Self-organization and polyolefin nucleation efficacy of 1,3:2,4-di-p-methylbenzylidene sorbitol

Recent studies have demonstrated that addition of a small quantity of dibenzylidene sorbitol (DBS) to a molten polymer may result in a physical gel if conditions permit the DBS molecules to self-organize into a three-dimensional network composed of highly connected nanofibrils. If the polymer crystallizes, DBS may also serve as a nucleating agent, promoting the formation of spherulites, especially in commercially important polyolefins such as polypropylene. We examine the thermal and mechanical properties, as well as the morphological characteristics, of an isotactic polypropylene copolymer with 3 wt % ethylene upon addition of less than 1 wt % of 1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS). From dynamic rheological measurements, pronounced complex viscosity increases, attributed to MDBS nanofibril network formation, are observed at concentration-dependent temperatures above the melting point of the nucleated copolymer. Transmission electron micrographs of RuO₄-stained sections confirm the existence of MDBS nanofibrils measuring on the order of 10 nm in diameter and, at higher concentrations, fibrillar bundles measuring up to about 200 nm across and several microns in length. The addition of MDBS at different concentrations is also found to promote increases in optical clarity, yield strength, tensile strength, and ultimate elongation of modified copolymer formulations. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2617–2628, 1997     

Fibril formation of 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol in a polypropylene melt

Binary mixtures of 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol (DMDBS) within the melt of polypropylene (PP) were studied at DMDBS contents of 0.4 and 1.0 wt %. DMDBS serves as a nucleating agent in PP crystallization by formation of a nanofibrillar network. The kinetics of the DMDBS solidification process within the PP melt and the ensuing nanofibrillar structure were studied by in situ small-angle X-ray scattering (SAXS) analysis combined with imaging by electron microscopy. The dynamic lag of the fibrillar structure formation kinetics and its temperature dependence indicate a nucleation and growth mechanism, controlled by the rate of nucleation. Investigation of the fibrillar structure by electron microscopy indicates a complex structure in which long and thin fibrils (less than 100 nm in cross-section) are composed of thinner nanofibrils (less than 10 nm in cross-section).     

Synthesis and self-assembly of dichalcone substituted carbazole-based low-molecular mass organogel

We report the synthesis and self-assembly of a new pi-conjugated dichalcone substituted carbazole-based low molecular mass organogelator. It could form stable gels in most halogen-aromatic solvents. The transmission electron microscopy (TEM) images revealed that the gel formed fibrous structures with diameter of 50-100 nm, which consisted of several thinner fibers. The FT-IR, UV-vis and XRD results suggested that the H-bonds and pi-pi interactions were the main driving forces for the formation of the self-assembled gel, in which the U-shaped molecules were stacked into lamellar structures. The fluorescent spectra showed that the emission of the xerogel red-shifted markedly compared with the sol state, which resulted from the aggregation of the molecules.     

Supercapacitors based on self-assembled graphene organogel

Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability.     

Mesomorphic self-assembly of 1,3-Diacylaminobenzenes

Some new examples of hydrogen-bonded 1,3-diacylaminobenzene mesogens are presented. This odd type of polymeric self-hydrogen bonded supramolecular association allows a nematic and/or a columnar order to be obtained. Such a mesogenic hydrogen-bonded arrangement (MHB) should be able to stabilize diverse mesomorphic molecular edifices such as layers, columns and tubes.     

Strongly fluorescent organogel system comprising fibrillar self-assembly of a trifluoromethyl-based cyanostilbene derivative

The entangled fibrillar structure and its strong fluorescence emission have been observed in a novel class of organogel systems consisting of a CF3-based pi-conjugated organogelator.     

Radical-type reactivity of the 1,3-dibora-2,4-diphosphoniocyclobutane-1,3-diyl

Despite through-space and through-bond B-B interactions, the stable 1,3-bora-2,4-diphosphoniocyclobutane-1,3-diyl displays some radical-type behavior, as illustrated by the spontaneous formation of the trans 1,3-adduct with trimethyltin hydride and a B-spiro derivative with bromotrichloromethane.     

Tailor-made chiral pyranopyrans based on glucose and galactose and studies on self-assembly of some crystals and low molecular weight organogel (LMOG)

InCl₃ catalyzed reactions of 2-C-acetoxymethylglycal derivatives with different phenolic compounds resulted in the formation of sugar based pyranoarenopyrans in good yields and moderate to excellent diastereoselectivity in favor of 10aR- or 12aR- or 14aR-products. One of the synthesized compounds, viz. (2R,3R,12aR)-2,3,5,12a-tetrahydro-2-methoxymethyl-3-methoxypyrano[2,3-b]naphtho[1,2-e]pyran gelated polar solvents like MeOH, EtOH and non-polar solvents like pentane, hexane, heptane, octane, pet. ether, etc. The SEM picture of the corresponding hexane xerogel exhibited a rare type of microtubular gel assembly, whereas the SEM pictures of MeOH and pet. ether xerogels showed different types of three-dimensional network. Study of the MeOH gel by Fluorescence spectroscopy, ¹H NMR and X-ray powder diffraction analysis indicated that the supramolecular assembly in the MeOH gel can be attributed to π-stacking. The crystal packing of (2R,3R,10aR)-3,10a-dihydro-2-methoxymethyl-3-methoxy-7-methyl-2H,5H-pyrano[2,3-b][1]benzopyran, a benzopyran analogue of the above organogelator was stabilized by C-H?O and C-H?π hydrogen bonds forming one-dimensional columns parallel to the [001] direction, whereas the corresponding benzopyran 3-epimer showed only C-H?O hydrogen bonds among the molecules.     

Reaction of 2,4-Diaryl-1,3-dithia-2,4-diphosphetane-2,4-disulfides with resorcinol

Russian Journal of General Chemistry -     

Light-harvesting organogel based on tris(phenylisoxazolyl)benzene

A novel light-harvesting organogel based on tris(phenylisoxazolyl)benzene, 1, was developed. A pyrene derivative, 2, possessing four phenylisoxazole substituents, was synthesised as an energy acceptor. The electronically excited-state energy of 1 was transferred to a small portion of 2 in the gel state, whereas the photo-induced energy transfer was not observed in solution. The coassembled structures of 1 and 2, formed in the decalin gel, exhibited light-harvesting behaviour. The study on the fluorescence quantum yield revealed that one molecule of 2 accepts the excited-state energy from approximately eight molecules of 1. Time-resolved fluorescence decay experiments revealed that the fluorescence resonance energy transfer is dominant in the energy transfer process in the gel state.     

A new dual-responsive organogel based on uracil-appended glycyrrhetinic acid

A novel functional tweezer based on uracil-appended glycyrrhetinic acid with excellent gelation ability was synthesized, and the gel could transform to sol by F(-) and Hg(2+).     

NMR spectra of 1,3-butadienes: VII—the conformation of 2,4-dimethyl-2,4-pentadiene

Proton magnetic resonance spectra of 2,4-dimethyl-2,4-pentadiene have been examined for a number of solution conditions and (for a CF₂Cl₂ solution) over a range of temperatures. Coupling constants for the ethylenic protons were obtained from double resonance (methyl decoupled) spectra. Further double resonance experiments established the sign of ⁴J_c. It is found that ⁴J_c = ?1·20 Hz and [⁴J_t] = 0·18 Hz. It is concluded that the compound exists in a single nonplanar conformation with an average dihedral angle (from the s-cis form) ? = 50° ± 15°. Some long range coupling constants involving the methyl group were found to be appreciable in spite of the lack of planarity of the diene chain.     

Crystal structure and theoretical investigation of the configurations of 1,3-dichloro-1,3-diazetidine-2,4-dione and 1,3-bis(trimethylsilyl)-1,3-diazetidine-2,4-dione

Crystal structures of 1,3-dichloro-1,3-diazetidine-2,4-dione ( 1 ) and the hitherto unknown compound 1,3-bis(trimethylsilyl)-1,3-diazetidine-2,4-dione ( 2 ) have been determined by X--ray crystallography: 1 : (CINCO)₂, M_r = 154.94, T = 295 K, orthorhombic, Pbca, a = 7.699(1), b = 6.706(1), c = 10.598(2) Å, V = 547.2(2) ų, Z = 4, d_x = 1.881 g/cm³, μ = 10.9 cm⁻¹, R = 3.14%, R_w = 2.82% (660 observations, 38 parameters). 2 : [(CH₃)₃SiNCO]₂, M_r = 230.41, T = 100 K, monoclinic, I2/a, a = 20.257(2), b = 6.416(1), c = 21.260(3) Å, β = 101.29(1)°, V = 2709.7(6) ų, Z = 8, d_x = 1.130 g/cm³, μ = 2.4 cm⁻¹, R = 4.86%, R_w = 4.39% (2375 observations, 151 parameters). In both compounds, the symmetry of the (XNCO)₂ framework (X = Cl, Si) was determined to be nearly C_2h with trans configuration of the exocyclic X atoms. Extreme values were observed for the angles between the ring plane and the exocyclic N–X bonds: 32.5(1)° in 1 and 2.5(2)° and 0.8(2)° in 2 , respectively. Quantum chemical procedures at various levels of theory (ab initio SCF and semi-empirical PM3) applied to 1 revealed the possible appearance of two isomers, a lower energy trans form and a higher energy cis form (approx. 2.4 kcal/mol above trans) differing mainly in the spatial arrangement of the chlorine atoms. The calculations excluded a planar heavy-atom configuration by missing a local energy minimum.     

A transparent photo-responsive organogel based on a glycoluril supergelator

The synthesis of an azo-benzene glycoluril supergelator is reported. The control over the gel/sol state can be accomplished by irradiation and heat, but also (in a unidirectional sense) by incorporation of the glycoluril into a more stable supramolecular assembly.     

Condensation of 1,3-thiazan-2,4-dithione

Thiopropiorhodanine condenses at the 4-thioketo group with quaternary salts of 2-methyl- and 2-methyl-5-methoxybenzothiazole to form merocyanins. N-Ethyl- and N-phenyl derivatives do not undergo this reaction.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 228–229, February, 1971.     

Abinitio方法研究2，4－二甲基－1，3－戊二烯结构

用ａｂｉｎｉｔｉｏ方法研究２，４－二甲基－１，３－戊二烯各种构象异构体的结构，找到ｓ－ｔｒａｎｓ和ｓ－ｃｉｓ两种稳定构象，且ｓ－ｔｒａｎｓ更稳定．对稳定构象的几何结构、电荷分布进行了研究，讨论了不同的电子基组对优化几何的影响，并计算了稳定构象的热力学常数，与实验结果进行了比较．     

Confinement effects on dipole-dipole interactions in nanofluids: the role of equilibrium fluctuations

When spin bearing molecules are enclosed in an elongated nanovoid, and each molecule diffuses across the whole volume in times much shorter than the characteristic times of NMR spin dynamics, a time independent average dipolar Hamiltonian emerges which couples the spins in each molecule equally with the spins in any other molecule. Baugh et al. [Science, 134, 1505 (2001)] have observed the remarkable orientation dependent linewidth in such a situation, and offered a convincing interpretation using the techniques of solid state NMR. In the present paper I show that, contrary to previous expectations, the same linewidth can be predicted with liquid NMR techniques, provided that one takes into account equilibrium fluctuations in the estimation of the dipolar field.     

Confinement effects on the glass transition of hydrogen bonded liquids

The glass transition behavior of glycerol and propylene glycol confined in nanoporous glass is investigated using differential scanning calorimetry. Both silanized and unsilanized porous glasses are used to confine the liquids with nominal pore sizes ranging from 2.5 to 7.5 nm, and the glass transition temperature (T(g)) and the limiting fictive temperature (T(f )') are measured on cooling and heating, respectively. The effect of pore fullness is also examined. We find that differences in T(g), DeltaC(p), and the enthalpy overshoot behavior observed on heating are significant between partially and completely filled pores for the case of the unsilanized controlled pore glasses (CPGs) but that the effect of pore fullness is insignificant for the silanized CPGs. In general, the behavior in the silanized CPGs is similar to the behavior in the completely filled unsilanized pores. For glycerol, this includes a small depression in T(f )' on the order of 5 K at 2.5 nm. For propylene glycol, similar behavior is found except that an additional glass transition is observed in both silanized and unsilanized systems approximately 30 K higher than the bulk and a slightly smaller depression on the order of 3 K at 2.5 nm is observed in the completely filled unsilanized pores and in partially and completely filled silanized pores. The results are compared to those in the literature, and the confinement effects are discussed.