Vibrational characterization and fluorescence optimization of polycyclic polymers

A systematic series of polycyclic novel polymers was studied by Raman spectroscopy. The effect of the sequential introduction of polycyclic aromatic ring substituents into the delocalized backbone was examined in relation to the variation of the relative ring breathing and stretching as well as the vinyl stretch frequencies. Replacement of the phenyl units by higher order acene moieties such as naphthyl and anthryl results in a shift of the characteristic stretching frequencies, and analysis of the vinyl stretch leads to the confirmation that higher order acene substitution into the delocalized backbone substantially weakens the vinyl bond. Semiquantitative integrated Raman analysis shows a well-defined variation of the vibrational characteristics with structure. The structural variation of the integrated Raman intensity elucidates the effect of the electronic and vibrational decoupling introduced by the continual systematic acene substitution and points toward the ability to tailor the vibrational characteristic of the polymeric systems much the same as the electronic characteristics are manipulated. Relative fluorescence yields calculated for absorption and fluorescence spectroscopy can be seen to be well-correlated with integrated Raman intensities, implying that the reduction of the vibrational intensity limits the avenues of nonradiation, hence optimizing the fluorescence yield.     

The characterization of polycyclic aromatic hydrocarbons by Raman spectroscopy

High quality Raman spectra, substantially free from fluorescence interference, have been obtained from 11 polycyclic aromatic hydrocarbons, in the solid state, using a Fourier Transform spectrometer. These spectra are rich in sharp bands and, merely by utilizing the limited number of strong peaks it is possible to characterize each hydrocarbon uniquely. The presence of an appreciable number of peaks of medium intensity in each spectrum considerably increases the specificity. The scope and limitations of these spectra for analytical purposes are discussed.     

Synthesis and characterization of macrocyclic vinyl aromatic polymers

The synthesis and characterization by size exclusion chromatography, liquid chromatography, NMR, matrix‐assisted laser desorption/ionization, thermal analysis, and other techniques of well‐defined and narrow molecular weight distribution macrocyclic polystyrene (PS), poly(2‐vinylpyridine), poly(α‐methylstyrene), poly (2‐vinyl‐naphthalene) (P2VN), and poly(9,9‐dimethyl‐2‐vinylfluorene) (PDMVF) containing a single 1,4‐benzylidene, methylidene, or 9,10‐anthracenylidene unit are reviewed. The absorption and emission spectroscopy of PS, P2VN, and PDMVF is also discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2139–2155, 2006     

Multidisciplinary characterization of novel emulsion polymers

A series of novel emulsion styrene‐butadiene copolymer blends were characterized using a multidisciplinary approach involving both analytical and rheological measurements. The blends were composed of 50/50 w/w high molecular weight (ca. 800,000 Da) ESBR and low molecular weight (ca. 200,000 Da) ESBR, each component having a different bound styrene level. When the difference in bound styrene between the two components was greater than 18%, a two phase co‐continuous morphology was observed by scanning probe microscopy, consistent with two glass transitions measured by temperature modulated DSC. Molecular weight and molecular weight distributions were characterized by both size exclusion chromatography and thermal field flow fractionation with multiangle light scattering detection. ThFFF was unique in its ability to detect ultra‐high molecular weight (> 10⁷ Da) fractions suggesting that traditional SEC often under‐estimates polymer molecular weight. Blending polymers of different molecular weights and styrene levels resulted in reduced molecular weight between entanglements which, based on rheological measurements, would be expected to improve processability.     

Synthesis of novel low-viscosity liquid epoxidized aromatic hyperbranched polymers

Low-viscosity liquid epoxidized aromatic hyperbranched polymers are synthesized by the reaction between epichlorohydrin (ECH) and carboxy-end hyperbranched polymers prepared from low-cost products trimellitic anhydride (B₃ TMA) and dihydroxy alcohols (A₂). The low-viscosity property, especially the lowest viscosity of epoxidized aromatic hyperbranched polymers is only 350 cp which has not reported among epoxidized aromatic hyperbranched polymers before, make them can be used to coatings and adhesion fields without organic solvent hopefully. The properties of the epoxidized aromatic hyperbranched polymers are measured by GPC, FT-IR and viscometer.     

Precursor synthesis strategy for polycyclic aromatic conjugated polymers on the application of supercapacitors

Polycyclic aromatics (PCAs) possess excellent photoelectric properties, but the construction of such compounds has been a quite challenging subject of study, mainly due to very low solubility. Herein we report a precursor synthesis strategy for polycyclic aromatic conjugated polymers. A soluble precursor polymer, that containing fusible “double U-shaped aromatic” (DUA) and perylenetetracarboxydiimide (PDI) units, was firstly synthesized by Suzuki coupling. The stereo aromatic units in polymer backbone were found to be converted into polycyclic aromatic units, i.e. hexa-peri-hexabenzocoronene (HBC), by chemical or electrochemical oxidation, which resulted in a formation of insoluble polycyclic aromatic conjugated polymers. The electrochemical oxidations that occurred at the interface of electrode and solution exhibited higher cyclization reactivity and leads to the formation of high quality films on the electrode surface. Characterization by Raman and UV-visible (UV-Vis) spectroscopy validated the successful formation of this HBC structure. Some potential applications of such thin films are being explored, and here we focus on the characteristics of supercapacitors based on their excellent electrochemical properties.     

A novel nomenclature of polycyclic aromatic hydrocarbons without using graph centre

In this paper, we develop a novel adjacency matrix, He-matrix, corresponding to the dualist graph. Without using the graph center concept, we advance a novel nomenclature of polycyclic aromatic hydrocarbons. Further, we derive some distinguishing theorems about PAH molecules and present some results of our automatic derivatization and automatic classification counting of fused PAH molecules.     

Identification and characterization of polycyclic aromatic hydrocarbons in coking wastewater sludge

GC‐MS analysis was performed on the coking sludge from a coking wastewater treatment plant (WWTP) to allow detailed chemical characterization of polycyclic aromatic hydrocarbons (PAHs). The identification and characterization of the isomers of PAHs was based on a positive match of mass spectral data of their isomers with mass spectra databases or based on a comparison of electron impact ionization mass spectra and retention times of target compounds with those reference compounds. In total, 160 PAH compounds including numerous N‐, O‐, S‐, OH‐, and Cl‐containing derivatives were positively identified for the first time. Quantitative analysis of target compounds was performed in the selected ion‐monitoring mode using the internal standard method. The total concentrations of selected compounds in the coking sludge samples from the anaerobic tank, aerobic tank, hydrolytic tank, and secondary clarifier of the WWTP ranged from 1690 ± 585 to 6690 ± 522 mg/kg, which were much higher than those in other industrial and municipal sludges. PAHs with four and five rings were found to be the dominant compounds, and diagnostic ratios of these compounds suggested that they had the characteristics of coal combustion and pyrolysis.     

Synthesis of functionalized polycyclic compounds via a novel aromatic oxy-Cope rearrangement

Polycyclic compounds have been prepared by aromatic dianionic oxy-Cope rearrangements involving the π bonds of two phenyl rings in a [3,3] sigmatropic rearrangement.     

A novel thiophene-fused polycyclic aromatic with a tetracene core: synthesis, characterization, optical and electrochemical properties

FeCl?-mediated oxidative cyclization was successfully used to construct an extended thiophene-pendant pyrene skeleton and synthesize a novel thiophene-fused polycyclic aromatic (THTP-C) with a tetracene core. The identity of the compound was confirmed by 1H-NMR, 13C-NMR, MS, and elemental analysis. Meanwhile, a single crystal of THTP-C was obtained and analyzed by X-ray single-crystal diffraction. THTP-C has a "saddle" shaped π-conjugated 1-D supramolecular structure, and favors highly ordered self-assembly by π-π interactions as evidenced by its concentration-dependent 1H-NMR spectra in solution. The optical properties of THTP-C were investigated by ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy and its electrochemical properties were investigated by cyclic voltammetry (CV). The relatively large band gap (2.86 eV), low E(HOMO) level (-5.64 eV) and intermolecular π-π interactions imply that THTP-C has a high stability against photo-degradation and oxidation, and may be a promising candidate for stable hole-transporting materials.     

Synthesis and characterization of some novel aromatic polyimides

Three new diamines 1,2-di(p-aminophenyloxy)ethylene, 2-(4-aminophenoxy)methyl-5-aminobenzimidazole and 4,4-(aminopheyloxy) phenyl-4-aminobenzamide were synthesized and polymerized with 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BP), 4,4′-(hexafluoroisopropyledene)diphthalic anhydride (HF) and 3,4,9,10-perylene tetracarboxylic acid dianhydride (PD) either by one step solution polymerization reaction or by two step procedure. The later includes ring opening poly-addition to give poly(amic acid), followed by cyclodehydration to polyimides with the inherent viscosities 0.62-0.97 dl/g. Majority of polymers are found to be soluble in most of the organic solvents such as DMSO, DMF, DMAc, m-cresol even at room temperature and few becomes soluble on heating. The degradation temperature of the resultant polymers falls in the ranges from 240 °C to 550 °C in nitrogen (with only 10% weight loss). Specific heat capacity at 300 °C ranges from 1.1899 to 5.2541 J g⁻¹ k⁻¹. The maximum degradation temperature ranges from 250 to 620 °C. T_g values of the polyimides ranged from 168 to 254 °C.     

Preparation and characterization of novel basic polysulfone polymers

Two synthesis routes for the preparation of novel base‐modified polysulfones (PSUs; Udel®) were investigated: (1) the addition of the basic aromatic ketones 2,2′‐dipyridylketone and 4,4′‐bis‐(diethylamino)benzophenone and the basic aromatic aldehydes N,N‐dimethylamino‐benzaldehyde, pyridine‐2‐aldehyde, pyridine‐3‐aldehyde, and pyridine‐4‐aldehyde to lithiated PSU and (2) the reaction of lithiated PSU with basic aromatic carboxylic acid esters such as 4‐N,N‐dimethylaminobenzoic acid ethylester, pyridine‐2‐carboxylic acid ethylester, pyridine‐3‐carboxylic acid ethylester, and pyridine‐4‐carboxylic acid ethylester. Both synthesis routes lead to a high degree of conversion, without the occurrence of crosslinking. This is remarkable, especially for the reaction of lithiated PSU with the ester compounds, because the ? (C?O)? Ar groups formed by the reaction of the ester with PSU–Li are not further converted with the remaining PSU–Li sites to (crosslinked) PSU? C(? OLi)? Ar? PSU alcoholates, as normally observed when esters are reacted with Li‐organic compounds. Starting with dilithiated PSU, we obtained degrees of substitution of 0.8–2 groups per PSU repeating unit. The structures and compositions of the modified PSU polymers were confirmed with NMR spectroscopy and elemental analysis. The modified polymers were also characterized via thermogravimetric analysis (thermal stability). Interestingly, the product of the reaction of lithiated PSU with 4,4′‐bis‐(diethylamino)benzophenone could be oxidized to a deep blue polymeric dye that showed proton self‐conductivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2874–2888, 2001     

Synthesis of polycyclic aromatic fluoranthenes

A general synthetic approach to polycyclic aromatic hydrocarbons containing a fluoranthene ring system is described. The method entails fusion of an indeno ring to an alternant hydrocarbon via reaction of an aryllithium derivative with cyclohexene oxide.     

Economical synthesis of novel class of heteroatom containing partially reduced polycyclic aromatic hydrocarbons

An efficient and convenient synthesis of 2-oxa- and 2-thia-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrenes has been described through base-induced ring transformation of 2-oxo-4-sec.amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by 4-oxotetrahydropyran and 4-oxotetrahydrothiopyran, respectively, in excellent yields.     

Closed-shell polycyclic aromatic hydrocarbon cations: a new category of interstellar polycyclic aromatic hydrocarbons

Density functional theory has been employed to calculate the harmonic frequencies and intensities of a range of polycyclic aromatic hydrocarbon (PAH) cations that explore both size and electronic structure effects on the infrared spectroscopic properties of these species. The sample extends the size range of PAH species considered to more than 50 carbon atoms and includes several representatives from each of two heretofore unexplored categories of PAH cations: (1) fully benzenoid PAH cations whose carbon skeleton is composed of an odd number of carbon atoms (C(odd) PAHs); and (2) protonated PAH cations (HPAH+). Unlike the radical electronic structures of the PAH cations that have been the subject of previous theoretical and experimental work, the species in these two classes have a 'closed'-shell electronic configuration. The calculated spectra of circumcoronene, C54H18, in both neutral and (radical) cationic form are also reported and compared with those of the other species. Overall, the C(odd) PAHs spectra are dominated by strong CC stretching modes near 1600 cm(-1) and display spectra that are remarkably insensitive to molecular size. The HPAH+ species evince a more complex spectrum consistent with the added contributions of aliphatic modes and their generally lower symmetry. Finally, for both classes of closed-shell cations, the intensity of the aromatic CH stretching modes is found to increase with molecular size far out of proportion with the number of CH groups, approaching a value more typical of neutral PAHs for the largest species studied.     

Fast atom bombardment combined with mass spectrometry for characterization of polycyclic aromatic hydrocarbons

A new approach using fast atom bombardment combined with mass spectrometry to characterize polycyclic aromatic hydrocarbons (PAHs) in the range of 128-252 u molecular weight is described. Sulfolane was employed as a liquid matrix for these π-conjugated hydrocarbons. Bombardment of sulfolane solution of certain PAHs with an atom beam produces both radical cation (M^+.) and protonated molecule [(M + H)⁺], with no evidence of fragmentation. Collisional activation of the fast atom bombardment-desorbed M^+. ions, however, results in several structure-specific fragment ions. Structural differences in a few isomeric hydrocarbons can be detected using the [(M + H)⁺]/[M^+.] abundance ratio and in the pyrene-fluoranthene pair by the B/E linked-field-collision-activated dissociation data. The [(M + H)⁺]/[M^+.] was found to be compound-specific and correlated well with certain properties (resonance energy, proton affinity, and ionizing energy) of PAHs.     

Thermodynamic and kinetic characterization of nitrogen-containing polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography

A series of five nitrogen-containing polycyclic aromatic hydrocarbons (NPAHs) was studied on polymeric octadecylsilica using methanol and acetonitrile as the mobile phase. The thermodynamic and kinetic behavior was examined as a function of ring number, annelation structure, and position of the nitrogen atom. The retention factors for the NPAHs are smaller than those for the parent PAHs in methanol, while the converse is true in acetonitrile. The changes in molar enthalpy are relatively comparable in both mobile phases with 1-aminopyrene having values of -5.0 +/- 0.2 kcal/mol in methanol and -6.3 +/- 0.7 kcal/mol in acetonitrile (1 cal = 4.184 J). However, the rate constants from mobile to stationary phase (k(sm)) and from stationary to mobile phase (k(ms)) demonstrate large differences as a function of mobile phase. For example, the rate constants k(ms) for 1-aminopyrene and 4-azapyrene are 675 and 62 s(-1), respectively, in methanol at 303 K. In contrast, the same solutes demonstrate rate constants of 3.47 and 3.9 x 10(-3) s(-1), respectively, in acetonitrile. The activation energies for transfer from mobile phase to transition state (deltaE(double dagger(m)) and from stationary phase to transition state (deltaE(double dagger(s)) also differ as a function of mobile phase. For example, the activation energies deltaE(double dagger(s)), for 1-aminopyrene are 21 and approximately 0 kcal/mol, whereas those for 4-azapyrene are 19 and 23 kcal/mol, in methanol and acetonitrile, respectively. Based on these thermodynamic and kinetic results, the relative contributions from the partition and adsorption mechanisms are discussed.