1. Field of the Invention
The present invention relates to a fabrication method of a nanomaterial, in particular to a fabrication method of a nanocomposite material and a nanomaterial by using a polymeric nanoporous template.
2. Description of the Related Art
Due to the mutual insolubility of chain segments and the effect of binding chemical bonds of a block copolymer, the block copolymer at a temperature below a specific temperature (which is called the order-disorder transition temperature) will be self-assembled to form an ordered microstructure in a state with minimum Gibbs free energy of thermodynamics. After the microphase separation takes place, a domain-size falls in a neighborhood of tens of nanometers. Therefore, the block copolymer at a temperature below the order-disorder transition temperature will form various nanostructures varied with the volume fraction of constituted block, and the nanostructures can be sphere, hexagonal cylinder, lamellae, bicontinuous (or gyroid) or perforated layer structure. Obviously, the major advantages of a block copolymer resides on the features of a nanoscale size, a diversification, and a periodic nanostructure that allow arrangements in a broad range, and thus such copolymer is very useful in academic and industrial applications.
Various kinds of nanostructures are synthesized and classified using the dimensionality of the nanostructure itself. All kinds of nanomaterials used for structural applications were suggested to build from the constituting elementary units, namely, 0D dots and particles, 1D nanowires and nanotubes, 2D coatings and films, and 3D bulks. A series of related syntheses and applications of inorganic nanostructures catch the world's attention and attract related scholars to do researches in this area. For example, nanowires and inorganic nanobelts were published by Professor Zhong-Lin Wang of Georgia Institute of Technology, wherein the manufacture and property measurement of a device including a sensor or a nanogenerator. It is not difficult to observe the popularity and significance of this field. Inorganic helix nanowires catch people's attention due to its mechanical strength and optical applications. Inorganic nanomaterials and composite materials can be prepared by different ways including a vapor-liquid-solid growth process, or a template having nanoholes and integrated with a chemical vapor deposition, an electrodeposition, or a sol-gel process. In addition, the self-assembly of a surfactant and an inorganic precursor can be synthesized into an inorganic nanowire and its composite material of different structures. However, it is still a challenging research at the present stage to prepare orderly arranged inorganic nanomaterials of different structures.
There are two main methods of producing inorganic nanomaterials of different structures by using a porous template, such as an anodic aluminum oxide (AAO) template and a block copolymer system to fill other different materials. However, the AAO template has holes mostly with a cylinder structure and belongs to a hard material, thereby incurring an inconvenient manufacturing process. At present, a common block copolymer system generally includes a polystyrene-polymethylmethacrylate (PS-PMMA) system and a polystyrene-polyimide (PS-PI) system. The PS-PMMA system is provided for removing the PMMA by an ultraviolet (UV) light to obtain a PS porous template. Due to the penetrability of the ultraviolet light, the larger the thickness, the higher is the difficulty for the ultraviolet light to penetrate and remove the PMMA. Therefore, most of these systems can be made as films. In addition, small molecules remained after the ultraviolet light decomposes the PMMA are removed by a solvent, and such process requires two steps including a dry process and a wet process. The PS-PI system removes PI by ozone. Similarly, this process involves a gas penetrability issue and complicated dry and wet processes, and thus the PS-PI can mostly only be used for the application of a film.
It is a primary objective of the present invention to provide a fabrication method of a nanomaterial by using a polymeric nanoporous template to produce a nanocomposite material having a nanostructure in a periodic arrangement and composed of a ceramics/polymer, metal/polymer or polymer/polymer, and organic/inorganic, inorganic/inorganic or organic/organic nanocomposite nanomaterial or an inorganic nanomaterial having a specific nanostructure.
According to the objective of the present invention, a fabrication method of a nanomaterial by using a polymeric nanoporous template is provided, and the method comprises the following steps. The block copolymer composed of at least one decomposable monomer and at least one undecomposable monomer polymerized with one another is used to prepare a block copolymer bulk, and a decomposable portion of the block copolymer bulk forms a plurality of nanostructures in a periodic arrangement. The block copolymer bulk is hydrolyzed selectively to degrade a chain segment of the decomposable portion by an alkaline solution. A polymeric nanoporous template having a plurality of holes can be obtained after removing the decomposable portion. Wherein, the diameter of the holes or the distance between centers of two adjacent holes is equal to 5-50 nm. A filler material is filled into the holes by a so-gel process to obtain a nanocomposite material having the same structure as the block copolymer bulk structure. The polymeric nanoporous template of the nanocomposite material is removed by an ultraviolet (UV) light, a calcination process, an organic solvent or a supercritical fluid to obtain a plurality of nanomaterials with reverse phases and identical to the aforementioned plurality of nanostructures.
Wherein, the decomposable monomer is selected form the group consisting of L-lactide, D-lactide and D,L-lactide and the non-biodegradable monomer may be styrene such that the polymeric nanoporous template is composed of polystyrene.
Wherein, the filler material is selected form the group consisting of silicon dioxide (SiO2), titanium dioxide (TiO2) and barium titanate (BaTiO3).
Wherein, the nanocomposite material is silicon dioxide/polystyrene (SiO2/PS) when the polymeric nanoporous template composed of polystyrene is blended with a tetraethyl orthosilicate solution, titanium dioxide/polystyrene (TiO2/PS) when the polymeric nanoporous template is blended with a titanium(IV) isopropoxide solution, and barium titanate/polystyrene (BaTiO3/PS) when the polymeric nanoporous template is blended with barium hydroxide dissolved in acetic acid and mixed into the titanium(IV) isopropoxide solution.
The fabrication method of nanomaterial by using a polymeric nanoporous template in accordance with the present invention has the following advantages:
(1) The polymeric nanoporous template manufactured in accordance with the present invention is composed of polymers, belonging to a soft material, and having the advantages of a simple and easy manufacture and a low cost.
(2) The block copolymer of the present invention is manufactured as a lump or a film, thus providing a broader scope of applicability.
(3) The decomposable portion of the block copolymer bulk in the present invention can be removed completely by a single step of hydrolysis to provide a porous polymeric nanoporous template.
(4) The arrageability of polymers is used for removing the decomposable portion to obtain a nanoporous polymer template with a large-range arrangement, specific structure and excellent regularity, and the nanoporous polymer template is very useful for designing devices.
(5) The present invention not just manufactures nanomaterials having different nanostructures, but also the block copolymer bulks, polymeric nanoporous templates and nanocomposite materials obtained from the manufacturing process can be applied to the manufacture or property measurement of other devices depending on their functions.
With reference to
The decomposable monomer used in this method may be a chiral molecule. Each of the plurality of nanostructures is a sphere, cylinder, lamella, bicontinuous (or gyroid), perforated layer or helix structure, and the shape of the nanostructure can be controlled by a volume fraction of the block copolymer bulk. If the nanostructure is in the shape of a sphere, then the overall nanostructure may be a body cubic structure in a periodic arrangement. If the nanostructure is in the shape of a cylinder, then the overall nanostructure may be in a hexagonal close-pack cylinder structure (also known as a hexagonal cylinder structure) in a periodic arrangement. In addition, the filler material can be a ceramic material, a polymer material, a metal material or any combination of the above, such that the produced nanocomposite material is composed of ceramic/polymer, metal/polymer or polymer/polymer. The nanomaterial comprises an organic/inorganic composite nanomaterial or an inorganic nanomaterial.
With reference to
In FIGS. S22-A to S22-E, alkaline solutions are used for removing PLLA, PDLA or PLA polymer composite portions by a hydrolysis to produce a polymeric nanoporous template having a plurality of holes, wherein the shape of the holes is the same as the shape of the original PLLA, PDLA or PLA, and the diameter of the holes or the distance between centers of two adjacent holes are equal to 5˜50 nm. In FIGS. S23-A to S23-E, the concept of nanoreactor is integrated, and a sol-gel process, an electrochemical synthesis or a chemical deposition is used for filling a ceramic, metal or polymer filler material to produce a nanocomposite material in various microstructures composed of ceramics/polymer, metal/polymer or polymer/polymer. In FIGS. S24-A to S24-E, an ultraviolet (UV) light is used for removing the polymer template to obtain an amorphous nanomaterial, or a calcination process is used for removing the polymeric nanoporous template to obtain crystalline nanomaterials.
The manufacturing method of the said block copolymer PS-PLLA may be as follows (and the method of producing the block copolymers, PS-PDLA and PS-PLA is used with the same principle as described below). To achieve the production of the block copolymer having a biodegradable portion, manufacturers can use the characteristics of a synthesis having a double headed initiator and an atom transfer radical polymerization (living polymerization), and the variety of selections of monomers to polymerize the biodegradable monomers (esters) and non-biodegradable monomers to provide a block copolymer system having a biodegradable portion. Therefore, the living polymerization method is used for synthesizing a series of polyester biodegradable diblock copolymers, and the synthesis method is divided into two sequential living polymerizations. Firstly, an atom transfer radical polymerization method is adopted to prepare a styrene polymer with a narrow molecular weight distribution, and then a living ring opening polymerization is adopted to achieve the polymerization effect.
With reference to
A gel permission chromatography (GPC) is used for measuring the molecular weight and the molecular weight distribution of the synthesized PS. Since there any be a discrepancy between the molecular weight measured by the GPC and the actual molecular weight up to several times, therefore a nuclear magnetic resonance (NMR) is adopted to measure the molecular weight of the chain segments of the polyester, but the measurement of the molecular weight distribution of the copolymer still relies on the result measured by the GPC.
The preparation method of a PS-PLLA diblock copolymer bulk and the identification of its nanostructure as shown in
The morphological observation made by the TEM adopts the mass-thickness contrast of a dye. For example, as shown in
In the method of preparing a polymeric nanoporous template composed of PS only as shown in
The nanocomposite material with different compositions such as silicon dioxide (SiO2)/PS, titanium dioxide (TiO2)/PS or barium titanate (BaTiO3)/PS as shown in
The nanomaterial is prepared by a sol-gel process as shown in
The present invention adopts the aforementioned bottom-up method to synthesize a polymeric nanoporous template with a variety of structures, not just capable of filling SiO2, TiO2 and BaTiO3 only, but also capable of filling other different filler materials such as polymers, metals, or functional materials, for producing various different functional nanocomposite material. After the polymeric nanoporous template is removed, nanomaterials in various different shapes can be obtained. With such technical platform, a series of fantastic nanomaterials can be developed by a combination of the nanostructure and different filler materials. Obviously, the present invention is a novel and useful technology.
In addition, the present invention is capable of producing a block copolymer film by a block copolymer besides a block copolymer bulk, and further manufacturing a polymeric nanoporous template in the shape of a porous film. For example, PS-PLLA is used for the manufacture in a manufacturing method as follows: 1 wt % of a block copolymer (PS-PLLA) solution is used for forming a film on an indium-tin oxide (ITO) conductive substrate by a spin coating method. By controlling the solvent and the volatilization speed appropriately, we can produce a block copolymer film having a nano cylindrical microstructure with a thickness of approximately 70 nm and regularly arranged in a vertical direction. To increase the adhesion of the block copolymer film with the inorganic conductive substrate and prevent the block copolymer film from being detached during a later process of degrading PLLA by a wet method, organic molecules on the surface of the ITO substrate are used for a chemical modification, such that the adhesion force at organic and inorganic interfaces can be enhanced. The prepared block copolymer film is submerged into an aqueous sodium hydroxide (NaOH)/methanol solution to remove the PLLA chain segments, so as to obtain a polymeric nanoporous template having holes of approximately 15˜20 nm. In
The electrochemical synthesis is adopted again to fill the filler material into the holes of the polymeric nanoporous template to produce a nanocomposite film. In the manufacturing method, the filler material is a conductive polymer (which is aniline in this embodiment), and monomers of the conductive polymer (aniline) are dissolved in dilute sulfuric acid, and then a tri-electrode (working, contact and reference electrodes) method is adopted, wherein the ITO substrate coated with a template having holes acts as a working electrode, a platinum electrode acts as a contact electrode and an Ag/AgCl electrode acts as a reference electrode, and a reaction potential is applied in an electrolysis bath to diffuse the polymer monomers, and an electro-chemical reaction takes place on the conductive substrate to perform electrical polymerization reaction. To diffuse the electrolyte into organic nanoholes, the experiment flow adds a tertiary alcohol as a surfactant, and then a capillary action force drives the aniline electrolyte to diffuse and enter into the holes for the electrical polymerization reaction, and the experimental result shows that it is difficult to control the uniformity of aniline to be grown in different holes if the speed of the electrical polymerization reaction is too fast, and thus the final distribution of the conductive polymers is affected. With a pulse electroplating method together with a control of the micro current, the conductive polymers can be deposited uniformly into the organic nanoholes of PS to produce a conductive polymer/polymer nanocomposite film.
While the invention has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.
Number | Date | Country | Kind |
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098122686 | Jul 2009 | TW | national |