CN104744648B - Method for preparing double-stimulation responsive surface through secondary photopolymerization - Google Patents

Abstract

A method for preparing a dual-stimuli-responsive surface by secondary photopolymerization relates to the field of graft modification of various substrate surfaces. In the first step, a cleavage-type photoinitiator is used to graft a pH-responsive compound on the surface. The pH-responsive polymer grafted on the surface can be used as a hydrogen donor and co-initiator for the next step. The second step uses hydrogen abstraction Based on the previous photopolymerization reaction, the photoresponsive compound modified by double bond was grafted by the type initiator. This method not only has the advantages of high efficiency, energy saving, economy, and environmental protection of photopolymerization, but also attaches the compound to the surface in a covalent bond, which is not easy to fall off. The smart surface prepared by the invention has good photoresponsiveness and pH responsiveness, and its surface polymer swelling performance and wetting performance can be reversibly controlled. This surface has potential applications in surface molecular switching, surface controlled release, and ion adsorption due to its good controllable wetting properties and mechanical effects.

Description

A method for preparing dual stimuli-responsive surfaces by secondary photopolymerization

technical field

The invention relates to grafting and modifying the surfaces of various base materials, and adopts different types of photoinitiators to prepare double stimulus responsive surfaces through a secondary photopolymerization method.

Background technique

There are some plants and animals that can respond to environmental stimuli in nature, such as mimosa, sunflower, chameleon and so on. Imitating these animal and plant phenomena, discovering and synthesizing some stimuli-responsive materials has aroused great interest of scientists. These compounds can produce wettability, volume, Changes in shape, mechanical properties, etc. With the development of society, fully researching and using these stimuli-responsive compounds to prepare smart materials will attract more and more attention. In the past few years, the main research was on the properties of the compound itself, focusing on solution and gel systems. In recent years, grafted stimuli-responsive materials have also been extensively studied on solid surfaces.

The construction of responsive smart surfaces by modifying stimuli-responsive compounds on the surface of various substrates is mainly divided into physical methods and chemical methods. In physical methods, compounds and surfaces generally rely on non-covalent bonds, and surface compounds are easy to fall off; while chemical methods Methods such as surface-induced redox polymerization, atom transfer radical polymerization, layer-by-layer self-assembly, etc. are to graft compounds on the surface in the form of covalent bonds, but most of the methods are relatively complicated and time-consuming and energy-consuming. For example, Abdullah M.Alswieleh et al. grafted pH-responsive compounds on the surface of silicon wafers by atom transfer radical polymerization (ATRP) to make the surface have pH-responsive properties. materials are prone to aging (A.M.Alswieleh, N.Cheng, G.J.Leggett, Langmuir: the ACS journal of surfaces and colloids, 30(2014) 1391-1400); Yueguo Dong et al. used photopolymerization method to graft temperature-responsive compound N on the surface - Isopropylacrylamide prepared temperature-stimuli-responsive surfaces (Y.Dong, X.Zhu, F.Shi, J.Nie, Applied Surface Science, 307(2014) 7-12), although a simple and fast surface light Polymerization method, but using only one type of photoinitiator to prepare a single environment (temperature) responsive surface.

We have now invented a method for fabricating multiple stimuli-responsive surfaces via secondary photopolymerization. This method not only utilizes the advantages of high efficiency, energy saving, economy, environmental protection, etc. of photopolymerization, but also uses two different types of free radical photoinitiators of cracking type and hydrogen abstraction type to carry out secondary photopolymerization according to different photopolymerization reaction mechanisms. The double reversible stimuli-responsive surface was prepared by modifying the substrate surface. In the first step, a cleavage-type initiator is used to graft pH-responsive compounds on the surface. This polymer can be used as a hydrogen donor and co-initiator for subsequent reactions. In the second step, a hydrogen-abstracting initiator is used to carry out photopolymerization on the basis of the previous one. Photoresponsive compound modified by reaction grafting double bond; this method is simple and easy, and the compound is covalently bonded to the surface, which is not easy to fall off. The prepared surface has potential applications in surface molecular switching, surface controlled release, and ion adsorption due to its good controllable wetting properties and mechanical effects.

Contents of the invention

The purpose of the present invention is to provide a simple and mild secondary photopolymerization method to prepare surfaces with dual reversible stimuli-responsive properties.

The present invention utilizes different photopolymerization reaction mechanisms, adopts two different types of free radical photoinitiators of cleavage type and hydrogen abstraction type, and prepares a double-stimuli-responsive surface through a secondary photopolymerization method. Taking the preparation of a dual reversible stimuli-responsive surface of pH and light as an example, dimethylaminoethyl methacrylate and 2-methyl-4-azobenzene acrylate were covalently bonded by secondary photopolymerization. Branches on different substrate surfaces. The method includes the following steps:

(1) Prepare a pH-responsive photopolymerization system solution, apply it to the surface of the modified substrate, light it for a certain period of time to cause photopolymerization, then immerse the substrate of the grafted polymer in ethanol for ultrasonic treatment, and blow it with nitrogen Dry and set aside. During the illumination process of this step, a spherical or striped photomask can be added to construct a pattern painting surface.

(2), prepare the photopolymerization system solution of environmental stimulus responsiveness, be coated on the base material surface obtained in step (1), irradiate for a certain period of time to make it take place the second photopolymerization reaction, the surface obtained is ultrasonically treated in ethanol , blown dry with nitrogen to obtain the final product.

(3) The product in step (2) is tested for light and stimulus responsiveness, swelling performance and wetting performance.

The method for preparing double stimulus-responsive surfaces by secondary photopolymerization is characterized in that it comprises the following steps:

(1) Prepare a pH-responsive photopolymerization system solution, apply it on the surface of the substrate, irradiate it for 60-900s to cause photopolymerization, immerse the modified substrate in ethanol and sonicate for 1-10min, blow with nitrogen dry for use;

(2) Prepare a photopolymerizable monomer responsive to light or temperature environment stimuli, apply it on the surface of the substrate obtained in step (1), light it for 60-900s to cause a secondary photopolymerization reaction, and then apply the substrate Ultrasound in ethanol for 1-10min to obtain the final product;

The initiator of the photopolymerization system in the step (1) adopts a cleavage type free radical photoinitiator, and the photopolymerization reaction in the step (2) adopts a free radical photoinitiator.

Further, photomasks of various shapes are used in the two-step photopolymerization process in steps (1) and (2).

Further, the substrates described in steps (1) and (2) are: silicon wafers, quartz wafers, glass wafers, iron wafers, copper wafers, PET films or polypropylene PP.

Further, the light source described in steps (1) and (2) is: mercury lamp, xenon lamp, UV-LED lamp, plate lamp or iodine-gallium lamp, and the light intensity is 10-1000mW/cm ² .

Further, it is characterized in that the photopolymerization system formula described in step (1):

(1) The monomer is a monomer containing a double bond at one end and a tertiary amine at the other end, accounting for 20%-98% of the mass fraction of the system,

The general formula is:

n≥1; R ₃ =H or CH ₃ ;

R ₁ and R ₂ are the following groups:

1≤m≤10

(2), the crosslinking agent is propoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate One or more mixtures of acrylate and trimethylolpropane trimethacrylate, accounting for 1%-10% of the system mass fraction;

(3), the initiator is cleavage type photoinitiator 2-hydroxyl-2 methyl-1-phenyl ketone (1173), 1-hydroxyl-cyclohexyl benzophenone (184), 2-methyl-2- (4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone (907), 2-hydroxyl-2-methyl-1-p-hydroxyethyl ether phenylacetone ( 2959), 2-phenylbenzyl-2-dimethylamino-1-(4-morpholinebenzylphenyl)-1-butanone (369), the mass fraction of the system is 0.1%-3%;

(4), all the other are solvent, and solvent is a kind of in ethanol, acetone, toluene, ethyl acetate.

Further, the system formula in the photopolymerization reaction described in step (2) is:

(1) The monomer is a photo- and temperature-responsive monomer with a double bond in the end group, accounting for 20%-80% of the mass fraction of the system; including the photo-responsive monomer, the general formula is:

R ₄ =H or CH ₃

_R is the following group:

0≤m≤5; 0≤p≤5

This monomer is either a temperature-responsive compound N-isopropylacrylamide;

(2), the crosslinking agent is propoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate One or more mixtures of methacrylates account for 0-10% of the system mass fraction;

(3), the initiator is one or more of the hydrogen abstraction type photoinitiator isopropylthioxanthone (ITX), benzophenone (BP), 2-ethylanthraquinone (2-EA) Mixed, the mass fraction of the system is 0.1%-3%;

(4), all the other are solvent, and solvent is a kind of in acetone, ethanol, methylene chloride, chloroform, toluene, ethyl acetate.

The preparation method of the present invention utilizes the photopolymerization method of high efficiency, energy saving and environmental protection, and makes full use of the different photopolymerization reaction mechanisms of different types of photoinitiators to graft pH-responsive and photoresponsive monomers in the form of covalent bonds. A dual reversible stimuli-responsive surface was obtained on the substrate, and the characteristics of this surface are as follows:

1. The reaction conditions in the whole process are mild, the reaction is rapid, and all of them are chemically modified. The polymer is grafted on the surface of the substrate in the form of covalent bonds, and the surface grafting is firm and not easy to fall off.

2. The surface of the substrate after graft modification shows good pH response performance, and changes in wetting performance and swelling performance will occur under different pH conditions.

3. The surface of the substrate after graft modification also exhibits good photoresponse performance, and the grafted azobenzene compound can have good photoisomerization performance on the surface.

Description of drawings

Fig. 1. The surface photoresponse ultraviolet-visible spectrogram prepared according to embodiment 1.

Fig. 2. The graph of the pH-responsive swelling change of the polymer on the surface of the substrate prepared according to Example 1.

Fig. 3. The XPS analysis spectrograms of the surface prepared according to Example 2 at different pHs.

Fig. 4. Changes in surface wetting properties of the surface prepared according to Example 2 under different light conditions and solutions with a specific pH value.

Figure 5. Changes in contact angles of surfaces prepared according to Example 2 under a series of different pH and illumination.

Figure 6. Comparison of surface contact angles under different lighting conditions.

Fig. 7 is the change of surface contact angle with time under different pH solutions of the surface prepared according to Example 3.

detailed description

The pH-responsive compound is dimethylaminoethyl methacrylate as an example, the English name is DMAEMA;

The photoresponsive compound is exemplified by 2-methyl-4-azobenzene acrylate, named MPA-Azo.

Embodiment 1: surface modification of quartz sheet

(1), silanization of quartz sheet: immerse the quartz sheet successively in ethanol, acetone, and deionized water for ultrasonic treatment for 5 minutes, blow dry with nitrogen, and put into "piranha" solution [concentrated sulfuric acid (98%wt.%) and hydrogen peroxide (30%wt.%) heated in a volume ratio of 7:3] for 2 hours, then rinsed with a large amount of deionized water, and dried with nitrogen to make the surface rich in hydroxylation. Take 10 mg of γ-methacryloxypropyltrimethoxysilane (γ-MPS) and add it to 10 mL of toluene solution, and immerse the hydroxylated quartz plate in it for 12 hours. Due to hydrolytic condensation, the surface of the quartz plate will be grafted A silane coupling agent with a double bond; wash the substrate grafted with the silane coupling agent with ethanol, and dry it with nitrogen gas for later use.

(2), preparation of pH-responsive photopolymerization system solution (DMAEMA-80wt.%, ethanol-16wt.%, photoinitiator 2-hydroxyl-2methyl-1-phenyl ketone-3wt.%, crosslinking agent three Hydroxymethylpropane triacrylate-1wt.%) is coated on the silanized quartz plate, irradiated with UV-S1000 point light source for 120s, the light intensity is 40mW/cm ² , the modified quartz plate is immersed in ethanol for 2 minutes and ultrasonicated with nitrogen gas Blow dry and set aside. In this step, a spherical mask is added during the illumination process to construct the microsphere pattern painting surface.

(3), prepare photoresponsive photopolymerization system solution (MPA-Azo-30wt.%, photoinitiator isopropylthioxanthone-3wt.%, acetone-67wt.%), apply in step (2) On the base material obtained in , irradiate with a UV curing light for 120s with a light intensity of 40mW/cm ² , and then sonicate in ethanol for 2 minutes to obtain the final product.

(4) Carry out photoresponsiveness test and pH responsiveness test to the product in step (3).

Embodiment 2: surface modification of glass sheet

(1), glass sheet silanization: the glass sheet is immersed in ethanol, acetone, deionized water and ultrasonically cleaned for 5 minutes, blown dry with nitrogen, and put into "piranha" solution [concentrated sulfuric acid (98%wt.%) and hydrogen peroxide (30%wt.%) heated in a volume ratio of 7:3] for 2 hours, then rinsed with a large amount of deionized water, and dried with nitrogen for later use. Take 10mg of γ-methacryloxypropyltrimethoxysilane (γ-MPS) and add it to 10mL of toluene solution, immerse the hydroxylated glass sheet in it for 12 hours, and graft the silane coupling agent with double bond on the surface of the glass sheet ; Clean the glass piece grafted with silane coupling agent with ethanol, and dry it with nitrogen gas for later use.

(2), prepare the photopolymerization system solution (DMAEMA-80wt.%, ethanol 9.9wt.%,-photoinitiator 2-hydroxyl-2 methyl-1-phenyl ketone-0.1wt.% of cross-linking pH response Agent trimethylolpropane triacrylate-10wt.%) is coated on the silanized substrate, irradiated with UV-LED for 300s, the light intensity is 40mW/cm ² , the modified substrate is immersed in ethanol for 2 minutes and ultrasonicated with Blow dry with nitrogen gas.

(3), prepare photoresponsive photopolymerization system solution (MPA-Azo-30wt.%, photoinitiator isopropylthioxanthone-0.1wt.%, acetone-69.9wt.%), be coated in step ( On the substrate obtained in 2), irradiate with a UV curing light for 300 s with a light intensity of 40 mW/cm ² , and then sonicate in ethanol for 2 minutes to obtain the final product.

(4) The above products were subjected to the classic host-guest recognition reaction between azobenzene and β-cyclodextrin, and studied the surface wetting caused by the coating and shedding of cyclodextrin and azobenzene on the surface under different light levels of 365nm and 450nm performance changes.

(5) Carry out photoresponsiveness test and pH responsiveness test to the product in step (3).

Embodiment 3: silicon wafer surface modification

(1), silicon wafer surface silanization: the silicon wafer is successively immersed in ethanol, acetone, deionized water and ultrasonically cleaned for 5 minutes, blown dry with nitrogen, and put into "piranha" solution [concentrated sulfuric acid (98%wt.%) and Hydrogen peroxide (30%wt.%) was heated in a volume ratio of 7:3] for 4 hours, then rinsed with a large amount of deionized water, and dried with nitrogen gas for later use. Take 10mg of γ-methacryloxypropyltrimethoxysilane (γ-MPS) and add it to 10mL of toluene solution, immerse the hydroxylated silicon chip in it for 12 hours, and graft the silane coupling agent with double bond on the surface of the silicon chip ; Clean the silicon chip grafted with silane coupling agent with ethanol, and dry it with nitrogen gas for later use.

(2), prepare pH-responsive photopolymerization system solution (DMAEMA-20wt.%, ethanol 74wt.%, -photoinitiator 2-hydroxyl-2methyl-1-phenyl ketone-3wt.%, crosslinking agent three Methylol propane triacrylate-3wt.%) is coated on the silanized silicon wafer, illuminated by a mercury lamp for 900s, with a light intensity of 10mW/cm ² , immerse the modified substrate in ethanol for 2 minutes, and dry it with nitrogen stand-by.

(3), prepare photoresponsive photopolymerization system solution (MPA-Azo-30wt.%, photoinitiator isopropylthioxanthone-0.1wt.%, acetone-69.9wt.%), be coated in step ( On the surface of the silicon wafer obtained in 2), irradiate with a UV curing light for 900 s with a light intensity of 10 mW/cm ² , and then sonicate in ethanol for 2 minutes to obtain the final product.

(4), carry out photoresponsiveness test and pH responsiveness test to product.

Embodiment 4: surface modification of iron sheet

(1), silanization on the surface of the iron sheet: put the iron sheet into NaOH solution for degreasing cleaning, then ultrasonically clean it with deionized water for 5 minutes, take 10 mg of γ-methacryloxypropyl trimethoxysilane (γ- MPS) was added to 10 mL of methanol solution, the pH was adjusted to 4 with acetic acid, and the treated iron sheet was immersed in it for 24 hours. The surface of the iron sheet was grafted with silane coupling agent, then cleaned with ethanol, and dried with nitrogen gas for later use.

(2), preparation of pH-responsive photopolymerization system solution (DMAEMA-80wt.%, ethanol-17wt.%, photoinitiator 2-hydroxyl-2methyl-1-phenyl ketone-1wt.%, crosslinking agent three Methylolpropane triacrylate-2wt.%) is coated on the surface of the silanized iron sheet, illuminated with a mercury lamp for 60s, with a light intensity of 100mW/cm ² , immerses the modified substrate in ethanol for 2 minutes, and blows it with nitrogen Dry and set aside.

(3), prepare photoresponsive photopolymerization system solution (MPA-Azo-30wt.%, photoinitiator isopropyl thioxanthone-1wt.%, acetone-69wt.%), apply in step (2) On the surface of the iron sheet obtained in , irradiate with a curing light for 60s at a light intensity of 100mW/cm ² , and then sonicate in ethanol for 2 minutes to obtain the final product.

(4) Carry out photoresponsiveness test and pH responsiveness test to the product in step (3).

Embodiment 5: PET film surface modification

(1), prepare pH-responsive photopolymerization system solution (DMAEMA-80wt.%, ethanol-14wt.%, photoinitiator 2-hydroxyl-2methyl-1-phenyl ketone-1wt.%, crosslinking agent three Methylolpropane triacrylate-5wt.%) is coated on the PET film, illuminated with a mercury lamp for 300s, the light intensity is 40mW/cm ² , the modified film is immersed in ethanol and ultrasonicated for 1 minute, and dried with nitrogen gas for use .

(2), preparation of photoresponsive photopolymerization system solution (MPA-Azo-30wt.%, photoinitiator isopropylthioxanthone-3wt.%, acetone-67wt.%), coated in step (1) On the base material obtained in , irradiate with a curing light for 300 s with a light intensity of 40 mW/cm ² , and then sonicate in ethanol for 1 minute to obtain the final product.

(3) Perform photoresponsiveness test and pH responsiveness test on the product in step (2).

Embodiment 6: surface modification of polypropylene PP

(1), prepare the photopolymerization system solution of pH response (DMAEMA-80wt.%, ethanol 16.9wt.%, photoinitiator 2-hydroxyl-2 methyl-1-phenyl ketone-0.1wt.%, crosslinking agent Trimethylolpropane triacrylate-3wt.%) is coated on the PP sheet, irradiated with UV-LED light for 120s, the light intensity is 50mW/cm ² , the modified substrate is immersed in ethanol and ultrasonicated for 1 minute, blown with nitrogen Dry and set aside.

(2), prepare photoresponsive photopolymerization system solution (MPA-Azo-20wt.%, photoinitiator isopropyl thioxanthone-0.1wt.%, acetone-79.9wt.%), be coated in step ( On the substrate obtained in 1), irradiate with a UV curing light for 120s with a light intensity of 50mW/cm ² , and then sonicate in ethanol for 1 minute to obtain the final product.

(3) Perform photoresponsiveness test and pH responsiveness test on the product in step (2).

The changes in pH and light-responsive wettability measured in Examples 4, 5, and 6 are similar to the results in Example 3, and the change in contact angle is within 3°.

Claims (4)

1. the method that two photopolymerization reactions prepare stimuli-responsive surface, it is characterised in that comprise the following steps：

(1) the Photopolymer System solution of pH responses, is prepared, is coated onto on substrate surface, it is anti-that illumination 60-900s brings it about photopolymerization Should, ultrasound 1-10min in this modified base material immersion ethanol is dried up with nitrogen stand-by；

(2) photo polymerization monomer of light or temperature environment stimulating responsive, the substrate surface obtained in being coated in step (1), are prepared On, illumination 60-900s brings it about secondary photopolymerization reaction, and then by this base material, ultrasound 1-10min obtains whole product in ethanol Thing；

Photopolymer System formula described in step (1)：

(1), monomer contains double bond for one end, and the other end contains the monomer of tertiary amine, and the mass fraction for accounting for system is 20%-98%,

Formula is：

n≥1；R₃=H or CH₃；

R₁、R₂For following group：

1≤m≤10

(2), cross-linking agent is the third oxidation trimethylolpropane trimethacrylate, pentaerythritol triacrylate, three hydroxyl first of ethoxyquin One kind in base propane triacrylate, trimethylolpropane trimethacrylate, trimethylol-propane trimethacrylate or Various mixing, account for system quality fraction for 1%-10%；

(3), initiator is crack type photoinitiator 1- hydroxy-cyciohexyl benzophenones (184), 2- methyl -2- (4- morpholinyls) -1- [4- (methyl mercapto) phenyl] -1- acetone (907), 2- hydroxy-2-methyl -1- are to ethoxy ether phenylacetone (2959), 2- benzene Base benzyl -2- dimethylamino -1- (4- morpholine benzyl phenyl) -1- butanone (369), accounts for system quality fraction for 0.1%-3%；

(4), remaining is solvent, and solvent is ethanol, acetone, toluene, the one kind in ethyl acetate；

System formulation described in step (2) in photopolymerization reaction is：

(1), monomer contains the light and temperature-responsive monomer of double bond for end group, and the mass fraction for accounting for system is 20%-80%；It is logical Formula is：

R₄=H or CH₃

R₅For following group：

0≤m≤5；0≤p≤5

This monomer or temperature-responsive compound N-N-isopropylacrylamide；

(2), cross-linking agent is the third oxidation trimethylolpropane trimethacrylate, pentaerythritol triacrylate, three hydroxyl first of ethoxyquin One or several mixing in base propane triacrylate, trimethylol-propane trimethacrylate, account for system quality point Number is 0-10%；

(3), initiator is hydrogen-capture-type light initiator isopropyl thioxanthone (ITX), benzophenone (BP), 2-ethyl-anthraquinone (2- EA one or more mixing in), accounts for system quality fraction for 0.1%-3%；

(4), remaining is solvent, and solvent is acetone, ethanol, dichloromethane, chloroform, toluene, the one kind in ethyl acetate.

2. method according to claim 1, it is characterised in that using various in this two steps photo-polymerization process in step (1) and (2) Photomask of different shapes.

3. method according to claim 1, it is characterised in that the base material described in step (1) and (2) is：Silicon chip, piezoid, glass Glass piece, iron plate, copper sheet, PET film or polypropylene PP.

4. method according to claim 1, it is characterised in that the light source described in step (1) and (2) is：Mercury lamp, xenon lamp, UV- LED or Iodine gallium light, light intensity 10-1000mW/cm²。