U.S. Pat. No. 7,135,523 B2 discloses a method for making a series of nanoscale microstructures, including helical microstructures and cylindrical microstructures. This method includes the steps of (1) forming a chiral block copolymer containing a plurality of chiral first polymer blocks and a second polymer blocks wherein the chiral first polymer blocks have a volume fraction ranging from 20 to 49%; (2) causing a phase separation in the chiral block copolymer. In a preferred embodiment, the chiral block copolymer is poly(styrene)-poly(L-lactide) (PS-PLLA) chiral block copolymer, and the copolymerization process is a living copolymerization process which includes the following steps: (a) mixing styrene with BPO and 4-OH-TEMPO to form 4-hydroxy-TEMPO-terminated polystyrene; and (2) mixing the 4-hydroxy-TEMPO-terminated polystyrene with [(η3-EDBP)Li2]2[η3-″Bu)Li(0.5Et2O)]2 and L-lactide in an organic solvent preferably CH2Cl2 to form the poly(styrene)-poly(L-lactide) chiral block copolymer. Transmission electron microscopy (TEM) and small X-ray scattering (SAXS) studies show that when the volume fraction of poly(L-lactide) is about 35-37%, nanoscale helices with a pitch of 43.8 nanometers and a diameter of 34.4 nanometers were observed.
US patent publication 2004/0265548 A discloses a nanopatterned template for use in manufacturing nanoscale objects. The nanopatterned template contains a nanoporous thin film with a periodically ordered porous geomorphology which is made from a process comprising the steps of: (a) using a block copolymerization process to prepare a block copolymer comprising first and second polymer blocks, the first and second polymer blocks being incompatible with each other; (b) forming a thin film under conditions such that the first polymer blocks form into a periodically ordered topology; and (c) selectively degrading the first polymer blocks to cause the thin film to become a nanoporous material with a periodically ordered porous geomorphology. In a preferred embodiment, the block copolymer is poly(styrene)-b-poly(L-lactide) (PS-PLLA) chiral block copolymer, the first polymer is poly(L-lactide), and the second polymer is polystyrene. Experimental results show that the first polymer blocks can be formed into a hexagonal cylindrical geomorphology with its axis perpendicular to a surface of the thin film. After hydrolysis to selectively degrade the first polymer blocks, a thin film having a series of repeated nanoscale hexagonal-cylindrical channels is obtained.
US patent publication 2006/0124467 A discloses metal nanodot arrays and fabrication methods thereof. A film of a block copolymer is deposited on a conductive substrate. The block copolymer comprises first polymer and second polymer blocks, wherein the first polymer blocks have a periodically ordered morphology. The first polymer blocks are selectively degraded to form a nanopatterned template comprising periodically ordered nanochannels. By electroplating, metal is deposited into the nanochannels that expose the conductive substrate, thus forming a metal nanodot array.
Rong-Ming Ho, et al. in an article entitled, “Helical Nanocomposites from Chiral Block Copolymer Templates”, J. AM. CHEM. SOC. 2009, 131, 1356-1357, disclose a three-dimensional ordered helical nanocomposite prepared with the combination of the self-assembly of a degradable block copolymer and sol-gel chemistry. PS with helical nanochannels is prepared first from the self-assembly of the PS-PLLA chiral block copolymer after hydrolysis, and then used as template. By exploiting the nanoreactor concept, sol-gel reaction is then carried out within the template so as to fabricate a helical nanocomposite. SiO2 nanohelices can be obtained after degradation of PS template under UV exposure.
The inventors of the invention of the present application in an article, entitled “Inorganic Gyroid with Exceptionally Low Refractive Index from Block Copolymer Templating”, Nano Lett. 2010, 10, 4944-5000, published on Internet on Nov. 3, 2010, disclose an antireflection structure of SiO2 gyroid having an exceptional low refractive index, e.g. as low as 1.1, prepared by first forming a layer of PS-PLLA chiral block copolymer with spin coating and solvent annealing, followed by the hydrolysis, sol-gel process, and degradation of PS template described above.
Details of the disclosures in the aforesaid US patent and patent publication, and the aforesaid articles are incorporated herein by reference.
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