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1963 Volume 5 Issue 2
1963, 5(2): 49-59
Abstract:
The effects of the catalyst concentration，the monomer concentration and the poly-merization temperature on the conversion，average molecular weight and microstructure of the polybutadienes obtained have been studied． Results showed that the characteris-tics of this catalyst system are the extremely low requirement of catalyst and the high and rather constant cis一1，4-content of the polymer．The rate of polymerization is，how-ever，too fast and the molecular weight of the polymer too high． Further studies aimed at controlling the polymerization rate and regulating the molecular weight of the poly-mers showed：(1) The rate of polymerization varies greatly with the solvents，the order of which being benzene> toluene > xylene > mesitylene．(2) Addition of phenyl一β-naphthylamine or N，N’-diphenyl-p-phenylene diamine lowers both the rate of polymerisa-tion and the molecular weight of the polymer．(3) The molecular weight of the poly- met can be regulated by controlling the water content in the system．(4) The molecular weight of the polymer can also be regulated by varying the ratio of the two components of a mixed solvent．(5) Addition of small amount of polynuclear hydrocarbons，such as naphthalene or anthracene to the heptane polymerization solution raised the molecular weight of the polymer to a considerable extent．The above results were discussed．
The effects of the catalyst concentration，the monomer concentration and the poly-merization temperature on the conversion，average molecular weight and microstructure of the polybutadienes obtained have been studied． Results showed that the characteris-tics of this catalyst system are the extremely low requirement of catalyst and the high and rather constant cis一1，4-content of the polymer．The rate of polymerization is，how-ever，too fast and the molecular weight of the polymer too high． Further studies aimed at controlling the polymerization rate and regulating the molecular weight of the poly-mers showed：(1) The rate of polymerization varies greatly with the solvents，the order of which being benzene> toluene > xylene > mesitylene．(2) Addition of phenyl一β-naphthylamine or N，N’-diphenyl-p-phenylene diamine lowers both the rate of polymerisa-tion and the molecular weight of the polymer．(3) The molecular weight of the poly- met can be regulated by controlling the water content in the system．(4) The molecular weight of the polymer can also be regulated by varying the ratio of the two components of a mixed solvent．(5) Addition of small amount of polynuclear hydrocarbons，such as naphthalene or anthracene to the heptane polymerization solution raised the molecular weight of the polymer to a considerable extent．The above results were discussed．
1963, 5(2): 60-64
Abstract:
Light scattering of a series of mixtures of two sharp fractions of polystyrene and polymethylmethacrylate in different proportions in toluene．and also of a sharp fraction of polystyrene in polymethyImethacrylate-toluene of different concentrations were inves-tigated．Since polymethylmethacrylate has equal refractive index as toluene，it will not contribute to the intensity of the scattered light from the solution． From the measure-ments of the light scattered at angles of 90°，45°and 135°，M>w and h2>z1/2 of polystyrene were calculated． Equal values of M>w and h2>z1/2 were obtained in all cases，while the slopes of the curves decrease steadily as the concentration of polymethyl-methacrylate in solution increased．The results indicate that the presence of polymethyl-methacrylate in the solution has no effect on (M)w and (h2)z1/2 of the polystyrene frac-tion.
Light scattering of a series of mixtures of two sharp fractions of polystyrene and polymethylmethacrylate in different proportions in toluene．and also of a sharp fraction of polystyrene in polymethyImethacrylate-toluene of different concentrations were inves-tigated．Since polymethylmethacrylate has equal refractive index as toluene，it will not contribute to the intensity of the scattered light from the solution． From the measure-ments of the light scattered at angles of 90°，45°and 135°，M>w and h2>z1/2 of polystyrene were calculated． Equal values of M>w and h2>z1/2 were obtained in all cases，while the slopes of the curves decrease steadily as the concentration of polymethyl-methacrylate in solution increased．The results indicate that the presence of polymethyl-methacrylate in the solution has no effect on (M)w and (h2)z1/2 of the polystyrene frac-tion.
1963, 5(2): 65-72
Abstract:
Thd polymerization of butadiene in benzene in the presence of titanium tetraiodide triisobutyl aluminium catalyst has been studied．It is found that the activity of this catalytic system depends upon the Al／Ti ratio and the temperature of polymerization．For each specified amount of titanium tetraiodide used，there iS a“critical Al／Ti ratio” at which the catalytic system displays highest activity，below which it shows no activity， and above which its activity decreases gradually (Fig．2)．Since the rate of polymerization can be lowered by increasing the AI／Ti ratio without suppression of ultimate conversion(Fig．3)，the polymerization reaction may be controlled with Al／Ti ratio to avoid“heat build—up”in the reaction mixture(Fig．4)．The advantage of this catalytic system is that whatever be the composition of the catalyst(e．g．Al／Ti)and the condition of polymerization (e．g．temperature)， no gel formation OCCURS and the cis-1，4-content of the polymer obtained always exceeds 90％ (Table 2)．The molecular weight(expressed as [n]) of the polymer depends upon two important factors，the amount of titanium tetraiodide used and the temperature of polymerization，with increasing either of which，the molecular weight decreases(Fig．5 and Fig．6)．The effect of AI／Ti on molecular weight is much less significant(Fig．6)． The molecular weight distribution of the polymer obtained with this catalyst is very narrow(Fig．7)．Therefore，it is presumed that the active sites may be of similar type，although the catalytic system itself is heterogeneous in character．
Thd polymerization of butadiene in benzene in the presence of titanium tetraiodide triisobutyl aluminium catalyst has been studied．It is found that the activity of this catalytic system depends upon the Al／Ti ratio and the temperature of polymerization．For each specified amount of titanium tetraiodide used，there iS a“critical Al／Ti ratio” at which the catalytic system displays highest activity，below which it shows no activity， and above which its activity decreases gradually (Fig．2)．Since the rate of polymerization can be lowered by increasing the AI／Ti ratio without suppression of ultimate conversion(Fig．3)，the polymerization reaction may be controlled with Al／Ti ratio to avoid“heat build—up”in the reaction mixture(Fig．4)．The advantage of this catalytic system is that whatever be the composition of the catalyst(e．g．Al／Ti)and the condition of polymerization (e．g．temperature)， no gel formation OCCURS and the cis-1，4-content of the polymer obtained always exceeds 90％ (Table 2)．The molecular weight(expressed as [n]) of the polymer depends upon two important factors，the amount of titanium tetraiodide used and the temperature of polymerization，with increasing either of which，the molecular weight decreases(Fig．5 and Fig．6)．The effect of AI／Ti on molecular weight is much less significant(Fig．6)． The molecular weight distribution of the polymer obtained with this catalyst is very narrow(Fig．7)．Therefore，it is presumed that the active sites may be of similar type，although the catalytic system itself is heterogeneous in character．
1963, 5(2): 73-76
Abstract:
Triethyltin maleate and fumarate were synthesi2ed and copolymerized with styrene and methyl methacrylate. Copolymers were obtained only when styrene was used.
Triethyltin maleate and fumarate were synthesi2ed and copolymerized with styrene and methyl methacrylate. Copolymers were obtained only when styrene was used.
1963, 5(2): 77-83
Abstract:
In this paper，further simplifications are suggested for the two-fraction method based on the solubility function and the treatment of fractionation data by using Tung functiorr which were proposed by the present authors in previous publications．The evaluation of the distribution parameters for a fraction from two intrinsic vis-cosity measurements in a good solvent and in a θ-solvent is shown to be not practical,because the required precision is not attainable in ordinary measurements． A new ap-proximation is suggested by taking the phase separation parameter Q to be equal to the volume ratio R of the concentrated and dilute phases．Then，the distribution para- meters for the two-fraction method can be readily evaluated． Actual calculations show that the distribution parameters thus calculated is not very sensitive to the value of Q taken，and therefore this approximation is iustified as a tentative simplification of the two．fraction method for the determination of molecular weight distributions．In the treatment of ordinary fractionation data by means of Tung function，all fractions except the first and the last ones can be approximated by a straight line for the integral distribution curve．The line passes through the points M (1＝1-2)＝Mn，M(1＝0)＝1-2Mn which corresponds roughly to a straight line with equal slope as the Tung function at M1-2 with b=2.7—3.0．This leads to a considerable saving in corn-putation but very slight difference to the result．The suggested simplifications have been applied to a sample of PMMA．The in-tegral distribution curve obtained by the suggested method are closer to the actual one obtained by sedmentation rate method than the usual Schulz-Dinlinger treatment．
In this paper，further simplifications are suggested for the two-fraction method based on the solubility function and the treatment of fractionation data by using Tung functiorr which were proposed by the present authors in previous publications．The evaluation of the distribution parameters for a fraction from two intrinsic vis-cosity measurements in a good solvent and in a θ-solvent is shown to be not practical,because the required precision is not attainable in ordinary measurements． A new ap-proximation is suggested by taking the phase separation parameter Q to be equal to the volume ratio R of the concentrated and dilute phases．Then，the distribution para- meters for the two-fraction method can be readily evaluated． Actual calculations show that the distribution parameters thus calculated is not very sensitive to the value of Q taken，and therefore this approximation is iustified as a tentative simplification of the two．fraction method for the determination of molecular weight distributions．In the treatment of ordinary fractionation data by means of Tung function，all fractions except the first and the last ones can be approximated by a straight line for the integral distribution curve．The line passes through the points M (1＝1-2)＝Mn，M(1＝0)＝1-2Mn which corresponds roughly to a straight line with equal slope as the Tung function at M1-2 with b=2.7—3.0．This leads to a considerable saving in corn-putation but very slight difference to the result．The suggested simplifications have been applied to a sample of PMMA．The in-tegral distribution curve obtained by the suggested method are closer to the actual one obtained by sedmentation rate method than the usual Schulz-Dinlinger treatment．
1963, 5(2): 84-90
Abstract:
The kinetic equation of polyesterification proposed by Tang is discussed from the view point of the medium effect on the ionization of weak acids，so that the ionization constant，Ke，of the reacting acid would not be a constant during the course of poly-condensation and consequently the 2 1/2 order kinetic equation would not be valid．Ex-perimental data show that Ke is actually a function of the extent of reaction．No ap-preciable conductivity is observed when the extent of reaction is over 0.65．Both the kinetic data of the present study and those of Flory for the polyesterification of ethy-lene glycol and adipic acid do not exactly follow the 2 1/2 order kinetic equation．
The kinetic equation of polyesterification proposed by Tang is discussed from the view point of the medium effect on the ionization of weak acids，so that the ionization constant，Ke，of the reacting acid would not be a constant during the course of poly-condensation and consequently the 2 1/2 order kinetic equation would not be valid．Ex-perimental data show that Ke is actually a function of the extent of reaction．No ap-preciable conductivity is observed when the extent of reaction is over 0.65．Both the kinetic data of the present study and those of Flory for the polyesterification of ethy-lene glycol and adipic acid do not exactly follow the 2 1/2 order kinetic equation．
1963, 5(2): 91-99
Abstract:
The permeability constants of both liquid water and water vapour through eleven polymer films have been measured at three temperatures by weighing method．The per-meation rate of liquid water in polyethylene，polycaprolactam，and polyethylene—tereph-thalate decreases gradually and approaches a limiting value owing to a change of structure in the polymer under the action of liquid water．The permeability constants of amor-phous polymers for both liquid water and saturated vapour are nearly the same at a given temperature，but the ratio of them increases slightly above unity with increasing temperature．In the case of crystalline polymers，the permeability constants for liquid water are several times greater than those for saturated vapour，suggesting the existence of viscous flow of the liquid water in the film．
The permeability constants of both liquid water and water vapour through eleven polymer films have been measured at three temperatures by weighing method．The per-meation rate of liquid water in polyethylene，polycaprolactam，and polyethylene—tereph-thalate decreases gradually and approaches a limiting value owing to a change of structure in the polymer under the action of liquid water．The permeability constants of amor-phous polymers for both liquid water and saturated vapour are nearly the same at a given temperature，but the ratio of them increases slightly above unity with increasing temperature．In the case of crystalline polymers，the permeability constants for liquid water are several times greater than those for saturated vapour，suggesting the existence of viscous flow of the liquid water in the film．
