Name: atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible light photocatalyst
Uploaded: 2016-04-22T13:00:00
Description: Watch this Scientific Journal Video about Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst at JoVE.com

The authors would like to acknowledge the University of Colorado Boulder for its support of this work.

CAUTION: Many of the chemicals used in this protocol are hazardous substances. Consult Material Safety Data Sheets (MSDS) and use appropriate personal protective equipment (PPE) when working with these substances.
1. Purification, Preparation, and Storage of Reagents
<ol>
	<li>Purify all solvents to be used using a solvent purification system according to manufacturer&#39;s protocol. If a solvent purification system is not available, use drying agents (e.g., molecular sieves, CaH<su...

<ol>
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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Convergence+of+Synthetic+Organic+and+Polymer+Chemistries.">The Convergence of Synthetic Organic and Polymer Chemistries.</a> Science. 309 (5738), 1200-1205 (2005).</li><li>di Lena, F., Matyjaszewski, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transition+Metal+Catalysts+for+Controlled+Radical+Polymerization.">Transition Metal Catalysts for Controlled Radical Polymerization.</a> Prog. Polym. Sci. 35 (8), 959-1021 (2010).</li><li>Rosen, B. 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A., Matyjaszewski, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled/living+Radical+Polymerization:+Features,+Developments,+and+Perspectives.">Controlled/living Radical Polymerization: Features, Developments, and Perspectives.</a> Prog. Polym. Sci. 32 (1), 93-146 (2007).</li><li>Kamigaito, M., Ando, T., Sawamoto, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metal-Catalyzed+Living+Radical+Polymerization.">Metal-Catalyzed Living Radical Polymerization.</a> Chem. 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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanostructured+Functional+Materials+Prepared+by+Atom+Transfer+Radical+Polymerization.">Nanostructured Functional Materials Prepared by Atom Transfer Radical Polymerization.</a> Nat. Chem. 1 (4), 276-288 (2009).</li><li>Ouchi, M., Terashima, T., Sawamoto, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precision+Control+of+Radical+Polymerization+via+Transition+Metal+Catalysis:+From+Dormant+Species+to+Designed+Catalysts+for+Precision+Functional+Polymers.">Precision Control of Radical Polymerization via Transition Metal Catalysis: From Dormant Species to Designed Catalysts for Precision Functional Polymers.</a> Acc. Chem. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Living+Radical+Polymerization+by+the+RAFT+Process-+A+Second+Update.">Living Radical Polymerization by the RAFT Process- A Second Update.</a> Aust. J. Chem. 62 (11), 1402-1472 (2009).</li><li>Moad, G., Rizzardo, E., Thang, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radical+Addition-Fragmentation+Chemistry+in+Polymer+Synthesis.">Radical Addition-Fragmentation Chemistry in Polymer Synthesis.</a> Polymer. 49 (5), 1079-1131 (2008).</li><li>Nicolas, 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=Nitroxide-Mediated+Polymerization.">Nitroxide-Mediated Polymerization.</a> Prog. Polym. Sci. 38 (1), 63-235 (2013).</li><li>Hawker, C. J., Bosman, A. W., Harth, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+Polymer+Synthesis+by+Nitroxide+Mediated+Living+Radical+Polymerizations.">New Polymer Synthesis by Nitroxide Mediated Living Radical Polymerizations.</a> Chem. Rev. 101 (12), 3661-3688 (2001).</li><li>Goto, A., Wakada, T., Fukuda, T., Tsujii, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Systematic+Kinetic+Study+in+Reversible+Chain+Transfer+Catalyzed+Polymerizations+(RTCPs)+with+Germanium,+Tin,+Phosphorus,+and+Nitrogen+Catalysts.">A Systematic Kinetic Study in Reversible Chain Transfer Catalyzed Polymerizations (RTCPs) with Germanium, Tin, Phosphorus, and Nitrogen Catalysts.</a> Macromol. Chem. Phys. 211 (5), 594-600 (2010).</li><li>Goto, A., Ohtsuki, A., Ohfuji, H., Tanishima, M., Kaji, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reversible+Generation+of+a+Carbon-Centered+Radical+from+Alkyl+Iodide+Using+Organic+Salts+and+Their+Application+as+Organic+Catalysts+in+Living+Radical+Polymerization.">Reversible Generation of a Carbon-Centered Radical from Alkyl Iodide Using Organic Salts and Their Application as Organic Catalysts in Living Radical Polymerization.</a> J. Am. Chem. 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Although the protocol demonstrates a specific example of this polymerization technique, the options available to the researcher performing this reaction are quite broad. Modifications can be made at a number of points throughout the protocol to allow for the optimization of whatever particular photoredox ATRP is being performed. As new monomers, initiators, and catalysts for this reaction come under investigation, the stoichiometry and solvent used to perform the reaction can and should be modified as part of optimizatio...

The synthesis of technologically advanced polymers requires precise control over polymer molecular weight, dispersity (&#208;), composition, and architecture.1,2 Controlled radical polymerizations (CRPs)3-8 have revolutionized the synthesis of well-defined polymers, with atom transfer radical polymerization (ATRP) being the most used CRP, largely due to operational simplicity and synthetic versatility.9-14 The crux of ATRP is the ability to reversibly deactivate the polymerization, controlling the equilibrium between a propagating radical and a dormant species. Enforcing a low concentration of active radicals greatly minimizes bimolecular termination pathways and allows for the synthesis of well-defined polymers. 
Traditional ATRP relies on a transition metal catalyst to mediate this equilibrium.3 These metal catalysts contaminate the polymer product and impede implementation in biomedical or electronic applications while also raising environmental concerns. Although significant strides have been made to reduce the catalyst concentration to ppm levels, these methodologies require more demanding experimental conditions and metal contamination is still not entirely eliminated.15,16
Reversible addition-fragmentation transfer17,18 and nitroxide-mediated polymerizations19,20 are CRPs that do not require metal catalysts, although they have been used less often than ATRP.3 Recently, reversible chain-transfer21 and reversible complexation22,23 variants of ATRP that can use organic catalysts were reported. However, these methodologies require the use of alkyl iodide initiators and are not effective with the alkyl bromides commonly employed in ATRP. A highly desirable CRP would match the performance, feasibility, and robustness of traditional ATRP while being catalyzed by an organic catalyst under mild conditions.
Here, we describe a methodology for the radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst. Through optimization of parameters such as stoichiometry, concentration, time, and light flux, the molecular weight of the polymers can be controlled.24, 25 Similar methodologies have been recently introduced using phenothiazine derivatives as photocatalysts for metal-free ATRP.26, 27 Because researchers in the field of polymerization catalysis are constantly developing new catalytic systems, the ability to compare catalyst performance across a number of metrics is vital. This ability to make comparisons relies heavily upon procedural consistency and clarity on the part of the researchers performing the experiments. As such, it is our goal that this video will be used to help precisely communicate the methods by which these polymers are synthesized and characterized.

<table border="0" cellpadding="0" cellspacing="0" width="572">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">perylene, min 98.0%</td>
			<td style="width:92px;">TCI America</td>
			<td style="width:128px;">TCP0078-025G</td>
			<td style="width:147px;">purify by sublimation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">N,N-dimethylformamide</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">EM-DX1726-1</td>
			<td style="width:147px;">Omnisolv</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">methyl methacrylate, 99%</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">200000-678</td>
			<td style="width:147px;">distilled prior to use, stored in refrigerator</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">ethyl &#945;-bromophenyl acetate&#160;</td>
			<td style="width:92px;">Aldrich</td>
			<td style="width:128px;">554065</td>
			<td style="width:147px;">distilled prior to use stored in refrigerator</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">butylated hydroxytoluene&#160;</td>
			<td style="width:92px;">Aldrich</td>
			<td style="width:128px;">W218405</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Chloroform-D</td>
			<td style="width:92px;">Cambridge Isotope Labs</td>
			<td style="width:128px;">DLM-7-100</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">tetrahydrofuran</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">EM-TX0279-1</td>
			<td style="width:147px;">Omnisolv</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">methanol</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">BDH1135</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">dichloromethane</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">EM-DX0831-1</td>
			<td style="width:147px;">Omnisolv</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">styrene, 99%</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">AAAA18481-0F</td>
			<td style="width:147px;">distilled prior to use, stored in refrigerator</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">glass scintillation vial, 20 mL</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">66022-065</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">screw top vial, 2 mL</td>
			<td style="width:92px;">Agilent</td>
			<td style="width:128px;">5182-0715</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">septum cap for screw top vial</td>
			<td style="width:92px;">Agilent</td>
			<td style="width:128px;">5182-0717</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">heavy wall pressure vessel, 100 mL</td>
			<td style="width:92px;">Synthware</td>
			<td style="width:128px;">P160005&#160;</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">syringe, 1 mL norm-ject</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">89174-491</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">NMR tube</td>
			<td style="width:92px;">New Era</td>
			<td style="width:128px;">NE-UL5-7&#39;</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">nylon syringe filter, 0.45 um</td>
			<td style="width:92px;">VWR</td>
			<td style="width:128px;">28143-240</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">glovebox</td>
			<td style="width:92px;">Mbraun</td>
			<td style="width:128px;">LABstar</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">solvent purification system</td>
			<td style="width:92px;">Mbraun</td>
			<td style="width:128px;">MB-SPS-800</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">stirplate</td>
			<td style="width:92px;">IKA</td>
			<td style="width:128px;">3582401</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:205px;">light-emitting diodes</td>
			<td style="width:92px;">Creative Lighting Solutions</td>
			<td style="width:128px;">CL-FRS1210-5M-12V-WH</td>
			<td style="width:147px;">2x 12-inch strips of 5500 K white LEDs were used for illumination</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:205px;">12V DC power supply for LEDs</td>
			<td style="width:92px;">Creative Lighting Solutions</td>
			<td style="width:128px;">CL-PS16001-40W</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">high performance liquid chromatograph&#160;</td>
			<td style="width:92px;">Agilent</td>
			<td style="width:128px;">G1310B, G1322A, G1329B, G1316A</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">gel permeation size-exclusion columns</td>
			<td style="width:92px;">Agilent</td>
			<td style="width:128px;">PL1110-6500</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">multi-angle light scattering detector</td>
			<td style="width:92px;">Wyatt</td>
			<td style="width:128px;">WTREOS</td>
			<td style="width:147px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">differential refractometer</td>
			<td style="width:92px;">Wyatt</td>
			<td style="width:128px;">WTREX</td>
			<td style="width:147px;"></td>
		</tr>
	</tbody>
</table>

atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible light photocatalyst

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

Table 1 shows the range of polymerization results achievable through this method. These data show that perylene is capable of serving as a photocatalyst for the polymerization of a number of functionalized vinyl monomers. For a specific monomer, adjustment of any of a number of reaction parameters such as solvent, stoichiometry, initiator, and light source leads to polymers with varying molecular weights and dispersities ranging from very good to rather broad. Fig...

Watch this Scientific Journal Video about Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst at JoVE.com

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The ...

The overall goal of this procedure is to produce well-defined polymethyl methacrylate using perylene as a visible light photocatalyst for atom transfer radical polymerization. The overall goal of this procedure is to produce well-defined polymethyl methacrylate using perylene as an organic photocatalyst for atom transfer radical polymerization. This method can help answer key questions in the field of organic catalysis and photoredox catalysis such as, can we replace transition metal complexes with organic dyes such as perylene?The main advantage of this technique is that the metal catalyst commonly used in atom transfer radical polymerization can be replaced with perylene, a common organic dye. Visual demonstration of this method is critical to ensure reproducibility among research groups, as the exact reaction setup can have a substantial impact on the outcome of the experiment. Prepare all reagents as described in the text protocol, and allow them to come to room temperature.Inspect all reagents prior to use to ensure there is no sign of contamination such as discoloration or formation of solid particles. In a nitrogen atmosphere glove box, place a small stir bar in a 100 milliliter reaction tube. Add 9.5 milligrams of perylene, and then 4.00 milliliters of dimethylformamide, or DMF.To this mixture, add 4.00 milliliters of methyl methacrylate, or MMA. Place the vial on a stir plate set to 900 rpm inside a 400 milliliter beaker illuminated by strips of white light-emitting diodes. Limit any illumination from other light sources.To initiate the reaction, add 65.6 microliters of ethyl alpha-bromophenylacetate, or EBP, via pipette. Stir the reaction for twenty-four hours under constant illumination. On the bench top, dispense 0.70 milliliters of the butylated hydroxytoluene, or BHT, in deuterated chloroform solution into a two milliliter vial, and seal with a septum cap.Bring this vial into the glove box where the polymerization is being performed. Use a syringe to remove 0.20 milliliters of the reaction mixture. Inject the contents of the syringe into the two milliliter vial containing the 250 ppm solution of BHT and deuterated chloroform.Draw back and push in the plunger several times to ensure thorough quenching of the polymerization. Next, transfer the contents of the two milliliter vial to an NMR spectroscopy tube. Analyze this sample via proton NMR spectroscopy for percent conversion.After analysis, pour the contents of the NMR spectroscopy tube into a clean 20 milliliter scintillation vial. Evaporate the solvent under reduced pressure. Then, redissolve the sample in 1.00 milliliters of tetrahydrofuran.Send the sample through a 0.45 micron syringe filter into a clean two milliliter vial. Analyze the sample via gel permeation chromatography, or GPC, coupled with multi-angle light scattering, to determine number average molecular weight, weight average molecular weight, and dispersity. To isolate and purify the product polymethyl methacrylate, first quench the polymerization reaction by pouring the contents of the reaction mixture into a fifty-fold excess of methanol and letting stir for at least one hour.Isolate the polymethyl methacrylate from the methanol by vacuum filtration. Then, rinse the polymer with an additional 100 milliliters of methanol. Redissolve the polymer in dichloromethane and repeat these steps twice.In a nitrogen atmosphere glove box, place 544 milligrams of polymethyl methacrylate macroinitiator into a 20 milliliter scintillation vial fitted with a small stir bar. Next, add 2.4 milligrams of perylene to the scintillation vial followed by 4.00 milliliters of dimethylformamide. Place the vial on a stir plate set to 900 rpm inside a beaker illuminated by strips of white LEDs.Limit any illumination from other light sources. To this mixture, add 4.96 milliliters of styrene via pipette and stir the reaction for twenty-four hours under constant illumination. Finally, isolate and purify the polymethyl methacrylate block polystyrene product, as before.Shown here are representative results of the polymerization of functionalized vinyl monomers using this technique. Tuning of reaction parameters can have a significant effect on the outcome of the polymerization. This figure shows the results of block copolymerization using an isolated polymethyl methacrylate macroinitiator, as described in the video procedure.The ability to chain extend in this fashion lends support to an atom transfer mechanism. After watching this video, you should have a working understanding of how to produce and isolate well-defined polymers and block copolymers using perylene as a visible light photocatalyst for atom transfer radical polymerization.

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Unit 1

Reactions of Alkenes

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Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Using Polystyrene-block-poly(acrylic acid)-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

We present a template-free method for &#8220;polymerizing&#8221; nanoparticles into long chains without side branches. A variety of nanoparticles are encapsulated in polystyrene-block-poly(acrylic acid) (PSPAA) shells and then used as monomers for their self-assembly. Spherical PSPAA micelles upon acid treatment are known to assemble into cylindrical micelles. Exploiting this tendency, the core-shell nanoparticles are induced to aggregate, coalesce, and then transform into long chains. When more than one type of nanoparticles are used, random and block &#8220;copolymers&#8221; of nanoparticles can be obtained. Detailed procedures are reported for the PSPAA encapsulation of nanoparticles, homo- and co-polymerization of the core-shell nanoparticles, separation and purification of the resulting nanoparticle chains. Transformations of single-line chains into double- and triple-line chains are also presented. The synergy between the polymer shell and the embedded nanoparticles leads to an unusual chain-growth polymerization mode, giving long nanoparticle chains that are distinct from the products of the traditional step-growth aggregation process.

Using Polystyrene-block-polyacrylic acid-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization

We report protocols for &#8220;polymerizing&#8221; various types of polymer-encapsulated metal nanoparticles into long chains of &#8220;homo-&#8220; and &#8220;co-polymers&#8221;.

We present a template-free method for &#8220;polymerizing&#8221; nanoparticles into long chains without side branches. A variety of nanoparticles are ...

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

We demonstrate a method for high-throughput catalyst screening using a parallel pressure reactor starting from the initial synthesis of a nickel &#945;-diimine ethylene polymerization catalyst. Initial polymerizations with the catalyst lead to optimized reaction conditions, including catalyst concentration, ethylene pressure and reaction time. Using gas-uptake data for these reactions, a procedure to calculate the initial rate of propagation (kp) is presented. Using the optimized conditions, the ability of the nickel &#945;-diimine polymerization catalyst to undergo chain transfer with diethylzinc (ZnEt2) during ethylene polymerization was investigated. A procedure to assess the ability of the catalyst to undergo chain transfer (from molecular weight and 13C NMR data), calculate the degree of chain transfer, and calculate chain transfer rates (ke) is presented.

A protocol for the high-throughput analysis of polymerization catalyst, chain transfer polymerizations, polyethylene characterization, and reaction kinetic analysis is presented.

We demonstrate a method for high-throughput catalyst screening using a parallel pressure reactor starting from the initial synthesis of a nickel ...

Development of a Backbone Cyclic Peptide Library as Potential Antiparasitic Therapeutics Using Microwave Irradiation

Protein-protein interactions (PPIs) are intimately involved in almost all biological processes and are linked to many human diseases. Therefore, there is a major effort to target PPIs in basic research and in the pharmaceutical industry. Protein-protein interfaces are usually large, flat, and often lack pockets, complicating the discovery of small molecules that target such sites. Alternative targeting approaches using antibodies have limitations due to poor oral bioavailability, low cell-permeability, and production inefficiency.
Using peptides to target PPI interfaces has several advantages. Peptides have higher conformational flexibility, increased selectivity, and are generally inexpensive. However, peptides have their own limitations including poor stability and inefficiency crossing cell membranes. To overcome such limitations, peptide cyclization can be performed. Cyclization has been demonstrated to improve peptide selectivity, metabolic stability, and bioavailability. However, predicting the bioactive conformation of a cyclic peptide is not trivial. To overcome this challenge, one attractive approach it to screen a focused library to screen in which all backbone cyclic peptides have the same primary sequence, but differ in parameters that influence their conformation, such as ring size and position.
We describe a detailed protocol for synthesizing a library of backbone cyclic peptides targeting specific parasite PPIs. Using a rational design approach, we developed peptides derived from the scaffold protein Leishmania receptor for activated C-kinase (LACK). We hypothesized that sequences in LACK that are conserved in parasites, but not in the mammalian host homolog, may represent interaction sites for proteins that are critical for the parasites&#39; viability. The cyclic peptides were synthesized using microwave irradiation to reduce reaction times and increase efficiency. Developing a library of backbone cyclic peptides with different ring sizes facilitates a systematic screen for the most biological active conformation. This method provides a general, fast, and facile way to synthesize cyclic peptides.

A simple and general method for the synthesis of cyclic peptides using microwave irradiation is outlined. This procedure enables the synthesis of backbone cyclic peptides with a collection of different conformations while retaining the side chains and the pharmacophoric moieties., and therefore, allows to screen for the bioactive conformation.

Protein-protein interactions (PPIs) are intimately involved in almost all biological processes and are linked to many human diseases. Therefore, there is ...

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 ...

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

We describe the catalytic insertion polymerization of 5-norbornene-2-carboxylic acid and 5-vinyl-2-norbornene to form functional polymers with a very high glass transition temperature.

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic ...

Preparation of Hollow Polystyrene Particles and Microcapsules by Radical Polymerization of Janus Droplets Consisting of Hydrocarbon and Fluorocarbon Oils

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) and fluorocarbon oil (perfluoro-n-octane, PFO) in aqueous surfactant (sodium dodecylsulfate, SDS) solutions. Since fluorocarbon oils are immiscible with hydrocarbon oils, the two oils are separated. Emulsions are prepared by stirring styrene/PFO/aqueous SDS solution mixtures at 80 &#176;C. The type of emulsions and the morphology of droplets in the emulsions are observed by light microscope and scanning confocal fluorescence microscope. It is found that oil droplets with Janus-type morphologies consisting of mutually immiscible styrene and PFO are formed in aqueous SDS solutions. Polystyrene particles are fabricated by radical polymerization of the ternary mixtures of styrene/PFO/aqueous SDS solution at 80 &#176;C. The morphologies of the polystyrene are confirmed by scanning electron microscopy and scanning transmission electron microscopy observations. These observations show the preparation of hollow polystyrene particles with a single hole on the surface. To our knowledge, this method is a novel strategy using the immiscibility of hydrocarbon and fluorocarbon oils. The hollow particles can also be applied to the preparation of microcapsules.

A protocol for the fabrication of hollow polymer particles and microcapsules by radical polymerization using emulsions consisting of styrene, perfluoro-n-octane, and aqueous SDS (sodium dodecylsulfate) solution is presented.

In this article, we have demonstrated a method for producing hollow particles and microcapsules using oil droplets consisting of hydrocarbon oil (styrene) ...

Constructing Thioether/Vinyl Sulfide-tethered Helical Peptides Via Photo-induced Thiol-ene/yne Hydrothiolation

Here, we describe a detailed protocol for the preparation of thioether-tethered peptides using on-resin intramolecular/intermolecular thiol-ene hydrothiolation. In addition, this protocol describes the preparation of vinyl-sulfide-tethered peptides using in-solution intramolecular thiol-yne hydrothiolation between amino acids that possess alkene/alkyne side chains and cysteine residues at i, i+4 positions. Linear peptides were synthesized using a standard Fmoc-based solid-phase peptide synthesis (SPPS). Thiol-ene hydrothiolation is carried out using either an intramolecular thio-ene reaction or an intermolecular thio-ene reaction, depending on the peptide length. In this research, an intramolecular thio-ene reaction is carried out in the case of shorter peptides using on-resin deprotection of the trityl groups of cysteine residues following the complete synthesis of the linear peptide. The resin is then set to UV irradiation using photoinitiator 4-methoxyacetophenone (MAP) and 2-hydroxy-1-[4-(2-hydroxyethoxy)-phenyl]-2-methyl-1-propanone (MMP). The intermolecular thiol-ene reaction is carried out by dissolving Fmoc-Cys-OH in an N,N-dimethylformamide (DMF) solvent. This is then reacted with the peptide using the alkene-bearing residue on resin. After that, the macrolactamization is carried out using benzotriazole-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBop), 1-hydroxybenzotriazole (HoBt), and 4-Methylmorpholine (NMM) as activation reagents on the resin. Following the macrolactamization, the peptide synthesis is continued using standard SPPS. In the case of the thio-yne hydrothiolation, the linear peptide is cleaved from the resin, dried, and subsequently dissolved in degassed DMF. This is then irradiated using UV light with photoinitiator 2,2-dimethoxy-2-phenylacetophenone (DMPA). Following the reaction, DMF is evaporated and the crude residue is precipitated and purified using high-performance liquid chromatography (HPLC). These methods could function to simplify the generation of thioether-tethered cyclic peptides due to the use of the thio-ene/yne click chemistry that possesses superior functional group tolerance and good yield. The introduction of thioether bonds into peptides takes advantage of the nucleophilic nature of cysteine residues and is redox-inert relative to disulfide bonds.

We present a protocol for the construction of thioether/vinyl sulfide-tethered helical peptides using photo-induced thiol-ene/thiol-yne hydrothiolation.

Here, we describe a detailed protocol for the preparation of thioether-tethered peptides using on-resin intramolecular/intermolecular thiol-ene ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...