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© 2020 the Partner Organisations. The most frequently used approach to preparing aggregation-induced emission fluorogen (AIEgen) particles is precipitation. Therefore, the addition of an AIEgen solution into water results in the formation of AIEgen particles in a very short time. Within such a short period of time and in the absence of proper mixing under shear, AIE particles are likely to be distributed in a wide range of sizes, thereby affecting their ultimate brightness and applications. Despite numerous attempts, the size of AIEgen particles is still within the range of 200-300 nm. For the first time, we developed a facile robust and cost-effective method for the fabrication of aggregation-induced emission nanoparticles with tuneable particle sizes <100 nm, high quantum yield, and excellent photostability. The direct diffusion of nanoparticles within the cell or in a single-celled organism, as an advantage of size reduction, opens new opportunities for biological and material studies. Such a significant reduction in AIE nanoparticle size has the potential for developing more efficient techniques for characterizing advanced nanomaterials and understanding biological processes and detection strategies.

Guanine tracts of human telomeric DNA sequences are known to fold into eight different four-stranded structures that vary by the conformation of guanine nucleotides arranged in the stack of G-tetrads in their core and by different kinds and orders of connecting loops, called G-quadruplexes. Here, we present a novel G-quadruplex structure formed in K+ solution by a human telomeric variant d[(GGGTTA)2GGGTTTGGG], htel21T18. This variant DNA is located in the subtelomeric regions of human chromosomes 8, 11, 17, and 19 as well as in the DNase hypersensitive region and in the subcentromeric region of chromosome 5. Interestingly, single A18T substitution that makes htel21T18 different from the human telomeric sequence results in the formation of a three-layer chair-type G-quadruplex, a fold previously unknown among human telomeric repeats, with two loops interacting through the reverse Watson-Crick A6·T18 base pair. The loops are edgewise; glycosidic conformation of guanines is syn·anti·syn·anti around each tetrad, and each strand of the core has two antiparallel adjacent strands. Our results expand the repertoire of known G-quadruplex folding topologies and may provide a potential target for structure-based anticancer drug design.

Crystallization is a conventional technique for fabricating physically cross-linked poly(vinyl alcohol)-based hydrogels (PVA) with desired properties. The creation of crystalline regions induced by the freeze-thaw process is attributed to the molecular organization that serves as the junction points containing folded chains. The current study employs an aggregation-induced emission fluorogen (AIEgen) to produce a new approach for studying the kinetics of the formation of crystalline regions induced by the freeze-thaw process. For the first time, this research directly links the effects of freeze-thaw cycles to the final physical and mechanical properties of PVA hydrogels by using AIEgen. The results of the study reveal an increase in the fluorescent properties during the freeze-thaw process that reflects the rise in the percentage of crystallinity. This approach can be employed effectively to demonstrate the crystallization process using significant color and brightness differences in crystalline regions compared to amorphous areas. This capability allows researchers to visualize the crystalline regions clearly in situ and to study their kinetics, formation, and transition in the solid state. The results of this study have implications for the broad class of gels derived through polymer crystallization from solution.

The light-harvesting efficiency of luminescent solar concentrators (LSCs) is encumbered by reabsorption of emission and concentration quenching. Energy transfer from a high-concentration donor to a low-concentration energy trap can reduce reabsorption losses while maintaining efficient light collection. Emissive aggregates enable this approach by reducing the impact of concentration quenching, which is detrimental to the entire energy transfer process. Here we describe a LSC that utilizes emissive aggregates as energy-transfer pairs for downconversion. We characterize the photophysics of a benzothiadiazole-based emissive aggregate, PITBT-TPE, that complements a highly emissive donor, DPATPAN, and functions as a highly emissive energy-transfer acceptor even at high concentrations in excess of 180 mM in the PMMA matrix. Monte Carlo simulations of LSCs that leverage these emissive aggregates as energy-transfer pairs predicted notable optical efficiencies at large concentrator dimensions. We demonstrate for the first time a LSC that utilizes donor and acceptor AIE chromophores to reduce reabsorption.

When proteostasis becomes unbalanced, unfolded proteins can accumulate and aggregate. Here we report that the dye, tetraphenylethene maleimide (TPE-MI) can be used to measure cellular unfolded protein load. TPE-MI fluorescence is activated upon labelling free cysteine thiols, normally buried in the core of globular proteins that are exposed upon unfolding. Crucially TPE-MI does not become fluorescent when conjugated to soluble glutathione. We find that TPE-MI fluorescence is enhanced upon reaction with cellular proteomes under conditions promoting accumulation of unfolded proteins. TPE-MI reactivity can be used to track which proteins expose more cysteine residues under stress through proteomic analysis. We show that TPE-MI can report imbalances in proteostasis in induced pluripotent stem cell models of Huntington disease, as well as cells transfected with mutant Huntington exon 1 before the formation of visible aggregates. TPE-MI also detects protein damage following dihydroartemisinin treatment of the malaria parasites Plasmodium falciparum. TPE-MI therefore holds promise as a tool to probe proteostasis mechanisms in disease.Proteostasis is maintained through a number of molecular mechanisms, some of which function to protect the folded state of proteins. Here the authors demonstrate the use of TPE-MI in a fluorigenic dye assay for the quantitation of unfolded proteins that can be used to assess proteostasis on a cellular or proteome scale.

Mitochondria and mitochondrial dynamics play vital roles in health and disease. With the intricate nanometer-scale structure and rapid dynamics of mitochondria, super-resolution microscopy techniques possess great un-tapped potential to significantly contribute to understanding mitochondrial biology and kinetics. Here we present a novel mitochondrial probe (MitoRed AIE) suitable for live mitochondrial dynamics imaging and single particle tracking (SPT), together with a multi-dimensional data analysis approach to assess local mitochondrial (membrane) fluidity. The MitoRed AIE probe localizes primarily to mitochondrial membranes, with 95 ms fluorophore on-time delivering 106 photons/ms, characteristics which we exploit to demonstrate live cell 100 fps 3D time-lapse tracking of mitochondria. Combining our experimental and analytical approaches, we uncover mitochondrial dynamics at unprecedented time scales. This approach opens up a new regime into high spatio-temporal resolution dynamics in many areas of mitochondrial biology.

In this work, we design and synthesize a malonitrile-functionalized TPE derivative (TPE-DCV), which can react with thiol group through thiol-ene click reaction, leading to the fluorescence change of the system. Combined with the unique AIE property, TPE-DCV can selectively detect glutathione (GSH) but not cysteine or homocysteine. As the cleavage of GSSG with the aid of glutathione reductase produces GSH, which turns on the fluorescence of TPE-DCV, the ensemble of TPE-DCV and GSSG can thus serve as a label-free sensor for enzymatic activity assay of glutathione reductase. We also apply TPE-DCV for the detection of intracellular GSH in living cells.

A group of new amphiphilic poly(phenylacetylene)s bearing polar oligo (ethylene oxide) pendants, poly{4-[2-(2-hydroxyethoxy)ethoxy]phenylacetylene) (1), poly(4-\{2-[2-(2-hydroxyethoxy)-ethoxy]ethoxy]pheny}acetylene) (2p), poly(3-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}phenylacetylene) (2m), poly(4-{2-[2-(2-methanesulfonyloxy ethoxy)ethoxy]ethoxy}phenylacetylene) (3), poly(4-{2-[2-(p-toluenesulfonyloxyethoxy) ethoxy]ethoxy)phenylacetylene) (4), poly(4-(2-[2-(2-trimethy]silyloxy-ethoxy)ethoxy]ethoxy}phenylacetylen e) (5), and poly(4-[2-[2-(2-chloroethoxy)ethoxy]ethoxy\}phenylacetylene) (6), were synthesized with organorhodium complexes as the polymerization catalysts. The structures and properties of the polymers were characterized with IR, UV, NMR, and thermogravimetric analysis. 1, 2p, and 2m, the three polymers containing pendants with hydroxyl groups, were oligomeric or insoluble. The organorhodium complexes worked well for the polymerization of the monomers without hydroxyl groups, giving soluble polymers 3-6 with a weight-average molecular weight up to similar to 160 x 10(3) and a yield up to 99\%. Z-rich polymers 3-6 could be prepared by judicious selections of the catalyst under optimal conditions. (c) 2005 Wiley Periodicals, Inc.

Two novel polyacetylenes bearing nonlinear optical chromophoric group poly(3-(4-[4-(n-butyloxy) phenylazophenyl]carbonyl)oxy-1-propyne) (poly(la)) and poly(3-(4-[4-(n-heptyloxy)phenylazophenyl]carbonyl)-oxy-1-propyne) (poly(1b)) were synthesized with [Rh(nbd)Cl](2)-Et3N as catalysts. These polyacetylenes are soluble by using an alkyl spacer and an alkyloxyl group as a substituent. They were characterized by FTIR, NMR, GPC and UV-Vis and their optical limiting and nonlinear optical properties were investigated using 8 ns pulse at 532 nm wavenumber. The results show that these soluble functional polyacetylenes possess optical limiting properties and large nonlinear optical properties and poly(1b) possesses better optical limiting and nonlinear optical properties than poly(1a).

Three conjugated molecules', 4-phenylethynyl-4'-[N,N-diethylamino]azobenzene (3a), 4-phenylethynyl-4'-{[N-ethyl-N-(2-hydroxyethyl)]amino}azobenzene (3b), and 4-phenylethynyl-4'-[N,N-di(2-hydroxyethyl)amino]azobenzene (3c), nonlinear optical properties were determined using Z-scan technique with 532 mu, 8 ns laser pulses. The results indicate that these compounds possess large nonlinear optical absorptions, which are attributed to the long pi-conjugation structure owing to the substituent of phenylethynyl group. The nonlinearity increases with an increase in the number of hydroxyl group, due to the regular arrangement induced by the strong hydrogen bond interaction between hydroxyl groups of molecules. Their nonlinearity enhancement mechanism was studied by FT-IR spectroscopy. (c) 2005 Elsevier Ltd. All rights reserved.

Two linear, stereoregular, and structurally defined PPV derivatives (PPVs), poly[distyrylbenzene-b-(ethylene oxide)]s, with respective 12 and 16 of ethylene oxide repeat units in the backbone, abbreviated as DE-1 and DE-2 there-inafter, have been prepared via a modified synthetic profile. Both DE-I and -2 were soluble in organic solvents and able to form robust and transparent film upon spin casting. Instrument characterization, such as FTIR, H-1 and C-13 NMR, UV-vis and fluorescence spectroscopy, revealed the final structures as designed and novel photophysical properties in solution. Apparent spectral evidences strongly suggested the all trans conjugated DE-I and -2 and the successful isomeirization process adopted. It was found that the aggregates were formed for both DE-I and -2 at approximately 60\% of methanol in methanol/dichloromethane (MeOH/DCM). Both DE-1 and -2 exhibited solution tailorable absorption and emission properties. Before aggregating point, the absorption profile experienced a blue shift with the increase of MeOH and a slight increase in quantum yields (QYs). At aggregating point, however, an apparent blue shift in emission profile was observed along with a remarkable decrease of QY due to aggregate quenching. (C) 2004 Elsevier Ltd. All rights reserved.

Organic-inorganic hybrid perovskite (C4H9NH3)(2)CuCl4 was prepared via the reaction between copper chloride and butylammoniam chloride. Its chemical structure was characterized by FT-IR and elemental analysis. Its thin film was obtained by spin-coating, and X-ray diffraction (XRD) measurements indicated the formation of two-dimensional layered perovskites structure, with the c-axis perpendicular to the substrate surface. The electronic structure, thermal properties and electrical properties of the hybrid perovskite (C4H9NH3)(2)CuCl4 were also studied by UV-vis, photoluminescience (PL), TGA, DSC, and Hall measurement. (c) 2005 Elsevier B.V. All rights reserved.

A series of new hyperbranched poly(aryleneethytiylene)s are synthesized by the copolycyclotrimerizations of tetraynes (I and II) with aliphatic monoynes (A-C) catalyzed by tantalum-, mobium-, and cobalt-based catalysts. All the reactions proceed smoothly and soluble polymers of high molecular weights (M-w up to 3.8 x 10(4)) are obtained in high yields (up to 97\%).

High molecular weight polyacetylenes hearing nonlinear chromophoric pendants poly [4-ethynyl-4'-(N,N-diethylamino)azobenzene-co-phenylacetylene]s [poly(EAAB-co-PA)s] were synthesized in moderate yields by [Rh(nbd)Cl](2)-Et3N. The azo unit in the copolymers call be effectively controlled by the monomer feed ratio. Whereas the homopolymer of EAAB possessed low solubility. all the copolymers, however, dissolved readily in common organic solvents when the poly(EAAB) molar content was less than 41.7\%. The structures and properties of the polymers were characterized and evaluated by UV. NMR, optical limiting, and nonlinear optical analyses. All the copolymers possessed high stereoregularity and thermal stability ( 300 degrees C). They can attenuate intense laser pulses, With Solutions of high concentrations showing better performances. The third-order nonlinear Susceptibility of the copolymers was as high as 4.62 X 10(-11) esu, which are two orders of magnitude larger than those of poly(PA), and larger than that of poly(N-carbazoylacetylene), and poly(1-naphthylacetylene). (c) 2005 Elsevier Ltd. All rights reserved.

Reported are the preparation and characterization of Pd/Ni nanoparticles in the core of water-dispersible nanotubes of a triblock copolymer. The preparation involves first the preparation of the triblock nanotubes and then the production of Pd nanoparticles inside the nanotube cores. Ni is introduced in the final step by electroless deposition using Pd as the catalyst. The challenges facing each reaction step are discussed.

The excellent electroluminescent (EL) properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HIPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75-85\%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, wh

1,1-Bis(2'-thienyl)-2,3,4,5-tetraphenyisilole (1) was prepared and characterized crystallographic ally. Silole 1 exhibited aggregation-induced emission (AIE) behavior like other 2,3,4,5-tetraphenylsiloles. Unexpectedly, aggregates formed in water/acetone (6:4 by volume) mixture emitted a blue light that peaked at 474 nm, while aggregates formed in the mixtures with higher water fractions emitted green light that peaked at 500 nm. Transmission electron microscopy demonstrated that the aggregates formed in the mixture with water fraction of 60\% were single crystals, while aggregates that formed in the mixture with water fraction of 90\% were irregular and poorly ordered particles. The unusual PL spectral reliance on aggregation order was further confirmed by PL emissions of macroscopic crystal powders and amorphous powders of the silole in the dry state. PL spectral blue shifting was observed upon aging of the poorly ordered aggregates formed in mixtures with water fractions of 70-90\%, and they finally exhibited the same blue emission as the crystalline aggregates. The as-deposited thin solid film was amorphous and it could be transformed to a transparent crystalline film upon treatment in the vapor of an ethanol/water (1: 1 by volume) mixture, along with PL spectral blue shifting due to changing of aggregation order. It was also found that the crystalline film showed a blue-shifted absorption spectrum relative to the amorphous film and the shift of the absorption edge of the spectra could match that of corresponding PL spectra. The FT-IR spectrum of crystal powders of I displayed more vibration modes compared with that of amorphous powders, suggesting the existence of different T-overlaps or different molecular conformations. The crystals of 1-methyl-1,2,3,4,5-pentaphenylsilole and hexaphenylsilole also showed blue-shifted PL emissions of their amorphous solids, with a comparable PL spectral shift of 1. Developing of a silole solution on a TLC plate readily brought

New hyperbranched polyphenylenes with high molecular weights are synthesized by the copolycyclotrimerizations of 1,4-diethynylbenzene (I) with phenylacetylene (A), 1-octyne (B), and 1-dodecyne (C) catalyzed by TaCl5-Ph4Sn. The polymers are completely soluble in common solvents such as toluene, THF, chloroform, and dichloromethane. The polymers are characterized by spectroscopic methods and all of the polymers give satisfactory analysis data corresponding to their expected molecular structures.

A novel class of biofunctional silole nanocrystals with the potential to create highly sensitive immunoassay was firstly demonstrated. Biolabels were constructed by encapsulating nanocrystalline hexaphenylsilole [Ph2Si(CPh)(4); HPS] within ultrathin polyelectrolyte layers via the layer-by-layer (LbL) technique that provided an "interface" for the attachment of antibodies. A high ratio of fluorescent dyes to biomolecules (F/P ratio; 2.4 x 10(3)) was achieved without self-quenching problem. The aggregation-induced emission (AIE) feature offered silole biolabels the sensitivity 40- to 140-fold higher than that of a start-of-the-art immumoassay using directly fluorescent-labeled antibodies. (C) 2004 Elsevier B.V. All rights reserved.

In the present work, we investigated self-assembling of a poly(phenylacetylene) carrying L-valine pendants (PPA-Val) in a water/methanol solution, upon evaporation of the solution on mica, and on the water surface. With intercalation of a fluorescence probe of Ru(phen)(2)(dppx)(2+) (phen = 1,10-phenanthroline, dppx = 7,8-dimethyldipyridophenazine) into the hydrophobic cavities associated by the PPA-Val chains, their helical structures were directly detected in solution with an in situ fluorescence microscope. Helical aggregates were observed with AFM upon evaporation of the solvents, suggesting that the helical structures in the solution are the building blocks of the helical aggregates. Self-assembling structures of PPA-Val on the water surface were, however, very different from that formed upon evaporation of its THF solution on the mica surface. The polymer chains associated into a monolayer of extended fibers on the water surface, whereas superhelical fibers formed on the mica surface. Water molecules play a critical role in inducing the polymer to form diverse morphological structures in its bulk solution and on its surface. In solution, the isotropic hydrophobic effect drove the polymer chains to form superhelical aggregates, while on the water surface, the hydrophobic effect concentrated mainly on the lateral part of the polymer, thus giving a monolayer of extended fibers.

cis,cis-1,2,3,4-Tetraphenylbutadiene (TPBD) exhibits aggregation-induced emission (AIE) in the UV-blue band: the photoluminescence (PL) quantum yield of TPBD aggregates can differ from that of molecularly dissolved species by 2 orders of magnitude (>200). When the isolated molecules in solutions are cooled to extremely low temperature, they also emit intense light comparable to that in the solid state. TPBD thin layer shows on-off fluorescence switching behavior that can be utilized for the sensing of organic vapors. The phenyl substituents in TPBD are twisted in the solid state, and excimer formation is greatly prohibited. The cooling-enhanced emission of the TPBD solution and the fluorescence switching behavior suggest that the aggregation-induced emission is caused by restricted intramolecular rotation of the phenyl groups. The intramolecular phenyl rotations of TPBD can be regarded as rotational relaxations around their equilibrium positions, from which mean relaxation time is defined based on an Arrhenius equation. All the PL behaviors of TPBD can be well explained qualitatively by the magnitude of the relaxation time.

A conjugated polymer consisting of carbazole and quinoxaline units (5) is synthesized in a high isolation yield (95\%). The polymer possesses a high molecular weight (similar to22kDa) and is completely soluble in common solvents. When 5 is used as an emitting layer in a multilayer electroluminescence (EL) device, it emits a blue light of 484 nm and exhibits a current efficiency of similar to0.7 cd/A.

The self-assembling processes of amphibilic chiral oligomer to prepare porous films and vesicular ethers were analyzed. The amphibilic molecules favored vesicular self-assembly to optimize solvent/molecule interfacial energy and high concentration which resulted in formation of porous film. The nanovesicles possessed unique structures of high selective interactions under which nanovesicles favor random stacking manner. The chiral carbon atom in amphibilic molecules in an asymmetric factor directed self-assembling process and chirality effect induced curvatures of self-assembled structures.

A simple rule governing the light transmission through a fullerene solution or solid is revealed, and a group of fullerene derivatives, glasses, and polymers are found to be able to continuously cut off lights of any wavelength in almost the entire UV and visible spectral region in a predictable and reliable manner. The solutions of aminated fullerenes 1-4 give structureless light transmission spectra well-resembling those of cutoff optical filters. The spectrum bathochromically moves with an increase in concentration (c), whose cutoff wavelength (lambda(c)) increases logarithmically with bc, i.e.,, lambda(c) = alpha log bc + k, where b is the path length and a and k are constants. The spectra are reproducible and stable, changing little over a long period of time. In the solutions, the fullerene molecules aggregate into nanoclusters and their average sizes increase with increasing concentration, suggesting that the formation and growth of the fullerene nanoaggregates are responsible for the concentratochromism. The chromic effects are also observed in the solid state: the transmission spectra of the fullerenated glasses and polymers 5-7 all red shift with increasing C-60 content. The spectrum of the parent polymer virtually does not vary with concentration, proving that the buckyball is the origin of the novel concentratochromism.

In this work, we synthesized amino acid-containing poly(phenylacetylene)s and demonstrated the possibility of tuning their hierarchical structures by internal and external perturbations. A valine-acetylene adduct, 4-ethynylbenzoyl-L-valine methyl ester (5), was readily polymerized by [Rh(nbd)Cl](2), and the resultant "polyester" (1) was selectively hydrolyzed by KOH to its "polyacid" congener, poly(4-ethynylben zoyl-L-valine) (2). (Supra)molecular structures of the polymers were characterized by NMR, IR, UV, CD, and AFM techniques. The macromolecules took helical chain conformations in solutions. Their Cotton effects varied to different extents, when the polymer, solvent, and pH changed respectively from 1 to 2, from methanol to THF, and from neutral to basic. Upon evaporation of their methanol solutions, 1 and 2 self-assembled into micellar spheres and helical cables, respectively. Changing the solvent of 1 to THF changed its folding structure to helical cables, while increasing the pH of the methanol solution of 2 led to the formation of random threads. The denaturation from helical cables to random threads is probably caused by the cleavage of interstrand hydrogen bonds by base-mediated ionization of carboxyl groups of the valine pendants.

A series of hyperbranched poly(ferrocenylenesilyne)s, [(eta(5)-C5H4)(2)FeSi(R)](n) {R = CH3 [1(1)], CH=CH2 [1(V)], n-C8H17 [1(8)], n-C12H25 [1(12)], n-C16H33 [1(16)], n-C18H37 [1(18)]}, was prepared in good isolation yields (up to 77 wt \%) by one-pot coupling reactions of dilithioferrocene with trichlorosilanes. While the polymers with small R groups [1(1) and 1(V)1 were partially soluble, those with Iona alkyl chains [1(m) with m greater than or equal to 8] were completely soluble and readily film forming. The polymers exhibited diagnostic solution properties of hyperbranched macromolecules; for example, 1(18) had a high absolute molecular weight (M-w = 5 x 10(5) Da) but a low intrinsic viscosity ([eta] = 0.02 dL/g). Spectroscopic analyses revealed that the polymers possessed rigid skeleton structures with extended conjugations, with their absorption spectra tailed into the infrared region (> 700 nm). With an increase in the alkyl chain length, the polymer changed from glassy to rubbery state. The polymers lost little of their weights when heated to similar to400 degreesC but ceramized when pyrolyzed at higher temperatures, with ceramization yield increasing with a decrease in the alkyl chain length. Sintering 1(1) and 1(V) in 700-1200 degreesC produced ceramics in similar to50\% yields. Higher temperature pyrolyses favored the formation of ceramics with bigger inorganic nanoclusters and better magnetic performances. The ceramic prepared from the calcination of 1(1) at 1200 degreesC contained large iron silicide nanocrystals and exhibited high magnetizability (up to similar to51 emu/g) but near-zero remanence and coercivity. This ceramic is thus an outstanding soft ferromagnet with a high magnetic susceptibility and practically nil hysteresis loss.

Diyne polycyclotrimerizations initiated by transition-metal catalysts afforded hyperbranched polyphenylenes, which exhibited low viscosity, outstanding thermal stability, and small optical dispersion. Under optimized reaction conditions, polycyclotrimerizations of 1,8-nonadiyne (1) and 1,9-decadiyne (2) catalyzed by TaCl5-Ph4Sn produced hyperbranched poly(1,2,4-benzenetriyl-1,5-pentanediyl) (3) and poly(1,2,4-benzenetriyl-1,6-hexanediyl) (4)(1-5) respectively, in high yields (up to 93\%). The polymers were completely soluble and film-forming, and possessed high molecular weights (M-w up to similar to1.4 x 101) but low intrinsic viscosities ([eta] down to 0.13 dL/g). Their structures and properties were analyzed and evaluated by IR, UV, NMR, SEC, TGA, DSC, spectrofluorometry, light scattering, and spectroellipsometry. The structural characterizations confirmed the expected hyperbranched molecular architectures of 3 and 4 (comprising of 1,2,4-benzene rings and alpha,omega-alkyl spacers) and revealed the regioselective feature of the diyne polycyclotrimerizations. Polymers 3 and 4 underwent glass transitions at 43 and 23 degreesC, respectively, and lost almost no weights when heated to similar to500 degreesC. Polymer 3 emitted LTV light upon excitation, whereas 4 was practically nonluminescent. The thin films of 3 were highly transparent (greater than or equal to99.5\% transmittance) and displayed an optical dispersion as low as 0.009 in the visible spectral region, much superior to those of the commercially important "organic glasses" such as poly(methyl methacrylate) and polycarbonates.

The crystal structure of 11-{[(4'-heptoxy-4-biphenylyl) carbonyl] oxy}-1-undecyne (A9EO7), an acetylene with a biphenyl mesogenic moiety, was studied by combination of electron diffraction (ED), wide-angle X-ray diffraction (WAXD), and molecular simulation of ED pattern and molecular packing. A9EO7 was found to adopt an orthorhombic P2(1)2(1)2 space group with cell parameters of a = 5.78 Angstrom, b = 7.46 Angstrom, and c = 63.26 Angstrom, for which molecular packing calculations were conducted to elucidate the molecular conformation. Its crystal morphology was observed using a transmission electron microscope (TEM) and an atom force microscope (AFM). A9EO7 crystal grew to form step like morphology. Crystallization behavior of A9EO7 in magnetic field was examined. Induced by magnetic field A9EO7 could crystallize in such a way that its molecular long axis was parallel to the substrate.

The synthesis, thermal stability and optical properties of functional hyperbranched polyarylenes were reported. The molecular structure of the polymers was determined by nuclear magnetic resonance (NMR) spectroscopy. The spectra showed that the hyperbranched polymers possessed a random molecular composition, an irregular stereostructure and a rigid core architecture. The optical limiting and tunable light emitting properties of the polymers make them suitable to be used for high-tech applications.

Impregnating the cores of triblock-copolymer nanotubes with Fe2O3 renders them superparamagnetic. The resultant polymer/Fe2O3 hybrid nanofibers (see TEM image) have interesting properties in magnetic fields. The nanofibers align themselves in the magnetic-field direction, and mixtures of the nanofibers and nanotubes undergo phase separation.

2,3,4,5-Tetraphenylsiloles with different 1,1-substituents on the ring silicon atoms, i.e., 1,1-dimethyl- 2,3,4,5-tetraphenylsilole (1), 1-methyl-1-(3-chloropropyl)-2,3,4,5-tetraphenylsilole (2), 1-methyl-1,2,3,4,5-pentaphenylsilole (3) and hexaphenylsilole (4), are synthesized and characterized. While all the siloles emit intense blue light readily observable by naked eyes under normal room illumination conditions, the film of their acyclic cousin without silicon, namely 1,2,3,4-tetraphenylbutadiene (5), does not fluoresce, revealing the vital role of the planar and rigid silacyclopentadiene ring in the solid-state photoluminescence process. The electronic transitions of the siloles can be tuned by varying the 1,1-substituents, and the inductive and conjugating effects of the aromatic rings confer low LUMO energy levels and high emission efficiencies on the phenyl-substituted siloles. The electroluminescence device of the 1-phenylsilole 3 shows a high brightness (4538 cd m(-2) at 18 V) and an excellent external quantum efficiency (0.65\% at 17 V and 94 mA cm(-2)).

Polyphenylacetylenes were synthesized by [Rn(nbd)Cl](2) and WCl6/Ph4Sn catalyst systems in N-2 at room temperature. Polymers with high yield and high molecular weight were obtained. Their structures were characterized by UV, IR, NMR and GPC, respectively. The fluorescence of the polymer solution with different concentration was investigated using variable excitation wavelength from UV to visible region. The relation between fluorescence and polymer structure was studied. The results showed that the molecular chain structure has great influence on fluorescence of the polymers. The emitting peak wavelength of fluorescence for the polymer of high stereoregularity is independent of solution concentration and excitation wavelength. The emitting peak wavelength of fluorescence for the polymer with disordered molecular chain arrangement varies with changing the solution concentration and excitation wavelength, and different emission sites in molecular chains and low emitting yield are shown. The measurement and analysis of fluorescence spectroscopy of polyphenylacetylenes may provide some useful information to judge the molecular chain arrangement in some conjugated polymers.

To clarify whether atom transfer radical polymerization can be extended to free radical ring-opening polymerization, the polymerization of 5,6 -benzo-2-methylene-1,3-dioxepane (BMDO) was carried out in the presence of ethyl alpha -bromobutyrate/CuBr/2,2'-bipyridine. The structure of poly(BMDO) was characterized by H-1 and C-13 NMR spectroscopy as well as gel permeation chromatography. The living polymerization of BMDO was identified by the following facts: a straight line of ln([M]0/[M]) versus polymerization time, linear increase of molecular weight with increasing conversion, and narrowing polydispersity. The mechanism of living free radical ring-opening polymerization was discussed.

While WCl6-Ph4Sn is a poor catalyst for the polymerization of 1-phenyl-butyne (PB) at room temperature, it effectively polymerizes PB in the presence of C-60, giving high molecular weight polymers in high yields. The polymer is soluble in THF and chloroform and spectroscopic analysis reveals that C-60 has copolymerized with PB. Thus, C-60 plays dual roles of comonomer and cocatalyst in the acetylene polymerization. The copolymers strongly attenuate 532-nm laser pulses, whose limiting performance is superior to that of parent C-60.

Carbon nanotubes are intractable, which hampers the progress in the nanotube research and limits the scope of their practical applications. In this work, we developed a simple process for solubilizing the carbon nanotubes and discovered novel electronic, optical, and mechanical properties of the nanomaterials. The nanotube-containing polyphenylacetylenes (NT-PPAs) are prepared by in situ polymerisations of phenylacetylene catalysed by WCl6-Ph4Sn and [Rh(nbd)Cl](2) in the presence of the nanotubes. The NT-PPAs are characterised by GPC, NMR, UV, FL, TGA, SEM, TEM, and XRD, and it is found that the nanotubes in the NT-PPAs are helically wrapped by the PPA chains. The short nanotubes thickly wrapped in the PPA chains are soluble in common organic solvents including THF, toluene, chloroform, and 1,4-dioxane. The NT-PPAs are macroscopically processible, and shearing the concentrated NT-PPA solutions readily aligns the nanotubes along the direction of the applied mechanical force. The fluorescence of PPA is largely quenched by the nanotubes, possibly via photoinduced charge transfer process from the PPA chains to the nanotube shells. The nanotubes dramatically stabilise the PPA chains against harsh laser irradiation, and the NT-PPA solutions effectively limit intense optical pulses, with the saturation fluence easily tunable by varying the nanotube contents.

A versatile process employing anionic surfactants has been developed for the preparation of processible nanocomposite films with electrical conductivity and magnetic susceptibility. Maghemite (g-Fe2O3) nanoclusters (similar to 10 nm in size) are coated with 4-dodecyl- benzenesulfonic acid, and polyaniline (PAn) chains are doped with 10-camphorsulfonic acid. The coated nanoclusters and doped polymers are soluble in common solvents, and casting the solutions readily gives free-standing nanocomposite films with nanocluster contents as high as similar to 50 wt \%. The g-Fe2O3/PAn nanocomposites show high conductivity (82-337 S cm(-1)) and magnetizability (up to similar to 35 emu/g g-Fe2O3).

A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized, whose mesomorphic properties are found to be easily "tunable" by simple mechanical perturbation. The polymerization of 10-[4-(4'-methoxyphenoxycarbonyl)phenoxycarbonyl]-1-decyne (4) initiated by the WCl6-Ph4Sn/dioxane complex yields polymer 5 with a M-w of 28400. The molecular structure of 5 is characterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC, POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strength disclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomena have been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom been reported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigid polyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments.

Polycyclotrimerization of diynes was explored as a new route to hyperbranched polymers in this investigation. Polymerization of terminal diynes of 1,8-nonadiyne and 1,9-decadiyne was studied using TaCl5, NbCl5, Mo(CO)(4)(nbd) and [Mo(CO)(3)cp](2) as catalysts (where nbd = 2,5-norbornadiene, cp = cyclopentadiene). A soluble polymer was obtained when the polymerization of 1,9-decadiyne was initiated by TaCl5 at low temperature (0 degrees C). The polymer, however, became partially soluble after purification, possibly due to the postpolymerization-induced crosslinking. NbCl5-catalyzed polymerization of 1,9-bis(trimethylsilyl)- 1,8-nonadiyne gave a completely soluble polymer. Soluble polymers were also obtained from the polymerization of 3,9-dodecadiyne initiated by NbCl5, Mo(CO)(4)(nbd), [Mo(CO)(3)cp](2), PdCl2-ClSiMe3 and Pd/C-ClSiMe3. IR, UV, and NMR spectroscopic analysis revealed that different catalysts gave polymers with different structures, ranging from linear polyenes to hyperbranched polyphenylenes. The polymers absorb UV light at around 250 nm and emit fluorescence at 340 nm when they are excited at 248 nm.

While WCl6-Ph4Sn fails to polymerize 1-phenyl-1-propyne (PP) at room temperature, high molecular weight (M-W up to 410 X 10(3)) polymers are obtained in high yields (up to 80\%) when the polymerizations of PP are carried out in the presence of C-60 using the W catalyst under the same conditions. The polymers are soluble in common organic solvents such as THF, chloroform, and toluene. Molecular structures of the polymers are characterized by FT-IR, UV, NMR, GPC and XRD, and it is found that C-60 is copolymerized with PP. Thus C-60 plays the dual roles of comonomer and cocatalyst in the polymerization reaction. C-60 contents of the copolymers can be easily changed by varying the C-60 amounts in the feed mixtures. The copolymers effectively limit strong 532 nm laser pulses, whose limiting performance is superior to that of parent C-60.

Carbon nanotube-containing poly(phenylacetylenes) (NT/PPAs) are prepared by in situ polymerizations of phenylacetylene catalyzed by WCl6-Ph4Sn and [Rh(nbd)Cl](2) (nbd = 2,5-norbornadiene) in the presence of the nanotubes. The NT/PPAs are characterized by GPC, NMR, UV, FL, TGA, SEM, TER;I, and XRD, and it is found that the nanotubes in the NT/PPAs are helically wrapped by the PPA chains. The short nanotubes thickly wrapped in the PPA chains are soluble in common organic solvents including tetrahydrofuran, toluene, chloroform, and 1,4-dioxane. The NT/PPAs are macroscopically processible, and shearing of the NT/PPA solutions readily aligns the nanotubes along the direction of the applied mechanical force. The nanotubes exhibit a strong photostabilization effect, protecting the PPA chains from photodegradation under harsh laser irradiation with incident fluence as high as 10 J/cm(2). The NT/PPA solutions effectively limit intense optical pulses, with the saturation fluence tunable by varying the nanotube contents.

We have investigated emission properties of a series of poly(phenylacetylene) samples with controlled amount of cis/trans ratio. We observed that both the emission efficiency and PL lifetime decrease with increasing cis content. These results seem to rule out the soliton model as the origin for the strong photoluminescence (PL) in PPAs. However, the PL results can be explained by the lower degree of stereoregularity with decreasing cis content resulting in short segments of cia PPA which give rise to strong PL due to the confinement effect.