDMS with nanostructures observed under an inverted microscope after 3 days;

Figure 10 shows the growth of C6 cells cultured on various modified PDMS for 1 to 3 days.

Among Fig. 3: a is the curve of flat PDMS; B is the curve change of the PDMS with nanostructure; C is the curve change of the PDMS with nanostructure modified by PVA;

In Fig. 4: 1 is the curve change of PDMS with nanostructure; 2 is the curve change of PDMS with nanostructure irradiated by plasma for 1 minute; 3 is the curve change of PDMS with nanostructure irradiated by PVA for 1 minute;

In Fig. 5: 4 is the curve change of flat PDMS; 5 is the curve change of flat PDMS irradiated by plasma for 1 minute; 6 is the curve change of PVA-modified flat PDMS by plasma irradiation for 1 minute;

In Fig. 10: 7 is flat PDMS; 8 is PVA modified flat PDMS; 9 is PDMS with nanostructure; 10 is PVA modified PDMS with nanostructure.

Detailed ways

The present invention is described in further detail according to the accompanying drawings:

Specific examples:

1. First cut the aluminum sheet with a purity of 99.9% and a thickness of about 0.2mm into the desired shape, and ultrasonically clean it in ethanol solution and deionized water for 5 minutes;

2. Put the above-mentioned aluminum sheet in a temperature-programmed furnace and burn it at high temperature for 3 hours to eliminate internal stress;

3. Put the above-mentioned aluminum sheet in the sulfuric acid, phosphoric acid, and nitric acid solution with a volume ratio of 2:2:1, keep it at 40°C for 20 minutes, remove the grease on the aluminum surface, and clean it with deionized water;

4. Then perform electrochemical polishing in sulfuric acid, phosphoric acid, and aqueous solution with a volume ratio of 2:2:1 for 15 minutes, with a voltage of 15V and a temperature of 25°C. With a carbon rod as a reference electrode, take it out and wash it with deionized water ;

5. Carry out the primary oxidation of the above-mentioned aluminum sheet in 0.6mol/L sulfuric acid for 2 hours, the voltage of the primary oxidation is 25V, keep the temperature below 15°C by water bath method, and take out the aluminum sheet;

6. The primary oxidized aluminum flakes are soaked at 60°C for 1 hour in a solution that is mixed with 6% phosphoric acid and 1.8% chromic acid by volume at a mass percentage concentration of 1:1. Remove the uneven oxide layer during primary oxidation;

7. Perform secondary oxidation on the above-mentioned aluminum sheet in 0.6mol/L sulfuric acid solution for 2 hours, the voltage is 25V, keep the electrolyte temperature below 15°C by water bath method, soak in phosphoric acid solution for half an hour after oxidation is completed , to prepare an anodized aluminum template.

8. To prepare polydimethylsiloxane polymer, the precursor polydimethylsiloxane and the curing agent are mixed evenly in a mass ratio of 10:1;

9. After cleaning the surface of the anodized aluminum template with deionized water, pour polydimethylsiloxane onto the anodized aluminum template, and heat it in a vacuum oven at 75°C for 1 hour to cure;

10. Soak in ethanol solution for half an hour, peel off the aluminum oxide film, and form a layer of nano-columns on the surface of the polymer;

11. Irradiate the prepared polymer in the plasma irradiation apparatus for 3 minutes, soak the irradiated polydimethylsiloxane polymer in 1% polyvinyl alcohol solution for 20 minutes, take it out and blow it with a hair dryer Dry.

The implementation steps of the change detection of the contact angle of the modified PDMS surface:

1. Put the PDMS sheet on the operating table, release a drop of deionized water from the contact angle meter, and the size of the water droplet is basically the same each time;

2. Measure the size of the contact angle with the angle measurement method of the contact angle meter's built-in software and record it.

Modified PDMS can be used to culture cells, and both nanostructures and PVA will have an important impact on cell growth. The specific implementation steps are as follows:

1. Make flat PDMS, flat PDMS modified with PVA, PDMS with nanostructures and PDMS with nanostructures modified with PVA, cut them into appropriate sizes and put them into 24-well plates;

2. Cell inoculation: digest monolayer C6 cells with 0.25% trypsin, prepare a single cell suspension with DMEM medium containing 10% fetal bovine serum, and inoculate the cells into a 24-well plate covered with PDMS;

3. For cell culture, put the 24-well plate into a CO ₂ incubator, and culture it for 1 day, 2 days and 3 days at 37°C, 5% CO ₂ and saturated humidity;

4. Aspirate the culture medium and observe the cell morphology under an inverted microscope;

5. The cells were digested with 0.25% trypsin, and the number of cells grown on each PDMS was calculated with a cell counting plate.

Fig. 1 is the height figure of the flat PDMS that atomic force microscope records; Fig. 2 is the height figure of the PDMS that has nanostructure that atomic force microscope records; The obvious difference, the structure of 100~200nm appears on the surface of PDMS, which shows that the structure of the surface of alumina can be successfully copied to PDMS by this template method.

Fig. 3 is the ATR-FTIR figure of PDMS after various modifications; PVA modification of the present invention detects with surface infrared ATR-FTIR, and a is the curve of flat PDMS; b is the curve of PDMS with nanostructure; c is PVA modification with The curves of PDMS with nanostructures, all three kinds of PDMS have strong peaks between 2950 cm ⁻¹ and 2970 cm ⁻¹ , which is the characteristic peak of Si–CH ₃ , while the PVA-modified PDMS with nanostructures has a strong peak between 3000 and 3800 cm −1 The broad peak between cm ⁻¹ is exactly the characteristic peak of –OH, indicating that PVA was successfully modified on the PDMS surface.

Fig. 4 is the change of the surface hydrophilicity of various modified PDMS with nanostructures after plasma irradiation for 1 minute; Fig. 5 is the change of the surface hydrophilicity of PDMS of various modified flat plates after 1 minute of plasma irradiation; Fig. 4 Middle: 1 is the curve change of PDMS with nanostructure; 2 is the curve change of PDMS with nanostructure after plasma irradiation for 1 minute; 3 is the curve change of PVA-modified PDMS with nanostructure after plasma irradiation for 1 minute; Fig. 5 Middle: 4 is the curve change of flat PDMS; 5 is the curve change of flat PDMS after plasma irradiation for 1 minute; 6 is the curve change of PVA-modified flat PDMS after plasma irradiation for 1 minute; PDMS modified by physicochemical simultaneous will show affinity Aqueous surface, and this property has good stability compared with plasma irradiation. Firstly, two kinds of PDMS, flat plate and nanostructured, were prepared, and these two kinds of PDMS were subjected to three different treatments: 1. without any treatment, 2. plasma treatment, 3. PVA modification followed by plasma deal with. The change of the contact angle was recorded every hour within six hours. The experimental results show that the contact angle on the PDMS surface will decrease rapidly after plasma irradiation, but the contact angle will quickly approach the original level within 4 hours, which is consistent with the plasma irradiation in the existing literature. It can change the surface properties of PDMS but cannot last for a long time, but the effect of PVA can last for a long time. Comparing Figure 4 and 1 and 4 and 2 and 5 in Figure 5, it can be found that pure physical modification has a significant effect on the surface. The change in hydrophilicity is not very large, but comparing 3 and 6 in the two figures, it can be found that physical modification has a significant promotion effect on chemical modification. Among all samples, PVA-modified PDMS with nanostructure has the best hydrophilicity and stability. Although physical modification itself cannot significantly affect the hydrophilicity and hydrophobicity of the surface, it can provide more reaction sites for PVA binding, thereby increasing the coverage of PVA, and finally promoting chemical modification. The difference between the surface contact angle after two weeks and that after 6 hours of irradiation is not more than 3%.

Figure 6 to Figure 9 are the growth morphology of C6 cells observed under an inverted microscope after 3 days on flat PDMS, PVA modified flat PDMS, PDMS with nanostructures, and PVA modified PDMS with nanostructures; Modified PDMS It can also affect the growth shape and growth quantity of cells. Mouse glioma cell C6 was cultured on four kinds of PDMS, which were flat PDMS, PVA modified flat PDMS, nanostructured PDMS, PVA modified PDMS with nanostructures. It can be seen from the figure that the number of cells dispersed on the flat PDMS is very limited, and the cell density on the PVA-modified flat PDMS has increased. It can be seen from Figure 8 that the growth of cells on the PDMS with nanostructures is more stretched, and the size and shape are more Uniformity, cell proliferation is more obvious, and finally, the growth of cells on the PVA-modified PDMS with nanostructures has the same direction, the cell density is high, the cell debris is less, and the cell growth state is the best.

Figure 10 shows the growth of C6 cells after culturing on various modified PDMS for 1 to 3 days. In the figure, 7 is flat PDMS; 8 is PVA modified flat PDMS; 9 is PDMS with nanostructure; 10 is PVA modification PDMS with nanostructures. It shows that C6 cells were cultured on the above four PDMS respectively, and the culture time was one day, two days, and three days respectively. The results were similar to those in Figure 4. The nanostructures can promote the growth and differentiation of cells, and can promote the chemical modification of PDMS , the combination of the two plays the greatest role in promoting the growth of cells.

Claims (7)

1. A physical and chemical joint modification method on the surface of polydimethylsiloxane, characterized in that, the anodized aluminum film is obtained by electrolytic aluminum sheet, and polydimethylsiloxane is poured onto the anodized aluminum On the template, after curing and stripping, the surface nanostructure of the polymer is produced, and then the surface of the polymer is activated by plasma irradiation, and the polyvinyl alcohol (PVA) is modified by soaking to introduce hydrophilic groups. 2. the physical and chemical joint modification method of polydimethylsiloxane surface according to claim 1, is characterized in that, the concrete steps that make anodic aluminum oxide film by the method for electrolytic aluminum flake are as follows: (1) Ultrasonic cleaning of the aluminum sheet in ethanol solution and deionized water for 5 minutes each, and burning in a temperature-programmed furnace at 500°C for 3 hours to eliminate internal stress; (2) In the mixed acid solution of sulfuric acid, phosphoric acid and nitric acid with a volume ratio of 2:2:1, keep at 40°C for 20 minutes to remove the grease on the aluminum surface, and clean it with deionized water; (3) Perform electrochemical polishing in sulfuric acid, phosphoric acid, and aqueous solution with a volume ratio of 2:2:1 for 15 minutes, keep the current below 2A, use a carbon rod as a reference electrode, take it out and wash it with deionized water; (4) Carry out primary oxidation in 6% phosphoric acid for 1 hour, the voltage is 55V, and the temperature is kept below 15°C by water bath method; (5) Soak the above-mentioned aluminum sheet in a solution of phosphoric acid with a mass percentage concentration of 6% and chromic acid with a mass percentage concentration of 1.8% in a volume ratio of 1:1, and soak it at 60°C for 1 hour to remove primary oxidation. layer; (6) Carry out secondary oxidation in 6% phosphoric acid solution for 1 hour, the voltage is 55V, and the temperature of the electrolyte is kept below 15°C by water bath method to prepare anodized aluminum template. 3. the physical and chemical combined modification method of polydimethylsiloxane surface according to claim 1, is characterized in that, the step of making the polydimethylsiloxane surface modification PVA of nanostructure is as follows: (1) To prepare polydimethylsiloxane polymer, the precursor polydimethylsiloxane and curing agent are mixed evenly in a mass ratio of 10:1; (2) Vacuum in a vacuum drying oven for half an hour to remove the bubbles generated during stirring; (3) After cleaning the surface of the anodized aluminum template with deionized water, pour the prepared polydimethylsiloxane onto the anodized aluminum template, and heat it in a vacuum oven at 75°C for 1 hour to cure; (4) Soak the anodized aluminum template cured by polydimethylsiloxane polymer in ethanol solution for half an hour, peel off the aluminum oxide film, and form a layer of nanostructure on the surface of the polymer; (5) Irradiate the prepared polymer in a plasma irradiation apparatus for 3 minutes; (6) Soak the irradiated polydimethylsiloxane polymer in 1% polyvinyl alcohol solution for 20 minutes, take it out and dry it with a hair dryer. 4. according to claim 1 or 2 or 3 described physical and chemical joint modification method of polydimethylsiloxane surface, it is characterized in that, the aluminum flake purity that adopts is 99.9%, and thickness is 0.2mm, and area is 18mm ² . 5. The physical and chemical joint modification method of polydimethylsiloxane surface according to claim 1, 2 or 3, characterized in that, the acid used is concentrated acid, and the ethanol concentration is 95%. 6. The physical and chemical joint modification method of polydimethylsiloxane surface according to claim 1, 2 or 3, characterized in that the experimental environment of the present invention is indoors under one atmospheric pressure. 7. according to claim 1 or 2 or 3 described physical and chemical joint modification method of polydimethylsiloxane surface, it is characterized in that, when preparing alumina template, aluminum flake and wire junction remain on the electrolytic solution , and wrapped with insulating tape for protection.

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