Preparation and properties of fluoroalkyl end-capped oligomer/fluoresceins nanocomposites

Self-assembled fluorinated oligomeric aggregates formed by fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers, N,N-dimethylacrylamide oligomers, and acrylic acid oligomers in methanol could recognize selectively fluoresceins as guest molecules to form a new class of fluorinated aggregates/fluoresceins nanocomposites. These fluorinated fluoresceins nanocomposites were found to exhibit an extraordinarily enhanced light absorption (λ_max: ca. 440 nm) compared to that (λ_maxs: 452 and 480 nm) of the parent fluorescein in the absence of fluorinated aggregates. On the other hand, fluoroalkyl end-capped 2-carboxyethyl acrylate oligomers, which possess no aggregate characteristic in methanol solutions, could not afford such an enhanced light absorption peak under similar conditions. Not only fluorescein but also fluorescein derivatives such fluoresceinamine, carboxyfluorescein, and fluorescein isothiocyanate afforded similar enhanced narrow absorption peaks under similar conditions. Naphthofluorescein was also encapsulated into these fluorinated oligomeric aggregate cores to afford fluorinated aggregates/naphthofluorescein composites, and these fluorinated naphthofluorescein composites afforded an extremely enhanced narrow absorption peak around 520 nm.     

Dispersion of single-walled carbon nanotubes in water by the use of novel fluorinated dendrimer-type copolymers

New fluorinated dendrimer-type block copolymers were applied to the dispersion of single-walled carbon nanotubes (SW-CNTs) and single-walled carbon nanotubes containing carboxy groups [(SW-CNT)-COOH] in water. Fluorinated block copolymer could disperse SW-CNTs more effectively in water, compared to that of the corresponding ABA triblock-type fluoroalkyl end-capped dimethylacrylamide oligomer [R_F-(DMAA)_n-R_F]. Dynamic light-scattering (DLS) measurements and transmission electron microscopy (TEM) images show that SW-CNTs could be smoothly encapsulated into fluorinated copolymeric aggregates cores. Interestingly, it was demonstrated that SW-CNTs could be in part released from the fluorinated copolymeric aggregates/SW-CNTs composites or encapsulated into these composites with increasing the dispersion times. On the other hand, fluorinated block copolymer and R_F-(DMAA)_n-R_F oligomer were not able to disperse well (SW-CNT)-COOH in water; however, ABA triblock-type fluoroalkyl end-capped acrylic acid oligomer was able to disperse quite effectively (SW-CNT)-COOH in water.     

Preparation and antibacterial activity of novel fluoroalkyl end-capped oligomers/silica nanocomposites-encapsulated low molecular biocides

Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomer [R_F-(DOBAA) _n -R_F] reacted with tetraethoxysilane (TEOS) and silica nanoparticles in the presence of low-molecular weight biocides such as hibitane, hinokitiol, and hinokioil under alkaline conditions to afford R_F-(DOBAA) _n -R_F/silica nanocomposites-encapsulated these biocides in excellent to moderate isolated yields. Fluoroalkyl end-capped N,N-dimethylacrylamide oligomer [R_F-(DMAA) _n -R_F] and acrylic acid oligomer [R_F-(ACA) _n -R_F]/silica nanocomposites-encapsulated hibitane were obtained under similar conditions. Dynamic light scattering measurements showed that the size of these fluorinated nanocomposites-encapsulated biocides thus obtained is nanometer size-controlled. Additionally, these fluorinated nanocomposites were shown to have a good dispersibility and stability in methanol and water. Of particular interest, these fluorinated nanocomposites-encapsulated biocides were found to have a good antibacterial activity against Staphylococcus aureus, and these nanocomposites were applied to the surface modification of traditional organic polymers such as poly(methyl methacrylate).     

Acceleration of Tri-Addition to [70]Fullerene by “Nanom Black” Fullerene Soot

We report the structure and properties of a fullerene soot called “Nanom Black,” which is prepared by removing fullerenes from the soot formed in fullerene production. Nanom Black remarkably accelerates the regioselective tri-addition of phenylcopper reagent to C₇₀, giving C₇₀Ph₃H at a reaction rate approximately 50-fold that in the absence of Nanom Black. Transmission electron microscopy, X-ray diffraction, and Raman data on Nanom Black are presented, and a mechanistic rationale is discussed.     

UV-induced switching behavior of novel fluoroalkyl end-capped vinyltrimethoxysilane oligomer/titanium oxide nanocomposite between superhydrophobicity and superhydrophilicity with good oleophobicity

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer suffered the sol–gel reaction under alkaline conditions in the presence of titanium oxide nanoparticles in tetrahydrofuran to afford the corresponding fluorinated oligomer/titanium oxide nanocomposites[R_F-(VM-SiO₂)_n-R_F/TiO₂] in excellent to moderate isolated yields. These fluorinated composites thus obtained were nanometer size-controlled fine particles, and exhibited good dispersibility and stability in traditional organic solvents except for water. These fluorinated nanocomposites were applied to the surface modification of glass to exhibit not only a completely superhydrophobic characteristic (a water contact angle: 180°) with a non-wetting property against water droplets but also a good oleophobicity imparted by fluoroalkyl segments in the composites on their surface. Of particular interest, we have found that the wettability for water can be switched between superhydrophobicity and superhydrophilicity by alternation of ultraviolet (UV) irradiation and dark storage with keeping a good oleophobicity on the modified surface treated with the anatase-type titanium oxide composite.     

Phosphorous-containing nadicimide resins: synthesis and characterization

A series of phosphorous-containing nadicimide end-capped resins, having different backbone, were prepared by reacting endo-5-norbornene- 2,3-dicarboxylic anhydride (nadic anhydride), pyromellitic dianhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) andtris [3-azo(4-aminophenyl)] phosphine oxide (TAZP) in dimethyl acetamide. Yields were essentially quantitative. Structural characterization of resins was done by elemental analysis, IR and¹H-NMR. Thermal behaviour of the resins was investigated by differential scanning calorimetry and thermogravimetric analysis, which revealed good high temperature performance. Isothermal ageing studies done at 340°C for various time periods showed good thermo-oxidative stability.     

含氟丙烯酸酯嵌段共聚物乳液的合成及表征

以PEDB(二硫代苯甲酸苯乙基酯)为链转移剂,进行AA(丙烯酸)、BA(丙烯酸丁酯)可逆加成-断裂链转移(RAFT)自由基聚合,得到数均相对分子质量可控、相对分子质量分布窄的聚合物P(AA-BA).以得到的聚合物为大分子RAFT自由基聚合剂,进行舍氟丙烯酸酯的扩链反应,制得稳定的含氟嵌段共聚物P(AA-BA)-b-PTFEA(甲基丙烯酸三氟乙酯)乳液.为了克服RAFT链转移剂在水中迁移慢的缺点,引入了自发相倒置的实验过程,即先进行AA、BA的本体聚合,然后在温和搅拌条件下滴加NaOH溶液,体系发生自发相倒置,产生稳定的亚微型聚合物颗粒,DLS测量乳液颗粒平均大小为4nm.乳液经TEM、DLS观测,粒径为50～60nm,颗粒分布均匀.     

N‐Type Organic Thermoelectrics: Improved Power Factor by Tailoring Host–Dopant Miscibility

In this contribution, for the first time, the polarity of fullerene derivatives is tailored to enhance the miscibility between the host and dopant molecules. A fullerene derivative with a hydrophilic triethylene glycol type side chain (PTEG‐1) is used as the host and (4‐(1,3‐dimethyl‐2,3‐dihydro‐1H‐benzoimidazol‐2‐yl)phenyl)dimethylamine n ‐DMBI) as the dopant. Thereby, the doping efficiency can be greatly improved to around 18% (<1% for a nonpolar reference sample) with optimized electrical conductivity of 2.05 S cm^?1, which represents the best result for solution‐processed fullerene derivatives. An in‐depth microstructural study indicates that the PTEG‐1 molecules readily form layered structures parallel to the substrate after solution processing. The fullerene cage plane is alternated by the triethylene glycol side chain plane; the n ‐DMBI dopants are mainly incorporated in the side chain plane without disturbing the π–π packing of PTEG‐1. This new microstructure, which is rarely observed for codeposited thin films from solution, formed by PTEG‐1 and n ‐DMBI molecules explains the increased miscibility of the host/dopant system at a nanoscale level and the high electrical conductivity. Finally, a power factor of 16.7 µW m^?1 K^?2 is achieved at 40% dopant concentration. This work introduces a new strategy for improving the conductivity of solution‐processed n‐type organic thermoelectrics.     

Crystallization behaviour and mechanical properties of polypropylene-based composites

The influence of glass fibres on the primary nucleation process, isothermal radial growth rate of spherulites and overall kinetic rate constant of isotactic polypropylene (iPP) has been examined. The polypropylene was also modified by means of acrylic acid (iPP^*) in order to improve the adhesion between the matrix and the fibres, and the relative properties were compared with those concerning the composites having as matrix plain MR Moreover the mechanical properties of injection-moulded composites containing iPP and iPP^* have been studied. These properties improved on increasing the fibre content. It was found that for the same glass-fibre content better values of the elongation at break and creep are observed in the case of reinforced polypropylenes having as matrix acrylic acid modified polypropylene.     

THE SINGLE CRYSTAL X-RAY STRUCTURE OF C70Me8; THE ORIGIN OF THE FULLERENE ADDITION PATTERNS FOR BULKY GROUPS

ABSTRACT

The first complete proof of the equatorial addition pattern in [70]fullerene is provided by a single crystal x-ray structure of C₇₀Me₈. Compared to the bonds in the parent fullerene, those having a methyl group attached are lengthened, those having two methyl groups adjacent at each end are shortened due to compression by these groups, and some hexagonal rings show greater delocalisation (more aromaticity) than the corresponding rings in the precursor fullerene. In contrast to the 1,2-addition of sterically undemanding groups, bulky groups generally undergo 1,4-addition, but only give 1,2-addition if there is a need to quench an intermediate radical. The manner in which this gives rise to the patterns seen in C₆₀ X ₆, C₆₀ X ₈ and C₇₀ X ₁₀, where X is bulky, is proposed.     

Core electron level structure in C<Subscript>60</Subscript>F<Subscript>18</Subscript> and C<Subscript>60</Subscript>F<Subscript>36</Subscript> fluorinated fullerenes

The structure of C1s and F1s core electron levels in C₆₀F₁₈ and C₆₀F₃₆ fluorinated fullerenes has been studied by X-ray photoelectron spectroscopy using synchrotron radiation. It is established that C1s levels of carbon atoms not bound to fluorine in these compounds are shifted down by 1.0 and 1.6 eV relative to the C1s level in the usual C₆₀ fullerene, so that the binding energies of the core electron levels in C₆₀F₁₈ and C₆₀F₃₆ amount to E _b (C1s, C-C) = 285.7 and 286.3 eV, respectively. These values are characteristic and can be used for the identification of both homogeneous fluorinated fullerenes and combined materials comprising a mixture of various fluorinated fullerenes with each other and with different carbon-containing based materials.     

Characterizing the surface properties of carbon nanotubes by inverse gas chromatography

Inverse gas chromatography (IGC) was used to characterize the surface properties of pristine multi-walled carbon nanotubes (MWNTs), as well as the poly(acrylic acid) sidewall covalently functionalized MWNTs (PAA-g-MWNTs) and hydroxyl group directly grafted MWNTs (MWNTols). The dispersive component of the surface energy ( ) and the acid/base character of these samples’ surfaces were estimated by the retention time with different non-polar and polar probes at infinite dilution region. The specific free energy (ΔG ^AB) and the enthalpy (ΔH ^AB) of adsorption corresponding to acid–base surface interactions were determined. By correlating ΔH ^AB with the donor and acceptor numbers of the probes, the acidic (K _A) and the basic K _D parameters of the samples’ were calculated. The results show that chemical modification successfully reduces the dispersive component of the surface energy of MWNTs. Furthermore, MWNTs grafted with hydroxyl groups exhibit a more basic character, while MWNTs grafted with poly(acrylic acid) show a more acidic character. Overall, IGC provides useful complementary information on the changes resulted from the chemical modifications of the surface.     

Calculation of Ionization Energy and Electron Affinity of Molecule of Hydro‐ and Fluorinefullerenes C60H(F) n (0 ≤ n ≤ 60)

Abstract

Vertical and adiabatic electron affinities (EA) and ionization energies (IE) of C₆₀H(F) _n (0 ≤ n ≤ 60) have been determined using semiempirical calculations with AM1 Hamiltonian. Comparison of the thermo‐chemical characteristics of the fluorinated and hydrogenated fullerene positive and negative ions has been carried out on the basis of these calculations.     

Triplet molecules of the D5 symmetry group based on C60 fullerene

The possibility of observing a non-zero-spin triplet state in highly symmetric derivatives of fullerene molecules with five double bonds, representing isomers of the type D₅-C₆₀(R-r ₆-R)₅ (where R = H or CH₃), is assessed based on the results of quantum-chemical calculations. The energies of isomer formation (endo-and exothermal process for the hydrogenated and methylated isomers, respectively) and the energies of terms are determined. The ground state corresponding to a non-zero-spin triplet e ₁ ² (³A₂) occurs approximately 0.3 eV below the zero-spin states. The results can be interpreted within the framework of the tight binding approximation for the pπ basis set orbitals of fullerene molecules (representing radially directed C2p hybrid atomic orbitals). The character of the open electron shell of isomers, delocalized over a large fullerene surface, suggests that, with high probability, the above non-zero-spin triplet state (rather than the e ₁ ² (¹E₂) state stabilized by the Jahn-Teller effect) is the ground state of the system.     

Synthesis of poly(3-hexylthiophene)-graft-poly(t-butyl acrylate-co-acrylic acid) and its role of compatibilizer for enhancement of mechanical and electrical properties of Nylon 66/multi-walled carbon nanotube composites

A compatibilizer, poly(3-hexylthiophene)-graft-poly(t-butyl acrylate-co-acrylic acid) was synthesized, where the acrylic aid was formed by hydrolysis of t-butyl acrylate unit. It has been identified that poly(3-hexylthiophene) backbone of the compatibilizer interacts with multi-walled carbon nanotubes (MWCNTs) via π–π interaction and the acrylic acid unit of the graft chain interacts with Nylon 66 (N66) matrix via hydrogen bonding. When a small amount of compatibilizer was added to N66/MWCNT composites, MWCNTs were more homogeneously dispersed in N66 matrix than the case without compatibilizer. As a consequence, mechanical and electrical properties of the composites with compatibilizer were largely improved as compared with those of composites without compatibilizer.     

In situ observations of fracture mechanisms for radial cracks in wood

This paper presents the findings of work carried out to describe the micromechanisms of radial crack growth in wood. TR and TL cracks are both radial cracks but TR grows radially and TL longitudinally. TR cracks are known to show higher fracture toughness than TL cracks. The TR fracture surfaces also indicate a more tortuous crack path. Since the reason for this is unclear, details of the TR crack growth mechanisms in green Pinus sylvestris L were studied. This was done by in-situ optical microscopy as the crack was cutting through alternating layers of soft earlywood and stiff latewood. At the scale of individual cells, the crack tip advanced by separating cell walls at the middle lamella in a splitting or peeling mode. At the scale of growth rings, stick-slip type of crack growth was observed and new crack planes were often formed. The stress distribution in a material with alternating stiff and soft layers is causing this. This stress distribution also contributes to the tendency for inclined cracks to deviate in the radial direction. For interpretation of fracture mechanisms, the importance of scale interaction and the combined influences of microstructure and stress state are emphasized.     

Confidence bounds for the reliability of binary capacitated two-terminal networks

Binary capacitated two-terminal reliability at demand level d (2TR_d) is defined as the probability that network capacity, generated by binary capacitated components, between specified source and sink nodes is greater than or equal to a demand of d units. For the components that comprise these networks, reliability estimates are usually obtained from some source of testing. For these estimates and depending on the type of testing, there is an associated uncertainty that can significantly affect the overall estimation of 2TR_d. That is, an accurate estimate of 2TR_d is highly dependent on the uncertainty associated to the reliability of the network components. Current methods for the estimation of network reliability and associated uncertainty are restricted to the case where the network follows a series-parallel architecture and the components are binary and non-capacitated. For different capacitated network designs, an estimate on 2TR_d can only be approximated for specific scenarios. This paper presents a bounding approach for 2TR_d by explaining how component reliability and associated uncertainty impact estimates at the network level. The proposed method is based on a structured approach that generates a α-level confidence interval (CI) for binary capacitated two-terminal network reliability. Simulation results on different test networks show that the proposed methods can be used to develop very accurate bounds of two-terminal network reliability.     

Amorphous phase-segregated copoly(ether)esterurethane thermoset networks with oligo(propylene glycol) and oligo[(rac-lactide)-co-glycolide] segments: synthesis and characterization

Completely amorphous copoly(ether)ester networks based on oligo(propylene glycol) and oligo[(rac-dilactide)-co-glycolide] segments were synthesized by crosslinking star-shaped hydroxyl-telechelic cooligomers using an aliphatic low-molecular weight diisocyanate. Two different network architectures were applied exhibiting differences in the phase-separation behavior. For networks from oligo(propylene glycol)-block-oligo[(rac-lactide)-co-glycolide] triols (G³OPG-bl-OLG) only one glass transition was obtained. However, networks from a mixture of oligo(propylene glycol) triols (G³OPG) and oligo[(rac-lactide)-co-glycolide] tetrols (P⁴OLG) with a ratio of components in a certain range show two glass transition temperatures (T _g) being attributed to two segregated amorphous phases. In this way a wide spectrum of mechanical properties can be realized and adjusted to the requirements of a specific application.     

Demonstration of covalent sidewall functionalization of single wall carbon nanotubes by NMR spectroscopy: Side chain length dependence on the observation of the sidewall sp3 carbons

Carboxylic acid-functionalized single walled carbon nanotubes (SWNTs) prepared via the reaction of an amino acid, NH₂(CH₂) _n CO₂H where n = 1 (glycine, GLY), 5 (6-aminohexanoic acid, AHA), 10 (11-aminoundecanoic acid, AUDA), with fluorinated single walled carbon nanotubes (F-SWNTs) have been characterized by MAS ¹³C NMR spectroscopy. The ease of observing the aliphatic CH₂ groups and the resolution of the signal are dependent on the length of the amino acid’s aliphatic chain. We have proposed that where substituent chains are short (making NMR data collection difficult) chemical modification to extend the chain length should alleviate analysis problems. In this regard, we have investigated the esterification of the carboxylic acid termini. The amino acid-functionalized SWNTs were esterified with an appropriate alcohol to ensure parity of the overall substituent length, i.e., GLY-SWNT (C₁) + 1-dodecanol (C₁₂) = DOD-GLY-SWNT (1), AHA-SWNT (C₅) + 1-octanol (C₈) = OCT-AHA-SWNT (2), and AUDA-SWNT (C₁₀) + 1-propanol (C₃) = PRO-AUDA-SWNT (3). The ¹³C NMR shift for the sp³ nitrogen-substituted carbon atoms of the SWNT sidewall is observed at δ ≈ 75 ppm. Increasing the length of SWNT sidewall functional groups enhances the ability to observe the sidewall sp³ carbon. The methylene carbon signal intensity is less attenuated in the dipolar dephasing spectrum of the ester-functionalized SWNTs than their associated amino acid derivatives, suggesting more motional freedom of the side chain in the solid state. The confirmation of the dipolar dephasing spectral effects was assisted by the characterization of the ester of AUDA-SWNT with 1,3-propanediol: PPD-AUDA-SWNT (4). Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.