A NOVEL EOR POLYMER (Ⅰ)—STUDY ON GELATION OF RESORCINOL-FORMALDEHYDE SYSTEMS

Factors affecting the gelation of resorcinol-formaldehyde systems have been examined overvariable ranges applicable to oilfield use. Gelation of resorcinol-formaldehyde (RF) system wassensitive to pH,salinity and hardness. Generally,this gel system could be used in fresh water orlow salinity brine at pH higher than about 9. The application would require careful monitoring ofinjection fluids to avoid premature gelation or prolonged shut-in times,especially under conditionsof low salinity and high pH. Salinity and hardness compatibilities of the system were improved bysulfomethylation of resorcinol. Aqueous sulfomethylated resorcinol formaldehyde (SMRF)system could be used in brine with higher salinity and hardness and at a wider pH range of 5--10.     

Solubility of stearic acid in supercritical CO_2-acetonitrile mixtures

The solubility of stearic acid in supercritical CO2 with acetonitrile (CH3CN) cosolvent was measured at 318.15 K in the pressure range from 9.5 to 16.5 MPa, and the cosolvent concentration ranges from 0. 0 to 5.5 mol% . The solubility increases with acetonitrile concentration and pressure, and it also increases with the apparent density of CO2 d1(moles of CO2 in per liter of fluid) at higher cosolvent concentrations. At lower d1, however, the solubility of the acid at lower acetonitrile concentrations is lower than that in pure CO2 provided that d1 is fixed, which is discussed qualitatively based on the clustering of the components in the system.     

INFLUENCE OF THERMAL AND NON—THERMAL EFFECTS OF ULTRASOUND ON ISOTHERMS OF PHENOL ON NKAⅡ RESIN

Adsorption equilibrium experiments of phenol on the NKA II resin are separately conducted in the presence and absence of ultrasound at ambient temperature.The isotherm of phenol on the polymer adsorbent in the presence of ultrasonic field is firstly reported.Results indicated that the isotherm of phenol determined in the presence of ultrasound is lower than that in the absence of ultrasound.In addition,experiments also show that the use of ultrasound to the adsorption system of the phenol aqueous solution and NKA Ⅱ resin could cause the rising of the temperature of the system in the order of 6^-C.The effect of ultrasound on the isotherm of the phenol on the NKA Ⅱ resin mostly ascribes to the thermal effect and the non-thermal effect of ultrasonic field.and the role of the later is greater than that of the former.     

Investigation on the gelation behavior of biodegradable poly(butylene succinate) during isothermal crystallization process

The early stage of polymer crystallization may be viewed as physical gelation process,i.e.,the phase transition of polymer from liquid to solid.Determination of the gel point is of significance in polymer processing.In this work,the gelation behavior of poly(butylene succinate)(PBS) at different temperatures has been investigated by rheological method.It was found that during the isothermal crystallization process of PBS,both the storage modulus(G′) and the loss modulus(G″) increase with time,and the rheological response of the system varies from viscous-dominated(G′G″),meaning the phase transition from liquid to solid.The physical gel point was determined by the intersection point of loss tangent curves measured under different frequencies.The gel time(t_c) for PBS was found to increase with increasing crystallization temperature.The relative crystallinity of PBS at the gel point is very low(2.5%-8.5%) and increases with increasing the crystallization temperature.The low crystallinity of PBS at the gel point suggests that only a few junctions are necessary to form a spanning network,indicating that the network is"loosely"connected,in another word,the critical gel is soft.Due to the elevated crystallinity at gel point under higher crystallization temperature,the gel strength S_g increases, while the relaxation exponent n decreases with increasing the crystallization temperature.These experimental results suggest that rheological method is an effective tool for verifying the gel point of biodegradable semi-crystalline polymers.     

Separation,determination of six impurities in methotrexate drug substance using ultra-performance liquid chromatography

Methotrexate(MTX) is an antineoplastic therapeutic medicine as antimetabolite of folic acid. In this paper, a sensitive and rapid ultra-performance liquid chromatographic(UPLC) method was developed and validated for the separation and determination of impurities in MTX drug substances. The UPLC method was accomplished on an Agilent Zorbax Extend C-18(50 mm 4.6 mm, 1.8 mm) with a gradient elution system composed of sodium dihydrogen phosphate in water(20 mmol/L, pH 3.0) and acetonitrile. The flow rate was 2.2 mL/min. The method was validated. The calibration curves displayed good linearity(r 0.999) within the tested concentration ranges. The limit of detection(LOD) and limit of quantification(LOQ) of the six analytes were all less than 0.774 mg/mL and 1.03 mg/mL. The relative standard deviation(RSD) for intra- and inter-day precision of the six analytes was less than 9.8%, including at the LOQ. The average recovery ranged from 95.2% to 103% except at the LOQ, where recovery ranged from 82.7% to 117%. The validated method was successfully used to determine the relative abundance of six impurities in the MTX drug substances.     

Solvent-induced molecular gel formation at room temperature and the preparation of related gel-emulsions

The gelation behaviors of four recently reported amphiphilic cholesteryl derivatives (1, 2, 3 and 4) have been evaluated. It was found that the gel formation process can be controlled by introduction of water at room temperature. Addition of water to an acetone solution of 4 immediately results in the system becoming turbid, and a gel subsequently forms within a few minutes. Interestingly, 4 is a super-gelator for a mixed solvent of acetone and water at room temperature, in particular when their volume ratio is close to 1:1 at which the critical gelation concentration (CGC) is 0.06% (w/v). It was found that the introduction of water favors the formation of gel networks, and the gel possesses smart and reversible thixotropic properties. FTIR and 1H NMR spectroscopy confirmed that hydrogen bonding is one of the main driving forces for the gelation of the solvents. XRD demonstrated that 4 self-assembled into a layered structure within the acetone-water mixed solvent gel. Furthermore, 1 and 2 can be used as excellent stabilizers for gel emulsions of alkanes and water. The maximum of the dispersed phase, water, in one of the gel-emulsions can be as high as 97% (v/v).     

IN SITU INTERFEROMETRIC STUDY ON THE GELATION PROCESS OF POLYACRYLIC ACID GELS*

In situ interferometry was used to investigate the gelation process of polyacrylic acid (PAA) gels. The basicprinciple of the in situ interferometry technique is illustrated. It can give sufficient information for non-destructive andsuccessful investigation of the whole gelation process. The effect of initiator concentration on the gelation process wasstudied. The polymerization rate of AA increases with increasing initiator concentration. The error arising from the thermaleffect in the gelation process can be neglected.     

Preparation and Identification of Angelica sinensis Polysaccharide-iron Complex

Angelica sinensis polysaccharide(ASP) was extracted from Angelica sinensis by boiling water. An Angelica sinensis polysaccharide-iron complex(APC) was prepared under the alkaline condition by adding a ferric chloride solution to the ASP solution. Then some identifiable properties of the complex were studied. The content of iron (Ⅲ) in the complex was determined with iodometry. The thermal property, the microscopic structure, the spectral characteristics, and N, C, H contents of the complex were examined by a variety of techniques including DSC, TEM, IR,NMR, and elemental analysis. The content of iron (Ⅲ) in the complex ranges from 10% to 40%. The DSC result shows that the melting point of the complex is about 450 ℃. The TEM result shows that the complex has an iron(Ⅲ)core(β-FeOOH core) linked by hydroxy and oxy bridges, with the polysaccharide chains attached to the surface of the core. The IR and NMR results also show that there is aβ-FeOOH core in the complex. The elemental analysis shows that the contents of N, C , H in the complex are, respectively, lower than those of N, C, H in ASP. All our studies indicate that the APC consists of aβ-FeOOH core surrounded by ASP.     

A New Method to Study the Sol-gel Transition Process of Organic/Inorganic Hybrid Materials

The sol-gel transition process of PMMA/SiO2 hybrid materials was first studied by means of the dynamic torsional vibration method. The different stages of the transition can be described by the change of torque. The temperature-dependent measurement of the gel time（ tg ） gives the possibility to determine the apparent activation energy.（ Ea ） of this transition according to Flory＇s gelation theory. The non-equilibrium thermodynamic fluctuation theory was used to predict the transition behavior. The isothermal transition experiments on hybrid sols with different TEOS（tetraethyl orthosilicate） contents were carried out. The results show that the Ea of a hybrid sol is higher than that of a non- hybrid sol of a TEOS-water-ethanol system. The increasing of TEOS content in a hybrid sol has no obvious effect on the Ea value, but it can enhance the sol-gel .reaction rate.     

Effect of intramolecular energy transfer on the rate of unimolecular isomerization: HCN --HNC

This paper reports calculations of the rate of isomerization of HCN - HCN based on the theory of Gary and Rice as extended by Zhao and Rice. The major task is to determine the effect of intramolecular energy transfer on the prediction of the rate of isomerization. Both the full three-dimensional (3D) system and the reduced two-dimensional (2D) system obtained from freezing CN bond at 1.159 A are analyzed to check the validity of the freezing bond approximation. Meanwhile, RRKM rates are calculated to test RRKM choice of the transition state by comparing to Gary-Rice three-state model. The comparison shows that the rates from 2D model and 3D model are differing up to 20% with 2D rates consistently larger. The intramolecular energy transfer modifies the isomerization rate for HCN system up to 30% that is modestly small by the expectation. The isomerization rate predicted from RRKM theory is greater than those of Gary-Rice three-state model theory up to 65%, and it overstimates the rates under all consider     

Adsorption isotherms and kinetic characteristics of methane on block anthracite over a wide pressure range

It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to perform the CH4 adsorption experiments using the gravimetric method at temperatures of 293.60 K, 311.26 K, 332.98 K and 352.55 K and pressures up to 19 MPa. The excess adsorption capacity of CH4 in dry block anthracite increased, followed by a sequence decrease with the increasing pressure. High temperature restrained the growth of the excess adsorption due to that the adsorption is an intrinsically physical and exothermic process. The excess adsorption peak decreased slowly with the increase of temperature and intersected at a pressure of more than 18 MPa; meanwhile, the pressure at the excess adsorption peak increased.The existing correlations were examined in terms of density rather than pressure. The DR+k correlation, with an average relative deviation of ±0.51%, fitted our data better than the others, with an average relative deviation of up to 2.29%. The transportation characteristics of CH4 adsorption was also investigated in this study, including the adsorption rate and diffusion in block coal. The kinetic data could be described by a modified unipore model. The adsorption rates were found to exhibit dependence on pressure and temperature at low pressures, while the calculated diffusivities exhibited little temperature dependence. In addition, the kinetic characteristics were compared between CH4 and CO2 adsorption on the block coal. The excess adsorption ratios of CO2 to CH4obtained from the DR+k model decreased with the increasing pressure.     

BINARY COMPETITIVE AND COOPERATIVE ADSORPTION OF AROMATIC COMPOUNDS ON POLYMERIC RESINS

The adsorption behaviors of 2-naphthalenesulfonic acid and aniline on a conventional macroporous resin Amberlite XAD4 and the other two newly-developed hypercrosslinked resins NDA101 and NDA100 were investigated in a single or binary batch system at 293 K and 313 K,respectively.All the adsorption isotherms of 2-naphthalenesulfonic acid and aniline on the test resins in both systems can fit well with the Langmuir equation,indicating that the adsorption is a favorable process.At the identical equilibrium concentration,the amount of aniline adsorbed on polymeric resins in the single system is higher than that in the binary system because of the competitive adsorption between 2-naphthalenesulfonic acid and aniline on the resin surface.However,the uptake amount of 2-naphthalenesulfonic acid in the binary system is markedly larger than that in the single system,which is presumably due to the cooperative effect arisen from the electrostatic interaction between 2-naphthalenesulfonic acid and aniline adsorbed on the resin surface.The simultaneous adsorption system was proven to be helpful for the selective adsorption toward 2-naphthalenesulfonic acid due to its larger selective index.     

THE METHOD OF LASER LIGHT SCATTERING ON NETWORK COPOLYMERIZATIONS

Laser light scattering method introduced in this paper is a new method to study macromolecular gelation.The most prominent features of the methods are its high sensitivity and use of the scanning technique, whereupon the parameters describing the properties of reaction process at a macro level can be obtained. They are the speed and the point of gelation and the point of phase separation. The parameters describing the inhomogeneous changes in reaction systems at a sub-micro level can also be obtained. They include a (the correlation coefficient) and (the mean squared dilectric constant fluctuation). Thus, the tracks describing the inhomogeneous changes in reaction systems can be traced. The method presented here will provide a new approach to decpening understanding of the gelation process.     

A NOVEL METHOD FOR CHARACTERIZING THE WHOLE PROCESS OF POLYMER GELATION*

A novel method was established to investigate the gelation process of polymers. The change of refractive index ofa polymer system during gelation was determined in situ in a prismatic cell. It can give reliable information on the wholegelation process. The apparatus and the execution of this technique are illustrated and the error is also discussed.     

Microencapsulation of n-Eicosane as Energy Storage Material

For heat energy storage application, polynrea microcapsules containing phase change material, n-eicosane, were synthesized by using interfacial polymerization method with toluene-2,4-diisocyanate (TDI) and diethylenetriamine(DETA) as monomers in an emulsion system. Poly(ethylene glycol)octyl-phenyl ether (OP), a nonionic surfactant,was the emulsifier for the system. The experimental result indicates that TDI was reacted with DETA in a mass ratio of 3 to 1. FF-IR spectra confirm the formation of wall material, polyurea, from the two monomers, TDI and DETA.Encapsulation efficiency of n-eicosane is about 75%. Microcapsule of n-eicosane melts at a temperature close to that of n-eicosane, while its stored heat energy varies with core material n-eicosane when wall material fixed.Thermo-gravimetric analysis shows that core material n-eicosane, micro-n-eicosane and wall material polyurea can withstand temperatures up to 130, 170 and 250℃, respectively.     

A method to accelerate the gelation of disulfide-crosslinked hydrogels

A glutathione-disulfide-ended poly(ethylene glycol)(GSSG-PEG-GSSG) was designed. It is a much more efficient accelerator than glutathione disulfide(GSSG) for the gelation of an 8arm-PEG-SH polymer solution, and the gelation time can be tuned from hours to minutes at the physiological p H and temperature. A mechanism was proposed to explain the different behaviors of the GSSG and GSSG-PEG-GSSG gelation systems. Due to the ever-going thiol-disulfide exchange reaction, the thiol-disulfide hydrogels also showed interesting swelling behavior.     

Significant downward trend of SO2 observed from 2005 to 2010 at a background station in the Yangtze Delta region,China

SO2 is an important gas in atmosphere with great environmental and climate implications.SO2 emission in China has been receiving great attention as the economy grows and the amount of coal consumption has increased in the past few decades.SO2 has been observed from July 2005 to June 2010 at Linan WMO GAW regional station(30.3 °N,119.73 °E,138 m a.s.l.) located in the Yangtze Delta region in eastern China.These observation data are analyzed to understand the trend of regional SO2 background concentration.Strict quality controls are conducted to ensure the temporal comparability of the data.Significant downward trend with ?2.4 ppb/yr(P < 0.0001) of surface SO2 is observed from 2005 to 2010,especially after 2008.The average concentration of SO2 from July 2005 to June 2008 is 14.2±3.1 ppb,which is slightly higher than the mean values of 13.5±5.1 ppb during 1999?2000 and is two folds of the average value(7.1±3.1 ppb) from July 2008 to June 2010.More than 50% of the SO2 has been cut down after 2008 in the Yangtze Delta region due to the implementation of stricter emission control measures.The peak SO2 concentration appears around 10 o’clock in the morning after 2009 while appears at night before 2009.These diurnal variations of SO2 might indicate that after 2009,more SO2 is from the vertical exchange process than from the local accumulation.     

Cr^3^+的水解聚合作用IV.两种"根+节"体系之间的过渡状态

The hydrolytic polymerization of chromium (III) ion in 0.040, 0.060, 0.080 and 0.160M Cr(NO3)3 solutions was studied pH-metrically in the medium of 0.5M NaNO3 at 40+/-1 C. The average number of OH- bound per Cr^3^+ at different pH was designated as Z, the gighest value of Z was found to be about 1.0. A family of curves of Z(pH)B, each at a definite concentration B of Cr(NO3)3, was obtained. The values of both B and pH were determined from the curves and a linear relationship between -lgB and pH was found for each value of Z. From the slope of each curve of-lgB(pH)z, a value of t was obtained, which increased from 1.51 to 2.06 when Z increased from 0.10 to 1.0. This implied that the polymerized hudrolysis products were of mixed types. The data of different Z value were treated by three different methods, namely, "core + links" method, project strip method and "homoligand formation constant" method. The results obtained showed the existence of "core + links" compounds not only with two hydroxyl bridges as Cr (Cr(OH)2)n^(^3^+^n^)^+(n = 1,2,3) but also with both one and two hydroxy bridges as Cr3(OH)3, indicating that the present system was a transition from t = 2 to t = 1. The hydrolysis constants of the above compounds are as follows: lgβ = -4.19, lgβ33 = -5.28, lgβ = -8.23, lgβ64 = 12.28. The above results are in agreement with those obtained at low and medium concentration of Cr(NO3)3. Furthermore, the constants obtained by means of different methods are in good agreement with each other as well as with those reported in previous papers.     

Methane Decomposition into Carbon Fibers over Coprecipitated Nickel-Based Catalysts

Decomposition of methane in the presence of coprecipitated nickel-based catalysts to produce carbon fibers was investigated. The reaction was studied in the temperature range of 773 K to 1073 K. At 1023 K, the catalytic activities of three catalysts kept high at the initial period and then decreased with the reaction time. The lifetimes of Ni-Cu-Al and Ni-La-Al catalysts are longer than that of Ni-Al catalyst. With three catalysts, the yield of carbon fibers was very low at 773 K. The yield of carbon fibers for Ni-La-Al catalyst was more than those for Ni-Al and Ni-Cu-Al catalysts. For Ni-La-Al catalyst, the elevation of temperature from 873 K up to 1073 K led gradually to an increase in the yield of carbon fibers. XRD studies on the Ni-La-Al catalyst indicate that La2NiO4 was formed. The formation of La2NiO4 is responsible for the increase in the catalytic lifetime and the yield of carbon fibers synthesized on Ni-La-Al at 773 1073 K. Carbon fibers synthesized on Ni-Al catalyst are thin, long carbon nanotubes. There are bamboo-shaped carbon fibers synthesized on Ni-Cu-Al catalyst. Carbon fibers synthesized on Ni-La-Al catalyst have large hollow core, thin wall and good graphitization.     

Influences of Triton X-100 on Hemoglobin Behaviors in Hemoglobin/Acyclovir/Triton X-100/H2O System

The influences of Triton X-100 on hemoglobin （Hb） behaviors were studied by the methods of UV-Vis spectrum, fluorescence spectrum, HPLC, conductivity, zeta potential and negative-staining transmission electron microscope in Hb/acyclovir/Triton X-100/H2O system. With the increase of Triton X-100 concentration in the system, the percentage of the free acyclovir increased from 58%--63% to 90%--94%. The static quenching constant and the association number of acyclovir to Hb decreased. The fluorescence spectrum, conductivity, zeta potential, fluorescence polarization and negative-staining morphology of Hb tended to recover to those of the original state of Hb in the same concentration of Hb. The interaction between Triton X-100 and Hb is stronger than that between acyclovir and Hb. Most Triton-X-100 was associated with Hb at low Triton X-100 concentration. But the interaction of Triton X-100 with Hb was apparently dominant in high Triton X-100 concentration. The Hb structure was unfolded and finally denatured.