High-pressure synthesis of cyclic phenylacetylene oligomer

New conjugated oligomers were prepared by reacting phenylacetylene under high pressure of 0.11 to 0.92 GPa at 100–200°C for 0–5 h. The number-average molecular weight M?_n, the weight-average molecular weight M?_w, and the oligomer yield increased with pressure, tem-perature, and time. The average molecular weight of the oligomer showed the maximum value (M?_n: 830, M?_w: 2400) under 0.92 GPa, the maximum pressure, where phenylacetylene was oligomerized at a constant temperature. The structure of the oligomer was investigated from ESR, infrared, UV–VIS, field desorption mass (FDMS) spectra, and ¹³C NMR spec-trum. Analysis of the FDMS spectrum revealed that the molecular weight of the oligomer was multiple of the monomer. ¹³C NMR spectrum of the oligomer showed the absence of sp-carbon (? C?). We found that the oligomer had a cyclic structure. The cyclic oligomers of pentamer or more were new compounds. © 1995 John Wiley & Sons, Inc.     

四叔丁基四氮杂卟啉配合物的合成、热稳定性及光限幅特性研究

采用无金属四氮杂卟啉与金属盐回流的方法合成了2种四叔丁基四氮杂卟啉配合物，其中四叔丁基四氮杂卟啉铅(II)配合物未见文献报道。研究了该2种配合物及其配体的电子吸收光谱行为、热稳定性及在532 nm对8 ns激光的光限幅特性。结果表明：该类配合物的Q带的最大吸收峰值λ_max在570~630 nm之间，B带的最大吸收峰值λ_max在330~350 nm之间，随中心金属离子不同，Q带吸收峰位置有明显差异；配合物在氮气气氛中的起始分解温度大于250 ℃，其在热重图上的失重过程对应着4个取代基(-C(CH₃)₃)的脱去，共轭大环在500 ℃以下没有分解；它们的光限幅机制属于激发三重态的反饱和吸收(RSA)，其中四氮杂卟啉铅配合物具有更强的光限幅效应，这与铅的重原子效应有关。     

Simulations of polymer crystallization under high pressure

High pressure crystallization of polypropylene was studied by means of PVT measurements and computer simulations. The isothermal crystallization behaviour were described by using a model which takes into account the effect of pressure on the temperature dependence of nucleation rate and linear growth rate. The agreement between the simulation and the experiments was seen in the tendency that the crystallization was accelerated by the high pressure. The non-isothermal crystallization behavior was also simulated by applying a generalized Avrami equation. The simulation curves well reproduced the experimental values below relative crystallinity 0.5 and below 100 MPa.     

Reaction of diphenyldiacetylene by annealing under elevated pressure

Reaction of diphenyldiacetylene (1,4-diphenylbutadiyne) by annealing under elevated pressure (0.1–500 MPa) was carried out. Diphenyldiacetylene reacted at 210°C with appearance of gas, and this temperature was independent of the pressure. The measurement of high pressure differential thermal analysis (DTA) revealed that the reaction temperature under elevated pressure was below 24–42°C of the exothermic peak temperature. This implied that exothermic reaction occurred under elevated pressure. Elementary analysis, gel permeation chromatography (GPC), FTIR, Raman scattering, and high resolution ¹³CNMR experiments were performed to characterize the structure of the product. It was indicated that the product was a mixture of derivative of condensed polycyclic aromatic compound with phenyl group and diphenyldiacetylene oligomer. The fraction of the derivatives increased with increasing pressure, and pressure accelerated the dehydrogenation of the derivatives. The number-averaged molecular weight (M_n) of the diphenyldiacetylene oligomer was 470–610 and the weight-averaged molecular weight (M_w) was 1700–2300. It was considered that the oligomer had a polyacene-based structure. © 1994 John Wiley & Sons, Inc.     

Dielectric relaxation in two liquid crystalline polyacrylates under high hydrostatic pressure

For two polyacrylates with p-cyano-phenyl benzoate side groups and different spacer lengths the dielectric relaxation was measured in the nematic and isotropic phase at pressures up to 5000 bar. The relaxation of the cyano groups was observed as a separate relaxation process; it seems to be closely correlated with the glass relaxation. The pressure dependence of the glass temperature and of the clearing temperature could be derived from the experiments.     

Thermodynamics of solutions of cyclic polymethylene ester oligomers in p‐dioxane and chloroform

Differential vapor pressures were measured for mixtures of two cyclic polymethylene ester oligomers in p‐dioxane and chloroform at 25, 30, 35, and 40 °C at five different concentrations ranging from 1 to 20 wt %. The Flory–Huggins interaction parameter (χ) as well as Leonard's interaction parameter (χ′) for flexible and semiflexible rings were calculated and compared to one another. A new method for the estimation of the number of segments of a cyclic polymer is proposed that allows Leonard's equations to be applied correctly to a particular cyclic compound. Consistent differences between χ and χ′ were observed for all studied mixtures, and the differences became smaller if the cyclic oligomers were considered semiflexible. Interestingly, the enthalpic parameter (κ) deduced from values of χ and χ′ did not differ within their uncertainties. This supports the prediction that mixing cyclic polymer compared to its linear counterpart is mainly due to a molecular configurational entropy difference and that this difference should become less pronounced as the cyclic compound becomes larger. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 443–455, 2000     

Polymerization of sterically congested α‐alkylacrylates under high pressure

A series of α‐alkylacrylates, including methyl ethacrylate (MEA), methyl α‐propylacrylate, methyl α‐isopropylacrylate (MiPA), methyl α‐butylacrylate (MnBA), and methyl α‐isobutylacrylate (MiBA), were successfully polymerized at 65 °C under high pressure (1–9 kbar). In contrast to results obtained at ambient pressure, all monomers yielded high molecular weight polymers (number‐average molecular weight = 4–18 × 10⁴), except for MiPA (number‐average molecular weight = 8 × 10³), probably because of the high steric hindrance of the isopropyl group. Polymerization kinetics under high pressure were obtained for MEA, MnBA, and MiBA. Overall activation volumes were estimated to be ?14.9, ?17.0, and ?11.6 mL mol^?1 for MEA (3–7 kbar), MnBA (3–7 kbar), and MiBA (5–9 kbar), respectively. Extrapolation to ambient pressure provided rates of polymerization for these monomers unaffected by the ceiling temperature effect. These values were further used to quantitatively assess the steric influence exerted by the α‐substituent on the polymerizability of these sterically congested acrylates with Meyer's steric parameter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 836–843, 2002; DOI 10.1002/pola.10161     

高硫石油焦高温热解过程及硫析出特性研究

为深入了解高硫石油焦在工业应用高温工况下的热解过程以及硫的析出特性,本研究采用高温固定床对青岛高硫石油焦进行了高温(900-1500℃)热解实验,考察了高温热解下热解气体释放规律,热解过程中焦的物理孔隙结构以及化学特性的演变,并对热解过程中硫的析出与演变特性进行了研究。结果表明,随着热解温度的升高,石油焦热解气中的H₂含量逐渐增加,CO含量变化不大,CH₄与CO₂含量则逐渐下降;热解焦的比表面积与平均孔隙均随热解温度的升高有所增加,颗粒的表面形态则受温度影响较小;热解温度的升高会降低石油焦中含有的非定型碳比例,提高其微晶结构的有序性以及石墨化程度;热解焦的气化活性随热解温度的升高先降低后升高,在1100℃附近有最小值; 1500℃高硫石油焦硫元素析出率达81.34%,仅少量硫醇类有机硫和噻吩环内的硫元素得以残存。     

Synthesis,characterization, and ring opening polymerization of poly(1,4‐cyclohexylenedimethylene terephthalate) cyclic oligomers

Cyclic oligomers of poly(1,4‐cyclohexylenedimethylene terephthalate) (PCT) were prepared by reaction of 1,4‐cyclohexanedimethanol (CHDM) with terephthaloyl chloride under diluted conditions and separated from the linear products by silica gel column at a yield of 23.7 wt %. Cyclic dimer, trimer, tetramer, pentamer, and hexamer were further separated by high performance liquid chromatography, and found to constitute 98% of the cyclics mixtures. The structures of PCT cyclics were confirmed by means of mass spectrometry, Fourier transform infrared, and ¹H NMR analysis. A series of experiments were carried out to study the effects of catalysts and cis/trans configuration of isomers of CHDM on the yield of cyclic oligomers. Ring opening polymerization of the cyclic oligomers was carried out by heating the sample mixtures at 310 °C for 30 min in the presence of antimony oxide. Polymerization was confirmed by inherent viscosity changes and infrared spectra of the resulting polyesters. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1828–1833, 2000     

Modelling of a high pressure calorimeter

The evaluation of the latent heat and enthalpy of fusion of food systems in the case of high pressure–low temperature processing is important for modelling purposes as well as for technical applications. A high pressure calorimeter has been designed for this purpose. The high pressure calorimeter was used to evaluate the latent heat during a pressure scan at constant temperature. It permits to measure the heat of phase transitions and to obtain the relationship between the initial freezing temperature T _ifp and the average pressure while the phase transition is going on. This work presents a modelling of results obtained from an experimental approach using a high pressure calorimeter and from a mathematical model developed from existing data on the phase change of pure water. The modelling work consisted in evaluating the latent heat measured in previous tests from computations taking into account the dependence of the latent heat of fusion of water on pressure. Models predicting the amount of frozen water in a food matrix under atmospheric conditions were used to determine the initial amount of frozen water in the sample. Then a stepwise procedure was operated in a program to reproduce the pressure rise occurring during a high pressure calorimeter test. The amount of melted ice at each pressure step was calculated using conventional ice fraction models, which were adapted to pressure dependence of the initial freezing temperature and the dependence of the latent heat pressure. The comparison was satisfactory, especially at low temperatures.     

Lamellar thickening of polyethylene under high pressure

Single crystal mat (SCM) samples of polyethylene (PE) were prepared from dilute solution of p-xylen, then they were annealed at pressures of 200 and 500 MPa. Lamellar thickness of the original and annealed SCM samples was measured by small-angle X-ray scattering method. Orientation of the molecular chain in those SCM samples was investigated by wide-angle X-ray diffraction pattern. From these X-ray measurements, annealing temperature dependence of the lamellar thickness, i.e., lamellar thickening, under high pressure was obtained. Melting process of the SCM samples was also investigated at 200 and 500 MPa by high pressure differential thermal analysis. Then correspondence between the lamellar thickening and the melting process was studied. The lamellar thickness increases markedly with approaching to the melting temperature of the orthorhombic crystal even in the high pressure region where the high pressure phase (hexagonal phase) appears. The annealing temperature dependence curve of the lamellar thickness at 200 MPa can be superimposed on the curve at 500 MPa by shifting the curve along the temperature scale by 47 K. Large scale lamellar thickening occurs in the orthorhombic crystal phase in the high pressure region. The formation process of extended-chain crystal is discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 535–543, 1997     

Synthesis of novel cyclic olefin polymers with excellent transparency and high glass‐transition temperature via gradient copolymerization of bulky cyclic olefin and cis‐cyclooctene

Novel cyclic olefin polymers (COPs) with excellent transparency and high glass‐transition temperature (T_g) synthesized from bulky norbornene derivative, exo‐1,4,4a,9,9a,10‐hexahydro‐9,10(1',2')‐benzeno‐l,4‐methanoanthracene (HBMN), and cis‐cyclooctene (COE) by ring‐opening metathesis copolymerization utilizing the “first‐generation Grubbs” catalyst, RuCl₂(PCy₃)₂(CHPh), and subsequent hydrogenation was reported herein. To get amorphous copolymers, it was of great importance to control the feed ratios and the polymerization time for gradient copolymerization. All these copolymers showed very high T_gs (141.1–201.2 °C), which varied with the content of HBMN. The films of the gradient copolymers with only one T_g were highly transparent. On the contrary, all the block copolymers synthesized through sequential addition showed two thermal transition temperatures, T_g and melt temperature (T_m), and the films of these block copolymers were opaque. The mechanical performances of the COPs were also investigated. It is the first report that transparent COP could be prepared from bulky norbornene derivative and monocyclic olefin. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3240–3249     

Possible existence of alkali metal orthocarbonates at high pressure

We investigate the possible existence of crystalline alkali metal orthocarbonates, A(4)CO(4), where A=Li, Na, K, Rb, and Cs. We study the equilibrium between the possible modifications of the orthocarbonate A(4)CO(4) and the binary mixture of the possible modifications of the alkali oxide A(2)O and those of the alkali metal carbonate A(2)CO(3) as function of pressure. In all cases, the orthocarbonate should be stable at sufficiently high pressure ranging from 22-32 GPa (Rb(4)CO(4)) to 200-220 GPa (Cs(4)CO(4)).     

Lithium hydroxide phase transition under high pressure: an ab initio molecular dynamics study.

The high-pressure phase transition in the deuterated lithium hydroxide crystalline state has been studied by Car-Parrinello molecular dynamics simulations, in the constant-pressure, constant-temperature ensemble. The recently developed metadynamics approach has been applied to encourage the system to transform into different phases in an affordable simulation time. A previously not completely characterized high-pressure phase has been obtained. The structural and spectroscopic properties have been studied and compared with the neutron scattering, infrared and Raman measurements. It has been found that the calculated structure differs slightly from the experimental hypothesis, and that the presence of strong hydrogen bonds is the source of the red shift and of the characteristic features of the OD-stretching bands in both IR and Raman spectra.     

Solid-phase reactions of aromatic amines with carboxylic acids under conditions of shear deformation and high pressure

Solid mixtures of carboxylic acids and aromatic amines react under shear deformation at high pressure (to 8 GPa) for form amides, in the case of ortho-phenylenediamine-substituted benzimidazoles are formed. Under these conditions the conversion rates are hundreds of thousands of times higher than when the same processes are carried out in liquid phase. The cyclization reaction is accelerated to a lesser degree than the reaction of formation of the corresponding amide. The increase of the length of the carboxylic acid radical prevents the cyclization reaction.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2147–2153, September, 1992.     

Synthesis of cyclic olefin polymers with high glass transition temperature by ring‐opening metathesis copolymerization and subsequent hydrogenation

Novel cyclic olefin polymers (COPs) derived from bulky cyclic olefin, exo‐1,4,4a,9,9a,10‐hexahydro‐9,10(1′,2′)‐benzeno‐l,4‐methanoanthracene (HBMN), with high glass transition temperature (T_g), excellent thermal stability, high transparency, and improved mechanical performance, have been achieved by ring‐opening metathesis polymerization and subsequent hydrogenation. The “first‐generation Grubbs” catalyst, RuCl₂(PCy₃)₂(CHPh) (Cy = cyclohexyl) ( G1 ), displays very high activity for homo/copolymerization with complete conversion. Homopolymer of the HBMN after complete hydrogenation showed a highest T_g of 223.6 °C. Copolymerization of HBMN with tricyclo[4.3.0.12,5]deca‐3‐ene or 5‐n‐hexylnorbornene was also carried out. These two series of COPs were characterized by gel permeation chromatography, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. The T_g of the resulted COPs linearly increased with HBMN content, which is easily controlled by changing feed ratios. The tensile test indicates that these copolymers have good mechanical performance as all these copolymers show a higher strain at break compared with commercial products (TOPAS^®). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2654‐2661     

Reversible addition‐fragmentation chain transfer polymerization of vinyl acetate under high pressure

In this work, high molecular weight polyvinyl acetate (PVAc) (M_n,GPC = 123,000 g/mol, M_w/M_n = 1.28) was synthesized by reversible addition‐fragmentation chain transfer polymerization (RAFT) under high pressure (5 kbar), using benzoyl peroxide and N,N‐dimethylaniline as initiator mediated by (S)‐2‐(ethyl propionate)‐(O‐ethyl xanthate) (X1) at 35 °C. Polymerization kinetic study with RAFT agent showed pseudo‐first order kinetics. Additionally, the polymerization rate of VAc under high pressure increased greatly than that under atmospheric pressure. The “living” feature of the resultant PVAc was confirmed by ¹H NMR spectroscopy and chain extension experiments. Well‐defined PVAc with high molecular weight and narrow molecular weight distribution can be obtained relatively fast by using RAFT polymerization at 5 kbar. © 2015 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym. Chem. 2015 , 53, 1430–1436     

Synthesis of high molecular weight polystyrene using AGET ATRP under high pressure

High molecular weight polystyrene (PS) was synthesized by ATRP. Under atmospheric pressure (1 bar), PS with M_n up to 200,000 was prepared using either ARGET or ICAR ATRP. Under high pressure (6 kbar), higher molecular weight PS could be obtained due to accelerated radical propagation and diminished radical termination in polymerization of styrene. Therefore, it was possible to synthesize PS with M_n > 1,000,000 and M_w/M_n < 1.25 using AGET ATRP under a pressure of 6 kbar at room temperature. This is the highest molecular weight linear PS prepared by a controlled radical polymerization.