Name: facile synthesis of worm-like micelles by visible light mediated dispersion polymerization using photoredox catalyst
Uploaded: 2016-06-08T15:00:00
Description: Watch this Scientific Journal Video about Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst at JoVE.com

CB is thankful for his Future Fellowship from Australian Research Council (ARC-FT12010096) and UNSW Australia.

1. Synthesis and Characterization of POEGMA Macro-CTA
<ol>
	<li>Add oligo(ethylene glycol) methyl ether methacrylate (OEGMA) (12 g, 4 &#215; 10-2 mol), 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPADB) (0.224 g, 8 &#215; 10-4 mol), 2,2&#8242;-azobis(2-methylpropionitrile) (AIBN) (16.4 mg, 0.1 mmol) and 50 ml acetonitrile (MeCN) to a 100 ml round bottom flask.</li>
	<li>Seal the flask with an appropriately sized rubber septum and steel wire and cool the flask from room temperature to &#60; ...

<ol>
	<li>Yu, Y., Eisenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+Morphology+through+Polymer&#8722;Solvent+Interactions+in+Crew-Cut+Aggregates+of+Amphiphilic+Block+Copolymers.">Control of Morphology through Polymer&#8722;Solvent Interactions in Crew-Cut Aggregates of Amphiphilic Block Copolymers.</a> J. Am. Chem. Soc. 119 (35), 8383-8384 (1997).</li><li>Zhang, L., Eisenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermodynamic+vs+Kinetic+Aspects+in+the+Formation+and+Morphological+Transitions+of+Crew-Cut+Aggregates+Produced+by+Self-Assembly+of+Polystyrene-b-poly(acrylic+acid)+Block+Copolymers+in+Dilute+Solution.">Thermodynamic vs Kinetic Aspects in the Formation and Morphological Transitions of Crew-Cut Aggregates Produced by Self-Assembly of Polystyrene-b-poly(acrylic acid) Block Copolymers in Dilute Solution.</a> Macromolecules. 32 (7), 2239-2249 (1999).</li><li>Zhang, L., Eisenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+Morphologies+of+'Crew-Cut'+Aggregates+of+Polystyrene-b-poly(acrylic+acid)+Block+Copolymers.">Multiple Morphologies of 'Crew-Cut' Aggregates of Polystyrene-b-poly(acrylic acid) Block Copolymers.</a> Science. 268 (5218), 1728-1731 (1995).</li><li>Yu, K., Zhang, L., Eisenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+Morphologies+of+&amp;#34;Crew-Cut&amp;#34;+Aggregates+of+Amphiphilic+Diblock+Copolymers+in+Dilute+Solution.">Novel Morphologies of &amp;#34;Crew-Cut&amp;#34; Aggregates of Amphiphilic Diblock Copolymers in Dilute Solution.</a> Langmuir. 12 (25), 5980-5984 (1996).</li><li>Blanazs, A., Ryan, A. J., Armes, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predictive+Phase+Diagrams+for+RAFT+Aqueous+Dispersion+Polymerization:+Effect+of+Block+Copolymer+Composition,+Molecular+Weight,+and+Copolymer+Concentration.">Predictive Phase Diagrams for RAFT Aqueous Dispersion Polymerization: Effect of Block Copolymer Composition, Molecular Weight, and Copolymer Concentration.</a> Macromolecules. 45 (12), 5099-5107 (2012).</li><li>Ladmiral, V., Semsarilar, M., Canton, I., Armes, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymerization-induced+self-assembly+of+galactose-functionalized+biocompatible+diblock+copolymers+for+intracellular+delivery.">Polymerization-induced self-assembly of galactose-functionalized biocompatible diblock copolymers for intracellular delivery.</a> J. Am. Chem. Soc. 135 (36), 13574-13581 (2013).</li><li>Sugihara, S., Blanazs, A., Armes, S. P., Ryan, A. J., Lewis, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqueous+Dispersion+Polymerization:+A+New+Paradigm+for+in+Situ+Block+Copolymer+Self-Assembly+in+Concentrated+Solution.">Aqueous Dispersion Polymerization: A New Paradigm for in Situ Block Copolymer Self-Assembly in Concentrated Solution.</a> J. Am. Chem. Soc. 133 (39), 15707-15713 (2011).</li><li>Wan, W. M., Hong, C. Y., Pan, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-pot+synthesis+of+nanomaterials+via+RAFT+polymerization+induced+self-assembly+and+morphology+transition.">One-pot synthesis of nanomaterials via RAFT polymerization induced self-assembly and morphology transition.</a> Chem. Comm. (39), 5883-5885 (2009).</li><li>Semsarilar, M., Jones, E. R., Blanazs, A., Armes, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+Synthesis+of+Sterically-Stabilized+Nano-Objects+via+RAFT+Dispersion+Polymerization+of+Benzyl+Methacrylate+in+Alcoholic+Media.">Efficient Synthesis of Sterically-Stabilized Nano-Objects via RAFT Dispersion Polymerization of Benzyl Methacrylate in Alcoholic Media.</a> Adv. Mater. 24 (25), 3378-3382 (2012).</li><li>Karagoz, 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=Polymerization-Induced+Self-Assembly+(PISA)+-+control+over+the+morphology+of+nanoparticles+for+drug+delivery+applications.">Polymerization-Induced Self-Assembly (PISA) - control over the morphology of nanoparticles for drug delivery applications.</a> Polym. Chem. 5 (2), 350-355 (2014).</li><li>Geng, Y., 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=Shape+effects+of+filaments+versus+spherical+particles+in+flow+and+drug+delivery.">Shape effects of filaments versus spherical particles in flow and drug delivery.</a> Nat Nano. 2 (4), 249-255 (2007).</li><li>Blanazs, A., 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=Sterilizable+gels+from+thermoresponsive+block+copolymer+worms.">Sterilizable gels from thermoresponsive block copolymer worms.</a> J. Am. Chem. Soc. 134 (23), 9741-9748 (2012).</li><li>Pei, Y., Thurairajah, L., Sugita, O. R., Lowe, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RAFT+Dispersion+Polymerization+in+Nonpolar+Media:+Polymerization+of+3-Phenylpropyl+Methacrylate+in+n-Tetradecane+with+Poly(stearyl+methacrylate)+Homopolymers+as+Macro+Chain+Transfer+Agents.">RAFT Dispersion Polymerization in Nonpolar Media: Polymerization of 3-Phenylpropyl Methacrylate in n-Tetradecane with Poly(stearyl methacrylate) Homopolymers as Macro Chain Transfer Agents.</a> Macromolecules. 48 (1), 236-244 (2015).</li><li>Fielding, L. A., Lane, J. A., Derry, M. J., Mykhaylyk, O. O., Armes, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermo-responsive+Diblock+Copolymer+Worm+Gels+in+Non-polar+Solvents.">Thermo-responsive Diblock Copolymer Worm Gels in Non-polar Solvents.</a> J. Am. Chem. Soc. 136 (15), 5790-5798 (2014).</li><li>Yeow, J., Xu, J., Boyer, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymerization-Induced+Self-Assembly+Using+Visible+Light+Mediated+Photoinduced+Electron+Transfer-Reversible+Addition-Fragmentation+Chain+Transfer+Polymerization.">Polymerization-Induced Self-Assembly Using Visible Light Mediated Photoinduced Electron Transfer-Reversible Addition-Fragmentation Chain Transfer Polymerization.</a> ACS Macro Lett. 4 (9), 984-990 (2015).</li><li>Xu, J., Jung, K., Corrigan, N. A., Boyer, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aqueous+photoinduced+living/controlled+polymerization:+tailoring+for+bioconjugation.">Aqueous photoinduced living/controlled polymerization: tailoring for bioconjugation.</a> Chem. Sci. 5 (9), 3568-3575 (2014).</li><li>Pei, Y., 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=RAFT+dispersion+polymerization+of+3-phenylpropyl+methacrylate+with+poly[2-(dimethylamino)ethyl+methacrylate]+macro-CTAs+in+ethanol+and+associated+thermoreversible+polymorphism.">RAFT dispersion polymerization of 3-phenylpropyl methacrylate with poly[2-(dimethylamino)ethyl methacrylate] macro-CTAs in ethanol and associated thermoreversible polymorphism.</a> Soft Matter. 10 (31), 5787-5796 (2014).</li></ol>

This visualized protocol demonstrates the ability to monitor the formation of worm-like micelles simply by observing the onset of gel-like behavior. The utility of this approach lies in the ability to monitor worm formation during the polymerization in comparison to other methods. This procedure can be performed using a two-step polymerization of two commercially available monomers (OEGMA and BzMA) to yield self-assembled POEGMA-b-PBzMA amphiphilic diblock copolymers.
It should be not...

The synthesis of nonspherical (and other) nanoparticle morphologies has traditionally been accomplished using a multistep self-assembly procedure starting with the synthesis and purification of well-defined amphiphilic diblock (or multiblock) copolymers. One of the most common self-assembly techniques was popularized by Eisenberg in the 1990s and involves the dissolution of the amphiphilic block copolymer in a common solvent for both polymer blocks followed by the slow addition of a solvent selective for one of the blocks1-3. As the selective solvent (typically water) is added, the block copolymer undergoes self-assembly to form polymeric nanoparticles. The final morphology (or mixtures of morphologies) of the nanoparticles are determined by a large number of factors such as the relative lengths of each polymer block, rate of water addition and the nature of the common solvent. However, this approach generally only allows for the production of nanoparticles at relatively low solids content (less than 1 wt%) and so limits its practical scalability4. In addition, the reproducible formation of &#34;intermediate&#34; phases such as worm-like micelles can be difficult owing to the narrow range of parameters required to stabilize this nonspherical morphology5.
The polymerization-induced self-assembly (PISA) approach partially addresses the drawbacks of the Eisenberg approach by utilizing the polymerization process itself to drive self-assembly in situ allowing for nanoparticle synthesis at much higher solids content (typically 10-30 wt%)6-8. In a typical PISA approach, a living polymerization process is used to chain extend a solvent soluble macroinitiator (or macro-CTA) with a monomer that is initially soluble in the reaction medium but forms an insoluble polymer. The PISA approach has been used to synthesize worm-like micelles by systematically testing a number of experimental parameters and using detailed phase diagrams as a synthetic &#34;roadmap&#34;5,9.
Despite their challenging synthesis, there is great interest in worm-like nanoparticles due to their interesting properties relative to their spherical counterparts. For example, we have demonstrated that drug loaded short and long worm-like micelles synthesized using a PISA approach have significantly higher in vitro cytotoxicity compared to spherical micelles or vesicles10. Others have shown a correlation between nanoparticle aspect ratio and blood circulation time in in vivo models11. Others have shown that the synthesis of worm-like nanoparticles using an appropriate PISA methodology yields a macroscopic gel due to the nanoscale entanglement of the nanoparticle filaments. These gels have demonstrated potential as sterilizable gels owing to their thermoreversible sol-gel behavior12.
This protocol describes a method allowing for the in situ monitoring of the formation of worm-like micelles by simply observing the solution viscosity during the polymerization. Previous studies of similar worm-like micellar gels have demonstrated that above a critical temperature, these nanoparticles undergo a reversible worm-sphere transition and so form free-flowing dispersions at elevated temperatures. To date, these systems have utilized a thermally sensitive azo compound to initiate the controlled polymerization13,14 and so gelation may not be readily observed in these systems during the thermal polymerization. From these studies, it was hypothesized that synthesizing PISA derived nanoparticles at lower temperatures may allow for observation of this gelation behavior in situ.
Recently we reported the use of a facile room temperature photopolymerization technique to mediate the PISA process to yield nanoparticles of different morphologies15. Here, a visualized protocol is presented for the reproducible synthesis of worm-like micelles by observing the solution viscosity behavior during the polymerization. The dispersion polymerization proceeds readily using commercially available light-emitting diodes (LEDs) (&#955; = 460 nm, 0.7 mW/cm2).

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4-Cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPADB)</td>
			<td>Sigma-Aldrich</td>
			<td>722995-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Oligo(ethylene glycol) methyl ether methacrylate (OEGMA)</td>
			<td>Sigma-Aldrich</td>
			<td>447935-500ML</td>
			<td>Average Mn 300, contains 100&#160;ppm MEHQ as inhibitor, 300&#160;ppm BHT as inhibitor</td>
		</tr>
		<tr>
			<td>2,2&#8242;-Azobis(2-methylpropionitrile) (AIBN)</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ru(bpy)3Cl2.6H2O</td>
			<td>Sigma-Aldrich</td>
			<td>544981-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Benzyl methacrylate (BzMA)</td>
			<td>Sigma-Aldrich</td>
			<td>409448-1L</td>
			<td>Contains monomethyl ether hydroquinone as inhibitor</td>
		</tr>
		<tr>
			<td>Aluminium oxide (basic)</td>
			<td>Chem-Supply Pty Ltd Australia</td>
			<td>AL08371000</td>
			<td></td>
		</tr>
		<tr>
			<td>95% Ethanol (EtOH)</td>
			<td>Sucrogen Bio Ethanol</td>
			<td>80889</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile (MeCN)</td>
			<td>Chem-Supply Pty Ltd Australia</td>
			<td>RP1005-G2.5L</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrahydrofuran (THF)</td>
			<td>Chem-Supply Pty Ltd Australia</td>
			<td>TA011-2.5L</td>
			<td></td>
		</tr>
		<tr>
			<td>Petroleum Spirits (40-60oC)</td>
			<td>Chem-Supply Pty Ltd Australia</td>
			<td>PA044-2.5L</td>
			<td></td>
		</tr>
		<tr>
			<td>Diethyl Ether</td>
			<td>Chem-Supply Pty Ltd Australia</td>
			<td>EA0362.5L</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethylacetamide (DMAc)</td>
			<td>VWR International Australia</td>
			<td>ALFA22916.M1</td>
			<td>For GPC analysis</td>
		</tr>
		<tr>
			<td>Pasteur pipettes (230 mm)</td>
			<td>Labtek</td>
			<td>355.050.503</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass beakers</td>
			<td>Labtek</td>
			<td>025.01.902 (2L)/ 2110654 (1L)</td>
			<td>2L beaker is for attaching LED strips to form the circular reactor</td>
		</tr>
		<tr>
			<td>Commercial LED strip</td>
			<td>EcoLab</td>
			<td>n/a</td>
			<td>&#955; = 460 nm, 4.8 W/m</td>
		</tr>
		<tr>
			<td>4 mL Glass Vials</td>
			<td>Labtek</td>
			<td>APC502214B</td>
			<td></td>
		</tr>
		<tr>
			<td>0.9 mL Quartz Cuvette</td>
			<td>Starna Scientific Ltd</td>
			<td>21/Q/2</td>
			<td></td>
		</tr>
		<tr>
			<td>Needle (0.8 mm x 38 mm)</td>
			<td>Beckton Dickson</td>
			<td>302017</td>
			<td>For deoxygenating reactions</td>
		</tr>
		<tr>
			<td>Needle (0.8 mm x 120 mm)</td>
			<td>B Braun Australia</td>
			<td>4665643</td>
			<td>For deoxygenating reactions</td>
		</tr>
		<tr>
			<td>Sleeve stopper septa (rubber septum)</td>
			<td>Sigma-Aldrich</td>
			<td>z564680/z564702</td>
			<td></td>
		</tr>
		<tr>
			<td>Stirring hotplates</td>
			<td>VWR International Australia/In Vitro Technologies</td>
			<td>97018-488/RADRR91200</td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>VWR International Australia</td>
			<td>412-0098</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum oven</td>
			<td>In Vitro Technologies</td>
			<td>MEMVO200</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

In this study, two-step polymerization protocol is used for the synthesis of worm-like micelles using a PISA approach (Figure 1). In the first step, the polymerization of OEGMA is performed yielding a POEGMA macro-CTA which can be used as a stabilizer in the subsequent polymerization step. The PET-RAFT polymerization proceeds under dispersion conditions owing to the insolubility of PBzMA in ethanol which ultimately leads to nanoparticle formation. During the polymerizatio...

Watch this Scientific Journal Video about Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst at JoVE.com

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

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 ...

The overall goal of this protocol is to demonstrate the Facile Synthesis of Worm-like Micelles using Visible Light Mediated Polymerization. This method involves the preparation of polymerate nanoparticles, which can be used for a range of applications such as nano medicine The main advantage of this procedure is the production of worm-like nanoparticles using two-step procedure. The implication of this technique extends towards the field of drug delivery because in a number of studies, drug loaded worm-like nanoparticles have shown to give increased cellular uptake.To begin this procedure, add the appropriate reagents as indicated in the text protocol, a magnetic stir bar and 50 milliliters of acetone nitrile to 100 milliliter round bottom flask. Seal the flask with an appropriately sized rubber septum and steel wire. Then, cool the flask to less than four degrees Celsius in an ice water bath.Following this, de-oxygenate the flask for thirty minutes by bubbling nitrogen directly into the reaction mixture through a 21 gauge needle with a second 21 gauge needle acting as a vent. Place the flask in an oil bath at 70 degrees Celsius for five and a half hours. Once the reaction is complete, quench the polymerization by immersing the flask directly in an ice water bath and exposing the contents to air.Next, remove the acetone nitrile by agitation under a continuous stream of compressed air. Then, redissolve the crude mixture in approximately 40 milliliters of tetrahydrofuran or THF. Now, add the contents of the flask dropwise to 400 milliliters of a rapidly stirred mixture of petroleum spirits and diethyl ether and continue to stir until the supernatant is no longer cloudy.Once the precipitation is complete, decant the supernatant and redissolve the polymer residue in approximately 40 milliliters of THF. Repeat the precipitation process at least two more times to ensure complete removal of the residual monomer. Then, remove the excess solvent from the purified homopolymer by agitation under a continuous stream of compressed air, followed by drying in a vacuum oven for four hours.At this point, determine the number average molecular weight of the homopolymer by nuclear magnetic resonance spectroscopy, using a previously reported method. Using gel permeation chromotography, calculate the polymer dispersity. If the molecular weight of your synthesized homopolymer deviates from the 9000 molecular weight presented here, it may still be possible to obtain a worm gel in the subsequent step.However, the reaction time will vary. At this point, prepare a one milligram per milliliter stock solution of the ruthenium based photo redux catalyst in ethanol. Store the stock solution in a refrigerator to minimize solvent evaporation.Next, plug a pasteur pipette with a small wad of cotton wool using a second pipette to help pack it tightly. Pour basic aluminum oxide into the pipette to give a height of approximately five centimeters. Then, remove the mono methyl ether hydroquinone inhibitor in BzMA by passing approximately three milliliters through the pipette and collecting the de-inhibited BzMA.Add the de-inhibited BzMA, the homopolymer, the ruthenium catalyst stock solution, acetone nitrile, ethanol, and magnetic stir bar, to a four milliliter glass vile. Then, perform the deoxygenation procedure as previously described. Following this, place the vile in a 2000 milliliter glass beaker lined with blue LED strips and irradiate at room temperature with magnetic stirring.After twenty hours, monitor the reaction vile routinely and remove it from the reactor when the high viscosity solution forms a freestanding gel when the vile is inverted. So if your reactor setup is different to that presented here, gelation which indicates the formation of worm-like micelles will still be observed, however at a different reaction time. And that will really depend on the rate of polymerization of your reactor.After removing the vile from the reactor, quench the polymerization by exposing the nanoparticle gel to air for a few minutes. Store the closed vial upright in the dark. For TEM imaging place approximately 40 milligrams of the crude nanoparticle gel in a four milliliter glass vial.Continuously agitate the nanoparticle gel using a vortex mixer and add four milliliters of ethanol dropwise over a period of at least five minutes. Remove any macroscopic aggregates from the diluted nanoparticle sample by filtering through glass wool. Finally, perform TEM imaging of the diluted nanoparticle sample according to a previously reported procedure.In this study a two step polymerization protocol is used for the synthesis of worm-like micelles using a PISA approach. During the polymerization the initially transparent reaction mixture becomes cloudy in accordance with the dispersion polymerization and eventually transitions to a highly viscous gel like state indicating the formation of worm-like micelles. Indications of a living polymerization are apparent with low polymer dispersities and a good correlation between the molecular weight and momomer conversion.In addition, gel permeation chromatography traces indicate a predominately unimodal distribution with varying conversion, although some high molecular termination and low molecular weight tailing is observed in this system. The formation of the worm-like micelle morphology is also achievable under different reaction conditions such as variable vial types and reagent compositions but also if the light source is applied in an intermittent fashion. This implies that despite the strong effect of light penetration on polymerization rates in most photopolymerization systems the gelation behavior in this protocol can still be used as a reliable indicator for worm-like micelle formation.After watching this video, you should have a good understanding of how to generate nanoparticles with programmable shape that are capable of self organizing into gel.

facile-synthesis-worm-like-micelles-visible-light-mediated-dispersion

Research

JoVE Journal

Chemistry

Facile and Efficient Preparation of Tri-component Fluorescent Glycopolymers via RAFT-controlled Polymerization

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and efficient synthesis of well-controlled fluorescent statistical glycopolymers using reversible addition-fragmentation chain-transfer (RAFT)-based polymerization is demonstrated. The synthesis starts with the preparation of &#946;-galactose-containing glycomonomer 2-lactobionamidoethyl methacrylamide obtained by reaction of lactobionolactone and N-(2-aminoethyl) methacrylamide (AEMA). 2-Gluconamidoethyl methacrylamide (GAEMA) is used as a structural analog lacking a terminal &#946;-galactoside. The following RAFT-mediated copolymerization reaction involves three different monomers: N-(2-hydroxyethyl) acrylamide as spacer, AEMA as target for further fluorescence labeling, and the glycomonomers. Tolerant of aqueous systems, the RAFT agent used in the reaction is (4-cyanopentanoic acid)-4-dithiobenzoate. Low dispersities (&#8804;1.32), predictable copolymer compositions, and high reproducibility of the polymerizations were observed among the products. Fluorescent polymers are obtained by modifying the glycopolymers with carboxyfluorescein succinimidyl ester targeting the primary amine functional groups on AEMA. Lectin-binding specificities of the resulting glycopolymers are verified by testing with corresponding agarose beads coated with specific glycoepitope recognizing lectins. Because of the ease of the synthesis, the tight control of the product compositions and the good reproducibility of the reaction, this protocol can be translated towards preparation of other RAFT-based glycopolymers with specific structures and compositions, as desired.

An efficient, three-step synthesis of RAFT-based fluorescent glycopolymers, consisting of glycomonomer preparation, copolymerization, and post-modification, is demonstrated. This protocol can be used to prepare RAFT-based statistical glycopolymers with desired structures.

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and ...

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled (functionalized) CNTs are used as stabilizers to produce Pickering type oil-in-water (O/W) emulsions. Lipids namely, Dimodan U and Phytantriol are used as emulsifiers, which in excess water self-assemble into the bicontinuous cubic Pn3m phase. This highly viscous phase is fragmented into smaller particles using a probe ultrasonicator in presence of conventional surfactant stabilizers or CNTs as done here. Initially, the CNTs (powder form) are dispersed in water followed by further ultrasonication with the molten lipid to form the final emulsion. During this process the CNTs get coated with lipid molecules, which in turn are presumed to surround the lipid droplets to form a particulate emulsion that is stable for months. The average size of CNT-stabilized nanostructured lipid particles is in the submicron range, which compares well with the particles stabilized using conventional surfactants. Small angle X-ray scattering data confirms the retention of the original Pn3m cubic phase in the CNT-stabilized lipid dispersions as compared to the pure lipid phase (bulk state). Blue shift and lowering of the intensities in characteristic G and G&#39; bands of CNTs observed in Raman spectroscopy characterize the interaction between CNT surface and lipid molecules. These results suggest that the interactions between the CNTs and lipids are responsible for their mutual stabilization in aqueous solutions. As the concentrations of CNTs employed for stabilization are very low and lipid molecules are able to functionalize the CNTs, the toxicity of CNTs is expected to be insignificant while their biocompatibility is greatly enhanced. Hence the present approach finds a great potential in various biomedical applications, for instance, for developing hybrid nanocarrier systems for the delivery of multiple functional molecules as in combination therapy or polytherapy.

We report on a smart application of carbon nanotubes for kinetic stabilization of lipid particles that contain self-assembled nanostructures in their cores. The preparation of lipid particles requires rather low concentrations of carbon nanotubes permitting their use in biomedical applications such as drug delivery.

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled ...

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.

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 ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE). Characterization of the copolymer revealed a narrow molecular distribution (PDI &#60; 1.03) and confirmed the degree of polymerization of mPEG122-b-(PheGE)15. The critical micelle concentration of the copolymer was evaluated using an established fluorescence method with the aggregation behavior evaluated by dynamic light scattering and transmission electronic microscopy. The potential of the copolymer for use in drug delivery applications was evaluated in a preliminary manner including in vitro biocompatibility, loading and release of the hydrophobic anti-cancer drug doxorubicin (DOX). A stable micelle formulation of DOX was prepared with drug loading levels up to 14% (wt%), drug loading efficiencies &#62; 60% (w/w) and sustained release of drug over 4 days under physiologically relevant conditions (acidic and neutral pH, presence of albumin). The high drug loading level and sustained release is attributed to stabilizing &#960;-&#960; interactions between DOX and the core-forming block of the micelles.

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &amp;#960;-&amp;#960; Stacking Interactions

The key steps of living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE) are described. The resulting block copolymer micelles (BCMs) were loaded with doxorubicin 14% (wt%) and sustained release of drug over 4 days under physiologically relevant conditions was obtained.

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic poly(&#945;-hydroxy acids) with expected molecular weights (&#62;140 kDa) and narrow molecular weight distributions (Mw/Mn &#60; 1.1). This ring-opening polymerization is mediated by Ni and Zn complexes in the presence of an alcohol initiator and a photoredox Ir catalyst, irradiated by a blue LED (400 - 500 nm). The polymerization is performed at a low temperature (-15 &#176;C) to avoid undesired side reactions. The complete monomer consumption can be achieved within 4 - 8 hours, providing a polymer close to the expected molecular weight with narrow molecular weight distribution. The resulted number-average molecular weight shows a linear correlation with the degree of polymerization up to 1000. The homodecoupling 1H NMR study confirms that the obtained polymer is isotactic without epimerization. This polymerization reported herein offers a strategy for achieving rapid, controlled O-carboxyanhydrides polymerization to prepare stereoregular poly(&#945;-hydroxy acids) and its copolymers bearing various functional side-chain groups.

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

A protocol for the controlled photoredox ring-opening polymerization of O-carboxyanhydrides mediated by Ni/Zn complexes is presented.

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

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 ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...

Facile Protocol for the Synthesis of Self-assembling Polyamine-based Peptide Amphiphiles (PPAs) and Related Biomaterials

Polyamine-based Peptide Amphiphiles (PPAs) are a new class of self-assembling amphiphilic biomaterials-related to the peptide amphiphiles (PAs). Traditional PAs possess charged amino acids as solubilizing groups (lysine, arginine), which are directly connected to a lipid segment or can contain a linker region made of neutral amino acids. Tuning the peptide sequence of PAs can yield diverse morphologies. Similarly, PPAs possess a hydrophobic segment and neutral amino acids, but also contain polyamine molecules as water solubilizing (hydrophilic) groups. As is the case with PAs, PPAs can also self-assemble into diverse morphologies, including small rods, twisted nano-ribbons, and fused nano-sheets, when dissolved in water. However, the presence of both primary and secondary amines on a single polyamine molecule poses a significant challenge when synthesizing PPAs. In this paper, we show a simple protocol, based on literature precedents, to achieve a facile synthesis of PPAs using solid phase peptide synthesis (SPPS). This protocol can be extended to the synthesis of PAs and other similar systems. We also illustrate the steps that are needed for cleavage from the resin, identification, and purification.

Facile Protocol for the Synthesis of Self-assembling Polyamine-based Peptide Amphiphiles PPAs and Related Biomaterials

The synthesis of polyamine-based peptide amphiphiles (PPAs) is a significant challenge due to the presence of multiple amine nitrogens, which requires judicious use of protecting groups to mask these reactive functionalities. In this paper, we describe a facile method for the preparation of these new class of self-assembling molecules.

Polyamine-based Peptide Amphiphiles (PPAs) are a new class of self-assembling amphiphilic biomaterials-related to the peptide amphiphiles (PAs). ...

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the activation of a broad variety of organic halides, including unactivated ones. These can then participate in various radical transformations such as reduction and cyclization reactions, as well as in the direct arylation of several (hetero)arenes. These transformations provide a straightforward access to a range of small molecules of interest in synthetic chemistry, as well as to biologically active natural products. Altogether, [(DPEPhos)(bcp)Cu]PF6 acts as a convenient photoredox catalyst which appears to be an attractive, cheap and complementary alternative to the state-of-the-art iridium- and ruthenium-based photoredox catalysts. Here, we report a detailed protocol for the synthesis of [(DPEPhos)(bcp)Cu]PF6, as well as NMR and spectroscopic characterizations, and we illustrate its use in synthetic chemistry for the direct arylation of (hetero)arenes and radical cyclization of organic halides. In particular, the direct arylation of N-methylpyrrole with 4-iodobenzonitrile to afford&#160;4-(1-methyl-1H-pyrrol-2-yl)benzonitrile and the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to afford natural product luotonin A are detailed. The scope and limitations of this copper-based photoredox catalyst are also briefly discussed.

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.