A method for preparing a liquid-like coating based on dynamic phase separation

Abstract

A preparation method of a liquid-like coating based on dynamic phase separation belongs to the technical field of functional surface coating, and specific schemes include the following steps: step one, adding silicone resin and hydroxyl-terminated linear PDMS into a volatile solvent, and processing by a homogenizer and an ultrasonic disrupter to form an incompletely compatible mixed system; step two, slowly adding a metal coupling agent into the mixed system, and stirring to make the metal coupling agent and the active groups of the silicone resin have a pre-crosslinking reaction to obtain a coating liquid; step three, coating the coating liquid on the surface of a flexible substrate, evaporating the solvent, making the phase separation disappear, and performing a thermal curing treatment to make the silicone resin and the PDMS end have crosslinking and complete M-O-Si structure construction, and obtain a liquid-like coating, wherein M is a metal element of the metal coupling agent. The application simultaneously realizes high hardness and low liquid adhesion, and solves the problem that the liquid repellency and mechanical properties are difficult to be considered together.

Description

Technical Field

[0001] This invention belongs to the field of functional surface coating technology, specifically relating to a method for preparing a liquid-like coating based on dynamic phase separation. This liquid coating has liquid-like surface properties, is anti-fouling and wear-resistant, and is suitable for flexible electronic devices and photovoltaic devices. Background Technology

[0002] Currently, liquid-repellent surface coatings are widely used in flexible electronics, photovoltaic devices, and display modules to achieve anti-fouling, anti-fingerprint, dustproofing, and improved device durability. While traditional superhydrophobic coatings possess excellent water repellency, they rely on micro / nano structures, resulting in poor mechanical stability and susceptibility to failure due to friction or impact. [1] While slip-fluid injected porous surfaces (SLIPS) can achieve excellent lubricity and anti-fouling properties, the injected fluid (such as lubricating oil) can suffer from problems such as loss, migration, and contamination. [2] It is difficult to use stably in the long term.

[0003] To prevent the loss of liquid components, some studies have proposed constructing liquid-like coatings by covalently grafting low surface energy polymer segments, such as polydimethylsiloxane (PDMS), onto the surface of a solid substrate. [3] These coatings exhibit excellent performance in terms of contact angle hysteresis, lubricity, and liquid repulsion. However, high PDMS content can reduce the degree of crosslinking, further affecting the coating's hardness and wear resistance. Furthermore, high PDMS content can also lead to uneven phase separation and increased optical haze. In addition, to improve hardness, some studies have introduced POSS (polyhedral oligomeric silsesquioxanes) or multifunctional crosslinking agents to enhance the coating's mechanical properties, but these often involve complex synthesis steps or a high proportion of inorganic additives, increasing process complexity and preparation costs.

[0004] Therefore, how to improve the mechanical strength, thermal stability, optical transparency, and industrial fabrication capability of coatings while maintaining the dynamic surface properties of "liquid-like" coatings remains a pressing problem that needs to be solved in current liquid-like coating technology.

[0005] [1] Chen, F., Wang, Y., Tian, ​​Y., Zhang, D., Song, J., Crick, CR, Carmalt, CJ, Parkin, IP, and Lu, Y. (2022). Robust and durable liquid-repellent surfaces. Chemical Society Reviews, 51, 8476–8583.

[0006] [2] Zang, X., Ni, Y., Wang, Q., Cheng, Y., Huang, J., Cao,

[0007] [3] Hu, Z., Chu, F., Shan, H., Wu, X., Dong, Z., and Wang, R. (2024). Understanding and utilizing droplet impact on superhydrophobic surfaces: phenomena, mechanisms, regulations, applications, and beyond. AdvancedMaterials, 36, 2310177. Summary of the Invention

[0008] The main technical problems of existing liquid-like coatings are:

[0009] The problem of balancing liquid adhesion and mechanical strength: Existing liquid-like coatings usually require a high content of polydimethylsiloxane (PDMS) to achieve dynamic wetting and low contact angle hysteresis (CAH < 2°), but a high PDMS content will significantly reduce the hardness and wear resistance of the coating, making it unsuitable for the long-term protection requirements of flexible devices.

[0010] Phase separation leads to reduced optical transparency and structural stability of the coating: During the coating preparation process, PDMS has poor compatibility with the resin matrix and is prone to forming micron-scale PDMS enrichment structures, resulting in increased optical haze and mechanical degradation.

[0011] Secondary technical issues:

[0012] Existing enhancement methods suffer from complexity and high cost: To improve coating strength, some studies have introduced high-rigidity components such as POSS or constructed complex interpenetrating networks. While effective, these methods increase the synthesis steps and material costs, which is not conducive to industrial applications.

[0013] The high risk of coating failure in complex operating environments: Existing coatings are prone to surface structural damage, loss of anti-fouling function, or degradation of device performance when subjected to stress conditions such as bending, wiping, high temperature or dust contamination.

[0014] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0015] A method for preparing a liquid-like coating based on dynamic phase separation includes the following steps:

[0016] Step 1: Add silicone resin and hydroxyl-terminated linear PDMS to a volatile solvent, and process them sequentially through a homogenizer and an ultrasonic disruptor (40kHz, 1-15min) at room temperature to disperse the PDMS into small liquids, forming an incompletely compatible mixed system, and inducing dynamic phase separation.

[0017] Step 2: Slowly add the metal coupling agent dropwise to the above mixture and continue stirring for 0.1-1 h to allow it to undergo a pre-crosslinking reaction with the active groups of the organosilicon resin, thus obtaining the coating solution;

[0018] Step 3: Apply the coating liquid evenly to the surface of the flexible substrate using screen printing, blade coating, or spraying. Let it stand at room temperature for 5-30 minutes to slowly evaporate the solvent and eliminate phase separation. Then, perform a thermosetting treatment to allow the silicone resin and PDMS ends to crosslink and complete the MO-Si structure construction, resulting in a liquid-like coating, where M is the metal element of the metal coupling agent. Preferably, the flexible substrate is a PET film or a PI film.

[0019] Furthermore, by mass fraction, the silicone resin accounts for 50-80 wt% of the coating solution, the hydroxyl-terminated linear PDMS accounts for 0.5-1.5 wt% of the coating solution, the metal coupling agent accounts for 1.0-5.0 wt% of the coating solution, and the volatile solvent accounts for 15-45 wt% of the coating solution. The linear PDMS content can be controlled within a very low range (0.5–1.5 wt%) to form a slip layer on the surface without affecting the structural stability and optical properties of the coating.

[0020] Furthermore, the silicone resin is a methoxysiloxane intermediate (MS) used to construct the crosslinked backbone.

[0021] Furthermore, the hydroxyl-terminated linear PDMS has a molecular weight of 1000-100000 g / mol and is used to construct a liquid-like dynamic interface.

[0022] Furthermore, the metal coupling agent includes one or more combinations of titanate coupling agents, aluminate coupling agents, and zirconate coupling agents; providing an M–O–Si structure to achieve “hard-flexible” synergistic enhancement.

[0023] Furthermore, the titanate coupling agent includes one or more combinations of tetrabutyl titanate, isopropyl titanate, and isooctyl titanate; the aluminate coupling agent includes one or more combinations of isopropyl aluminate and butyl aluminate; and the zirconate coupling agent includes isopropyl zirconate.

[0024] Furthermore, the volatile solvent is a weakly polar solvent, including anhydrous ethanol, isopropanol, methanol, or low-polarity esters. Preferably, the low-polarity ester is ethyl acetate, used to induce dynamic phase separation.

[0025] Furthermore, in step three, the thickness of the liquid-like coating is 1-100µm.

[0026] Furthermore, in step three, the temperature for heat curing is 25-200℃, and the time is 0.1-20h.

[0027] Depending on the actual needs, 0-2 wt% of surface additives or UV stabilizers may be added in step one or step two to improve anti-pollution or photostability.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention simultaneously achieves high hardness and low liquid adhesion, solving the problem of "difficulty in balancing liquid repellency and mechanical properties" in coatings: It employs an M–O–Si covalent cross-linked network to construct a "hard-flexible" framework. Even with a PDMS content as low as 0.5wt%, the coating hardness exceeds 9H (ASTM D3363 standard), achieving a nano-indentation hardness (H=0.53GPa) 2.5 times that of ordinary PET substrates. Simultaneously, the coating surface contact angle hysteresis (CAH) is less than 2°, allowing water droplets and oil droplets (such as hexadecane) to slide off quickly, exhibiting excellent broad-spectrum anti-fouling properties.

[0030] 2. High optical transparency, solving the problem of "phase separation causing coating whitening or increased haze": The coating light transmittance remains above 90% in the range of 400–800nm, the surface roughness is only 0.7nm (measured by AFM), there is no obvious phase separation structure or micro-nano agglomeration, and it is suitable for fields with high requirements for visual transparency, such as displays and optoelectronic devices.

[0031] 3. Excellent wear resistance and long-lasting anti-fouling properties, solving the problem of "rapid decay of anti-fouling effect with wear and tear": After 500 steel wool abrasion treatments (13kPa pressure), the CAH value of the coating remains below 10°, and the fingerprint liquid residue rate is less than 20%, which is far superior to the unprotected PET surface (residue rate >60%), demonstrating excellent wiping resistance, fingerprint resistance and anti-graffiti performance.

[0032] 4. Improved high-temperature resistance, solving the problem of "poor thermal stability of flexible coatings": Thermogravimetric analysis shows that the coating of the present invention still retains 85.8 wt% of its mass at 800℃, which is far higher than the thermal stability level of conventional polymer substrates such as PET, making it suitable for high-temperature exposure environments such as photovoltaic modules.

[0033] 5. Simple process, suitable for spraying and adaptable to large-area flexible substrates, solving the problem of "incompatibility between complex process and large-scale preparation": This invention adopts conventional mechanical stirring and spray curing process, without the need for high-energy auxiliary equipment, and can form a uniform coating on 0.5m×10m flexible PET film, with good potential for large-scale production and industrial transformation. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the contact angle hysteresis (CAH) of water and hexadecane droplets on the coating surface;

[0035] Figure 2 These are the nanoindentation curves of the coating and PET film prepared in Example 1;

[0036] Figure 3 These are the thermogravimetric curves of the coating and PET film prepared in Example 1;

[0037] Figure 4 This is the UV-Vis transmittance curve of the coating prepared in Example 1;

[0038] Figure 5 These are images of coatings prepared by large-area spraying using the process described in Example 1;

[0039] Figure 6 A schematic diagram of the contact angle hysteresis (CAH) of water and hexadecane after the coating in Example 1 is rubbed with steel wool. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] Example 1:

[0042] A method for preparing a liquid-like coating based on dynamic phase separation includes the following steps:

[0043] Organosilicon resin (60 wt%) and hydroxyl-terminated linear PDMS (0.5 wt%) were added to ethanol (36.5 wt%) and dispersed at room temperature by homogenization (10000 rpm, 10 min) and ultrasonic disruption (40 kHz, 5 min) to disperse PDMS into small liquids, forming an incompletely compatible mixed system, which induced dynamic phase separation.

[0044] Add the coupling agent tetrabutyl titanate (3wt%) slowly dropwise to the above mixture and continue stirring for 0.5h to allow it to undergo a pre-crosslinking reaction with the active groups silanol and hydroxyl functional groups of the organosilicon resin, thus obtaining the coating solution.

[0045] The obtained coating liquid was evenly applied to the PET film on the surface of the flexible substrate by spraying, and the coating thickness was controlled to be about 20µm.

[0046] The solvent was allowed to evaporate slowly at room temperature for 20 minutes, and the phase separation disappeared. Then, it was heat-cured at 120°C for 60 minutes to allow the silicone resin and PDMS ends to crosslink and complete the Ti–O–Si structure construction, resulting in a liquid-like coating (SLC).

[0047] Example 2

[0048] The difference from Example 1 is that the hydroxyl-terminated linear PDMS accounts for 1 wt% of the coating solution, the silicone resin accounts for 59.5 wt% of the coating solution, and the remaining steps are the same as in Example 1.

[0049] Example 3

[0050] The difference from Example 1 is that: hydroxyl-terminated linear PDMS accounts for 1.5 wt% of the coating solution, and silicone resin accounts for 59 wt% of the coating solution, while the remaining steps are the same as in Example 1.

[0051] Example 4:

[0052] A method for preparing a liquid-like coating based on dynamic phase separation includes the following steps:

[0053] Organosilicon resin (60 wt%) and hydroxyl-terminated linear PDMS (0.2 wt%) were added to isopropanol (36.8 wt%). The mixture was first homogenized at room temperature (10000 rpm, 10 min), and then dispersed using an ultrasonic homogenizer (40 kHz, 5 min) to disperse the PDMS into small liquids, resulting in a non-compliant homogeneous dispersion system that induced dynamic phase separation.

[0054] Subsequently, 3 wt% isopropyl zirconate was slowly added dropwise to the dispersion system as a metal coupling agent, and the reaction was continuously stirred for 30 minutes to promote the coupling agent to form a Zr–O–Si cross-linked structure with the active silanol or hydroxyl functional groups of the organosilicon resin in the system, thus obtaining the coating solution.

[0055] The obtained coating solution was uniformly applied to the surface of a flexible PET substrate by spraying, and the wet film thickness was controlled to be about 10µm to ensure the integrity of the film layer.

[0056] After coating, the sample was left to stand at room temperature for 15 minutes until phase separation disappeared. Then, the sample was placed in an oven and heat-cured at 100°C for 40 minutes to complete the crosslinking and curing process, finally obtaining a liquid-like coating.

[0057] Example 5:

[0058] A method for preparing a liquid-like coating based on dynamic phase separation includes the following steps:

[0059] Organosilicon resin (70wt%) and hydroxyl-terminated linear PDMS (1wt%) were added to anhydrous ethanol (26wt%). The mixture was then dispersed at room temperature by a homogenizer (10000rpm, 10min) and an ultrasonic homogenizer (40kHz, 5min) to disperse the PDMS into small liquids, forming an incompletely compatible mixed system that induced dynamic phase separation behavior.

[0060] Tetrabutyl titanate (3wt%) was slowly added dropwise to the above mixture as a coupling agent, and the mixture was stirred continuously for 30 minutes to promote the pre-crosslinking of the coupling agent with the silanol or hydroxyl functional groups in the organosilicon resin, forming the initial Ti–O–Si crosslinked structure, and thus obtaining the coating solution.

[0061] The obtained coating solution was evenly applied to the surface of the flexible PET film using a spraying method, and the wet film thickness was controlled to be about 20µm to ensure that the subsequent film formation was uniform and continuous.

[0062] The solvent was allowed to evaporate slowly at room temperature for 20 minutes, and the phase separation disappeared. Then, it was heat-cured at 120°C for 60 minutes to allow the silicone resin and PDMS ends to crosslink and complete the Ti–O–Si structure construction, resulting in a liquid-like coating.

[0063] Comparative Example 1

[0064] The difference from Example 1 is that: hydroxyl-terminated linear PDMS accounts for 0.2 wt% of the coating solution, and silicone resin accounts for 60.3 wt% of the coating solution, while the remaining steps are the same as in Example 1.

[0065] Comparative Example 2

[0066] The difference from Example 1 is that: hydroxyl-terminated linear PDMS accounts for 2 wt% of the coating solution, and silicone resin accounts for 58.5 wt% of the coating solution, while the remaining steps are the same as in Example 1.

[0067] A summary table of the main performance indicators of the liquid-like coating prepared in Example 1:

[0068]

[0069] By using the component ratios and process path in Example 1, it is possible to achieve: the formation of a PDMS-enriched layer on the coating surface, providing ultra-low contact angle hysteresis (<2°), see... Figure 1 With increasing PDMS content, the contact angle hysteresis (CAH) of water droplets and hexadecane droplets (5 μL) initially decreased and then increased. The CAH of both water droplets and hexadecane droplets was minimized at a PDMS content of 0.5 wt%, indicating optimal hydrophobicity of the coating. The introduction of a Ti–O–Si crosslinking network significantly improved the coating hardness (see...). Figure 2 ) and thermal stability (heat resistance up to 800℃, see Figure 3 The coating has a light transmittance of >90%, maintaining the display performance of flexible devices. (See [link]). Figure 4 It has strong adaptability to spraying and is suitable for large-area flexible substrates (>0.5m×10m). See [link / reference]. Figure 5 It retains excellent stain resistance even after 500 cycles of steel wool abrasion. Figure 6 .

[0070] This invention proposes a method for preparing a liquid-like coating based on a solvent-induced dynamic phase separation mechanism. By controlling the aggregation-dissipation behavior between polymeric PDMS and a low-polarity solvent, a surface-enriched PDMS brush structure is achieved. Simultaneously, a metal coupling agent is introduced to form a MO-Si covalent crosslinking network, endowing the coating with excellent hardness (>9H), high transparency (>90%), low CAH (<2°), and resistance to wear and fingerprints at extremely low PDMS content (0.5-1.5wt%). This method is suitable for surface protection of optoelectronic devices such as flexible OLEDs, solar cells, and ACEL devices.

[0071] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a liquid-like coating based on dynamic phase separation, characterized in that, Includes the following steps: Step 1: Add silicone resin and hydroxyl-terminated linear PDMS to a volatile solvent, and then process them sequentially through a homogenizer and an ultrasonic disruptor to disperse the PDMS into small liquids, forming an incompletely compatible mixed system. Step 2: Slowly add the metal coupling agent dropwise to the above mixture and stir to allow it to undergo a pre-crosslinking reaction with the active groups of the organosilicon resin, thus obtaining the coating solution; Step 3: Apply the coating liquid to the surface of the flexible substrate, allow it to stand to evaporate the solvent, and the phase separation disappears. Then, perform a thermosetting treatment to crosslink the silicone resin and PDMS ends and complete the MO-Si structure construction to obtain a liquid-like coating, where M is the metal element of the metal coupling agent. By mass fraction, the silicone resin accounts for 50-80 wt% of the coating solution, the hydroxyl-terminated linear PDMS accounts for 0.5-1.5 wt% of the coating solution, the metal coupling agent accounts for 1.0-5.0 wt% of the coating solution, and the volatile solvent accounts for 15-45 wt% of the coating solution; The organosilicon resin is a methoxysiloxane intermediate, and the volatile solvent includes anhydrous ethanol, isopropanol, methanol, or low-polarity esters.

2. The preparation method according to claim 1, characterized in that: The molecular weight of the hydroxyl-terminated linear PDMS is 1000-100000 g / mol.

3. The preparation method according to claim 1, characterized in that: The metal coupling agent includes one or more combinations of titanate coupling agents, aluminate coupling agents, and zirconate coupling agents.

4. The preparation method according to claim 3, characterized in that: The titanate coupling agent includes one or more combinations of tetrabutyl titanate, isopropyl titanate, and isooctyl titanate; the aluminate coupling agent includes one or more combinations of isopropyl aluminate and butyl aluminate; and the zirconate coupling agent includes isopropyl zirconate.

5. The preparation method according to claim 1, characterized in that: In step three, the thickness of the liquid-like coating is 1-100µm.

6. The preparation method according to claim 1, characterized in that: In step three, the temperature for heat curing is 25-200℃ and the time is 0.1-20h.

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