Patent Application
20210040278
The disclosure relates to a method for manufacturing anisotropic polymer particles, and more particularly to a method for manufacturing anisotropic polymer particles using a two-step solvent on-film annealing technique.
In recent years, anisotropic polymer particles have received growing attention because of their unique properties and morphologies. The anisotropic polymer particles can be applied to a variety of areas, such as drug delivery, optical traps, and e-paper display. Until now, a few techniques to produce the anisotropic polymer particles have been reported. However, most of the proposed techniques are complicated or require the addition of surfactants, which restrain possible applications of the anisotropic polymer particles.
A simple and facile method to prepare the anisotropic polymer particles (i.e., a thermal annealing strategy) has been previously reported, in which polymer microspheres are annealed on polymer films at elevated temperatures. Although the anisotropic polymer particles have been successfully made, the functions of the thus prepared polymer particles might be altered because of thermal degradation problems at elevated annealing temperatures.
Therefore, an object of the disclosure is to provide a simple and versatile method to prepare anisotropic polymer particles that may have different shapes.
According to the disclosure, there is provided a method for manufacturing anisotropic polymer particles, which includes the steps of:
a) preparing on a substrate a polymeric composite which includes a film of a first polymer formed on the substrate and a plurality of microspheres of a second polymer deposited on the film of the first polymer, the second polymer being different from the first polymer;
b) subjecting the polymeric composite on the substrate to a first solvent vapor annealing treatment in a vapor atmosphere of a first solvent, which is a solvent for the first polymer and which is a non-solvent for the second polymer, to permit the first polymer to swell and partially cover the microspheres of the second polymer; and
c) after step b), subjecting the polymeric composite on the substrate to a second solvent vapor annealing treatment in a vapor atmosphere of a second solvent, which is a solvent for the second polymer and which is a non-solvent for the first polymer, to permit the second polymer to swell and cover back the film of the first polymer, so as to transform the microspheres of the second polymer into the anisotropic polymer particles.
Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment(s) with reference to the accompanying drawings, of which:
Referring to
a) preparing on a substrate a polymeric composite which includes a film of a first polymer formed on the substrate and a plurality of microspheres of a second polymer deposited on the film of the first polymer, the second polymer being different from the first polymer;
b) subjecting the polymeric composite on the substrate to a first solvent vapor annealing treatment in a vapor atmosphere of a first solvent, which is a solvent for the first polymer and which is a non-solvent for the second polymer, to permit the first polymer to swell and partially cover the microspheres of the second polymer;
c) after step b), subjecting the polymeric composite on the substrate to a second solvent vapor annealing treatment in a vapor atmosphere of a second solvent, which is a solvent for the second polymer and which is a non-solvent for the first polymer, to permit the second polymer to swell and cover back the film of the first polymer, so as to transform the microspheres of the second polymer into the anisotropic polymer particles; and
d) dissolving the first polymer with a third solvent to remove the film of the first polymer so as to obtain the anisotropic polymer particles.
In certain embodiments, the first polymer and the second polymer are independently selected from polystyrene, polymethyl methacrylate, polylactide, polycaprolactone, polyvinylpyrrolidone, poly(lactic-co-glycolic acid), and combinations thereof.
In certain embodiments, the first polymer is polymethyl methacrylate and the second polymer is polystyrene.
In certain embodiments, the first solvent is selected from acetic acid, diethyl sulfate, nitroethane, ethanolamine, and combinations thereof.
In certain embodiments, the first solvent is acetic acid.
In certain embodiments, the second solvent is selected from cyclohexane, n-octane, n-dodecane, methylcyclohexane, benzene, o-xylene, ethyl benzene, and combinations thereof.
In certain embodiments, the second solvent is cyclohexane.
In certain embodiments, the third solvent is selected from acetic acid, diethyl sulfate, nitroethane, ethanolamine, and combinations thereof.
In certain embodiments, the third solvent is acetic acid.
In certain embodiments, step a) is implemented by evaporation, spin coating, blade coating, spray coating, slot die coating, inject coating, or combinations thereof.
In certain embodiments, the microspheres of the second polymer are prepared by emulsion polymerization, dispersion polymerization, suspension polymerization, microfluidics, non-solvent precipitation, templating, electrospraying, thermospraying, or combinations thereof.
In certain embodiments, in step a), the microspheres of the second polymer deposited on the film of the first polymer are arranged in a discrete sphere pattern, a single-layered aggregated sphere array, or a multi-layered aggregated sphere array.
In certain embodiments, in step a), the film of the first polymer has a thickness ranging from 10 nm to 100 μm.
In certain embodiments, in step a), the microspheres of the second polymer have an average size ranging from 10 nm to 100 μm.
In certain embodiments, in step a), the substrate is selected from a glass substrate, a silicon substrate, and a combination thereof.
In certain embodiments, each of the first and second solvent vapor annealing treatments is implemented in a chamber.
In certain embodiments, in step b), the first solvent vapor annealing treatment is implemented at a first annealing temperature ranging from 0° C. to 150° C. for a first annealing time period of up to 48 hours. When the first annealing temperature is lower than 0° C., the vapor pressure of the first solvent in the chamber may be too low for proper implementation of the first solvent vapor annealing treatment. When the first annealing temperature is higher than 150° C., the vapor pressure of the first solvent in the chamber may be too high for proper implementation of the first solvent vapor annealing treatment. When the first annealing time period is more than 48 hours, the anisotropic polymer particles may not be obtained.
In certain embodiments, in step c), the second solvent vapor annealing treatment is implemented at a second annealing temperature ranging from 0° C. to 150° C. for a second annealing time period of up to 48 hours. When the second annealing temperature is lower than 0° C., the vapor pressure of the second solvent in the chamber may be too low for proper implementation of the second solvent vapor annealing treatment. When the second annealing temperature is higher than 150° C., the vapor pressure of the second solvent in the chamber may be too high for proper implementation of the second solvent vapor annealing treatment. When the second annealing time period is more than 48 hours, the anisotropic polymer particles may not be obtained.
The morphology changes of the polymeric composite of the first and second polymers during the first and second solvent vapor annealing treatments are caused by not only surface tensions but also interfacial tensions of the first and second polymers that are swollen by the vapors of the first and second solvents. When the microspheres of the second polymer and the film of the first polymer are annealed in the vapor atmosphere of the first solvent during the first solvent vapor annealing treatment, the swelling degree for the microspheres of the second polymer is much less than that for the film of the first polymer due to that the first solvent is a solvent for the first polymer but is a non-solvent for the second polymer. The surface tension of the microspheres of the second polymer with the first solvent vapor annealing treatment is similar to that of the microspheres of the second polymer without the first solvent vapor annealing treatment. The surface tension of the film of the first polymer with the first solvent vapor annealing treatment is affected more significantly by the presence of the first solvent. Therefore, in the first solvent vapor annealing treatment, the film of the first polymer is selectively swollen by the first solvent, and gradually climbs up and coats the surfaces of the microspheres of the second polymer, while the microspheres of the second polymer are maintained in a spherical shape.
In the second solvent vapor annealing treatment, the polymeric composite is annealed in the vapor atmosphere of the second solvent, which is a solvent for the second polymer but is a non-solvent for the first polymer. Therefore, the second polymer can cover back the film of the first polymer while the morphology of the film of the first polymer is maintained, so as to transform the microspheres of the second polymer into the anisotropic polymer particles.
By using the method for manufacturing anisotropic polymer particles according to the disclosure, the anisotropic polymer particles having unique and complicated shapes, such as half-eaten-peach-shaped, snowman-shaped, and bowler-hat-shaped morphologies can be successfully prepared. The strategy of using the vapors of the first and second solvents not only solves the thermal degradation problem of polymers at elevated annealing temperatures, which is often encountered in prior art, but also have the advantage of selectively annealing different components (i.e., the first and second polymers) of the polymeric composite in sequence, which is inaccessible by other approaches.
Examples of the disclosure will be described hereinafter. It is to be understood that these examples are exemplary and explanatory and should not be construed as a limitation to the disclosure.
Referring to
An open bottle containing acetic acid was placed in a sealed glass chamber for 12 hours. The PS/PMMA composite together with the glass substrate was then placed in the glass chamber. A first vapor annealing treatment was conducted at 30° C. in a vapor atmosphere of acetic acid for 12 hours. The PS/PMMA composite together with the glass substrate was removed from the annealing chamber, followed by drying at room temperature to remove residual acetic acid therefrom.
The PS/PMMA composite together with the glass substrate was again placed in the glass chamber that contained an open bottle of cyclohexane. A second vapor annealing treatment was carried out at 30° C. in a vapor atmosphere of cyclohexane for 12 hours. The PS/PMMA composite together with the glass substrate was then taken out from the annealing chamber and dried at room temperature to remove residual cyclohexane therefrom.
The PS/PMMA composite together with the glass substrate was dipped in acetic acid for 48 hours to remove PMMA so as to obtain anisotropic PS particles.
Morphologies of the PS/PMMA composite before the first and second vapor annealing treatments, at the end of the first vapor annealing treatment conducted for 12 hours, and at the end of the second vapor annealing treatment conducted for 12 hours, and morphologies of the anisotropic PS particles thus obtained were examined using a Zeiss optical microscope (OM) and a JEOL scanning electron microscope (SEM, JSM-7401F) with accelerating voltage of 5 kV. Before examinations, the sample was dried using a vacuum pump and coated with a platinum film with a thickness of about 4 nm.
The results are shown in
The procedures of Example 1 were repeated except that the second vapor annealing treatment was carried out for 3 hours, instead of 12 hours.
Morphology of the PS/PMMA composite after the first vapor annealing treatment conducted for 12 hours and the second vapor annealing treatment conducted for 3 hours, and morphology of the anisotropic PS particles thus obtained were examined using the JEOL scanning electron microscope (SEM, JSM-7401F). The results are shown in
The procedures of Example 1 were repeated except that the second vapor annealing treatment was carried out for 6 hours, instead of 12 hours.
Morphology of the PS/PMMA composite after the first vapor annealing treatment conducted for 12 hours and the second vapor annealing treatment conducted for 6 hours, and morphology of the anisotropic PS particles thus obtained were examined using the JEOL scanning electron microscope (SEM, JSM-7401F). The results are shown in
The procedures of Example 1 were repeated except that the second vapor annealing treatment was carried out for 15 hours, instead of 12 hours.
Morphology of the PS/PMMA composite after the first vapor annealing treatment conducted for 12 hours and the second vapor annealing treatment conducted for 15 hours, and morphology of the anisotropic PS particles thus obtained were examined using the JEOL scanning electron microscope (SEM, JSM-7401F). The results are shown in
The procedures of Example 1 were repeated except that the second vapor annealing treatment was carried out for 30 hours, instead of 12 hours.
Morphology of the PS/PMMA composite after the first vapor annealing treatment conducted for 12 hours and the second vapor annealing treatment conducted for 30 hours, and morphologies of the anisotropic PS particles thus obtained were examined using the JEOL scanning electron microscope (SEM, JSM-7401F). The results are shown in
The procedures of Example 1 were repeated except that the first vapor annealing treatment was carried out for 3 hours, instead of 12 hours.
Morphology of the PS/PMMA composite after the first vapor annealing treatment conducted for 3 hours and the second vapor annealing treatment conducted for 12 hours, and morphology of the anisotropic PS particles thus obtained were examined using the JEOL scanning electron microscope (SEM, JSM-7401F). The results are shown in
The procedures of Example 1 were repeated except that the first vapor annealing treatment was carried out for 6 hours, instead of 12 hours.
Morphology of the PS/PMMA composite after the first vapor annealing treatment conducted for 6 hours and the second vapor annealing treatment conducted for 12 hours, and morphology of the anisotropic PS particles thus obtained were examined using the JEOL scanning electron microscope (SEM, JSM-7401F). The results are shown in
The PS microspheres were first annealed in a vapor atmosphere of acetic acid for 12 hours. The PMMA film was formed by spin-coating to obtain a polymeric composite, in which the PS microspheres were completely covered by the PMMA film. The polymeric composite was subjected to a first solvent vapor annealing treatment in the vapor atmosphere of acetic acid for 12 hours, followed by a second solvent vapor annealing treatment in a vapor atmosphere of cyclohexane for 12 hours. After that, the PMMA film was selectively removed using acetic acid, so as to obtain PS particles.
The PS particles thus obtained were examined using the JEOL scanning electron microscope (SEM, JSM-7401F). The results are shown in
As shown in OM images of
Furthermore, as shown in SEM images (f) to (q) of
In addition, the PS microspheres may aggregate together, as shown in SEM image (n), in which PMMA starts to wet the neighboring PS microspheres at the end of the first solvent vapor annealing treatment conducted for 12 hours, resulting in formation of a double volcano-shaped PMMA film, as shown in SEM image (o). At the end of the second solvent vapor annealing treatment conducted for 12 hours, the aggregated PS microspheres can cover back the PMMA film, generating PS particles with twin holes, as shown in SEM image (p). After the PMMA film is selectively removed by acetic acid, the anisotropic bowler-hat-shaped PS particles formed from single, double, or even triple PS microspheres can be observed, as shown in SEM image (q).
For the anisotropic PS particles of Example 2, a small protrusion formed on the anisotropic PS particles, which is indicated by an arrow in image (a′) of
For the anisotropic PS particles of Example 3, they are of a snowman-shaped morphology, as shown in image (b′) of
For the anisotropic PS particles of Examples 4 and 5, they are of a bowler-hat-shaped morphology, as shown in images (c′) and (d′) of
For the anisotropic PS particles of Example 6, they are of a half-eaten-peach-shaped morphology, as shown in image (a′) of
For the anisotropic PS particles of Example 7, they are of a snowman-shaped morphology, as shown in image (b′) of
For the PS particles of Comparative Example 1, they maintain a spherical shape, as shown in images (a′) and (b′) of
In view of the aforesaid, the method for manufacturing anisotropic polymer particles according to the disclosure can successfully prepare anisotropic polymer particles having unique and complicated shapes, such as half-eaten-peach-shaped, snowman-shaped, and bowler-hat-shaped morphologies. The strategy of using vapors of the first and second solvents can solve thermal degradation problem of polymers at elevated annealing temperatures, which is often encountered in prior art.
In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment(s). It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure.
While the disclosure has been described in connection with what is (are) considered the exemplary embodiment(s), it is understood that this disclosure is not limited to the disclosed embodiment(s) but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
