METHOD FOR PREPARING POROUS HYDROGEL THROUGH FREEZING-ILLUMINATION

Abstract

The present invention discloses a freezing-illumination method for preparing porous gels, comprising the steps of: (a) synthesizing the gels containing dynamic exchangeable bonds; (b) illuminating the gels under frozen state by certain wavelength light source; (c) elevating the temperature and melt the ice crystals within the gels to get the porous structure. The dynamic exchangeable bonds existing in the gels include double/multi-sulfur bond, hydrazine bond, boronic ester bond. Catalyst is also included in the gel composition to activate the bond exchange reactions under illumination. This new method for preparing porous gels is easy to operate and suitable for most kinds of gels. Meanwhile, it can spatially control the pore structure within the gels by local illumination.

Claims

1. A freezing-illumination method for preparing porous hydrogels, the method comprising the following steps: synthesizing the gels containing reversible exchangeable bonds; illuminating the gels under frozen state by certain wavelength light source; elevating temperature and melting ice crystals within the gels to obtain porous structures.

2. The method of claim 1, wherein the dynamic exchangeable bonds include double/multi-sulfur bond, hydrazine bond, boronic ester bond, host-gest interaction bond.

3. The method of claim 1, wherein the gel composition includes a catalyst which can activate the reversible exchangeable bonds under the illumination by light source with certain wavelength; and wherein the amount of the catalyst ranges 0.05-5% by weight of the dry gel.

4. The method of claim 1, wherein for the double/multi-sulfur bond, the catalyst is a photo-radical initiator; for the hydrazine bond, the catalyst is a photo-base generator; for the boronic ester bond, the catalyst is a photo-acid generator, for the host-gest interaction bond, no catalyst is included.

5. The method of claim 1, wherein addition of the catalyst includes in situ introduction during the gel formation or diffusion into the gel after the gel formation.

6. The method of claim 1, wherein the wavelength of the light source is 200-470 nm, and the illumination time is 0.5 min-24 hours.

7. The method of claim 1, wherein the illumination process includes uniformly irradiation or locally irradiation by a mask.

8. The method of claim 1, wherein the freezing process includes uniformly freezing or directionally freezing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1: the image of laser scanning confocal microscope for example 1.

[0038] FIG. 2: the image of laser scanning confocal microscope for example 2.

[0039] FIG. 3: the image of laser scanning confocal microscope for example 3.

[0040] FIG. 4: the image of laser scanning confocal microscope for example 4.

[0041] FIG. 5: the image of laser scanning confocal microscope for example 5.

DETAILED EMBODIMENTS OF THE PRESENT INVENTION

[0042] A further illustration of the invention is made with examples. However, the protection scope of the present invention is not limited by these examples.

Example 1 (Disulfide Bond)

[0043] Materials: Acrylamide (AAm) and 2-hydroxy-4-(2-hydroxyethoxy)-2-methyl propiophenone (12959) purchased from J&K. N,N-bis(acryloyl) cystamine (BISAC) purchased from Alfa Aesar. Ammonium persulfate and N,N,N,N-tetramethylethylenediamine purchased from Sinopharm.

[0044] Preparation: 500 mg acrylamide and 5 mg N,N-bis(acryloyl) cystamine were dissolved in 5 ml deionized water. After fully dissolved, 100 L ammonium persulfate and 10 L N,N,N,N-tetramethylethylenediamine were added into the solution. The solution was transferred to a sealed glass vessel quickly. 24 hour later, the resulting gel was immersed in a solution which contains the 2-hydroxy-4-(2-hydroxyethoxy)-2-methyl propiophenone (photo-catalyst) for 24 h. The gel was frozen by a cooling stage. Under the freezing condition, the gel was exposed by UV irradiation integrally for 5 min. After thawing, the gel swelled in the deionized water to obtain porous gels. The laser scanning confocal microscope was applied to characterize the pore structure of the obtained gel.

Example 2 (Boronic Ester Bond)

[0045] Materials: m-acrylamido phenylboronic acid, and the structure was as follow:

##STR00001##

[0046] N-[Tris(hydroxymethyl)methyl]acrylamide was purchased from Alfa Aesar, and the structure as follow:

##STR00002##

[0047] Acrylamide (AAm) was purchased from J&K. Ammonium persulfate and N,N,N,N-tetramethylethylenediamine were purchased from Sinopharm. Diphenyliodonium nitrate was purchased from Aladdin.

[0048] Preparation: 446 mg acrylamide, 60 mg m-acrylamido phenylboronic acid and 55 mg N-[Tris(hydroxymethyl)methyl]acrylamide were dissolved in the 5 ml deionized water. After fully dissolved, 100 L ammonium persulfate and 10 L N,N,N,N-tetramethylethylenediamine were added into the solution. The solution was transferred to a sealed glass vessel quickly. 24 hours later, the resulting gel was immersed in a solution which contains the diphenyliodonium nitrate (control the pH=10) for 24 hours. The gel was frozen by a cooling stage. Under the freezing condition, the gel was exposed by UV irradiation integrally for 5 min. After thawing, the gel swelled in the water to obtain porous gels. The laser scanning confocal microscope was applied to characterize the pore structure of the porous gel.

Example 3 (Hydrazine Bond, Locally Illumination)

[0049] Materials: Polyethylene glycol was terminated by benzoyl hydrazine (Mn=2000), and the structure was as follow.

##STR00003##

[0050] Tris[(4-aldehyde-phenoxy)-methyl] ethane, and the structure was as follow:

##STR00004##

[0051] Tetraphenylborate quaternary ammonium (Photobase generator).

[0052] Preparation: 45.4 mg polyethylene glycol terminated by benzoyl hydrazine and 5.8 mg Tris[(4-aldehyde-phenoxy)-methyl] ethane were dissolved in the 1.0 ml dimethylsulfoxide. After fully dissolved, 0.5 L acetic acid was added into the solution. The solution was transferred to a sealed glass vessel quickly. 24 hours later, the resulting gel was immersed in a solution which contains the photobase generator (control the pH<6) for 24 hours. The gel was frozen by a cooling stage. Under the freezing condition, the gel was exposed by UV irradiation using a photo mask with a SCI pattern for 5 min. After thawing, the gel swell in the water to obtain porous gels. The laser scanning confocal microscope was applied to characterize the pore structure of the porous gel.

Example 4 (Host-Gust Interaction)

[0053] Materials: Acrylamido cyclodextrin, and the structure was as follow:

##STR00005##

[0054] Acrylamido azobenzene, and the structure was as follow:

##STR00006##

[0055] Acrylamide (AAm) purchased from J&K. Ammonium persulfate and N,N,N,N-tetramethylethylenediamine purchased from Sinopharm.

[0056] Preparation: 100 mg acrylamide, 60 mg acrylamido cyclodextrin and 10 mg acrylamido azobenzene were dissolved in the 5 ml deionized water. After fully dissolved, 100 L ammonium persulfate and 10 L N,N,N,N-tetramethylethylenediamine were added into the solution. The solution was transferred to a sealed glass vessel quickly. 24 hour later, the resulting hydrogel was immersed in the deionized water for 24 hours. The hydrogel was frozen by a cooling stage. Under the freezing condition, the hydrogel was exposed by UV irradiation integrally for 5 min. After thawing, the hydrogel swelled in the water to obtain the porous hydrogels. The laser scanning confocal microscope was applied to characterize the pore structure of the porous gel.

Example 5 (Hydrophobic Monomer)

[0057] Materials:

[0058] butyl methacrylate (BA) purchased from sigma-aldrich and phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide (819) purchased from J&K. N,N-bis(acryloyl) cystamine (BISAC) purchased from Alfa Aesar.

[0059] Preparation: 500 mg butyl methacrylate and 5 mg N,N-bis(acryloyl) cystamine were dissolved in 5 ml dimethyl sulfoxide. After fully dissolved, 4 mg ammonium persulfate and 10 L N,N,N,N-tetramethylethylenediamine were added into the solution. The solution was transferred to a sealed glass vessel quickly. 24 hours later, the resulting gel was immersed in a dimethyl sulfoxide solution which contains the phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (photo-catalyst) for 24 hours. The gel was frozen by a cooling stage. Under the freezing condition, the gel was exposed by UV irradiation integrally for 5 min. After thawing, the gel swelled in the dimethyl sulfoxide to obtain porous gels. The laser scanning confocal microscope was applied to characterize the pore structure of the obtained gel.