CN104528629B - Janus micro-sphere array that a kind of homogeneity is excellent and preparation method thereof - Google Patents

Abstract

The invention discloses a Janus microsphere array with excellent uniformity, wherein each Janus microsphere is in the shape of a round cake as a whole, and the upper surface of the Janus microsphere has a regular stripe pattern. Its preparation is a combination of self-assembled single-layer colloidal crystals and physical thermal embossing, including the preparation of 36.74 μm PSt-MCC as the imprinting substrate by the drop coating method, and the preparation of the PDMS wrinkle template as the stamp by the mechanical stretching method. The microspheres were preheated at 100°C for 15 minutes, and then covered with a wrinkle template and a certain load, and the heating was kept higher than the PStT _g temperature for a period of time. After cooling, the template is removed to obtain a circular pie-shaped Janus microsphere array with a regular stripe pattern on the upper surface. By adjusting the annealing temperature and load, Janus microspheres with different degrees of deformation were obtained. The present invention utilizes a simple operation method to simultaneously construct patterns on the surface of PSt microspheres and prepare Janus microsphere arrays with excellent uniformity, avoiding the complicated preparation process, poor uniformity, and poor shape of Janus microspheres prepared by most synthetic methods. The appearance is not easy to control the shortcomings.

Description

A Janus microsphere array with excellent uniformity and preparation method thereof

technical field

The invention relates to the microstructure processing technology of polymer microspheres, in particular to a process method for embossing polystyrene microspheres using a PDMS wrinkle template.

Background technique

Anisotropic particles impart distinct physical or chemical properties to a single particle due to their reduced symmetry compared to spherically symmetric particles. As a large class of anisotropic particles, Janus (anisotropic) particles have two half-faces with different structural shapes and/or chemical compositions. have potential application prospects. Most of the existing Janus microsphere synthesis methods still have the disadvantages of poor repeatability, low shape controllability, cumbersome preparation steps and low yield. In particular, the preparation of monodisperse polymer microspheres with uniform shape and size needs further study. However, the "top-down" strategy of preparing Janus particles by post-modification of existing symmetrical particles has attracted more and more attention from the academic community due to its wide application range and good uniformity of the obtained particles.

Contents of the invention

In view of the above prior art, the present invention provides a combination of "bottom-up" self-assembled single-layer colloidal crystals and "top-down" physical hot embossing to prepare Janus microspheres with excellent uniformity and its array method. The present invention selects 36.74 μm polystyrene microsphere single-layer colloidal crystals as the substrate, uses PDMS wrinkles with periodic sinusoidal stripe patterns prepared by mechanical stretching as the embossing template, and realizes the upper drum by simple physical hot embossing. Preparation of olive-shaped Janus microspheres with regular stripe pattern and their arrays. And it is possible to control the morphology of Janus microspheres by changing the parameters of the imprinting process. This method avoids the use of expensive instruments and cumbersome and complicated operation steps.

In order to solve the above-mentioned technical problems, the present invention proposes a Janus microsphere array with excellent uniformity, the whole of each Janus microsphere in the Janus microsphere array is in the shape of a round pie, and the upper surface of the Janus microsphere has a Regular stripe pattern.

A method for preparing a Janus microsphere array with excellent uniformity proposed by the present invention combines self-assembled single-layer colloidal crystals with physical thermal embossing, and includes the following steps:

Step 1, using the drop coating method to prepare polystyrene microsphere single-layer colloidal crystals with a particle size of 36.74 μm, and the polystyrene microsphere single-layer colloidal crystals are used as the embossing substrate;

Step 2, using a mechanical stretching method to prepare a polydimethylsiloxane wrinkle template with striped wrinkles, and the polydimethylsiloxane wrinkle template is used as a stamp;

Step 3. Preheat the embossed substrate prepared in step 1 at 100°C for 15 minutes, then cover the imprinted substrate with the stamp prepared in step 2, add a load of 10-40g, and anneal at a temperature higher than that of polystyrene Heating at the glass transition temperature of ethylene for 1 h; cooling to room temperature with the furnace, removing the stamp and unloading to obtain a Janus microsphere array with excellent uniformity.

Further speaking, in the first step, 15 μl of 36.74 μm polystyrene microsphere aqueous solution with a volume fraction of 1% was taken with a pipette gun, dropped onto a clean cover glass, and dried naturally at room temperature. Styrene microsphere monolayer colloidal crystals are the imprinting substrate.

The specific content of step two includes:

First, mix the polydimethylsiloxane prepolymer and the crosslinking agent at a mass ratio of 10:1, pour it into a petri dish, and stir it fully with a glass rod to form a uniform prepolymer;

After the above prepolymer is degassed in a circulating water multi-purpose vacuum pump for 0.5-1.5 hours, it is cured by heating at 60-80°C for 3-6 hours to obtain a polydimethylsiloxane elastomer;

Cut the above-mentioned polydimethylsiloxane elastomer into a rectangle of 6cm×2cm, and treat it with oxygen plasma for 30 minutes under the state of pre-stretching 10%, and the retraction speed during the treatment is 0.1-0.5mm/ min, a polydimethylsiloxane wrinkle template with striped wrinkles was obtained after retraction.

In the third step, the annealing temperature is 110°C or 120°C.

In the preparation method of the present invention, the degree of deformation of the microspheres is regulated through the technical parameters of the external load and the annealing temperature.

Compared with prior art, the beneficial effect of the present invention is:

The method of the invention has the characteristics of quickness, simplicity and good repeatability. Janus microsphere arrays with excellent uniformity can be prepared in one step. The invention avoids the disadvantages of poor repeatability, poor particle uniformity, low shape controllability, cumbersome preparation steps and low yield that most existing Janus microsphere synthesis methods have.

Description of drawings

Fig. 1 is the optical microscope picture of the PDMS wrinkle appearance obtained by the PDMS wrinkle template prepared by mechanical stretching method in Example 1 of the present invention;

Fig. 2 is an optical microscope picture of the olive-shaped Janus microsphere array prepared when the embossing parameter is 110°C-1h-10g in Example 1 of the present invention;

3 is an optical microscope picture of the olive-shaped Janus microsphere array prepared when the embossing parameter is 120°C-1h-10g in Example 2 of the present invention;

Fig. 4 is an optical microscope picture of the olive-shaped Janus microsphere array prepared when the embossing parameters are 120°C-1h-40g in Example 3 of the present invention.

detailed description

The method of the present invention will be further described below in conjunction with specific examples. The examples are provided for ease of understanding and by no means to limit the invention.

Embodiment 1: The Janus microsphere array with excellent uniformity is prepared, comprising the following steps:

Step 1. Prepare polystyrene microsphere single-layer colloidal crystals with a particle size of 36.74 μm by drop coating method, and the polystyrene microsphere single-layer colloidal crystals are used as the embossing substrate; the specific content is: use a pipette gun to take 15 μl of 36.74 μm PSt microsphere aqueous solution with a volume fraction of 1% was dropped onto a clean cover glass, and dried naturally at room temperature to obtain a PSt-MCC imprinted substrate.

Step 2, using the mechanical stretching method to prepare a polydimethylsiloxane wrinkle template with striped wrinkles, the polydimethylsiloxane wrinkle template is used as a stamp; the specific content is: first, polydimethylsiloxane Oxymethane (PDMS) Prepolymers and Crosslinkers 184 (purchased from U.S. Dow Corning Company) was mixed according to a mass ratio of 10:1, poured into a petri dish, and fully stirred with a glass rod to form a uniform prepolymer; After degassing for 1 hour, heat at 70°C for 4 hours to cure; obtain PDMS elastomer; finally, cut the above-mentioned PDMS elastomer into a rectangle of 6cm×2cm, and use oxygen plasma in the state of pre-stretching 10% After processing for 30 minutes, the retraction speed during the processing was 0.1mm/min. After retraction, a PDMS wrinkle template with striped wrinkles was obtained. The PDMS wrinkle morphology of the wrinkle template is shown in Figure 1.

Step 3. Preheat the imprinted substrate prepared in step 1 at 100°C for 15 minutes, then cover the imprinted substrate with the PDMS wrinkle template with striped wrinkles prepared in step 2, add a load of 10g, and place in an oven Keep the annealing temperature at 110°C and heat for 1 hour; cool down to room temperature with the furnace to remove the PDMS wrinkle template and unload it to obtain a Janus microsphere array with excellent uniformity.

Observed under an optical microscope, the whole of each Janus microsphere in the Janus microsphere array is in the shape of a round cake (that is, the original spherical microsphere decreases in size in the vertical direction (height) when it is subjected to a vertically downward external force, and the size in the lateral direction decreases. size increases, and the upper and lower surfaces of the microspheres are plane), the upper surface of the Janus microspheres has a regular stripe pattern. The Janus microsphere array obtained in Example 1 is shown in the optical mirror image of FIG. 2 .

Example 2: The steps for preparing a Janus microsphere array with excellent uniformity are basically the same as in Example 1, except that the annealing temperature in Step 3 is 120°C. The obtained circular pie-shaped Janus microsphere array is shown in the light microscope image of FIG. 3 .

Example 3: Preparation of a Janus microsphere array with excellent uniformity. The steps are basically the same as in Example 1, except that the loading in step 3 is 40 g, and the annealing temperature is 120° C. The obtained circular pie-shaped Janus microsphere array is shown in the light microscope image of FIG. 4 .

To sum up, the method of the present invention mainly utilizes the PDMS wrinkled template to perform physical thermal embossing on the PSt-MCC microsphere substrate to prepare olive-shaped Janus microsphere arrays with excellent uniformity. By adjusting the imprinting parameters such as annealing temperature and external load, Janus microspheres with controllable deformation degree in the Janus microsphere array can be obtained. The method of the invention avoids the disadvantages of poor uniformity, complicated preparation process and difficult shape control when preparing Janus microspheres by most prior synthesis methods.

Although the present invention has been described above in conjunction with the drawings, the present invention is not limited to the above-mentioned specific embodiments, and the above-mentioned specific embodiments are only illustrative and not restrictive. Under the inspiration, many modifications can be made without departing from the gist of the present invention, and these all belong to the protection of the present invention.

Claims (4)

1. the preparation method of the Janus micro-sphere array of a homogeneity excellence, the entirety of each Janus microsphere in Janus micro-sphere array is patty, the upper surface of described Janus microsphere is with regular streaks pattern, it is characterized in that, preparation method is to be combined with physical thermal impressing by self-assembled monolayer colloidal crystals, and comprises the following steps:

Step one, utilize drop-coating to prepare polystyrene microsphere monolayer colloidal crystals that particle diameter is 36.74 μm, this polystyrene microsphere monolayer colloidal crystals is as imprinting substrates；

Step 2, utilizing the preparation of mechanical stretching method with the polydimethylsiloxane wrinkle template of bar shaped wrinkle, this polydimethylsiloxane wrinkle template is as seal；

Step 3, the imprinting substrates that step one prepares is preheated 15min at 100 DEG C, the seal that then capping step two prepares on this imprinting substrates, additional 10-40g load, annealing temperature be higher than polystyrene glass transition temperature under heat 1h；Cool to room temperature with the furnace, take off seal and unload, obtain the Janus micro-sphere array that homogeneity is excellent.

2. the preparation method of the Janus micro-sphere array that homogeneity is excellent according to claim 1, it is characterized in that, in described step one, 36.74 μm of polystyrene microsphere aqueous solution 15 μ l that volume fraction is 1% are taken with liquid-transfering gun, drip on the coverslip of cleaning, naturally drying under room temperature environment, obtained polystyrene microsphere monolayer colloidal crystals is imprinting substrates.

3. the preparation method of the Janus micro-sphere array that homogeneity is excellent according to claim 1, it is characterised in that described step 2 includes:

First, after polydimethylsiloxane prepolymer body and cross-linking agent are mixed for 10:1 in mass ratio, pour in culture dish, be sufficiently stirred for the uniform prepolymer of formation with Glass rod；

Above-mentioned prepolymer after degassed 0.5-1.5 hour, is heated 3-6h at 60-80 DEG C and solidifies in the multiplex vacuum pump of circulating water type；Obtain polydimethylsiloxaneelastomer elastomer；

Above-mentioned polydimethylsiloxaneelastomer elastomer is cut into the rectangle of 6cm × 2cm, 30min is processed with oxygen plasma when prestretched 10%, retraction speed in processing procedure is 0.1-0.5mm/min, obtains the polydimethylsiloxane wrinkle template with bar shaped wrinkle after retraction.

4. the preparation method of the Janus micro-sphere array that homogeneity is excellent according to claim 1, it is characterised in that in described step 3, annealing temperature is 110 DEG C or 120 DEG C.