Alcohol solvent effect on the self-assembly behaviors of lignin oligomers

The interactions between lignin oligomers and solvents determine the behaviors of lignin oligomers self-assembling into uniform lignin nanoparticles(LNPs).Herein,several alcohol solvents,which readily interact with the lignin oligomers,were adopted to study their effects during solvent shifting process for LNPs’production.The lignin oligomers with widely distributed molecular weight and abundant guaiacyl units were extracted from wood waste(mainly consists of pine wood),exerting outstanding self-assembly capability.Uniform and spherical LNPs were generated in H_(2)O-n-propanol cosolvent,whereas irregular LNPs were obtained in H_(2)O-methanol cosolvent.The unsatisfactory self-assembly performance of the lignin oligomers in H_(2)O-methanol cosolvent could be attributed to two aspects.On one hand,for the initial dissolution state,the distinguishing Hansen solubility parameter and polarity between methanol solvent and lignin oligomers resulted in the poor dispersion of the lignin oligomers.On the other hand,strong hydrogen bonds between methanol solvent and lignin oligomers during solvent shifting process,hindered the interactions among the lignin oligomers for self-assembly.

Human islet amyloid polypeptide oligomers stabilized and probed by MAS NMR

The capture and characterization of oligomers are extremely important in the studies of amyloid aggregation of proteins and peptides.Oligomers are critical intermediates that can impact the structures of amyloid fibrils.Moreover,it is widely accepted that oligomers are the most toxic species along the aggregation pathway[1e4].The studies of oligomers are believed to shed light on the molecular mechanism of amyloid fibrillation and probably the medical clues for related diseases.In vitro investigations of amyloid oligomers are challenging due to their transient and polymorphic nature[5].This is particularly evident in the case of human type-2 diabetes-associated islet amyloid polypeptide(hIAPP),which tends to rapidly form polymorphic fibrils within minutes[6].Notably,hIAPP demonstrates a higher propensity for rapid aggregation compared to other amyloid proteins such as a-synuclein[7].

Highly efficient and stable organic solar cells with SnO_(2)electron transport layer enabled by UV-curing acrylate oligomers

The interfaces between the inorganic metal oxide and organic photoactive layer are of outmost importance for efficiency and stability in organic solar cells(OSCs).Tin oxide(SnO_(2))is one of the promising candidates for the electron transport layer(ETL)in high-performance inverted OSCs.When a solution-processed SnO_(2)ETL is employed,however,the presence of interfacial defects and suboptimal interfacial contact can lower the power conversion efficiency(PCE)and operational stability of OSCs.Herein,highly efficient and stable inverted OSCs by modification of the SnO_(2)surface with ultraviolet(UV)-curable acrylate oligomers(SAR and OCS)are demonstrated.The highest PCEs of 16.6%and 17.0%are achieved in PM6:Y6-BO OSCs with the SAR and OCS,respectively,outperforming a device with a bare SnO_(2)ETL(PCE 13.8%).The remarkable enhancement of PCEs is attributed to the optimized interfacial contact,leading to mitigated surface defects.More strikingly,improved light-soaking and thermal stability strongly correlated with the interfacial defects are demonstrated for OSCs based on SnO_(2)/UV cross-linked resins compared to OSCs utilizing bare SnO_(2).We believe that UV cross-linking oligomers will play a key role as interfacial modifiers in the future fabrication of large-area and flexible OSCs with high efficiency and stability.

Optical Properties of Oligo（fluorene-vinylene） Functionalized Anthracene Linear Oligomers： Effect of π-extension

The photo-physical properties of oligo（fluorene-vinylene） functionalized anthracene linear oligomers （An-OFVn （n=1-4）） have been systemically investigated through experimental and theoretical methods. The steady-state spectral measurement shows that the increasing of fluorene-vinylene （FV） group could lead to the red shift of absorption spectra and restrain the excimer formation between oligomers. Quantum chemical calculations exhibit that the energy levels of HOMO, LUMO, and the band gap gradually converge to a constant in accompany with the increasing of FV unit. Meanwhile, the electronic cloud which distributes on the branch arms, also gradually enhances and makes the absorption spectral shape of oligomers become similar to that of branch arms step by step. The time-resolved fluorescence tests exhibits that the lifetime of excimer emission would be almost invariable after the number of FV group in oligomer is ≥2. In nonlinear optical test, the two-photon photoluminescence efficiency and two-photon absorption cross-section will both gradually enhance and be close to an extremum after the number of FV unit is equal to 4. These results will provide a guideline for the design of novel photo-electronic materials.

π-CONJUGATED OLIGOMERS IN SUPRAMOLECULAR CRYSTALS AND THEIR OPTOELECTRONIC FUNCTIONS

Functional organic molecular materials and conjugated oligomers or polymers now allow the low-cost fabrication of thin films for insertion into new generations of electronic and optoelectronic devices. The performance of these devices relies on the understanding and optimization of several complementary processes. Our goal is to discuss the relationship between the molecular stacking structures and their optoelectronic properties that are of importance in all these areas. The concept of intermolecular interaction should be taken here in the special sense that is inter-dipole coupling. Specifically, we will address the impact of inter-dipole interaction between adjacent molecules in aggregate state on the solid-state emission properties.

SYNTHESIS, CHARACTERIZATION AND RING-OPENING POLYMERIZATION OF CYCLIC (ARYLENE PHOSPHONATE) OLIGOMERS

A series of cyclic (arylene phosphonate) oligomers were prepared by reaction of phenylphosphonic dichloride (PPD) with various bisphenols under pseudo-high dilution conditions via interfacial polycondensation. The yield of cyclic (arylene phosphonate) oligomers is over 85% by using hexadecyltrimethylammoniun bromide as phase transfer catalyst (PTC) at 0 'C . The structures of the cyclic oligomers were confirmed by a combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and IR analysis. These cyclic oligomers undergo facile ring-opening polymerization in the melt by using potassium 4,4'-biphenoxide as the initiator to give linear polyphosphonate. Free-radical ring-opening polymerization of cyclic(arylene phosphonate) oligomers containing sulfur linkages was also performed in the melt using 2,2'-dithiobis(benzothiazole) (DTB) as the initiator at 270 °C and the resulting polymer had a Mw, of 8 × 103 with a molecular weight distribution of 4. Ring-opening copolymerization of these cyclic oligomers with cyclic carbonate oligomers was also achieved. The average molecular weight of the resulting copolymer is higher than the corresponding homopolymer and the thermal stability of the copolymer is better than the corresponding homopolymer.

A Comparative Study of Electrochemical Capacitance of Graphene Oxide Affected by Oligomers of p-phenylenediamine and Hydrazine Hydrate in Solvothermal Condition

A systematic investigation of the graphene oxide composite reduced by either p-phenylenediamine oligomers or hydrazine hydrate was performed with field emission scanning electron microscopy,high resolution transmission electron microscopy,X-ray diffraction,fourier transform infrared,and X-ray photoelectron spectroscopy analyses.The electrical capacitance of the composite was evaluated by a cyclic voltammetry technique,while the properties of these prototype supercapacitors were measured by a chronopotentiometry technique.It was found that,under the solvothermal condition,the graphene oxide reduced by p-phenylenediamine oligomers was observed to have higher electrical capacitance than that reduced by hydrazine.The improved electrical capacitance can be attributed to that p-phenylenediamine oligomers are the more effective spacers for graphene layers;and they could also provide some pseudo-capacitance to the graphene oxide composite based on their conjugate structure.The results imply that graphene oxide modified by diamine oligomers has a good potential in energy storage devices.

Cyclic Oligomers of Phenolphthalein Polyarylene Ether Sulfone (Ketone): Preparation Through Cyclo-depolymerisation of Corresponding Polymers

Cyclic oligomers of phenolphthalein polyarylene ether sulfone(ketone) were prepared through cyclo-depolymerisation of corresponding polymers using CsF as the catalyst in dipolar aprotic solvent DMAc and DMF, and a family of macrocycles containing from dimer up to at least heptamer were confirmed by GPC, HPLC and MALDI-TOF-MS. The yields of cyclics get as high as 86.3% and 87.9% respectively.

Flavonoid oligomers from Chinese dragon’s blood,the red resins of Dracaena cochinchinensis

A detailed chemical investigation of the red resins from Dracaena cochinchinensis(Chinese dragon’s blood)yielded five new flavonoid oligomers,named cochinchinenins D-H(1-5),together with a known biflavonoid,cinnabarone(6),and a mixture of two known biflavonoids,socotrin-4'-ol(7)and homoisosocotrin-4'-ol(8).Of these new compounds,1-3 were biflavonoids and 4 and 5 were triflavonoids.Their structures were determined on the basis of spectroscopic analysis.The isolated compounds were tested for cytotoxicity(Cdc25),antibacterial(PEPT)and antifungal(YNG)activities.

Blue/red-shift of the p-Phenylene-ethynylene Oligomers Absorption Spectra

The absorption spectra of the p-phenylene-ethynylene（p-PPE） oligomers（up to n = 12） were estimated by DFT and TD-DFT methods. The effective conjugation length（ECL） of the corresponding polymer was obtained by extrapolating the first excitation energies of the oligmers to infinite chain length with an alternative exponential function. The absorption spectral red-shift mainly depends on the ？-conjugation segment of oligomers resulting from the planarization of the backbone. The excitation mechanism of the rotamer has been investigated sufficiently by analyzing the orbital density variation upon the conformational rotations around the cylindrical triple-bonded carbon which is believed to impact significantly on the optical spectrum. The calculated results further indicate that rotation about the cylindrical triple bond interrupts the conjugation of rod-like oligomers to lead an angle-dependence of the corresponding excitation energy. The results are helpful to interpret the conformational-dependent spectroscopic phenomena of p-phenyleneethynylene and derivatives oligomers and polymers observed in ensemble and single molecule spectroscopy.

STRUCTURAL STUDIES ON THE OLIGOMERS FROM THE POLYSACCHARIDE OF GRACILARIA TEXTORII (RHODOPHYTA) USING β-AGARASE AND 13C-NMR SPECTROSCOPY

The 60% ethanolic extract from Gracilaria textorii (Rhbdophyta) was degraded with B- agarase, and certain charged (sulfated) and neutral oligosaccharides were separated by using DEAE Sephadex A 25 and Bio- gel P6 , P2 chromatographic techniques . Some of the charged oligomers were verified to be neoagarotetraose - 63- sulfate ( DP2 ). neoagarohexaose- 63 】 65 - disulfate ( DP3 ) and neoagarooctaose- 63, 65, 67-trisulfate (DP4) by using 13C-and ’H-NMR spectroscopy . One neutral oligomer was assumed to be a mixture of methylated neoagarotetraoses (DP2 ) by 1H-NMR spectroscopy .These oligomers assigned by their chemical shifts may be used as the model compounds for the structural investigation of the agar- type sulfated polysaccharides using the B- agarase degradation method .

Can we switch production of toxic Aβ oligomers to neuroprotective Aβ monomers to allow synapse regeneration?

Alzheimer＇s disease （AD） is a complex neurological disor- der characterized by a progressive dementia. The amyloid hypothesis states that pathogenesis is driven by the accumu- lation of amyloid β（Aβ） peptides within the brain （Hardy and Higgins, 1992）, which have multiple effects including activation of glial cells and synapse degeneration. For many years therapeutic strategies were based upon the discovery of compounds that reduced the production of Aβ in vitro and in vivo. However, the amyloid hypothesis is not universally accepted; critics pointed out poor correlations between con- centrations of Aβ in the brain and clinical disease and that, although numerous compounds reduced the production of Aβ in animal models, few had any clinical benefit in AD pa- tients. The failure of Aβ-1owering therapies in translational research has resulted in important modifications of the amy- loid hypothesis.

BLUE LIGHT-EMITTING COIL-ROD-COIL BLOCK OLIGOMERS WITH RIGID p-HEXAPHENYL AS CHROMOPHORE

The synthesis and characterization of coil-rod-coil triblock oligomers, poly（ethylene oxide）-b-p-hexaphenyl-b- poly（ethylene oxide）, are described. The number of repeating ethylene oxide units in each flexible block are 3 （EO3-PHP- EO3）, 8 （EOs-PHP-EO8）, 13 （EO13-PHP-EO13）, and 17 （EO17-PHP-EO17）, respectively. The structures of these oligomers are confirmed by ^1H-NMR, 13C-NMR, EA, and MALDI-TOF mass spectrometry. The introduction of soluble poly（ethylene oxide） coils to the rigid p-hexaphenyl segment significantly improves the solubility of the oligomers, so they can form smooth thin films by spin-coating from their solutions. The oligomers are quite thermally stable and have 1% weight loss temperatures at above 340℃ under nitrogen. They can emit strong blue light in both solution and film state, and have fluorescence quantum yields of about 40% in chloroform. They are expected to have potential applications in optoelectronic devices.

Syntheses, Confirmation and Properties of Porphyrin Oligomers with Alkoxyl Linkages

A new and general synthesis of a porphyrinK(Ⅰ) with two alkoxyl linkages is described. The synthesis involves the reaction of dibromopropane with phenolic porphyrin to form ω-bromopropylporphyrin ether. This ether then reacts with another phenolic porphyrin to give the target compounds. The properties of the target compounds were confirmed by means of elemental analysis, UV-Vis, IR, and ~ 1H NMR spectroscopies. Their spectral properties and thermal stability were also studied.

SYNTHESES OF POLYSTYRENE RESINS CONTAINING POLYETHER OLIGOMERS AND THEIR EXTRACTION FOR GOLD (Ⅲ)

Three polystyrene resins containing polyether oligomers as extractants were synthesized andtheir extraction properties were studied. Gold (III) ion could be extracted rapidly by the resins(T_(1/2),<lmin. )with high efficiency and capacity (for LS-B resin that were 99. 8% and 95. 8mg/gRrespectively) from aqueous solution but most of the co-existing metal ions such as Pd (II),Cu(II), Zn (II), Pb (II) and Cd (II) were remained. The extraction capacity and strippingpercentage for gold (III) remained unchanged in four extraction-stripping cycles. The resins also showed good column extraction-elution properties.

SYNTHESIS OF ORGANOGERMANE OLIGOMERS VIA LIGAND SUBSTITUTION POLYMERIZATION FROM 1, 4-DIOXANE COMPLEX OF GERMANIUM DICHLORIDE

Some organogermanium oligomers with different side groups were synthesized via ligand substitution polymerization from I, l-dioxane complex of germanium dichloride with different organolithium compounds. The oligomers were isolated through either precipitation from methanol or extraction using toluene with a yield of no less than 50%. The weight average molecular weight (M-w) of the oligomers is ranging from 1.4 x 10(3) to 5.9 x 10(3) depending on the type and alkyl length of the organolithium compounds used.

Dihydroxy Capped Triblock DTC and CL Oligomers Prepared by an Alkyl Glycol/Yttrium Phenolate System

Dihydroxy capped triblock oligomers of 2, 2-dimethyltrimethylene carbonate (DTC) andε-caprolactone (CL) with number-average molecular weight from 3,000 to 12,000 g/mol have beensynthesized by alkyl glycol initiator in the presence of yttrium tri(2, 6-di-tert-butyl-4-methylphenolate)s (Y(OAr)3) catalyst. They are expected to be used as macroinitiators for thedesign of new polymeric materials.

Syntheses of Novel Macrocyclic Polyarylate Oligomers Based on Phenolphthalein and m-Phthaloyl dichloride

Novel macrocyclic oligomers were synthesized through the condensation of phenolphthalein and m phthaloyl dichloride with triethylamine as catalyst in the mixed solution of methylene chloride and THF via pseudo high dilution technique. The oligomers were characterized by IR, 1H NMR , MS, WAXD, TGA and DSC. It was found that the 3∶3 adduct(molar ratio of phenolphthalein to m phthaloyl dichloride) and the 4∶4 adduct were the main products and there was a small amount of crystalline in the macrocyclic mixtures. When the mixtures were heated to 360 ℃ , the crystalline disappeared.

Construction of human Fab library and screening of a single-domain antibody of amyloid-beta 42 oligomers

Screening humanized antibodies from a human Fab phage display library is an effective and quick method to obtain beta-amyloid oligomers. Thus, the present study prepared amyloid-beta 42 oli- gomers and constructed a have human Fab phage display library based on blood samples from six healthy people. After three rounds of biopanning in vitro, a human single-domain antibody that spe- cifically recognized amyloid-beta 42 oligomers was identified. Western blot and enzyme-linked im- munosorbent assay demonstrated this antibody bound specifically to human amyloid-beta 42 tetramer and nonamer, but not the monomer or high molecular weight oligomers. This study suc- cessfully constructed a human phage display library and screened a single-domain antibody that specifically recognized amyloid-beta 42 oligomers.

Linear and Nonlinear Optical Properties of Novel Multi-branched Oligomers

We investigate the fluorene-vinylene unit dependent photo-physical properties of multi- branched truxene based oligomers （Tr-OFVn, n=1-4） employing steady-state absorption and emission spectroscopy, transient absorption spectroscopy, two-photon fluorescence, and z-scan technique. The results show that the increasing of fluorene-vinylene unit leads to a red-shift in the spectra of absorption and fluorescence, and shortens the excited state lifetime. Meanwhile, two-photon fluorescence efficiency and two-photon absorption cross section of truxene based oligolners gradually enhance in company with the extension of π- conjugated length. In addition, the values of two-photon absorption cross section modeled on the sum-over-state approach agree well with the experimental ones. The results indicate multi-branched truxene based oligomers bearing organic materials for two-photon applications.