CN115093597A

CN115093597A - Preparation method of super-hydrophobic polystyrene film

Info

Publication number: CN115093597A
Application number: CN202210875706.7A
Authority: CN
Inventors: 张利君; 祖煦; 杨梅; 李中波; 贾依文; 刘心语
Original assignee: Anhui Agricultural University AHAU
Current assignee: Anhui Agricultural University AHAU
Priority date: 2022-07-25
Filing date: 2022-07-25
Publication date: 2022-09-23
Anticipated expiration: 2042-07-25
Also published as: CN115093597B

Abstract

The invention discloses a preparation method of a super-hydrophobic polystyrene film, which adopts a sol-gel method, takes methyl triethoxysilane as a precursor, tetraethoxysilane as a precursor, absolute methanol as a solvent and ammonia water as a catalyst to prepare silicon dioxide sol, prepares nano silicon dioxide gel, utilizes a non-solvent induced phase separation principle, takes PS as a base material, tetrahydrofuran as a good solvent, absolute ethanol and nano silicon dioxide sol as non-solvents, and adopts a dropping coating method to prepare the PS super-hydrophobic film on a glass substrate. The super-hydrophobic film provided by the method can provide certain experimental support and theoretical basis for preparation, production and application of the PS super-hydrophobic coating, is simple and efficient, and is easy to perform experimental operation.

Description

Preparation method of super-hydrophobic polystyrene film

Technical Field

The invention belongs to the field of composite films and material chemistry, and particularly relates to a preparation method of a super-hydrophobic polystyrene film.

Background

The super-hydrophobic material is a bionic functional material based on the lotus leaf effect, the static contact angle of water drops on the surface of the material is more than 150 degrees, and the rolling angle is less than 10 degrees. The super-hydrophobic material has the characteristics of self-cleaning, water resistance, pollution resistance, corrosion resistance and the like, so that the super-hydrophobic material has wide application prospects in the aspects of electric appliances, building materials, chemical engineering, national defense, military and the like.

At present, research on super-hydrophobic materials is mainly focused on high polymer coatings such as polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polypropylene (PP), Polystyrene (PS) and the like and plastic products, and relatively few related researches on preparing super-hydrophobic films by taking Polystyrene (PS) as a raw material are carried out.

Disclosure of Invention

The invention provides a preparation method of a super-hydrophobic polystyrene film, provides certain experimental support and theoretical basis for preparation, production and application of a PS super-hydrophobic coating, and is simple, efficient and easy for experimental operation.

The preparation method of the super-hydrophobic polystyrene film adopts a sol-gel method, and takes methyl triethoxysilane as a precursor, tetraethoxysilane as a precursor, anhydrous methanol as a solvent and ammonia water as a catalyst to prepare silicon dioxide sol; and then, by utilizing a non-solvent induced phase separation method, adding 20% by volume of absolute ethanol into 3 wt% of PS/THF solution by taking PS as a substrate, Tetrahydrofuran (THF) as a good solvent and nano-silica sol as a non-solvent, continuously adding 10% by volume of nano-silica sol into the mixed solution, uniformly dripping the mixed solution on a glass substrate by using an injector after blending, standing for 24 hours, and airing at room temperature to prepare the super-hydrophobic film.

The volume ratio of the absolute ethyl alcohol is 20%. The volume ratio herein means the volume ratio of absolute ethanol to the mixed solvent of tetrahydrofuran and absolute ethanol, i.e., V _THF ：V _{Anhydrous ethanol} ＝8：2。

The volume ratio of the added nano silica sol is 10%. The volume ratio here refers to the volume ratio of the nano-silica sol to the THF solvent, the absolute ethyl alcohol and the mixed solvent of the nano-silica sol, namely V _THF ：V _{Anhydrous ethanol} ：V _{Nano-silica sol} ＝7：2：1。

The invention adopts a non-solvent induced phase separation method and a sol-gel method, wherein the former method is simple and efficient and has strong repeatability, and the latter method is simple and energy-saving and is beneficial to the construction of a nano structure.

The reagents used in the invention can be prepared independently for later use, and the addition of the reagents does not cause chemical change of PS, so that the superhydrophobic performance of the film comes from the construction of surface micro-topography.

Compared with the traditional method for preparing the polystyrene super-hydrophobic film, the invention has the advantages that:

1. by using a non-solvent induced phase separation principle and a sol-gel method, the preparation process is simple, energy-saving, short in preparation time, low in cost and strong in repeatability;

2. the obtained super-hydrophobic film has large surface roughness and certain wear resistance.

Drawings

FIG. 1 is a graph showing the influence of the amount of Methyltriethoxysilane (MTES) and the rotational speed for preparing a hydrophobic coating by a spin coating method on the hydrophobic property of a silica coating;

FIG. 2 is a surface micro-topography (SEM) of a nanosilica sol coating;

FIG. 3 is a water contact angle of the surface of a coating film prepared by a spin coating method and a drop coating method using PS/THF solutions of different mass concentrations;

FIG. 4 is a surface micro-topography of a coating film prepared from a PS solution with a mass concentration of 3%, wherein a, b and c, d are surface micro-topography (SEM) of the coating film prepared by spin coating and drop coating at a magnification of 400,3000, respectively, and the inset is the water static contact angle value (WCA) of the prepared coating film;

FIG. 5 is a graph showing water static contact angle values of PS films prepared by a spin coating method and a drop coating method after adding ethanol in different volume ratios to a 3% mass concentration PS solution;

FIG. 6 is a surface micro-topography (SEM) of a PS film prepared by a dropping coating method after adding 20% by volume of absolute ethanol;

FIG. 7 is a graph showing the water static contact angle values of coating films prepared by adding 20% by volume of ethanol and nano-silica sols having different volume ratios to a 3% by mass PS/THF solution;

FIG. 8 is a static contact angle image of a coating film prepared by adding a nano silica sol of 10% by volume by a dropping method in a PS/THF-ethanol solution of 3% mass concentration;

FIG. 9 shows rolling angle values (SA) of PS films prepared by adding 20% by volume of ethanol and 10% by volume of nano-silica sol and applying a 3% by mass PS solution by a dropping coating method;

FIG. 10 is a surface micro-topography (SEM) of a PS film prepared by a dropping coating method after adding ethanol with a volume ratio of 20% and nano-silica sol with a volume ratio of 10%;

FIG. 11 is an infrared spectrum of a PS film, wherein (a) no non-solvent is contained, and (b) ethanol, (c) silica, (d) ethanol and silica are used as non-solvents, respectively.

Detailed Description

Example 1:

in the embodiment, a sol-gel method is adopted, methyltriethoxysilane is taken as a precursor, tetraethoxysilane is taken as a precursor, anhydrous methanol is taken as a solvent, and ammonia water is taken as a catalyst to prepare silicon dioxide sol, and a spin coating method is adopted to modify a silicon dioxide hydrophobic coating on the surface of glass. The influences of the concentration of the methyl triethoxysilane and the tetraethyl orthosilicate, the proportion of the methyl triethoxysilane to the tetraethyl orthosilicate, the using amount of ammonia water, the spin-coating rotating speed and the like on the hydrophobic performance of the finally obtained hydrophobic coating are researched.

The embodiment process comprises the following steps: preparation of experimental samples, optimization of experimental conditions and preparation of hydrophobic coatings.

1. Preparation of test samples

Preparation of silica sol: 63.4mL of absolute ethyl alcohol, 8.3mL of ammonia water and 5mL of deionized water were measured by a measuring cylinder, added to a 500mL distillation flask with a stirrer, and stirred uniformly. When the temperature in the water bath kettle rises to 60 ℃, the distillation flask filled with the reagent is placed in the water bath kettle and fixed by an iron support, the openings at two sides are sealed by rubber plugs, a thermometer with the dosage range of 100 ℃ is used for measuring the temperature of the solution in the distillation flask, and the opening at the middle of the distillation flask is connected with a condenser tube. When the temperature of the solution in the distillation flask rises to 60 ℃, 10.7mL of TEOS is dripped into the distillation flask by a rubber head dropper at the frequency of 1d/20s, and after the dripping is finished, the constant temperature reaction is carried out for 2 h. Then, a solution of MTES (ethanol as a solvent) of a certain concentration, which has been heated and stirred, is slowly added dropwise over a period of 30 minutes. Keeping the temperature at 60 ℃ for 24h after the dropwise addition is finished, pouring the prepared solution into a 100mL beaker after the reaction is finished, and aging for 48h to obtain the silicon dioxide sol.

2. Optimization of the Experimental conditions

In the experiment, the influence of the dosage of the methyltriethoxysilane and the ammonia water and the spin-coating rotating speed on the hydrophobic performance of the super-hydrophobic silicon dioxide coating is researched by controlling a variable method, wherein the dosage of the deionized water is fixed at 5mL, the dosage of the tetraethyl silicate is fixed at 10.7mL, and the dosages of the methyltriethoxysilane and the ammonia water are gradually changed. The spin coating conditions were respectively: 3500rpm, 60s and 3000rpm, 60 s.

3. Preparation of hydrophobic coatings

(1) Cutting the glass sheet into 2cm multiplied by 2cm, carrying out ultrasonic cleaning by sequentially using a sodium hydroxide solution with the concentration of 5%, absolute ethyl alcohol and deionized water, washing the glass sheet and a glass vessel by the deionized water after each cleaning, blow-drying the glass sheet by nitrogen, putting the glass sheet back into the dried glass vessel, ensuring that each solution for each cleaning passes through the glass sheet, and carrying out ultrasonic cleaning for 30 minutes by an ultrasonic cleaning machine.

(2) And (3) spin-coating at 3000rpm, 60s, 3500rpm and 60s by using a spin-coating instrument, air-drying at room temperature for 30 minutes after the spin-coating is finished, then drying in an oven at 120 ℃ for 10 minutes, taking out, and cooling to room temperature to obtain the hydrophobic coating modified by silicon dioxide. Fig. 1 shows the influence of the amount of Methyltriethoxysilane (MTES) and the rotational speed for preparing the hydrophobic coating by the spin coating method on the hydrophobic property of the silica coating, when the spin coating speed for modifying the silica sol on the glass sheet is 3500rpm and the spin coating time is 60s (red curve in fig. 1), the static contact angle of the hydrophobic silica coating shows a trend of increasing and then decreasing with the increase of the amount of methyltriethoxysilane, and reaches a maximum value of 154.1 ° at 5.6 mL. The static contact angle of the silicon dioxide hydrophobic coating prepared under the conditions that the spin-coating speed is 3500rpm and the spin-coating time is 60s is larger than the hydrophobic angle of the silicon dioxide hydrophobic coating obtained under the preparation conditions that the spin-coating speed is 3000rpm and the spin-coating time is 60 s. It can be seen that the hydrophobic property of the prepared silica coating is best when the dosage of the methyltriethoxysilane is 5.6mL and the spin coating preparation conditions of the coating are 3500rpm and 60 s. FIG. 2 is a microscopic morphology (SEM) of the surface of the nano silica sol coating, spherical protrusions can be clearly observed on the surface of the coating, the surface of the spherical surface is smooth, and micro particles are distributed on the surface of the micro-sized particles. The special nano multilevel rough structure is similar to the special appearance of the surface of the lotus-like leaf, so the nano multilevel rough structure has good hydrophobic property.

Example 2:

in this example, PS is used as a substrate, tetrahydrofuran is used as a good solvent, and a method of preparing a PS hydrophobic film on a glass substrate by a spin coating method and a drop coating method is used.

The embodiment process comprises the following steps: preparation and optimization of experimental samples and a process for preparing a thin film.

1. Preparation and optimization of Experimental samples

Preparing a PS solution: 0.2g of PS was accurately weighed, added to a capped reagent bottle containing 20mL of Tetrahydrofuran (THF), and stirred for 2 hours to obtain a PS/THF solution with a mass concentration of 1 wt.%. PS/THF solutions having mass concentrations of 1%, 2%, 3%, 4%, 5%, and 10% were prepared in the same manner.

2. Preparation of hydrophobic films

(1) Spin coating method: and ultrasonically cleaning a glass sheet with the size of 2cm multiplied by 2cm with absolute ethyl alcohol and pure water for 10 minutes, and drying. Coating the prepared different PS solutions on the surface of glass by a KW-4A spin coater through a spin coating method, wherein the spin coating parameters are as follows: 1500rpm, 30 s. And (5) drying at room temperature. FIG. 3 is a water contact angle of the surface of a coating film prepared by a spin coating method and a drop coating method using PS/THF solutions of different concentrations; the water contact angles of PS coating films prepared by 3% and 10% concentrations are the largest, but the viscosity of the 10% solution is too high, and the PS/THF solution with the concentration of 3% is easy to gel in the preparation process, so that the PS/THF solution with the concentration of 3% is adopted in the research.

(2) And (3) a dropping method: and ultrasonically cleaning a glass sheet with the size of 2cm multiplied by 2cm with absolute ethyl alcohol and pure water for 10 minutes, and drying. The different PS solutions prepared above were applied to the glass surface by drop coating using a 1mL syringe. And (5) drying at room temperature. The morphology of the coating film formed by the 3% concentration is shown in fig. 4, and it can be seen that the PS sample prepared by the solution with the 3% concentration prepared by the spin coating method has a porous structure uniformly distributed on the surface (fig. 4a, b), and the porous structure makes the PS sample have larger surface roughness. On the other hand, although the PS samples prepared by the dropping method also have a porous structure on the surface (fig. 4c and d), the distribution is not uniform, and the number of the pores is not as large as that of the surface of the film prepared by the spin coating method, so that the water contact angle of the surface of the coating film prepared by the spin coating method is larger than that of the surface of the coating film prepared by the dropping method in comparison with the case of not adding any non-solvent.

Example 3:

in the embodiment, PS is used as a base material, tetrahydrofuran is used as a good solvent, absolute ethyl alcohol is used as a non-solvent, and a method for preparing the PS superhydrophobic film on a glass substrate by further adopting a spin-coating method and a drop-coating method by utilizing the principle of non-solvent induced phase separation.

The embodiment process comprises the following steps: preparation and optimization of experimental samples and preparation of super-hydrophobic films.

1. Preparation and optimization of Experimental samples

(1) Preparing a PS solution: accurately weighing 0.6g of PS, adding the PS into a reagent bottle with a cover and containing 20mL of Tetrahydrofuran (THF), and stirring for 2 hours to obtain a PS/THF solution with the mass concentration of 3%;

(2) addition of anhydrous ethanol: PS/THF solutions containing different ratios of ethanol were prepared. After PS was sufficiently dissolved in THF, anhydrous ethanol was added to the prepared PS/THF solution in a certain ratio (volume ratio: 0%, 10%, 20% and 30%) by syringe, and stirring was continued until it was uniformly mixed, at which time the solvents were THF and anhydrous ethanol.

2. Preparation of super-hydrophobic film

In example 2, a spin coating method and a drop coating method are adopted, and fig. 5 shows the contact angle values of the coating films prepared by adding ethanol in different proportions into a PS solution with a concentration of 3%, which indicates that under the experimental conditions that the volume ratio of the drop coating method to the ethanol reaches 20%, the water contact angle can exceed 150 degrees, the rolling angle is about 10 degrees, and the superhydrophobic requirement is met. FIG. 6 is a surface micro-topography (SEM) of a membrane prepared by a dropping coating method after absolute ethyl alcohol is added, PS macromolecules are converted into a bead chain structure and are composed of polymer spheres with large and small sizes, a porous structure is arranged in the middle of the polymer structure to form a secondary hierarchical structure, and the porous structure with proper size and distribution and a proper amount of nano-scale polymer spheres jointly promote the surface of a sample to have super-hydrophobic performance.

Example 4:

the method comprises the steps of preparing silicon dioxide sol by a sol-gel method, using methyltriethoxysilane as a precursor, tetraethoxysilane as a precursor, absolute methanol as a solvent and ammonia water as a catalyst, then using PS as a base material, tetrahydrofuran as a good solvent, absolute ethanol and nano silicon dioxide sol as a non-solvent, and further preparing the PS superhydrophobic film on a glass substrate by a drop coating method by utilizing a non-solvent induced phase separation principle.

The embodiment process comprises the following steps: preparation and optimization of experimental samples and preparation of hydrophobic films.

1. Preparation and optimization of Experimental samples

(1) Preparing a PS solution: 0.6g of PS was accurately weighed, added to a capped reagent bottle containing 20mL of Tetrahydrofuran (THF), and stirred for 2 hours to obtain a 3% PS/THF solution.

(2) Addition of anhydrous ethanol: to the prepared PS/THF solution was added 20% by volume of absolute ethanol and stirring was continued until it was well mixed.

(3) Adding nano-silica sol: preparing PS/THF-ethanol solution containing nano-silica sol with different proportions. Adding nano-silica sol in a certain proportion (volume ratio: 0%, 10%, 20%) into the prepared PS/THF-ethanol solution by using a syringe, and continuing stirring until the nano-silica sol is uniformly mixed, wherein the solvents refer to THF, absolute ethyl alcohol and nano-silica sol.

2. Preparation of hydrophobic films

A PS thin film is prepared by a spin coating method and a drop coating method in example 2, fig. 7 is a contact angle value of a coating film prepared by adding nano silica sol in different proportions to a PS/THF-ethanol solution with a concentration of 3%, fig. 8 and 9 show static contact angle and rolling angle images of the coating film under the optimal experimental conditions, respectively, which shows that when the experimental conditions are the drop coating method, a volume ratio of ethanol is 20%, and a volume ratio of nano silica is 10%, a superhydrophobic surface with a surface water contact angle of more than 150 ° and a rolling angle of 6 ° can be formed. FIG. 10 is a surface micro-topography (SEM) of a film prepared by a drop coating method after addition of absolute ethanol and nano-silica sol, and it can be seen that SiO ₂ The solution and the ethanol are added simultaneously, so that the rolling contact angle is further reduced while the super-hydrophobic property caused by the secondary hierarchical structure is kept, the super-hydrophobic property of the film is improved, and the method realizes simple preparation of the super-hydrophobic film.

Example 5:

in this example, after replacing the prepared substrate in example 1 with a common aluminum foil substrate, the change of the performance of the thin film infrared spectroscopy is compared to show that the addition of the reagent does not chemically change the PS, and all the reagents can be prepared separately for later use.

The procedures of the embodiment are as follows:

the film of example 1 was applied by drop coating on a common aluminum foil substrate to produce a larger area film which was more easily peeled than the glass substrate. FIG. 11 is an infrared spectrum of a PS composite film prepared using PS as a substrate, tetrahydrofuran as a good solvent, and anhydrous ethanol and nano-silica sol as a non-solvent. FIG. 11b shows no significant change, nor a new absorption peak, compared to FIG. 11a, indicating that the addition of ethanol does not chemically change PS; FIG. 11c is at 466cm, as compared to FIG. 11a ^-1 、955cm ^-1 、1072cm ^-1 、1271cm ^-1 A new absorption peak appears, wherein, at 466cm ^-1 The absorption peak appeared to the left and right due to bending vibration of Si-O bond at 955cm ^-1 The absorption peak is caused by bending vibration of Si-OH bond at 1072cm ^-1 On the left and right appear very strongThe absorption peak is caused by antisymmetric stretching vibration of Si-O-Si bond and is 1271cm ^-1 The absorption peak appeared at is Si-CH ₃ The silicon methyl possibly remained in the preparation process of the nano silica sol due to the bending vibration of the bond is proved by research, the residue of the silicon methyl plays a certain role in maintaining the hydrophobicity of the film, and fig. 11d is the superposition effect of fig. 11b and c, which shows that the addition of the reagent does not cause the chemical change of the PS, and the used reagents can be prepared separately for later use, thereby realizing the simple preparation of the super-hydrophobic film.

Claims

1. A preparation method of a super-hydrophobic polystyrene film is characterized by comprising the following steps:

step 1: preparing nano silicon dioxide sol by adopting a sol-gel method and taking methyl triethoxysilane as a precursor, tetraethoxysilane as a precursor, anhydrous methanol as a solvent and ammonia water as a catalyst;

step 2: the super-hydrophobic polystyrene film is prepared by using a non-solvent induced phase separation method, taking PS as a base material, taking tetrahydrofuran as a good solvent and taking absolute ethyl alcohol and nano silica sol as non-solvents.

2. The method of claim 1, wherein:

in the step 2, absolute ethyl alcohol is added into the THF solution of PS, nano-silica sol is continuously added into the mixed solution, the nano-silica sol is uniformly dripped on a glass substrate by an injector after blending, and the mixture is kept stand for 24 hours and dried at room temperature to prepare the super-hydrophobic film.

3. The production method according to claim 2, characterized in that:

the THF solution of PS had a mass concentration of 3 wt%.

4. The method of claim 2, wherein:

the volume ratio of the absolute ethyl alcohol is 20%.

5. The method of claim 2, wherein:

the volume ratio of the added nano silica sol is 10%.