“Sock-Ball” Chromatographic Separation of High Molecular Weight Fullerenes with Sock-Shaped Stationary Phase

A method for “Sock-Bail” chromatographic separation of high molecular weight fullerenes is described. A prepared sock-shaped stationary phase (Sock-SAF-phase) was used for HPLC separation of several polycyclic aromatic hydrocarbons (PAHs) and fullerenes. Fullerenes, as ball-shaped molecules, are much more strongly retained than PAHs on this stationary phase and have the eluted order C₅₀ < C₇₀ < C₇₆ < C₇₈ < C₈₄ in the mobile phase of n-hexane/dichloromethane (100/0 ～ 80/20). In contrast, chromatography on the corresponding unmodified silica phase or SC-3OH-phase (an intermediate phase of Sock-SAF-phase) gave no separation of fullerenes. This fact indicated that the separation of fullerenes on Sock-SAF-phase was related to the selective interaction with the sock moiety.     

多环芳烃的超临界流体色谱分离研究

烃中多环芳烃（晕苯和卵苯）的分离是极其困难的。研究了在不同极性毛细管填充ＳＦＣ柱上多环芳烃的分离条件。选用国产１５０ｍｍＣＮ填充柱,ＣＯ＿２为流动相,线性升压,ＦＩＤ检测,可在２６ｍｉｎ内将烃中三到十环多环芳烃分离,定量重复性良好。     

Hopping conduction in “pure” polypropylene

A recently developed theory of steady-state conduction in high-density polyethylene is applied to “pure” polypropylene (PP) in the temperature range 50–93°C. Morphological changes occur in PP, including a disordered-amorphous to monoclinic-amorphous transition between 50 and 80°C, where, with increasing temperature T, free volume increases, and decreases with decreasing amorphous fraction. The latter competing processes lead to large increases in hopping site separation, λ, in the transition region, followed either by saturation or a maximum in λ vs. T. We speculate that segmental and/or main chain molecular motions lower apparent activation energies, are “pinned“ by applied field, and impeded by dangling bonds in regions surrounding the surfaces of crystallites. Our analysis is semi-quantitative only, because the latter mechanisms have not been adequately quantified, and the relative contributions of each are unknown. Measurements were carried out on heated and cooled disordered-amorphous, and 106°C, 17-h annealed, 43% crystalline samples. Hopping distances, obtained from measured current vs. applied field characteristics, ranged from 1.2 to 5.2 nm. Apparent activation energies up to 1.80 eV were obtained from In (I/T) vs. (1/T) plots. Remarkable plateaus in the temperature range of the transition were observed in these plots, implying some carrier conduction with near zero activation energy. Possible explanations for the latter, and the electronic nature of the carriers are given. X-ray and density flotation measurements enabled crystallinity determinations. © 1994 John Wiley & Sons, Inc.     

The “disturbing zone” in overpressure layer chromatography (OPLC)

This paper describes the fundamental factors causing the “disturbing zone” in OPLC. This phenomenon of distorted substance zones appears when the OPLC separation is started with a dry layer and is due to interaction between the gas that is physically bound to the surface of the sorbent (m_a) and the gas molecules dissolved in the eluent (m_s). Possibilities for elimination of the adverse effects of disturbing zones ultimately depend on the establishment of operating conditions that inhibit their initial formation. Since modification of the location of the disturbing zone is only possible within a very narrow range, the sole solution to this problem is to conduct a pre-run, which may be carried out with hexane in the case of separation of apolar compounds. For separation of polar substances, the pre-run may also be performed with hexane or with a solvent of the mobile phase in which the components are unable to migrate. The selection of this solvent may be considered during the optimization of the eluent system.     

Synthesis and characterization of star graft copolymers with asymmetric mixed “V‐shaped” side chains via “click” chemistry on a hyperbranched polyglycerol core

The star graft copolymers composed of hyperbranched polyglycerol (HPG) as core and well defined asymmetric mixed “V‐shaped” identical polystyrene (PS) and poly(tert‐butyl acrylate) as side chains were synthesized via the “click” chemistry. The V‐shaped side chain bearing a “clickable” alkyne group at the conjunction point of two blocks was first prepared through the combination of anionic polymerization of styrene (St) and atom transfer radical polymerization of tert‐butyl acrylate (tBA) monomer, and then “click” chemistry was conducted between the alkyne groups on the side chains and azide groups on HPG core. The obtained star graft copolymers and intermediates were characterized by gel permeation chromatography (GPC), GPC equipped with a multiangle laser‐light scattering detector (GPC‐MALLS), nuclear magnetic resonance spectroscopy and fourier transform infrared. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1308–1316, 2009     

焦炉降尘中多环芳烃的毛细管超临界流体色谱分析

研究了９个多环芳烃混合样品的超临界流体色谱分析条件，并与毛细管气相色谱法做了比较。超临界流体色谱的条件是：柱温１１０℃；程序升压９．０ＭＰａ（５ｍｉｎ）１．４ＭＰａ／ｍｉｎ２８．０ ＭＰａ。各组分保留时间的相对标准偏差为 １．４％～３．０％，定量分析的相对误差为１．４％～６．０％，比毛细管气相色谱法具有明显的优越性。试验了焦炉降尘样品，发现该样品主要由双环和三环的多环芳烃类物质组成。其中萘含量约占８０％。     

On the applicability of the “abt” concept

Kaiser's “abt” concept rests on the experimental establishment of a linear relation between band width at half height, b_0.5, and capacity ratio, k, according to His column specification quantity, h_real, is dependent on the square of the slope a, obtained from a linear regression analysis based on this relation. It is shown in the present paper that an improvement of the experimental conditions leading to a lower extra-column contribution to band broadening, b, introduces a tendency towards a negative curvature in the plot at low k values. The mean slope increases, and an uncritical linear regression would yield an h_real-value which is higher than before and which would be in the opposite direction to the requirements of a reliable column specification. Generally the linear regression analysis has to be moved to higher k regions in cases of curvature, especially as it is also shown that h_real is an estimation of the traditional HETP value, H∞, that would be obtained when k approaches infinity. This theoretically expected relation is a strong motivation for the use of h_real as a column specification, since the b_0.5-value associated with H∞ is expected to be practically independent of b.     

稠环芳烃在烷基膦酸改性锆镁复合氧化物固定相上的反相液相色谱保留行为

以稠环芳烃为探针 ,考察了烷基膦酸改性锆镁复合氧化物材料的反相色谱性能。研究了稠环芳烃类化合物的结构与其保留值的关系 ,比较了烷基膦酸改性锆镁复合氧化物固定相和十八烷基键合硅胶 Zorbax ODS对稠环芳烃异构体的选择性 ,并对可能的保留机理进行了讨论。以甲醇 -水 (体积比为 75∶ 2 5)为流动相 ,在烷基膦酸改性锆镁复合氧化物固定相上分离了 8种稠环芳烃类化合物     

Efficient synthesis of monodisperse,highly crosslinked,and “living” functional polymer microspheres by the ambient temperature iniferter‐induced “living” radical precipitation polymerization

The facile and efficient one‐pot synthesis of monodisperse, highly crosslinked, and “living” functional copolymer microspheres by the ambient temperature iniferter‐induced “living” radical precipitation polymerization (ILRPP) is described for the first time. The simple introduction of iniferter‐induced “living” radical polymerization (ILRP) mechanism into precipitation polymerization system, together with the use of ethanol solvent, allows the direct generation of such uniform functional copolymer microspheres. The polymerization parameters (including monomer loading, iniferter concentration, molar ratio of crosslinker to monovinyl comonomer, and polymerization time and scale) showed much influence on the morphologies of the resulting copolymer microspheres, thus permitting the convenient tailoring of the particle sizes by easily tuning the reaction conditions. In particular, monodisperse poly(4‐vinylpyridine‐co‐ethylene glycol dimethacrylate) microspheres were prepared by the ambient temperature ILRPP even at a high monomer loading of 18 vol %. The general applicability of the ambient temperature ILRPP was confirmed by the preparation of uniform copolymer microspheres with incorporated glycidyl methacrylate. Moreover, the “livingness” of the resulting polymer microspheres was verified by their direct grafting of hydrophilic polymer brushes via surface‐initiated ILRP. Furthermore, a “grafting from” particle growth mechanism was proposed for ILRPP, which is considerably different from the “grafting to” particle growth mechanism in the traditional precipitation polymerization. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Drug Design of “Undruggable” Targets

Drug innovation is not only reflected in the discovery of new chemotypes of active compounds against existing targets but also more dependent on the innovation of drug targets. Currently, a number of attractive and validated targets could not be targeted pharmacologically. Some have been described as “undruggable”. In this review, we summarized the current situation of “undruggable” targets, and the design strategies for “undruggable” targets, hoping to provide references for the development of innovative drugs.     

Block copolymers by transformation of “living” carbocationic into “living” radical polymerization. II. ABA-type block copolymers comprising rubbery polyisobutene middle segment

A general method for the transformation of “living” carbocationic into “living” radical polymerization, without any modification of chain ends, is reported for the preparation of ABA block copolymers. For example, α,ω-difunctional polyisobutene, capped with several units of styrene, Cl-St-PIB-St-Cl, prepared cationically (M_n = 7800, M_w/M_n = 1.31) was used as an efficient difunctional macroinitiator for homogeneous “living” atom transfer radical polymerization to prepare triblock copolymers with styrene, PSt-PIB-PSt (M_n = 28,800, M_w/M_n = 1.14), methyl acrylate, PMA-PIB-PMA (M_n = 31,810, M_w/M_n = 1.42), isobornyl acrylate, PIBA-PIB-PIBA (M_n = 33,500, M_w/M_n = 1.21), and methyl methacrylate, PMMA-PIB-PMMA (M_n = 33,500, M_w/M_n = 1.47). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3595–3601, 1997     

Preparation of phenolic microspheres in water/“water” system

Phenolic microspheres were obtained by condensation of resorcinol and formaldehyde via a novel water/“water” suspension polymerization (WWSP) system, which was proposed and constructed for the first time. Resorcinol/formaldehyde aqueous solutions, ammonium sulfate aqueous solution, hydroxyethyl cellulose (HEC), and sodium hydroxyl were employed as water phase, “water” phase, stabilizer for protecting colloid, and catalyst, respectively. Stable and perfect phenolic microspheres were prepared in this special WWSP system. Particle sizes, size distribution, as well as morphology of microspheres were investigated by scanning electron microscope and computerized image analysis program. The results showed that particle size increased from 0.38 to 2.22 µm along with the increase of concentration of ammonium sulfate in “water” phase from 1.5% to 12.5% and the ratio of resorcinol to formaldehyde from 1:1.5 to 1:4. On the contrary, the particle size decreased from 1.80 to 0.30 µm with the increase of the amount of HEC from 0.1 to 1.0 g and amount of catalyst from 0.05 to 0.2 g. The polydispersity index value of the resulting microspheres is quite narrow, ranging from 1.01 to 1.30, which meant that the morphology of phenolic microspheres was unique. Copyright © 2011 John Wiley & Sons, Ltd.     

“Bicarburet of Hydrogen”. Reappraisal of the Discovery of Benzene in 1825 with the Analytical Methods of 1968

The historical background and the admirable analytical procedure that led Michael Faraday to the discovery of benzene in 1825 are discussed. Using modern techniques of instrumental analysis, the author retraces the isolation and analysis of benzene, and shows that the starting material used by Faraday must have been a very complex mixture of hydrocarbons, which would make severe demands even on present-day preparative analytical techniques, since it contains more than 300 components at concentrations greater than 100 ppm. The magnitude of the changes in analytical techniques can be seen from the fact that it is no longer necessary to isolate individual compounds, and that a great deal of information can be obtained with a much smaller quantity of material and in a much shorter time. Nevertheless, Faraday's persistence, experimental skill, and accuracy of measurement remain an example to the analyst of today.     

Facile synthesis of polyester dendrimer via combining thio‐bromo “Click” chemistry and ATNRC

This article reports on developing an efficient synthesis approach to aliphatic polyester dendrimer, poly(thioglycerol‐2‐propionate) (PTP), by combination of thio‐bromo “Click” chemistry with atom transfer nitroxide radical coupling (ATNRC). Through the one‐pot two‐step method, linear polystyrene with hydroxyl end groups (l‐PS‐2OH) was obtained by first atom transfer radical polymerization of styrene and following termination using 4‐(2,3‐dihydroxypropoxy)‐TEMPO (DHP‐TEMPO) to capture the PS macroradicals via ATNRC method. Using l‐PS‐2OH as support, the dendritic repeating units divergently were grown from the hydroxyl end groups via esterification and thio‐bromo “Click” reaction two‐step process. In every generation, the resulting intermediates l‐PS‐d‐PTP (G1‐G4) can be easily isolated from the excessive unreacted monomers by simple precipitation in ethanol without help of time, labor and solvent consuming column chromatographic purification. At last, cleavage of the alkoxyamine group between the PS support and dendrimer at elevated temperature (125 °C) provided the targeted polyester dendrimer PTP up to the fourth generation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1762–1768     

A “quasi‐flexible” automatic docking processing for studying stereoselective recognition mechanisms. Part I. Protocol validation

The main purpose of this work is the development and validation of a general scheme based on a systematic and automatic “quasi‐flexible” docking approach for studying stereoselective recognition mechanisms. To achieve our goals we explore the conformational and configurational space for small‐ or medium‐size flexible molecules in a systematic way, seeking a method that is both reasonably accurate and relatively fast from the computational point of view. In particular, we have developed a general computational protocol for the global molecular interaction evaluation (“Glob‐MolInE”) to efficiently explore the orientational and conformational space of flexible selectors and selectands used in modern chiral high‐performance liquid chromatography (HPLC); the enantioselective binding of the selector (S)‐N‐(3,5‐dinitrobenzoyl)‐leucine‐ n‐propylamide (S)‐ 1 towards the selectand N‐(2‐naphthyl)‐alanine methyl ester 2 has been studied; the global minimum obtained for the homochiral associate [S( 1 )/S( 2 )] (Pop. >99%) is very close (RMS≃0.20) to the crystallographically determined structure. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 515–530, 2000     

Synthesis of a “molecular rope curtain”: Preparation and characterization of a sliding graft copolymer with grafted poly(ethylene glycol) side chains by the “grafting onto” strategy

A sliding graft copolymer (SGC) with poly(ethylene glycol) (PEG) side chains was prepared by ester formation between terminal carboxyl groups of oxidized PEG methyl ether with molecular weight of 2000 (mPEG2000‐COOH) and hydroxyl groups of a polyrotaxane consisting of PEG and cyclodextrins (CDs). Formation of the SGC structure was confirmed by ¹H NMR, attenuated total reflectance Fourier‐transformed infrared, and gel permeation chromatography. The SGC was soluble in good solvents of PEG and insoluble in poor solvents of PEG. Estimation of the number of grafted mPEG chains suggested a “rope‐curtain” like structure, in which an mPEG chain is connected to each CD ring. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011