The authors have no acknowledgements.

1. Synthesis of CMP Thin Films through Sequential Addition
<ol>
	<li>Self-assembled monolayer (SAM) functionalization of gold on mica.
	<ol>
		<li>Prepare 1 mM solution of 11-thioacetyl-undecane acid-propargyl amide14 in ethanol (SAM-solution). Mix using ultrasonic bath till solution is clear. Protect the bottle from light using aluminum foil.</li>
		<li>Obtain gold coated mica wafer under argon. After withdrawal from the storage container immerse the mica wafer directly to the SAM-solution for 18 hr.</li>
		<li>Take the prepared Au-mica wafer out of the SAM-solution, rinse with ethanol and dry under nitrogen stream. Afterwards store the substrate protected from light and under inert gas.</li>
	</ol>
	</li>
	<li>Precursor solutions.
	<ol>
		<li>Weigh 18.64 mg Cu-catalyst (Tetrakis(acetonitrile)copper(I)hexafluoro-phosphate), 20.83 mg tetraphenylmethane (TPM)-alkyne and 24.22 mg TPM-azide and fill each component into a separate Schlenk flask. See Figure 1 for TPM-alkyne and TPM-azide, the synthesis is described in Reference15. Evacuate and refill with inert gas (N2 or argon) 3 times.</li>
		<li>Add 25 ml water-free tetrahydrofuran (THF) to each Schlenk flask. Protect the flasks with TPM-azide and TPM-alkyne from light using aluminum foil.</li>
	</ol>
	</li>
	<li>Prepare apparatus for CMP fabrication. 
	Note: The synthesis apparatus is shown in Figure 2.
	<ol>
		<li>Use a 250 ml one neck round bottom flask. Fill in 130 ml THF. Put the prepared substrate coated with alkyne terminated SAM in the sample compartment. Use a sample holder, so that the substrate is standing upright.</li>
		<li>Connect the apparatus to the Schlenk line via the junction on top of the reflux cooler.</li>
		<li>Evacuate and ventilate with inert gas 3 times.</li>
	</ol>
	</li>
	<li>Sequential addition under inert conditions.
	<ol>
		<li>Set the heater to 90 &#176;C and wait till the THF is refluxing.</li>
		<li>Let out THF from the sample compartment over the outlet at the bottom of the sample compartment. Close the outlet.</li>
		<li>Give 1 ml of the prepared TPM-azide solution and 0.5 ml of the Cu(I) catalyst solution to the sample compartment via the screw cap with septum. Use a syringe with a hollow needle to transfer the solutions sequentially from the Schlenk flask to the reaction apparatus. Note: The sequence has no influence to the reaction.</li>
		<li>Wait approximately 30 min.</li>
		<li>Let out the reaction solution over the outlet at the bottom of the sample compartment. Close the outlet and collect the condensed THF for rinsing the sample. Wait approximately 30 min.</li>
		<li>Let out the rinsing solution over the outlet at the bottom of the sample compartment. Close the outlet.</li>
		<li>Give 1 ml of the prepared TPM-alkyne solution and 0.5 ml of the Cu(I) catalyst solution to the sample compartment via the screw cap with septum. Use a syringe with a hollow needle to transfer the solutions sequentially from the Schlenk flask to the reaction apparatus. Note: The sequence has no influence to the reaction.</li>
		<li>Wait approximately 30 min.</li>
		<li>Let out the reaction solution over the outlet at the bottom of the sample compartment. Close the outlet and collect the condensed THF for rinsing the sample. Wait approximately 30 min.</li>
		<li>Repeat steps 1.4.3 to 1.4.9 until the desired amount of layers is reached. Note: One layer is approximately 1 nm thick.</li>
		<li>Take out the CMP-coated mica substrate, rinse it with THF, ethanol and dry it under nitrogen stream.</li>
	</ol>
	</li>
</ol>
2. Transfer of CMP Nanomembranes
<ol>
	<li>Poly(methyl methacrylate) (PMMA) solution.
	<ol>
		<li>Prepare a solution of 4% (wt) PMMA (M 996 kDa) in ethyl acetate. Dissolve the PMMA using ultrasonic bath till the solution is clear.</li>
	</ol>
	</li>
	<li>Spin coating of PMMA solution.
	<ol>
		<li>Set the spin coater to ramp time 10 sec from 0 to 4,000 rpm, holding time 40 sec and ramp time 10 sec from 4,000 to 0 rpm.</li>
		<li>Place the CMP coated mica substrate on the spin coater and put the PMMA solution on the wafer till it is completely covered. Start the spin coater.</li>
		<li>After spin coating is completed, put the sample for 5 min on a heating plate at 90 &#176;C.</li>
		<li>Cut off 1 mm from each edge of the coated mica substrate. Use a scissor to cut the edges.</li>
	</ol>
	</li>
	<li>Transfer of PMMA coated CMP nanomembrane.
	<ol>
		<li>Prepare solution of I2/KI/H2O (1:4:40 m/m/m) and of KI/H2O (1:10 m/m).</li>
		<li>Fill the I2/KI H2O solution in a 150 ml crystallizing dish and fill the KI/H2O solution in a 100 ml crystallizing dish. Put the PMMA coated CMP gold on mica substrate, with mica in contact to solution, on top of the I2/KI/H2O solution. Be careful that it does not sink. Wait at least 5 min.</li>
		<li>Put the PMMA coated CMP gold mica substrate from the I2/KI/H2O solution on top of the KI/H2O solution, with mica in contact to solution. Be careful that it does not sink. Wait at least 5 min.</li>
		<li>Fill distilled water in a 250 ml crystallizing dish. Strip off the PMMA/CMP/gold film from the mica. Do this by slightly immersing the substrate, beginning from one edge, in distilled water. Hold the substrate so that the mica is pointing to the water. Note: The procedure is shown in Figure 3.</li>
		<li>Dip-coat the PMMA/CMP/gold on the silicon wafer. Do this by approaching the PMMA/CMP/gold slowly with the wafer until it touches edge of the swimming PMMA/CMP/gold membrane. Pull out the silicon wafer slowly, once the Si-wafer is in contact with the PMMA/CMP/gold membrane.</li>
		<li>Strip the PMMA/CMP/gold film off from the silicon wafer. Do this by slightly immersing the substrate, beginning from one edge, in the I2/KI/H2O solution. Wait 15 min.</li>
		<li>After the gold is completely etched, transfer the PMMA/CMP membrane to water via the silicon wafer. Wait 15 min.</li>
		<li>Repeat step 2.3.7 three times to wash the membrane with water.</li>
		<li>Transfer the washed PMMA/CMP membrane to the desired substrate, e.g., a microscope slide or a gold coated silicon wafer, via the method mentioned in step 2.3.5. Let the PMMA/CMP substrate dry in air for at least 2 hr.</li>
	</ol>
	</li>
	<li>Dissolution of PMMA.
	<ol>
		<li>Put the PMMA/CMP substrate in acetone. Wait 30 min. Take out the substrate and rinse it with acetone.</li>
		<li>Repeat step 2.4.1 three times.</li>
		<li>Let the CMP substrate dry for at least 2 hr.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Lindemann, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+Freestanding+Conjugated+Microporous+Polymer+Nanomembranes+for+Gas+Separation.">Preparation of Freestanding Conjugated Microporous Polymer Nanomembranes for Gas Separation.</a> Chemistry of Materials. 26 (24), 7193-71 (2014).</li><li>Kim, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+Ultrathin+Films+of+Molecular+Networks+through+Layer-by-Layer+Cross-Linking+Polymerization+of+Tetrafunctional+Monomers.">Preparation of Ultrathin Films of Molecular Networks through Layer-by-Layer Cross-Linking Polymerization of Tetrafunctional Monomers.</a> Macromolecules. 44 (18), 7092-7095 (2011).</li><li>Vonh&#246;ren, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrafast+Layer-by-Layer+Assembly+of+Thin+Organic+Films+Based+on+Triazolinedione+Click+Chemistry.">Ultrafast Layer-by-Layer Assembly of Thin Organic Films Based on Triazolinedione Click Chemistry.</a> ACS Macro Letters. 4 (3), 331-334 (2015).</li><li>Shekhah, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Step-by-Step+Route+for+the+Synthesis+of+Metal&#8722;Organic+Frameworks.">Step-by-Step Route for the Synthesis of Metal&#8722;Organic Frameworks.</a> Journal of the American Chemical Society. 129 (49), 15118-15119 (2007).</li><li>Shekhah, O., Wang, H., Zacher, D., Fischer, R. A., W&#246;ll, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+Mechanism+of+Metal&#8211;Organic+Frameworks:+Insights+into+the+Nucleation+by+Employing+a+Step-by-Step+Route.">Growth Mechanism of Metal&#8211;Organic Frameworks: Insights into the Nucleation by Employing a Step-by-Step Route.</a> Angewandte Chemie International Edition. 48 (27), 5038-5041 (2009).</li><li>Shekhah, O., Liu, J., Fischer, R. A., W&#246;ll, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MOF+thin+films:+existing+and+future+applications.">MOF thin films: existing and future applications.</a> Chemical Society Reviews. 40 (2), 1081-1106 (2011).</li><li>Liu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deposition+of+Metal-Organic+Frameworks+by+Liquid-Phase+Epitaxy:+The+Influence+of+Substrate+Functional+Group+Density+on+Film+Orientation.">Deposition of Metal-Organic Frameworks by Liquid-Phase Epitaxy: The Influence of Substrate Functional Group Density on Film Orientation.</a> Materials. 5 (9), 1581-1592 (2012).</li><li>Such, G. K., Quinn, J. F., Quinn, A., Tjipto, E., Caruso, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assembly+of+Ultrathin+Polymer+Multilayer+Films+by+Click+Chemistry.">Assembly of Ultrathin Polymer Multilayer Films by Click Chemistry.</a> Journal of the American Chemical Society. 128 (29), 9318-9319 (2006).</li><li>Ai, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon+Nanomembranes+(CNMs)+Supported+by+Polymer:+Mechanics+and+Gas+Permeation.">Carbon Nanomembranes (CNMs) Supported by Polymer: Mechanics and Gas Permeation.</a> Advanced Materials. 26 (21), 3421-3426 (2014).</li><li>Jiang, J. -. X., Cooper, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=in+Functional+Metal-Organic+Frameworks:+Gas+Storage,+Separation+and+Catalysis.">in Functional Metal-Organic Frameworks: Gas Storage, Separation and Catalysis.</a> Topics in Current Chemistry. (ed Martin Schr&#246;der) Ch. 293, 1-33 (2010).</li><li>Dawson, R., Cooper, A. I., Adams, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoporous+organic+polymer+networks.">Nanoporous organic polymer networks.</a> Progress in Polymer Science. 37 (4), 530-563 (2012).</li><li>Muller, T., Br&#228;se, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Click+Chemistry+Finds+Its+Way+into+Covalent+Porous+Organic+Materials.">Click Chemistry Finds Its Way into Covalent Porous Organic Materials.</a> Angewandte Chemie International Edition. 50 (50), 11844-11845 (2011).</li><li>Tsotsalas, M., Addicoat, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalently+linked+organic+networks.">Covalently linked organic networks.</a> Frontiers in Materials. 2, (2015).</li><li>Kleinert, M., Winkler, T., Terfort, A., Lindhorst, T. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modular+approach+for+the+construction+and+modification+of+glyco-SAMs+utilizing+1,3-dipolar+cycloaddition.">A modular approach for the construction and modification of glyco-SAMs utilizing 1,3-dipolar cycloaddition.</a> Organic &amp; Biomolecular Chemistry. 6 (12), 2118-2132 (2008).</li><li>Plietzsch, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Four-fold+click+reactions:+Generation+of+tetrahedral+methane-+and+adamantane-based+building+blocks+for+higher-order+molecular+assemblies.">Four-fold click reactions: Generation of tetrahedral methane- and adamantane-based building blocks for higher-order molecular assemblies.</a> Organic &amp; Biomolecular Chemistry. 7, (2009).</li><li>Greenler, R. 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The authors have nothing to disclose.

For the synthesis of the CMP-film the solution of the catalyst has to be fresh. A broken catalyst (i.e., oxidized) is indicated by a blue coloration of the solution. The fresh solution is colorless.
A crucial point is to cut the edges of the mica substrate after spin coating PMMA. Also defects in the substrate should be cut, i.e., each spot were the PMMA can come in contact with the mica substrate, because of a missing gold layer. Otherwise the gold layer cannot be stripped o...

The preparation of ultra-thin polymer membranes is of high interest for applications in gas separation and nanofiltration. Challenges in the synthesis are represented by (a) the control of the membrane thickness and the homogeneity and (b) transfer of such fragile membranes. To overcome challenge (a), molecular layer-by-layer synthesis1 has shown great promise in controlling the thickness and homogeneity of thin films grown at the solid-liquid interface.2,3 Controlling the number of layers linearly controls the film thickness. The l-b-l method has been successfully used to fabricate surface mounted metal organic frameworks (SURMOFs),4-7 also the synthesis of thin polymer films via l-b-l reaction of polymer chains was demonstrated.8 The challenge (b) concerns the handling of these ultra-thin membranes. To avoid rupture or wrinkling of the nanomembranes sacrificial supports of coatings have shown great promise. 9
Here we will present a detailed protocol for synthesis of conjugated microporous polymer (CMP)10-13 thin films through sequential addition of the molecular building blocks, with desired thickness and composition. The preparation of free-standing CMP nanomembranes is achieved by using a sacrificial support. To handle and transfer the CMP nanomembranes to other supports we will describe a simple protocol to protect the membranes with sacrificial coatings and their upfloating to the liquid air interface and subsequent transfer using dip-coating.

<table>
	<tbody>
		<tr>
			<td>Acetone</td>
			<td>VWR BDH Prolabo</td>
			<td>20066.330</td>
			<td>AnalR NORMAPUR</td>
		</tr>
		<tr>
			<td>Potassium iodide</td>
			<td>VWR BDH Prolabo</td>
			<td>26846.292</td>
			<td>AnalR NORMAPUR</td>
		</tr>
		<tr>
			<td>Ethyl acetate</td>
			<td>VWR BDH Prolabo</td>
			<td>23882.321</td>
			<td>AnalR NORMAPUR</td>
		</tr>
		<tr>
			<td>Tetrahydrofurane (THF)</td>
			<td>VWR BDH Prolabo</td>
			<td>28559.320</td>
			<td>HiPerSolv CHROMANORM</td>
		</tr>
		<tr>
			<td>THF waterfree</td>
			<td>Merck Millipore</td>
			<td>1.08107.1001</td>
			<td>SeccoSolv</td>
		</tr>
		<tr>
			<td>Iodine</td>
			<td>Sigma-Aldrich</td>
			<td>20,777-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrakis(acetonitrile)copper(I)hexafluoro-phosphate</td>
			<td>Sigma-Aldrich</td>
			<td>346276-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(methyl methacrylate) 996 kDa (PMMA)</td>
			<td>Sigma-Aldrich</td>
			<td>182265-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>1.1.1.1 Methanetetrayltetrakis(4-azidobenzene) (TPM-azide)</td>
			<td></td>
			<td></td>
			<td>provided by AK Prof. Br&#228;se. Institute of organic chemistry, Karlsruhe Institute of Technology. Synthesized according to9</td>
		</tr>
		<tr>
			<td>1.1.1.1 Methanetetrayltetrakis(4-ethinylenebenzene) (TPM-alkyne)</td>
			<td></td>
			<td></td>
			<td>provided by AK Prof. Br&#228;se. Institute of organic chemistry, Karlsruhe Institute of Technology. Synthesized according to9</td>
		</tr>
		<tr>
			<td>11-thioacetyl-undecaneacid propargylamide</td>
			<td></td>
			<td></td>
			<td>provided by AK Prof. Br&#228;se. Institute of organic chemistry, Karlsruhe Institute of Technology. Synthesized according to8</td>
		</tr>
		<tr>
			<td>gold/titan coated silicium-wafer</td>
			<td>Georg Albert PVD, 76857 Silz, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>gold coated mica</td>
			<td>Georg Albert PVD, 76857 Silz, Germany</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

layer-by-layer synthesis and transfer of freestanding conjugated microporous polymer nanomembranes

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in combination with their outstanding thermal and chemical stability, and low densities. However, their insoluble nature causes problems in their processing since usually applied techniques such as spin coating are not available. Especially for membrane applications, where the processing of CMP as thin films is desirable, the processing problems have hindered their commercial application.
Here we describe the interfacial synthesis of CMP thin films on functionalized substrates via molecular layer-by-layer (l-b-l) synthesis. This process allows the preparation of films with desired thickness and composition and even desired composition gradients.
The use of sacrificial supports allows the preparation of freestanding membranes by dissolution of the support after the synthesis. To handle such ultra-thin freestanding membranes the protection with sacrificial coatings showed great promise, to avoid rupture of the nanomembranes. To transfer the nanomembranes to the desired substrate, the coated membranes are upfloated at the air-liquid interface and then transferred via dip coating.

The membranes are characterized by infrared reflection absorption spectroscopy (IRRAS).16 Figure 4 shows IRRA-spectra from a CMP-membrane transferred to a gold wafer. Typical bands from the vibrations of the aromatic backbone are at 1,605 cm-1, 1,515 cm-1 and 1,412 cm-1. Unreacted alkyne and azide groups can be observed by characteristic bands at 2,125 cm-1 and 1,227 cm-1. Figure 5 shows a scanning electron microscopy (SEM...

Watch this Scientific Journal Video about Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes at JoVE.com

Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in ...

layer-layer-synthesis-transfer-freestanding-conjugated-microporous

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9.3K Views.  Karlsruhe Institute of Technology. In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

Video: Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall.

The objective of this research was to form synthetic plant cell wall tissue using layer-by-layer assembly of nanocellulose fibrils and isolated lignin assembled from dilute aqueous suspensions.&#160; Surface measurement techniques of quartz crystal microbalance and atomic force microscopy were used to monitor the formation of the polymer-polymer nanocomposite material.

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and ...

A Technique to Functionalize and Self-assemble Macroscopic Nanoparticle-ligand Monolayer Films onto Template-free Substrates

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and scalable technique efficiently functionalizes metallic nanoparticles with thiol-ligands in a miscible water/organic solvent mixture allowing for rapid grafting of thiol groups onto the gold nanoparticle surface. The hydrophobic ligands on the nanoparticles then quickly phase separate the nanoparticles from the aqueous based suspension and confine them to the air-fluid interface. This drives the ligand-capped nanoparticles to form monolayer domains at the air-fluid interface.&#160; The use of water-miscible organic solvents is important as it enables the transport of the nanoparticles from the interface onto template-free substrates.&#160; The flow is mediated by a surface tension gradient3,4 and creates macroscopic, high-density, monolayer nanoparticle-ligand films.&#160; This self-assembly technique may be generalized to include the use of particles of different compositions, size, and shape and may lead to an efficient assembly method to produce low-cost, macroscopic, high-density, monolayer nanoparticle films for wide-spread applications.

A simple, robust and scalable technique to functionalize and self-assemble macroscopic nanoparticle-ligand monolayer films onto template-free substrates is described in this protocol.

This protocol describes a self-assembly technique to create macroscopic monolayer films composed of ligand-coated nanoparticles1,2. The simple, robust and ...

Fabrication of Large-area Free-standing Ultrathin Polymer Films

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films. Typically, ultrathin films are prepared using either sacrificial layers, which may damage the film or affect its mechanical properties, or they are made on freshly cleaved mica, a substrate that is difficult to scale. Further, the size of ultrathin film is typically limited to a few square millimeters. In this method, we modify a surface with a polyelectrolyte that alters the strength of adhesion between polymer and deposition substrate. The polyelectrolyte can be shown to remain on the wafer using spectroscopy, and a treated wafer can be used to produce multiple films, indicating that at best minimal amounts of the polyelectrolyte are added to the film. The process has thus far been shown to be limited in scalability only by the size of the coating equipment, and is expected to be readily scalable to industrial processes. In this study, the protocol for making the solutions, preparing the deposition surface, and producing the films is described.

We describe a method for the fabrication of large-area (up to 13 cm diameter) and ultrathin (as thin as 8 nm) polymer films. Instead of using a sacrificial interlayer to delaminate the film from its substrate, we use a self-limiting surface treatment suitable for arbitrarily large areas.

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films.  Typically, ultrathin films are prepared ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

Formation of Biomembrane Microarrays with a Squeegee-based Assembly Method

Lipid bilayer membranes form the plasma membranes of cells and define the boundaries of subcellular organelles. In nature, these membranes are heterogeneous mixtures of many types of lipids, contain membrane-bound proteins and are decorated with carbohydrates. In some experiments, it is desirable to decouple the biophysical or biochemical properties of the lipid bilayer from those of the natural membrane. Such cases call for the use of model systems such as giant vesicles, liposomes or supported lipid bilayers (SLBs). Arrays of SLBs are particularly attractive for sensing applications and mimicking cell-cell interactions. Here we describe a new method for forming SLB arrays. Submicron-diameter SiO2 beads are first coated with lipid bilayers to form spherical SLBs (SSLBs). The beads are then deposited into an array of micro-fabricated submicron-diameter microwells. The preparation technique uses a "squeegee" to clean the substrate surface, while leaving behind SSLBs that have settled into microwells. This method requires no chemical modification of the microwell substrate, nor any particular targeting ligands on the SSLB. Microwells are occupied by single beads because the well diameter is tuned to be just larger than the bead diameter. Typically, more 75% of the wells are occupied, while the rest remain empty. In buffer SSLB arrays display long-term stability of greater than one week. Multiple types of SSLBs can be placed in a single array by serial deposition, and the arrays can be used for sensing, which we demonstrate by characterizing the interaction of cholera toxin with ganglioside GM1. We also show that phospholipid vesicles without the bead supports and biomembranes from cellular sources can be arrayed with the same method and cell-specific membrane lipids can be identified.

Supported lipid bilayers and natural membrane particles are convenient systems that can approximate the properties of cell membranes and be incorporated in a variety of analytical strategies. Here we demonstrate a method for preparing microarrays composed of supported lipid bilayer-coated SiO2 beads, phospholipid vesicles or natural membrane particles.

Lipid bilayer membranes form the plasma membranes of cells and define the boundaries of subcellular organelles. In nature, these membranes are ...

Bioengineering

Preparation of Light-responsive Membranes by a Combined Surface Grafting and Postmodification Process

In order to modify the surface tension of commercial available track-edged polymer membranes, a procedure of surface-initiated polymerization is presented. The polymerization from the membrane surface is induced by plasma treatment of the membrane, followed by reacting the membrane surface with a methanolic solution of 2-hydroxyethyl methacrylate (HEMA). Special attention is given to the process parameters for the plasma treatment prior to the polymerization on the surface. For example, the influence of the plasma-treatment on different types of membranes (e.g.&#160;polyester, polycarbonate, polyvinylidene fluoride) is studied. Furthermore, the time-dependent stability of the surface-grafted membranes is shown by contact angle measurements. When grafting poly(2-hydroxyethyl methacrylate) (PHEMA) in this way, the surface can be further modified by esterification of the alcohol moiety of the polymer with a carboxylic acid function of the desired substance. These reactions can therefore be used for the functionalization of the membrane surface. For example, the surface tension of the membrane can be changed or a desired functionality as the presented light-responsiveness can be inserted. This is demonstrated by reacting PHEMA with a carboxylic acid functionalized spirobenzopyran unit which leads to a light-responsive membrane. The choice of solvent plays a major role in the postmodification step and is discussed in more detail in this paper. The permeability measurements of such functionalized membranes are performed using a Franz cell with an external light source. By changing the wavelength of the light from the visible to the UV-range, a change of permeability of aqueous caffeine solutions is observed.

A plasma-induced polymerization procedure is described for the surface-initiated polymerization on polymer membranes. Further postmodification of the grafted polymer with photochromic substances is presented with a protocol of conducting permeability measurements of light-responsive membranes.

In order to modify the surface tension of commercial available track-edged polymer membranes, a procedure of surface-initiated polymerization is ...

Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl dimethyl azlactone) (PGMA-b-PVDMA), are presented. Due to the high reactivity of azlactone groups towards amine, thiol, and hydroxyl groups, PGMA-b-PVDMA surfaces can be modified with secondary molecules to create chemically or biologically functionalized interfaces for a variety of applications. Previous reports of patterned PGMA-b-PVDMA interfaces have used traditional top-down patterning techniques that generate non-uniform films and poorly controlled background chemistries. Here, we describe customized patterning techniques that enable precise deposition of highly uniform PGMA-b-PVDMA films in backgrounds that are chemically inert or that have biomolecule-repellent properties. Importantly, these methods are designed to deposit PGMA-b-PVDMA films in a manner that completely preserves azlactone functionality through each processing step. Patterned films show well-controlled thicknesses that correspond to polymer brushes (~90 nm) or to highly crosslinked structures (~1-10 &#956;m). Brush patterns are generated using either the parylene lift-off or interface directed assembly methods described and are useful for precise modulation of overall chemical surface reactivity by adjusting either the PGMA-b-PVDMA pattern density or the length of the VDMA block. In contrast, the thick, crosslinked PGMA-b-PVDMA patterns are obtained using a customized micro-contact printing technique and offer the benefit of higher loading or capture of secondary material due to higher surface area to volume ratios. Detailed experimental steps, critical film characterizations, and trouble-shooting guides for each fabrication method are discussed.

Surface fabrication methods for patterned deposition of nanometer thick brushes or micron thick, crosslinked films of an azlactone block co-polymer are reported. Critical experimental steps, representative results, and limitations of each method are discussed. These methods are useful for creating functional interfaces with tailored physical features and tunable surface reactivity.

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl ...

Engineering

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...

Procedure for the Transfer of Polymer Films Onto Porous Substrates with Minimized Defects

The fabrication of devices containing thin film composite membranes necessitates the transfer of these films onto the surfaces of arbitrary support substrates. Accomplishing this transfer in a highly controlled, mechanized, and reproducible manner can eliminate the creation of macroscale defect structures (e.g., tears, cracks, and wrinkles) within the thin film that compromise device performance and the usable area per sample. Here, we describe a general protocol for the highly controlled and mechanized transfer of a polymeric thin film onto an arbitrary porous support substrate for eventual use as a water filtration membrane device. Specifically, we fabricate a block copolymer (BCP) thin film on top of a sacrificial, water-soluble poly(acrylic acid) (PAA) layer and silicon wafer substrate. We then utilize a custom-designed, 3D-printed transfer tool and drain chamber system to deposit, lift-off, and transfer the BCP thin film onto the center of a porous anodized aluminum oxide (AAO) support disc. The transferred BCP thin film is shown to be consistently placed onto the center of the support surface due to the guidance of the meniscus formed between the water and the 3D-printed plastic drain chamber. We also compare our mechanized transfer-processed thin films to those that have been transferred by hand with the use of tweezers. Optical inspection and image analysis of the transferred thin films from the mechanized process confirm that little-to-no macroscale inhomogeneities or plastic deformations are produced, as compared to the multitude of tears and wrinkles produced from manual transfer by hand. Our results suggest that the proposed strategy for thin film transfer can reduce defects when compared to other methods across many systems and applications.

We present a procedure for highly controlled and wrinkle-free transfer of block copolymer thin films onto porous support substrates using a 3D-printed drain chamber. The drain chamber design is of general relevance to all procedures involving transfer of macromolecular films onto porous substrates, which is normally done by hand in an irreproducible fashion.

The fabrication of devices containing thin film composite membranes necessitates the transfer of these films onto the surfaces of arbitrary support ...

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly successful in the synthesis of graphene nanoribbons, nanographenes and intrinsically reactive and instable, yet attractive species. It is based on the combination of solution chemistry aimed at preparation of appropriate molecular precursors for further ultra-high vacuum surface assisted transformations. This approach also owes its success to an incredible development of characterization techniques, such as scanning tunneling/atomic force microscopy and related methods, which allow detailed, local characterization at atomic scale. While the surface-assisted synthesis can provide molecular nanostructures with outstanding precision, down to single atoms, it suffers from basing on metallic surfaces and often limited yield. Therefore, the extension of the approach away from metals and the struggle to increase productivity seem to be significant challenges toward wider applications. Herein, we demonstrate the on-surface synthesis approach for generation of non-planar nanographenes, which are synthesized through a combination of solution chemistry and sequential surface-assisted processes, together with the detailed characterization by scanning probe microscopy methods.

A combination of solution and surface assisted synthesis opens new directions in the atomically precise synthesis of nanostructures. Scanning tunneling microscopy (STM) supplemented by non-contact atomic force microscopy (nc-AFM) enables detailed characterization of newly designed and generated carbon-based nano-objects.