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. 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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infrared+Study+of+Adsorbed+Molecules+on+Metal+Surfaces+by+Reflection+Techniques.">Infrared Study of Adsorbed Molecules on Metal Surfaces by Reflection Techniques.</a> The Journal of Chemical Physics. 44 (1), (1966).</li></ol>

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>Tetrahydrofuran (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&amp;auml;se. Institute of organic chemistry, Karlsruhe Institute of Technology. Synthesized according to &lt;sup&gt;9&lt;/sup&gt;.</td></tr><tr><td>1.1.1.1 Methanetetrayltetrakis(4-ethinylenebenzene) (TPM-alkyne)</td><td></td><td></td><td>Provided by AK Prof. Br&amp;auml;se. Institute of organic chemistry, Karlsruhe Institute of Technology. Synthesized according to &lt;sup&gt;9&lt;/sup&gt;.</td></tr><tr><td>11-thioacetyl-undecaneacid propargylamide</td><td></td><td></td><td>Provided by AK Prof. Br&amp;auml;se. Institute of organic chemistry, Karlsruhe Institute of Technology. Synthesized according to &lt;sup&gt;8&lt;/sup&gt;.</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

Universidad San Sebastian

Research

JoVE Journal

Chemistry

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

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 ...

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Fabrication of the Thermoplastic Microfluidic Channels

In our lab, we have successfully isolated nucleic acids directly from microliter and submicroliter volumes of human blood, urine and stool using polymer/nanoparticle composite microscale lysis and solid phase extraction columns. The recovered samples are concentrated, small volume samples that are PCRable, without any additional cleanup. Here, we demonstrate how to fabricate thermoplastic microfluidic chips using hot embossing and heat sealing. Then, we demonstrate how to use in situ light directed surface grafting and polymerization through the sealed chip to form the composite solid phase columns. We demonstrate grafting and polymerization of a carbon nanotube/polymer composite column for bacterial cell lysis. We then show the lysis process followed by solid phase extraction of nucleic acids from the sample on chip using a silica/polymer composite column. The attached protocols contain detailed instructions on how to make both lysis and solid phase extraction columns.

Here we demonstrate how to fabricate thermoplastic microfluidic chips using hot embossing and heat sealing. Then we demonstrate how to use in situ light directed surface grafting and polymerization through the sealed chip to form the composite solid phase columns.

In our lab, we have successfully isolated nucleic acids directly from microliter and submicroliter volumes of human blood, urine and stool using ...

Biology

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

We propose a simple self-assembly technique of silica colloidal nanoparticles to create a nanofluidic junction between two microchannels in polydimethylsiloxane (PDMS). Using this technique, a nanoporous bead membrane with a pore size down to ~45 nm was built inside a microchannel and applied to electrokinetic preconcentration of DNA samples.

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its ...

Engineering

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 ...

Bioengineering

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 ...

Synthesis of Hydrogels with Antifouling Properties As Membranes for Water Purification

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and thus achieving stable water permeability through membranes over time. Here, we report a facile method to prepare hydrogels based on zwitterions for membrane applications. Freestanding films can be prepared from sulfobetaine methacrylate (SBMA) with a crosslinker of poly(ethylene glycol) diacrylate (PEGDA) via photopolymerization. The hydrogels can also be prepared by impregnation into hydrophobic porous supports to enhance the mechanical strength. These films can be characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to determine the degree of conversion of the (meth)acrylate groups, using goniometers for hydrophilicity and differential scanning calorimetry (DSC) for polymer chain dynamics. We also report protocols to determine the water permeability in dead-end filtration systems and the effect of foulants (bovine serum albumin, BSA) on membrane performance.

This paper reports practical methods to prepare hydrogels in freestanding films and impregnated membranes and to characterize their physical properties, including water transport properties.

Hydrogels have been widely utilized to enhance the surface hydrophilicity of membranes for water purification, increasing the antifouling properties and ...

Self-Assembly of Polymer-Grafted Metal Organic Framework Monolayers

Synthesis and Characterization of Self-Assembled Metal-Organic Framework Monolayers Using Polymer-Coated Particles

Metal-organic frameworks (MOFs) are materials with potential applications in fields such as gas adsorption and separation, catalysis, and biomedicine. Attempts to enhance the utility of MOFs have involved the preparation of various composites, including polymer-grafted MOFs. By directly grafting polymers to the external surface of MOFs, issues of incompatibility between polymers and MOFs can be overcome. Polymer brushes grafted from the surface of MOFs can serve to stabilize the MOF while enabling particle assembly into self-assembled metal-organic framework monolayers (SAMMs) via polymer-polymer interactions.
Control over the chemical composition and molecular weight of the grafted polymer can allow for tuning of the SAMM characteristics. In this work, instructions are provided on how to immobilize a chain transfer agent (CTA) onto the surface of the MOF UiO-66 (UiO = Universitetet i Oslo). The CTA&#160;serves as initiation sites for the growth of polymers. Once polymer chains are grown from the MOF surface, the formation of SAMMs is achieved through self-assembly at an air-water interface. The resulting SAMMs are characterized and shown to be freestanding by scanning electron microscopy imaging. The methods presented in this paper are expected to make the preparation of SAMMs more accessible to the research community and thereby expand their potential use as a&#160;MOF-polymer composite.

Author Spotlight: Exploring Self-Assembled MOF-Polymer Composites

A protocol for the synthesis and characterization of self-assembled metal-organic framework monolayers is provided using polymer-grafted, metal-organic framework (MOF) crystals. The procedure shows that polymer-grafted MOF particles can be self-assembled at an air-water interface resulting in well-formed, free-standing, monolayer structures as evidenced by scanning electron microscopy imaging.

Metal-organic frameworks (MOFs) are materials with potential applications in fields such as gas adsorption and separation, catalysis, and biomedicine. ...