Azide-functionalized Polymer Research Articles

Tailoring the density of carbon nanotube networks through chemical self-assembly by click reaction for reliable transistors

Semiconducting single-walled carbon nanotubes (sc-SWNTs) are attracting considerable interest for use as active layers in various electronic applications such as field-effect transistors (FETs) because of their extremely high intrinsic charge carrier mobility and solution processability at low costs. However, it is challenging to achieve a constant sc-SWNT density for ensuring commercial-level, uniform performance in FETs based on random-network SWNT films formed by solution processing. This paper reports a facile method for sorting sc-SWNT and precisely controlling the density of random-network sc-SWNT films by azide-functionalized polymer. The chemical self-assembly of SWNTs is performed between azide-functionalized polymer-wrapped sc-SWNTs and alkyne-based substrate via click reaction. A high-purity sc-SWNT ink is obtained by the conjugated polymer wrapping method using an azide-functionalized polyfluorene in methylcyclohexane. The sc-SWNTs are then chemically bound to a substrate with an alkyne adhesive layer through a Cu-catalyzed azide-alkyne cycloaddition reaction. FETs with dense and uniform SWNT films with a linear density of 30 (±2) tubes μm−1 exhibit markedly high hole mobility of up to 25.4 cm2 V−1 s−1 and excellent performance uniformity. Furthermore, the SWNT films anchored on the substrates are highly resistant to exogenous disruptions, such as sonication in organic solvents, leading the great potential for applications such as biosensors that require strong adhesive strength.

Synthesis and self-assembly behavior of amphiphilic methyl α-D-glucopyranoside-centered copolymers

A series of well-defined polymers with various content of reactive oxirane groups (25–100 mol%) were synthesized via atom transfer radical polymerization (ATRP). The acetal derivatives of methyl α-D-glucopyranoside used as bi-, tri-, and tetrafunctional initiators allowed us to design macromolecules containing a sugar moiety in the center with V- and star-shaped topologies, and a length of each polymethacrylate segment in the range of 30–75 units. Various degrees of oxirane ring opening via aminolysis with mono- and diamines (20–100 %) or azidation (100 %) have demonstrated that the reactivity of pendant epoxide groups incorporated into the polymer was strongly dependent on the nucleophile agent and reaction environment. The complete transformation in the reaction with ethylenediamine and sodium azide yielded amphiphilic copolymers with differential solubility (diamine-functionalized polymers in polar protic solvents, e.g., water, versus azide-functionalized polymers in polar aprotic solvents, e.g., dimethylformamide). A few polymeric forms, that is unimers (0.5–1 nm), micelles (5–30 nm), aggregates (170–290 nm) and superaggregates (> 4,500 nm), were indicated by DLS measurements of water-soluble ethylenediamine derivatives of copolymers. Both the epoxy-functionalized polymers and their modified derivatives are potential materials for biomedical applications.

Sequential “Click” Approach to Polyhedral Oligomeric Silsesquioxane-Based Shape Amphiphiles

This paper reports a highly efficient and modular sequential “click” approach for the syntheses of shape amphiphiles based on polymer-tethered polyhedral oligomeric silsesquioxane (POSS). This approach combines both “grafting-to” and “post-functionalization” strategies. It involves the copper-catalyzed Huisgen [3 + 2] cycloaddition (CuAAC) for POSS–polymer ligation and subsequent thiol–ene addition reaction for POSS cage functionalization. Starting from a readily available POSS precursor bearing one alkyne and seven vinyl groups (VPOSS–alkyne), the CuAAC reaction is effective in ensuring the stoichiometric bonding between POSS and azide-functionalized polymers, with no need for fractionation in the purification process. The modularity was demonstrated in two representative polymer systems, hydrophobic polystyrene (PS) and hydrophilic poly(ethylene oxide) (PEO), by the synthesis of VPOSS–PS and VPOSS–PEO. The thiol–ene reaction was subsequently applied to convert all the vinyl groups on the POSS cage quant...

Oligonucleotide and Polymer Functionalized Nanoparticles for Amplification-Free Detection of DNA

Sensitive and quantitative nucleic acid testing from complex biological samples is now an important component of clinical diagnostics. Whereas nucleic acid amplification represents the gold standard, its utility in resource-limited and point-of-care settings can be problematic due to assay interferants, assay time, engineering constraints, and costs associated with both wetware and hardware. In contrast, amplification-free nucleic acid testing can circumvent these limitations by enabling direct target hybridization within complex sample matrices. In this work, we grew random copolymer brushes from the surface of silica-coated magnetic nanoparticles using azide-modified and hydroxyl oligo ethylene glycol methacrylate (OEGMA) monomers. The azide-functionalized polymer brush was first conjugated, via copper-catalyzed azide/alkyne cycloaddition (CuAAC), with herpes simplex virus (HSV)-specific oligonucleotides and then with alkyne-substituted polyethylene glycol to eliminate all residual azide groups. Our methodology enabled control over brush thickness and probe density and enabled multiple consecutive coupling reactions on the particle grafted brush. Brush- and probe-modified particles were then combined in a 20 min hybridization with fluorescent polystyrene nanoparticles modified with HSV-specific reporter probes. Following magnetic capture and washing, the particles were analyzed with an aggregate fluorescence measurement, which yielded a limit of detection of 6 pM in buffer and 60 pM in 50% fetal bovine serum. Adoption of brush- and probe-modified particles into a particle counting assay will result in the development of diagnostic assays with significant improvements in sensitivity.

Highly efficient thermal glue for carbon nanotubes based on azide polymers

Equilibrium molecular dynamics (EMD) simulations and experimental data show that the thermal contact resistance (TCR) between carbon nanotube (CNT) and azide-functionalized polymer with C-N bond is significantly decreased compared to that with Van der Waals force interaction. EMD simulations indicate that C-N covalent bond between CNT and polymer is the most efficient way to reduce TCR, and we measured the lowest thermal interface resistance of Si/CNT/Polymer/Cu thermal interface material as 1.40 mm2 KW−1 with CNTs of 10 μm length. These results provide useful information for future designs of thermal glue for carbon-based materials with better thermal conduction.

Controlled folding of polystyrene single chains: design of asymmetric covalent bridges

α-Shaped polystyrene origamis with variable sizes and loop diameters were synthesized using a simple folding strategy. Linear polystyrene precursors containing precisely incorporated reactive functions (i.e. alkyne and activated ester moieties) were first synthesized by sequence-controlled copolymerization of styrene (donor comonomer) with functional N-substituted maleimides (acceptor comonomers). These copolymers were prepared by nitroxide mediated polymerization in the presence of a commercially available alkoxyamine (i.e. BlocBuilder® MA). Discrete amounts (i.e. one molar equivalent as compared to the alkoxyamine) of triisopropylsilyl-protected N-propargyl maleimide and pentafluorophenyl 4-maleimidobenzoate were added at precise moments during the polymerization of a large excess of styrene. Due to the kinetically favored cross-propagation of donor and acceptor comonomers, the N-substituted maleimides were incorporated in precise regions of the polystyrene chains. Linear precursors with variable chain-lengths and sequence distributions were synthesized and characterized using 1H NMR, size exclusion chromatography (SEC) and FT-IR spectroscopy. Afterwards the chains were folded in solution using a two-step strategy. The pentafluorophenyl activated ester moieties were first reacted with 11-azido-3,6,9-trioxaundecan-1-amine, thus leading to azide-functionalized polymers. Subsequently, intramolecular azide–alkyne Huisgen cycloadditions were performed in dilute DMF solutions in the presence of a copper-based catalyst. SEC, 1H NMR, and FT-IR measurements indicated the formation of folded polymer chains containing asymmetric covalent bridges.

Hairy Carbon Nanotube@Nano-Pd Heterostructures: Design, Characterization, and Application in Suzuki C−C Coupling Reaction

Poly(glycidyl methacrylate), PGMA, was prepared via ATRP in bulk solution, and its epoxy groups were further acid-hydrolyzed in order to obtain a polymer with glycerol moieties (noted POH). The POH chain end C-Br bonds were subjected to a nucleophilic attack by NaN(3), resulting in azide-terminated POH (POH-N(3)). The CNTs were modified by in-situ-generated alkynylated diazonium cations from the para-alkynylated aniline of the formulas H(2)N-C(6)H(4)-C≡C-H, yielding CNT-C(6)H(4)-C≡C-H nanotubes. The azide-functionalized polymer POH-N(3) was clicked to the alkynyl-modified CNTs giving CNT@POH hybrids, which were further subjected to an oxidation resulting in carboxylated polymer-modified CNTs (noted CNT@PCOOH). The as-designed hairy CNTs served as efficient platforms for the in-situ synthesis and massive loading of 3 nm sized palladium nanoparticles (NPs). The CNT@PCOOH@Pd heterostructures prepared so far exhibited an efficient catalytic effect in the C-C Suzuki coupling reaction and were regenerated up to four times without any significant loss of catalytic activity.