More Like this

1. Enhancing photoluminescence of conjugated nanoparticles through graft polymer architectures

   https://doi.org/10.1039/D3MA00165B  

   Masucci, Ashley E.; Ghasemi, Masoud; Pester, Christian W.; Gomez, Enrique D. (June 2023, Materials Advances)

   Polymer nanoparticles are an emerging class of materials with potential impact in sensing, catalysis, imaging, cosmetics, and therapeutics. Here, a collection of graft polymers with conjugated polythiophene backbones were synthesized via a grafting-to approach. We functionalized polythiophene backbones with side chains of either poly(3-hexylthiophene) (P3HT), poly(ethylene oxide), or poly(methyl methacrylate) (PMMA) via copper-catalyzed azide–alkyne click chemistry. The backbones, graft polymers and a linear poly(3-hexylthiophene) were fabricated into nanoparticles through precipitation in aqueous media. We measured the absorption and emission spectra of the polymers dissolved in chloroform and as nanoparticles suspended in water. Compared to linear P3HT, all graft polymer nanoparticles exhibit higher quantum yields. Moreover, the addition of PMMA side chains increased the quantum yield by more than two orders of magnitude. This versatile approach to conjugated graft copolymer synthesis demonstrates a route for enhancing photoluminescence of conjugated polymer nanoparticles that could be beneficial for a variety of applications, such as biosensing and bioimaging. 

   more » « less
2. Confinement Effects in Dynamics of Ionic Liquids with Polymer‐Grafted Nanoparticles

   https://doi.org/10.1002/cphc.202200219  

   Liu, Siqi; Li, Ruhao; Tyagi, Madhusudan; Akcora, Pinar (June 2022, ChemPhysChem)

   Ionic liquid mixed with poly(methyl methacrylate)-grafted nanoparticle aggregates at low particle concentrations was shown to exhibit different dynamics and ionic conductivity than that of pure ionic liquid in our previous studies. In this work, we report on the quasi-elastic neutron scattering results on ionic liquid containing polymer-grafted nanoparticles at the higher particle concentration. The diffusivity of imidazolium (HMIM + ) cations of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM-TFSI) in the presence of poly(methyl methacrylate)-grafted iron oxide nanoparticles and the ionic conductivity of solutions were discussed through the confinement. Analysis of the elastic incoherent structure factor suggested the confinement radius decreased with the addition of grafted particles in HMIM-TFSI/solvent mixture, indicating the confinement that is induced by the high concentration of grafted particles, shrinks the HMIM-TFSI restricted volume. We further conjecture that this enhanced diffusivity occurs as a result of the local ordering of cations within aggregates of poly(methyl methacrylate)-grafted particles. 

   more » « less
3. Ion Channels in Sulfonated Copolymer-Grafted Nanoparticles in Ionic Liquid

   https://doi.org/10.1039/D2SM00725H  

   Li, Ruhao; Han, Yuke; Akcora, Pinar (June 2022, Soft Matter)

   The use of ionic liquids as solvent for polymers or polymer-grafted nanoparticles provides an exciting feature to explore electrolyte-polymer interaction. 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIm-TFSI) holds specific interactions with the polymer through ion-dipole or hydrogen bonding. For this work, poly(methyl methacrylate)-b-poly(styrene sulfonate) (PMMA-b-PSS) copolymer-grafted Fe3O4 nanoparticles with different sulfonation levels (~4.9-10.9 mol% SS) were synthesized and their concentration dependent ionic conductivities were reported in acetonitrile and HMIm-TFSI/acetonitrile mixture. We found that conductivity enhancement with the particle concentration in acetonitrile was due to the aggregation of grafted particles, hence sulfonic domain connectivity. The ionic conductivity was found to be related to the effective hopping transfer within ionic channels. To the contrary, the conductivity decreased or remained constant with increasing particle concentration in HMIm-TFSI/acetonitrile. This result was attributed to the ion coupling between ionic liquid and copolymer domains. 

   more » « less
4. Nickel-Fe3O4 Magnetic Nanoparticles Supported on Multiwalled Carbon Nanotubes: Effective Catalyst in Suzuki Cross Coupling Reactions

   https://doi.org/10.3390/catal11040495  

   Folsom, Sojeong K.; Ivey, Destiny J.; McNair, Frank S.; Siamaki, Ali R. (April 2021, Catalysts)

   Nickel-Fe3O4 nanoparticles supported on multi-walled carbon nanotubes (Ni-Fe3O4/MWCNTs) were synthesized by mechanical grinding of a sample of nickel salt, Fe3O4 and MWCNTs using a ball-mill mixer. The preparation method allows for bulk production of Ni-Fe3O4 nanoparticles at room temperature without the necessity of any solvent or chemical reagent. The nanoparticles prepared by this method exhibit small particles size of 5–8 nm with uniform dispersion of nickel nanoparticles on the surface of multi-walled carbon nanotubes. The Ni-Fe3O4/MWCNTs demonstrated remarkable catalytic activity for Suzuki cross coupling reactions of functionalized aryl halides and phenylboronic acids with excellent turnover number and turnover frequency (e.g., 76,000 h−1) using Monowave 50 conventional heating reactor at 120 °C within a very short reaction time of 15 min. The catalyst is air-stable and exhibits easy removal from the reaction mixture due to its magnetic properties, recyclability with no loss of activity, and significantly better performance than the other well-known commercial nickel catalyst. The Ni-Fe3O4/MWCNTs nanoparticles were fully characterized by a variety of spectroscopic techniques including X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). Since nickel offers similar properties to other more expensive transition metals including the most widely used palladium counterpart in cross coupling catalysis, this work demonstrates a promising lower-cost, air-moisture stable and efficient alternative catalyst based on nickel nanoparticles for cross coupling reactions. 

   more » « less
5. A Degradable Difunctional Initiator for ATRP That Responds to Hydrogen Peroxide

   https://doi.org/10.3390/polym14091733  

   Hill, Lawrence; Sims, Hunter; Nguyen, Ngoc; Collins, Christopher; Palmer, Jeffery; Wasson, Fiona (May 2022, Polymers)

   Mid-chain degradable polymers can be prepared by atom transfer radical polymerization from difunctional initiators that include triggers for the desired stimuli. While many difunctional initiators can respond to reducing conditions, procedures to prepare difunctional initiators that respond to oxidizing conditions are significantly less available in the literature. Here, a difunctional initiator incorporating an oxidizable boronic ester trigger was synthesized over four steps using simple and scalable procedures. Methyl methacrylate was polymerized by atom transfer radical polymerization using this initiator, and the polymerization kinetics were consistent with a controlled polymerization. The polymer synthesized using the difunctional initiator was found to decrease in molecular weight by 58% in the presence of hydrogen peroxide, while a control experiment using poly(methyl methacrylate) without a degradable linkage showed a much smaller decrease in molecular weight of only 9%. These observed molecular weight decreases were consistent with cleavage of the difunctional initiator via a quinone methide shift and hydrolysis of the methyl ester pendent groups in both polymers, and both polymers increased in polydispersity after oxidative degradation. 

   more » « less