Dependence of flory-Huggins ? parameters on the copolymer composition for solutions of poly(methyl methacrylate-ran-n-butyl methacrylate) in cyclohexanone
Abstract:Intermolecular interactions in random copolymer systems depend on the copolymer composition as being observed as a miscibility window in the random copolymer blends. The copolymer composition dependencies of the Flory‐Huggins χ parameter and the heats of mixing ▵HM(∞) at infinite dilution were studied for the solutions of poly(methyl methacrylate‐ran‐n‐butyl methacrylate) (MMAnBMA) in cyclohexanone (CHN). The copolymer composition dependencies of χ obtained from osmotic pressures and of ▵HM(∞) measured with a … Show more
“…The experimental results of χ for the copolymer solutions in CHN determined from osmotic pressures at 25 °C by use of eq 29 are summarized in Table . In Figure is shown the dependence of χ on the core volume fraction of polymer, together with the results for the solutions of the homopolymers PMMA and PnBMA obtained in the previous work . The dashed lines in Figure are experimental ones which are given by the following equations: The parameters χ 1 defined as are plotted against the copolymer composition in Figure . 2 Dependence of interaction parameter χ on the core volume fraction φ 2 of polymer in CHN at 25 °C.…”
Section: Resultsmentioning
confidence: 78%
“…The surface ratios s j / s i , in many cases, have been determined from the molecular models represented by a cylinder for polymers and a sphere for solvents 28 or from the van der Waals radius and surface obtained from Bondi's table . The surface ratio s j / s i mainly affects the trend of χ with concentration. , In our previous work, the slope of the χ vs concentration curve calculated for CHN/PMMA and CHN/PnBMA did not reproduce well the experimental one generated by use of the surface area obtained from Bondi's table. In this work, therefore, s iBMA / s CHN was arbitrarily chosen to reproduce the slope of the φ 2 −χ curve in Figure e, using the values of X CHN/iBMA and c CHN/iBMA shown in Table .…”
Section: Resultsmentioning
confidence: 83%
“…The characteristic pressure p * for PiBMA was determined from γ estimated according to the group contribution method proposed by Manzini and Crescenzi . The characteristic parameters for PMMA and PnBMA were obtained using the same method as in the previous work …”
The Flory interaction parameters χ for blends of random
copolymers consisting of binary
combinations of methyl methacrylate (MMA), n-butyl
methacrylate (nBMA), and isobutyl methacrylate
(iBMA) monomers were calculated using the Flory equation-of-state
theory with modified combining rules
extended to random copolymer systems. In order to determine the
intersegmental or intermolecular
parameters necessary for the calculation of χ for the blends, osmotic
pressures, heats of mixing at infinite
dilution, and excess volumes of mixing for solutions of the
methacrylate random copolymers in
cyclohexanone were measured, and the equation-of-state theory was
applied to these solutions. Using
the intersegmental parameters thereby determined, the theory gives
U-shaped curves for the temperature
dependence of χ for the blends. Namely, the theory shows that
miscibility of these polymer blends is of
the upper critical solution temperature type, which is consistent with
the miscibility results obtained
experimentally in our previous work. The interaction parameters
χ calculated for PiBMA/PnBMA were
much smaller than those for PMMA/PiBMA and PMMA/PnBMA. This result
is also consistent with the
experimental results of miscibility. The calculated χ parameters
were compared with those evaluated
using two other methods, i.e., from the dependence of miscibility on
the copolymer composition of the
random copolymer blends and from the osmotic pressures for the random
copolymer solutions. It was
found that the χ values obtained using all three methods were nearly
the same.
“…The experimental results of χ for the copolymer solutions in CHN determined from osmotic pressures at 25 °C by use of eq 29 are summarized in Table . In Figure is shown the dependence of χ on the core volume fraction of polymer, together with the results for the solutions of the homopolymers PMMA and PnBMA obtained in the previous work . The dashed lines in Figure are experimental ones which are given by the following equations: The parameters χ 1 defined as are plotted against the copolymer composition in Figure . 2 Dependence of interaction parameter χ on the core volume fraction φ 2 of polymer in CHN at 25 °C.…”
Section: Resultsmentioning
confidence: 78%
“…The surface ratios s j / s i , in many cases, have been determined from the molecular models represented by a cylinder for polymers and a sphere for solvents 28 or from the van der Waals radius and surface obtained from Bondi's table . The surface ratio s j / s i mainly affects the trend of χ with concentration. , In our previous work, the slope of the χ vs concentration curve calculated for CHN/PMMA and CHN/PnBMA did not reproduce well the experimental one generated by use of the surface area obtained from Bondi's table. In this work, therefore, s iBMA / s CHN was arbitrarily chosen to reproduce the slope of the φ 2 −χ curve in Figure e, using the values of X CHN/iBMA and c CHN/iBMA shown in Table .…”
Section: Resultsmentioning
confidence: 83%
“…The characteristic pressure p * for PiBMA was determined from γ estimated according to the group contribution method proposed by Manzini and Crescenzi . The characteristic parameters for PMMA and PnBMA were obtained using the same method as in the previous work …”
The Flory interaction parameters χ for blends of random
copolymers consisting of binary
combinations of methyl methacrylate (MMA), n-butyl
methacrylate (nBMA), and isobutyl methacrylate
(iBMA) monomers were calculated using the Flory equation-of-state
theory with modified combining rules
extended to random copolymer systems. In order to determine the
intersegmental or intermolecular
parameters necessary for the calculation of χ for the blends, osmotic
pressures, heats of mixing at infinite
dilution, and excess volumes of mixing for solutions of the
methacrylate random copolymers in
cyclohexanone were measured, and the equation-of-state theory was
applied to these solutions. Using
the intersegmental parameters thereby determined, the theory gives
U-shaped curves for the temperature
dependence of χ for the blends. Namely, the theory shows that
miscibility of these polymer blends is of
the upper critical solution temperature type, which is consistent with
the miscibility results obtained
experimentally in our previous work. The interaction parameters
χ calculated for PiBMA/PnBMA were
much smaller than those for PMMA/PiBMA and PMMA/PnBMA. This result
is also consistent with the
experimental results of miscibility. The calculated χ parameters
were compared with those evaluated
using two other methods, i.e., from the dependence of miscibility on
the copolymer composition of the
random copolymer blends and from the osmotic pressures for the random
copolymer solutions. It was
found that the χ values obtained using all three methods were nearly
the same.
“…All experimental data of the copolymer solutions of present interest in either toluene or in chloroform 3 can be modeled quantitatively by means of eqn (1). Only two parameters need to be adjusted, because k is given by the molar masses of the components (eqn (2)) and c can be set zero.…”
Section: Theoretical Backgroundmentioning
confidence: 99%
“…Only little experimental material can be found on this matter in the literature. [1][2][3] An early work 1 deals with the system cyclohexanone/poly(methyl methacrylate-ran-n-butyl methacrylate) and uses osmotic and caloric measurements up to a maximum of 27 wt% polymer. The authors describe and discuss their results in terms of the classical Flory-Huggins theory extended to multicomponents.…”
The interaction of toluene with P(MMA-ran-t-BMA) and with the corresponding homopolymers was determined via vapor pressure measurements at 30, 50 and 70 °C. A unified thermodynamic approach served for the modeling of the results. It is capable of describing the behavior of the different solutions by means of two adjustable parameters, one representing the effective number of solvent segments and the other accounting for the interactions between the components. The solvent quality of toluene passes a maximum, a minimum and another maximum upon an increase of the t-BMA content of the copolymer at all temperatures. A similar behavior is discernable from vapor pressure data of chloroform published for the same copolymers. The heats of mixing for toluene depend strongly on temperature; at 50 °C they are all endothermal with the exception of PMMA, for which the value obtained from vapor pressures at 30 °C agrees very well with published caloric data.
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