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1987 Volume 4 Issue 4
1987, 4(4): 1-5
Abstract:
ESR,1H-NMR and IR were combined so as to give information concerning the mechanism of butadiene polymerization in the presence of catalyst system Fe(phen)Cl3-(i-C4H9)3Al. It was shown by the ESR spectra that the iron in active species is reduced into Fe(Ⅱ) by triisobatyl aluminium during the polymerization and the signal of free radical could be observed,so a reduction mechanism is proposed. Two systems, Fe(phen)Cl3-(i-C4H9)3Al and Fe(phen)Cl3-(i-C4H9)3Al-butadiene, have diffferent spectra in ESR. The former gives a very wide signal(△Hpp=900G), but the latter shows a more sharp one (△Hpp=50G). The overall polymerization mechanism has been proposed, which is supported by1H-NMR and IR spectra measurements of the system.
ESR,1H-NMR and IR were combined so as to give information concerning the mechanism of butadiene polymerization in the presence of catalyst system Fe(phen)Cl3-(i-C4H9)3Al. It was shown by the ESR spectra that the iron in active species is reduced into Fe(Ⅱ) by triisobatyl aluminium during the polymerization and the signal of free radical could be observed,so a reduction mechanism is proposed. Two systems, Fe(phen)Cl3-(i-C4H9)3Al and Fe(phen)Cl3-(i-C4H9)3Al-butadiene, have diffferent spectra in ESR. The former gives a very wide signal(△Hpp=900G), but the latter shows a more sharp one (△Hpp=50G). The overall polymerization mechanism has been proposed, which is supported by1H-NMR and IR spectra measurements of the system.
1987, 4(4): 6-11
Abstract:
Micka's equation is reduced to some simple forms for terminal potentials, which explain the a.c. oscillopolarogram obtained at various current densities in solutions containing only supporting electrolyte. The theoretical conclusions are qualitatively confirmed through experimental work.
Micka's equation is reduced to some simple forms for terminal potentials, which explain the a.c. oscillopolarogram obtained at various current densities in solutions containing only supporting electrolyte. The theoretical conclusions are qualitatively confirmed through experimental work.
1987, 4(4): 12-15
Abstract:
Nine organic acids including monoacid, diacid and hydroxycarboxylic acid were used as additives in a. c. etching of aluminum foil in hydrochloric acid medium. The results show, as reported in previous paper with additives of sulfuric acid that these additives are essential in formation of a compact etch film, which is broken through during each anodic cycle of the ac-current, thus a high density of etch pits and a large surface area magnification can be obtained. For a certain a. c. frequency there exists an optimum additive concentration Cm, the greater the first dissociation constant of the acid, the lower the Cm. Cm also decreases with increase of a. c. frequency. It is proposed, that the organic acid anion was competitively adsorbed with (Cl-) ion, forming a buffer layer, which decreases the solubility of etch film. The effects of the concentration of hydrochloric acid, the current density of a. c. and the overall concentration of Cl- ion on etching process were also discussed.
Nine organic acids including monoacid, diacid and hydroxycarboxylic acid were used as additives in a. c. etching of aluminum foil in hydrochloric acid medium. The results show, as reported in previous paper with additives of sulfuric acid that these additives are essential in formation of a compact etch film, which is broken through during each anodic cycle of the ac-current, thus a high density of etch pits and a large surface area magnification can be obtained. For a certain a. c. frequency there exists an optimum additive concentration Cm, the greater the first dissociation constant of the acid, the lower the Cm. Cm also decreases with increase of a. c. frequency. It is proposed, that the organic acid anion was competitively adsorbed with (Cl-) ion, forming a buffer layer, which decreases the solubility of etch film. The effects of the concentration of hydrochloric acid, the current density of a. c. and the overall concentration of Cl- ion on etching process were also discussed.
1987, 4(4): 16-20
Abstract:
From the electrophoretic and conductrometric measurements it was deduced that the increase of zeta potential of PS latex with increasing concentration of electrolytes was mainly due to the ion exchange occurred between the surface groups on the latex particle and the cations in the solution. According to the Langmuir's equation of adsorption and Stern's electrical double layer model, the adsorption free energy and number of the adsorption sites of surface active cations on PS latex were evaluated from electrophoretic data. Increasing the electrolyte concentration enhanced the number of adsorption sites of latex particle and hence the adsorption amount of surface active cations.
From the electrophoretic and conductrometric measurements it was deduced that the increase of zeta potential of PS latex with increasing concentration of electrolytes was mainly due to the ion exchange occurred between the surface groups on the latex particle and the cations in the solution. According to the Langmuir's equation of adsorption and Stern's electrical double layer model, the adsorption free energy and number of the adsorption sites of surface active cations on PS latex were evaluated from electrophoretic data. Increasing the electrolyte concentration enhanced the number of adsorption sites of latex particle and hence the adsorption amount of surface active cations.
1987, 4(4): 21-25
Abstract:
In this paper changes of shape of absorption signal, absorbance and dissipation of germaniutn in the standard graphite tube, zirconium-coated and tungsten-coated graphite tubes have been studied. It shows experimentally a larger enhancement of analytical sensitivity of germanium in the zirconium-coated and tungsten-coated graphite tubes was obtained. The appearance temperature of germanium appear is 1770K in the tungsten-coated graphite tube. The △H° value of germanium was 106.2 kcal/mol calculated according to equation:△H°=γTapp. It corresponds to the heat of evaporation of solid germanium (89.5kcal/mol). Therefore, the atom formation of germanium is the reduction of GeO2 by carbide of tungsten following by the sublimation of germanium.
In this paper changes of shape of absorption signal, absorbance and dissipation of germaniutn in the standard graphite tube, zirconium-coated and tungsten-coated graphite tubes have been studied. It shows experimentally a larger enhancement of analytical sensitivity of germanium in the zirconium-coated and tungsten-coated graphite tubes was obtained. The appearance temperature of germanium appear is 1770K in the tungsten-coated graphite tube. The △H° value of germanium was 106.2 kcal/mol calculated according to equation:△H°=γTapp. It corresponds to the heat of evaporation of solid germanium (89.5kcal/mol). Therefore, the atom formation of germanium is the reduction of GeO2 by carbide of tungsten following by the sublimation of germanium.
1987, 4(4): 26-30
Abstract:
Seattering intensity distrihuticrs from rolyethylene and irradiated rolyethylene were experimentally studied by small angle light seattering method and compared with those calculated on two-dimensional truncated spherulite model. The results indicated that both the truncation effect and internal disorder might widen the profile of scattering intensity distribtion curves. The degree of widening increases with the truncation and disorder.The truncation results in the increase of the scattering intensity in the smail angle region while the internal disorder shows influence on the wide angle region. It seems that the internal disorder has much more effect than truncation.The results agree well with that reported in literature.
Seattering intensity distrihuticrs from rolyethylene and irradiated rolyethylene were experimentally studied by small angle light seattering method and compared with those calculated on two-dimensional truncated spherulite model. The results indicated that both the truncation effect and internal disorder might widen the profile of scattering intensity distribtion curves. The degree of widening increases with the truncation and disorder.The truncation results in the increase of the scattering intensity in the smail angle region while the internal disorder shows influence on the wide angle region. It seems that the internal disorder has much more effect than truncation.The results agree well with that reported in literature.
1987, 4(4): 31-34
Abstract:
The positron annihilation technique was used to study the properties of styrene-isoprene-styrene block copolymer in the temperature of -80 to 100℃. In the temperature spectrum of the longest lifetime τ3, in addition to two transition temperatures which correspond to the glass transition temperatures of polyisoprene and polystyrene, an irregularity was observed. This transition temperature is interpreted as the glass transtion temperature of the interphase in block copolymers.
The positron annihilation technique was used to study the properties of styrene-isoprene-styrene block copolymer in the temperature of -80 to 100℃. In the temperature spectrum of the longest lifetime τ3, in addition to two transition temperatures which correspond to the glass transition temperatures of polyisoprene and polystyrene, an irregularity was observed. This transition temperature is interpreted as the glass transtion temperature of the interphase in block copolymers.
1987, 4(4): 35-39
Abstract:
The kinetic data related respectively to S2O82- formation and O2 evolution on PbO2 anode in H2SO4 and H2SO4-(NH4)2SO4 solutions were obtained by methoed of resolving the steady state polarization curve. The Tafel slopes for both S2O82- formation and O2 evolution were 2.303 RT/βF (β=0.52-0.55) at potential higher than+2.25V vs SHE. The current efficiency of S2O82- formation was lower than 29% and it almost remained unchanged with potentials. The reaction order of S2O82- formation with respect to sulfate ions was found to be zero, while the O2 evolution rate was found to deerease slightly with the increase of sulfate concentration at high potential. A mechanism for above two processes was proposed.
The kinetic data related respectively to S2O82- formation and O2 evolution on PbO2 anode in H2SO4 and H2SO4-(NH4)2SO4 solutions were obtained by methoed of resolving the steady state polarization curve. The Tafel slopes for both S2O82- formation and O2 evolution were 2.303 RT/βF (β=0.52-0.55) at potential higher than+2.25V vs SHE. The current efficiency of S2O82- formation was lower than 29% and it almost remained unchanged with potentials. The reaction order of S2O82- formation with respect to sulfate ions was found to be zero, while the O2 evolution rate was found to deerease slightly with the increase of sulfate concentration at high potential. A mechanism for above two processes was proposed.
INVESTIGATION OF IONIC CONDUCTIVITY OF POLYETHYLENE OXIDE NETWORK CONIPLEXES WITH SODIUM THIOCYANATE
1987, 4(4): 40-44
Abstract:
Some ethoxy polyethylene glycol monomethacrylate macromers containing small amount of dimethacrylate were synthesized by "Macromonomer Technique". They crosslinked on heating and polyethylene oxide networks were obtained. The complexes of the networks with sodium thiocyanate had a higher conductivity than that of corresconding linear polyethylene oxides by two orders (10-5Ω-1cm-1/298K). IR spectra of the network systems showed strong signals of amorphous construction. Effects of solvents and salt concentration on the crystallinity of the complexes were observed. can be obtained. By selecting suitable solvent and salt concentration high amorphous complexes with the highest conductivity and good hot-press processibility
Some ethoxy polyethylene glycol monomethacrylate macromers containing small amount of dimethacrylate were synthesized by "Macromonomer Technique". They crosslinked on heating and polyethylene oxide networks were obtained. The complexes of the networks with sodium thiocyanate had a higher conductivity than that of corresconding linear polyethylene oxides by two orders (10-5Ω-1cm-1/298K). IR spectra of the network systems showed strong signals of amorphous construction. Effects of solvents and salt concentration on the crystallinity of the complexes were observed. can be obtained. By selecting suitable solvent and salt concentration high amorphous complexes with the highest conductivity and good hot-press processibility
1987, 4(4): 45-48
Abstract:
This paper presents a study on the effect of segment structure on the compatibility and dynamic mechanical damping properties of multiblock copolymer networks. A series of copolymer networks with various segment structures which dampes mechanical vibration over a temperature range of 50 degrees were prepared from vinyl-terminated oligomer as soft segment and vinyl polymers as hard segment, respectively. Somel soft and hard segments in copolymer networks were found to be semicompatibile and many of the copolymer networks based on these formulations resulted in tanδ>1.75 over the desired temperature range.
This paper presents a study on the effect of segment structure on the compatibility and dynamic mechanical damping properties of multiblock copolymer networks. A series of copolymer networks with various segment structures which dampes mechanical vibration over a temperature range of 50 degrees were prepared from vinyl-terminated oligomer as soft segment and vinyl polymers as hard segment, respectively. Somel soft and hard segments in copolymer networks were found to be semicompatibile and many of the copolymer networks based on these formulations resulted in tanδ>1.75 over the desired temperature range.
1987, 4(4): 49-52
Abstract:
A new approach has been worked out for carboxylation of nitrotoluene. o-Nitrotoluene or p-nitrotoluene was converted into the corresponding nitrophenylacetic acids by treatiag the nitro compound with alkaline salts of phenol and carbon dioxide in an aprotic dipolar solvent. The reaction occurs at 60-80℃ and atmospheric pressure and when mol ratio of alkaline salts of phenol with nitrotoluene attains 4:1, nitrophenylacetic acid. can be obtained quantitatively The carboxylation of m-nitrotoluene failed of success under the same conditions.
A new approach has been worked out for carboxylation of nitrotoluene. o-Nitrotoluene or p-nitrotoluene was converted into the corresponding nitrophenylacetic acids by treatiag the nitro compound with alkaline salts of phenol and carbon dioxide in an aprotic dipolar solvent. The reaction occurs at 60-80℃ and atmospheric pressure and when mol ratio of alkaline salts of phenol with nitrotoluene attains 4:1, nitrophenylacetic acid. can be obtained quantitatively The carboxylation of m-nitrotoluene failed of success under the same conditions.
1987, 4(4): 53-57
Abstract:
This paper reports the results of fluorescence lifetime measurements of some coumarin and rhodamine laser dyes. The factors which might lengthen or shorten the values of lifetime were considered. The correlation of lifetime values with structural factors of dyes is discussed briefly.
This paper reports the results of fluorescence lifetime measurements of some coumarin and rhodamine laser dyes. The factors which might lengthen or shorten the values of lifetime were considered. The correlation of lifetime values with structural factors of dyes is discussed briefly.
1987, 4(4): 58-60
Abstract:
Graft copolymers with polyethylene (PE) backbone and polystyrene (PS) grafts were prepared by copolymerization of norbornene-capped polystytene macromer (PS-NB) with ethylene using Ziegler-Natta catalysts. Purified products were characterized by GPC and IR. The relatively low conversion of PS-NB was attributed to micro-phase separation in the copolymerization. The graft copolymers exhibited mechanical properties similar to those of PE obtained with tbe same catalyst system.
Graft copolymers with polyethylene (PE) backbone and polystyrene (PS) grafts were prepared by copolymerization of norbornene-capped polystytene macromer (PS-NB) with ethylene using Ziegler-Natta catalysts. Purified products were characterized by GPC and IR. The relatively low conversion of PS-NB was attributed to micro-phase separation in the copolymerization. The graft copolymers exhibited mechanical properties similar to those of PE obtained with tbe same catalyst system.
1987, 4(4): 61-65
Abstract:
In a supporting electrolyte containing 2×10-4M DMG, 0.025M Na2B4O7 at pH=9.4, a sensitive adsorptive complex wave of copper-DMG was obtained by using single-sweep polarography. The peak potential is -0.34V (vs. SCE). The peak height changes linearly with the concentration of copper in the range of 5×10-8 to 3×10-6M. The method has been applied successfully for the trace copper determination in waste water.
In a supporting electrolyte containing 2×10-4M DMG, 0.025M Na2B4O7 at pH=9.4, a sensitive adsorptive complex wave of copper-DMG was obtained by using single-sweep polarography. The peak potential is -0.34V (vs. SCE). The peak height changes linearly with the concentration of copper in the range of 5×10-8 to 3×10-6M. The method has been applied successfully for the trace copper determination in waste water.
1987, 4(4): 66-68
Abstract:
A novel catalyst Fe(naph)2-Phen-AlEt2Cl-Al(i-Bu)3 for polymerization of butadiene is reported. The catalytic activity of the catalyst was found to be higher than that of known iron catalyst consisting of Fe compound-AlR3-Phen. The vulcanizate of polybutadiene prepared by the title catalyst shows good physical properties.
A novel catalyst Fe(naph)2-Phen-AlEt2Cl-Al(i-Bu)3 for polymerization of butadiene is reported. The catalytic activity of the catalyst was found to be higher than that of known iron catalyst consisting of Fe compound-AlR3-Phen. The vulcanizate of polybutadiene prepared by the title catalyst shows good physical properties.
1987, 4(4): 69-70
Abstract:
The dynamic mechanical properties of butadiene isoprene copolymer prepared with lanthanide catalysts (Ln-PBI) have been studied using torsinal pendulum method. The content of cis-unit in Ln-FBI is high. The glass transition temperatures accord with those calculated from the FOX law for random copolymers. When the butadiene content in Ln-PBI is higher than 80wt% a new TX transition was observed over the temperture range from 233K to 243K. The results of 13C-NMR and X-ray diffraction spectra indicated that both the length of butadiene segments and the crystallinity increase with increase of butadiene content when the later is above 80% in the copolymers. The existense of the TX transition is related to the crystalization of long segments of butadiene in Ln-PBI.
The dynamic mechanical properties of butadiene isoprene copolymer prepared with lanthanide catalysts (Ln-PBI) have been studied using torsinal pendulum method. The content of cis-unit in Ln-FBI is high. The glass transition temperatures accord with those calculated from the FOX law for random copolymers. When the butadiene content in Ln-PBI is higher than 80wt% a new TX transition was observed over the temperture range from 233K to 243K. The results of 13C-NMR and X-ray diffraction spectra indicated that both the length of butadiene segments and the crystallinity increase with increase of butadiene content when the later is above 80% in the copolymers. The existense of the TX transition is related to the crystalization of long segments of butadiene in Ln-PBI.
1987, 4(4): 71-73
Abstract:
Supported liquid membranes (SLM) were prepared with poly (4-methylpentene-1) (TPX) as support polymer and tributyl phosphate (TBP), dibutyl phthalate (DBP) and dibutyl sebacate (DBS) as supported liquids. The performance of oxygen enrichment of these membranes has been compared. The permeabilities of the supported liquid membranes were higher in varying degrees than that of pure TPX, while their separation factors were lower. The separation factor αO/N of SLM containing DBS was higher than that of SLM with TBP and DBP. SEM photographs were recorded to elucidate the difference in the performance of the SLM obtained.
Supported liquid membranes (SLM) were prepared with poly (4-methylpentene-1) (TPX) as support polymer and tributyl phosphate (TBP), dibutyl phthalate (DBP) and dibutyl sebacate (DBS) as supported liquids. The performance of oxygen enrichment of these membranes has been compared. The permeabilities of the supported liquid membranes were higher in varying degrees than that of pure TPX, while their separation factors were lower. The separation factor αO/N of SLM containing DBS was higher than that of SLM with TBP and DBP. SEM photographs were recorded to elucidate the difference in the performance of the SLM obtained.
1987, 4(4): 74-76
Abstract:
A relationship between the molecular internal rotating steric factor (σ) and crosslinking parameter(β) is established by taking the effect of the flexibility of polymer chain on β value into account. The σ value obtained by this method is close to those reported in the literature by other methods.
A relationship between the molecular internal rotating steric factor (σ) and crosslinking parameter(β) is established by taking the effect of the flexibility of polymer chain on β value into account. The σ value obtained by this method is close to those reported in the literature by other methods.
1987, 4(4): 77-79
Abstract:
In the supporting electrolyte containing 0.10M potassium hydrogen phthalate at pH4.0, a sensitive derivative peak of nickel(Ⅱ)-thiosemicarbazide complex was found by using single-sweep oscillopolarography. The peak potential is -0.80V (SCE). The change of the peak height with the concentration of Ni(Ⅱ) appeared linear in the range from 2.0×10-7 to 8.0×10-6M. The character of the peak wave has been studied. It is confirmed that the peak wave is a catalytic pre-wave with adsorptive property and the adsorbed species may be Ni(TSC)22+.
In the supporting electrolyte containing 0.10M potassium hydrogen phthalate at pH4.0, a sensitive derivative peak of nickel(Ⅱ)-thiosemicarbazide complex was found by using single-sweep oscillopolarography. The peak potential is -0.80V (SCE). The change of the peak height with the concentration of Ni(Ⅱ) appeared linear in the range from 2.0×10-7 to 8.0×10-6M. The character of the peak wave has been studied. It is confirmed that the peak wave is a catalytic pre-wave with adsorptive property and the adsorbed species may be Ni(TSC)22+.
