Article pubs.acs.org/jced
Sorption of Benzene, Dichloromethane, and 2‑Butanone by Poly(methyl methacrylate), Poly(butyl methacrylate), and Their Copolymers at 323.15 K Using a Quartz Crystal Balance Howard C. Wong, Scott W. Campbell, and Venkat R. Bhethanabotla* Department of Chemical & Biomedical Engineering, University of South Florida, Tampa, Florida 33620-5350, United States ABSTRACT: Isothermal solubilities at 323.15 K of benzene, dichloromethane, and 2-butanone in poly(methyl methacrylate), poly(butyl methacrylate), and two different poly(methyl methacrylate)-poly(butyl methacrylate) copolymers are reported. Results were obtained for the concentrated polymer regime with a quartz crystal balance and are represented to within experimental error by a modified Flory−Huggins equation.
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INTRODUCTION As part of a continuing study of how the activities of solvents in solution with copolymers vary with the copolymer group composition, we report new sorption data at 323.15 K for benzene, dichloromethane, and 2-butanone in poly(butyl methacrylate) and two poly(methyl methacrylate)/poly(butyl methacrylate) [PMMA/PBMA] copolymers of different compositions. The data were obtained in the concentrated polymer regime, measured with the same quartz crystal balance used in previous studies.1−3 Results for these solvents with poly(methyl methacrylate) were reported previously3 and are included here for completeness. The activities of 2-butanone in poly(methyl methacrylate) at 321.65 K have been reported by Tait and Abushihada4 for 2butanone weight fractions of between approximately 0.03 and 0.6. Sé and Aznar5 measured vapor−liquid equilibria for benzene in poly(methyl methacrylate) at 303.15 and 313.15 K for solvent weight fractions between approximately 0.01 and 0.1. The activities of benzene in poly(butyl methacrylate) at 323.65 K were reported by Wohlfarth6 for solvent weight fractions of between approximately 0.3 and 0.5 and at 293.2 to 353.2 K by Wibabwa et al.7 for solvent weight fractions up to about 0.3. Activities in poly(butyl methacrylate) under conditions similar to those in ref 7 have been reported for 2-butanone8 and dichloromethane.9 Infinite dilution activity coefficients at temperatures of between 453 and 493 K have been reported by Tochigi et al.10 for benzene and 2-butanone in poly(methyl methacrylate), from 363 to 383 K by Hao et al.11 for benzene in poly(methyl methacrylate), and from 343 to 413 K by Hao et al.11 for dichloromethane and benzene in poly(butyl methacrylate). © XXXX American Chemical Society
The only related data located for these solvents in PMMA/ PBMA copolymers are the infinite dilution activity coefficients reported by Eser and Tihminlioglu12 for dichloromethane in the PMMA/PBMA(85:15) copolymer at temperatures of between 423 and 473 K.
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EXPERIMENTAL SECTION Materials. Poly(methyl methacrylate) and poly(butyl methacrylate) were obtained from Polysciences, Inc., with weight-averaged molecular weights of 185 000 and 250 000, respectively. PMMA/PBMA (75:25) is a copolymer of poly(methyl methacrylate) and poly(butyl methacrylate) that is 75 wt % poly(methyl methacrylate). It was obtained from Polysciences, Inc. PMMA/PBMA (40:60) is 40 wt % poly(methyl methacrylate) and was obtained from Rohm and Haas Company. Both copolymers had weight-averaged molecular weights of 250 000. Benzene, dichloromethane, and 2-butanone were of HPLC grade and were of 99.95% purity. They were obtained from Aldrich Chemical Co. and were degassed as described by Bhethanabotla and Campbell.13 No further purification was attempted. The quartz crystals that were used had a 5 MHz base frequency and were supplied by Crystek Corporation of Fort Myers, Florida. Apparatus and Procedure. The experimental apparatus and procedure have been described fully in an earlier publication.1 The basic measurement principle is that mass deposited on the surface of a piezoelectric quartz crystal induces a frequency shift in the crystal. Briefly, the polymer is coated onto a Received: July 9, 2016 Accepted: October 13, 2016
A
DOI: 10.1021/acs.jced.6b00612 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 1. Coefficients in the Vapor Pressure Equation (Equation 3) and Second Virial Coefficients B11 for the Solvents, Used in the Activity Calculations solvent
A
B
C
D
B11/cm3 mol−1
benzene dichloromethane 2-butanone
−6.98273 −7.36864 −7.71476
1.33213 1.76727 1.71061
−2.62863 −3.34295 −3.68770
−3.33399 −1.43530 −0.75169
−1292 −678 −1908
observed for any of the solvents in PBMA or the two PMMA/ PBMA copolymers. In this paper and the previous one,3 the sorption and desorption weight fractions, after verifying that there was no evidence of hysteresis, were averaged at equal activities. In two earlier papers,1,2 data were presented for each of the individual sorption/desorption runs. A statistical analysis of these data indicates that hysteresis was not evident for any of the data except possibly the first point (a1 = 0.527) of the toluene (1)poly(styrene) (2) system at 298.15 K. The solvent and sorption cell temperatures are maintained to ±0.01 and ±0.3 K, respectively. The uncertainty in solvent activity σa1 is1
quartz crystal and then exposed to solvent vapor at a known temperature and pressure. At equilibrium, the weight fraction w1 of solvent in the polymer is calculated from w1 =
Δf Δf + Δf0
(1)
where Δf 0 is the frequency shift due to the presence of the polymer coating and Δf is the additional frequency shift due to solvent sorption when the polymer is exposed to solvent vapor. For the measurements reported here, Δf 0 values ranged from 861 to 2693 Hz with an average value of 1600 Hz. Using a mass sensitivity of 5.65 × 106 m2/kg·s for the crystals employed here,1 the film thickness for the largest Δf 0 value quoted above is approximately 0.5 μm. Solvent vapor is generated in a cell maintained at a temperature below 323.15 K. The sorption cell, containing the polymer-coated crystal, is connected to the solvent cell via a heated line and is maintained at 323.15 K. In a sorption run, pressure is varied by increasing the temperature of the solvent cell while keeping the temperature of the sorption cell constant. In a desorption run, the temperature of the solvent cell is decreased at constant sorption cell temperature. At each point, the activity of the solvent in the polymer is calculated from ⎡ −B ⎤ P a1 = sat exp⎢ 11 (P1sat − P)⎥ ⎣ RT ⎦ P1
⎛ d ln P1sat ⎞ σa1/a1 = ⎜ σT ⎟ ⎝ dT ⎠323.15 K
where σT is the uncertainty in the sorption cell temperature. Values of the vapor pressure derivatives are similar for all three solvents, resulting in an approximately ±2% uncertainty in solvent activity. To within first order, the uncertainty σw1 in the solvent weight fraction can be derived from eq 1 and is
σw1 =
(2)
⎛ σΔf ⎜ + ⎝ Δf0
(
1+
where B11 is the second virial coefficient of the solvent at the sorption cell temperature (estimated using the Tsonopoulos14 correlation) and P and P1sat are the system pressure (solvent vapor pressure at the solvent cell temperature) and solvent vapor pressure at the sorption cell temperature, respectively. A pressure gauge in the system of 1 Torr resolution was used only to monitor for leaks. Values of P and P1sat needed for the calculation of activities were obtained from the Wagner equation ⎛P⎞ ln⎜ ⎟ = (1 − x)−1[Ax + Bx1.5 + Cx 3 + Dx 6] ⎝ PC ⎠
(4)
w1 σΔf0 ⎞ ⎟ 1 − w1 Δf0 ⎠ w1 1 − w1
2
)
(5)
where σΔf and σΔf 0 are uncertainties in Δf and Δf 0. Uncertainties in Δf varied by ±1 Hz at the lowest solvent weight fractions to ±5 Hz at the highest. Maximum uncertainties in Δf 0 were from 15 to 30 Hz. These uncertainties translate to a maximum uncertainty (for the worst case of Δf 0 = 861 Hz) of 0.01 in solvent weight fraction. As argued in our previous study,3 viscoelastic effects are expected to be negligible for the data reported here.
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(3)
RESULTS Solvent weight fractions in each of the two polymers and two copolymers are given as functions of solvent activity for benzene, dichloromethane, and 2-butanone in Tables 2, 3, and 4, respectively. Also shown in these tables is the number of sorption runs and desorption runs for each solvent + polymer system. All weight fractions given in these tables are averaged over all sorption and desorption data at equal solvent activities. Standard deviations in w1 values at a given activity were computed and then averaged over all points to obtain the average standard deviations shown in Tables 2−4. All of these standard deviations are within the experimental uncertainty in w1. The activities for 2-butanone in PMMA, reported previously,3 are in good agreement with those of Tait and Abushihada.4 For the case of PBMA, some additional comparisons can be made between the data reported here and those reported in the literature. Figure 1 shows the results of the present study (T = 323.15 K, Mw = 250 000) for benzene + PBMA, along with those
where x = 1 − (T/TC) and where TC and PC are the critical temperature and critical pressure of the solvent. The solvent cell temperature is used in eq 3 to obtain P, and the sorption cell temperature is used to obtain P1sat. Values for the second virial coefficients and the parameters in eq 3, taken from Reid et al.,15 are given in Table 1 for the solvents studied here. As noted in an earlier paper3 reporting the solubilities of these solvents in PMMA/PEMA copolymers, hysteresis, in which the sorption/desorption curves do not superimpose, was found to be an issue. Specifically, t tests comparing sorption and desorption runs indicated that hysteresis was evident for systems with homopolymer PMMA at solvent weight fractions below approximately 0.1. We believe this to be tied to the glassy nature of PMMA. These points were not included with the reported data as they do not represent an equilibrium state. On the other hand, no hysteresis was evident for any systems with PEMA or the copolymers. For the present study, no hysteresis was B
DOI: 10.1021/acs.jced.6b00612 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Table 2. Experimental Weight Fractions w1 of Benzene (1) in PMMA, PBMA, and PMMA-PBMA Copolymers (2) as a Function of Benzene Activity a1 at 323.15 K, the Number of Sorption and Desorption Runs, and the Average Standard Deviation in Measurements of w1
a1 0.139 0.172 0.222 0.283 0.340 0.408 0.485 0.528 0.575 0.624 0.675 0.731 0.792 sorption/desorption runs avg std devn in w1
Table 4. Experimental Weight Fractions w1 of 2-Butanone (1) in PMMA, PBMA, and PMMA-PBMA Copolymers (2) as a Function of 2-Butanone Activity a1 at 323.15 K, the Number of Sorption and Desorption Runs, and the Average Standard Deviation in Measurements of w1
PMMA
PMMA/PBMA (75:25)
PMMA/PBMA (40:60)
PBMA
w1
w1
w1
w1
a1
0.050 0.061 0.080 0.098 0.122 0.152 0.173 0.195 0.221 0.254 0.296
0.052 0.067 0.086 0.107 0.134 0.166 0.186 0.210 0.237 0.269 0.303
0.041 0.052 0.072 0.093 0.114 0.141 0.175 0.196 0.220 0.250 0.285 0.329
2/2
2/2
2/2
0.005
0.001
0.004
0.095 0.126 0.165 0.214 0.275 0.332 0.400 0.476 0.520 0.567 0.617 0.669 0.726 sorption/desorption runs avg std devn in w1
0.139 0.156 0.175 0.198 0.226 2/2 0.002
PMMA
PMMA/PBMA (75:25)
PMMA/PBMA (40:60)
PBMA
w1
w1
w1
w1
0.102 0.112 0.125 0.142 0.165 0.193 2/2
0.029 0.039 0.051 0.066 0.083 0.105 0.120 0.135 0.153 0.180 0.211 3/0
0.020 0.025 0.034 0.045 0.058 0.072 0.090 0.114 0.128 0.146 0.166 0.193 0.223 2/2
0.017 0.023 0.031 0.040 0.053 0.067 0.085 0.109 0.123 0.141 0.163 0.188 4/1
0.002
0.003
0.002
0.001
Table 3. Experimental Weight Fractions w1 of Dichloromethane (1) in PMMA, PBMA, and PMMA-PBMA Copolymers (2) as a Function of Dichloromethane Activity a1 at 323.15 K, the Number of Sorption and Desorption Runs, and the Average Standard Deviation in Measurements of w1
a1 0.142 0.179 0.224 0.278 0.342 0.415 0.501 0.539 0.602 0.669 0.715 0.766 0.819 sorption/desorption runs avg std devn in w1
PMMA
PMMA/PBMA (75:25)
PMMA/PBMA (40:60)
w1
w1
w1
w1
0.074 0.093 0.114 0.140 0.173 0.216 0.268 0.293 0.336 0.387 0.428 0.470
0.074 0.096 0.118 0.148 0.184 0.228 0.281 0.307 0.350 0.400 0.438 0.478
0.074 0.094 0.118 0.149 0.185 0.229 0.283 0.311 0.354 0.404 0.437 0.469
2/2
2/2
2/2
0.004
0.002
0.001
0.089 0.105 0.126 0.157 0.195 0.245 0.279 0.304 0.330 0.354 3/3 0.006
PBMA
Figure 1. Cross-study comparison of activities a1 of benzene (1) in PBMA as a function of benzene weight fraction w1. ■ = present study, 323.15 K; ⧫ = Wohlfarth,6 323.65 K; ▲ = Wibawa et al.,7 313.2 K; and ● = Wibawa et al.,7 333.2 K.
reported by Wohlfarth6 at 323.65 K (Mw = 73 600) and by Wibawa et al.7 at 313.2 and 333.2 K (Mw = 337 000), which bracket the temperature of the present study. The results of the latter suggest that the temperature dependence of activity on weight fraction is weak, and good agreement is observed among all data sets. Figure 2 compares the results of the present study for 2butanone + PBMA to those reported by Wibawa et al.8 at the same temperature and polymer molecular weight conditions as for benzene. Again, the temperature dependence is weak, and agreement between the two investigations is excellent.
Figure 3 compares the results of the present study for dichloromethane + PBMA to those reported by Wibawa et al.9 at the same temperature and polymer molecular weight conditions as for benzene and 2-butanone. Here, the temperature dependence suggested by the latter study is much larger than for the other two systems under comparison, and the activities reported by the two investigations are not in agreement. The dashed line in Figure 3 was obtained using the Flory− Huggins model with a χ parameter obtained by linear extrapolation of the infinite dilution activity coefficients reported by Hao et al.11 Specifically, weight-based infinite dilution activity C
DOI: 10.1021/acs.jced.6b00612 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Assuming this relationship could be extrapolated to 323.15 K, the value so calculated was related to the Flory−Huggins χ parameter through ⎛ M ⎞ 1 χ = ln⎜Ω1∞ 1 r ⎟ − 1 + M2 ⎠ r ⎝
(7)
where M1 and M2 are the molecular weights of the solvent and polymer, respectively, and r is the ratio of molar volumes V2/V1. This value of χ (−0.06) was then used in the Flory−Huggins equation to generate the dashed line in Figure 3. Although the comparison to the data is imperfect, in that it assumes a thermodynamic model and involves an extrapolation over temperature, it suggests that the results reported here are conformal with infinite dilution activity coefficients measured at higher temperatures. Data Correlation. As in our previous investigation,3 experimental solvent activities were fitted to a modification of the Flory−Huggins activity model in which the χ parameter is assumed to be a linear function of the volume fraction. Hence, the Gibbs excess energy is given by Φ Φ NGE = N1 ln 1 + N2 ln 2 + Φ1Φ2(N1 + rN2)[A Φ1 + BΦ2] RT X1 X2 (8)
Figure 2. Cross-study comparison of activities a1 of 2-butanone (1) in PBMA as a function of 2-butanone weight fraction w1. ■ = Present study, 323.15 K; ▲ = Wibawa et al.,8 313.2 K; and ● = Wibawa et al.,8 333.2 K.
where Ni represents the number of moles, Xi represents the mole fractions, and Φi represents the volume fractions of the solvent and polymer for i = 1 and 2. The variable r is the ratio of molar volumes, V2/V1, and A and B are constants that are obtained by fitting experimental data. We do not ascribe any theoretical significance to this modification of the Flory−Huggins equation. Our interest here is simply in providing an algebraic representation that describes the data to within experimental uncertainty, and the modification is entirely analogous to using a higher-order Margules or Redlich−Kister expansion (when needed) to fit VLE data for solvent mixtures to within experimental uncertainty. In eq 8, the volume fraction of component i is expressed as Φi =
VX i i ∑j VjXj
(9)
Molar volumes of the homopolymers were evaluated at 323.15 K using reported values of the density and thermal expansion coefficient for PMMA16 and the reported density for PBMA.16 For the copolymers, specific volumes were assumed to be a weight fraction average of those of pure PMMA and PBMA and were converted to molar volumes using the given molecular weights. The modified Rackett equation17 was used to obtain molar volumes of the solvents. For convenience, the molecular weights and molar volumes of all species are given in Table 5. Figure 3. Cross-study comparison of activities a1 of dichloromethane (1) in PBMA as a function of dichloromethane weight fraction w1. ■ = present study, 323.15 K; ⧫ = Wibawa et al.,9 313.2 K; and ● = Wibawa et al.,9 333.2 K. The dashed line is the Flory−Huggins model with the χ parameter obtained from infinite dilution activity coefficients reported by Hao et al.11
Table 5. Molecular Weights Mi and Molar Volumes Vi of Solvents and Polymers
coefficients for dichloromethane in PBMA in the temperature range of 343 to 413 K were fitted to within an average deviation of 3% to the following equation: Ω1∞ = 0.0104T (K) − 1.376
(6) D
species i
Mi/g mol−1
Vi/cm3 mol−1
benzene dichloromethane 2-butanone PMMA PMMA/PBMA (75:25) PMMA/PBMA (40:60) PBMA
78.11 84.93 72.11 185 000 250 000 250 000 250 000
92.41 64.44 93.23 156 800 220 100 231 500 244 600
DOI: 10.1021/acs.jced.6b00612 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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The expression for solvent activity a1, derived from eqs 8 and 9, is ⎡ 1⎤ ln a1 = ln(Φ1) + ⎢1 − ⎥Φ2 + [2(A − B)Φ1 + B]Φ2 2 ⎣ r⎦ (10)
Parameters A and B are determined by minimizing the sum of the squares of the differences between experimental and calculated activities. In these calculations, experimental weight fractions are converted to volume fractions using M
Φ1 =
w1 V 2 2
M1 V1
−
(
M w1 V1 1
−
M2 V2
)
(11)
Values of A and B for each solvent + polymer pair are shown in Table 6, along with resulting average deviations between Table 6. Parameters for Use in the Modified Flory−Huggins Equation (Equation 10)a B
χ
system
A
benzene(1)-PMMA benzene(1)-PMMA/ PBMA (75:25) benzene(1)-PMMA/ PBMA (40:60) benzene(1)-PBMA dichloromethane(1)PMMA dichloromethane(1)PMMA/PBMA (75:25) dichloromethane(1)PMMA/PBMA (40:60) dichloromethane(1)PBMA 2-butanone(1)-PMMA 2-butanone(1)PMMA/PBMA (75:25) 2-butanone(1)PMMA/PBMA (40:60) 2-butanone(1)-PBMA
0.791 0.219
0.305 0.107
0.0002 0.002
0.531 0.156
0.007 0.002
0.216
0.048
0.001
0.124
0.003
0.158 0.715
0.069 0.081
0.001 0.003
0.109 0.362
0.006 0.018
0.037
−0.130
0.002
−0.045
0.005
0.039
−0.144
0.001
−0.050
0.006
0.104
−0.102
0.003
0.001
0.007
0.598 0.448
0.414 0.446
0.002 0.001
0.487 0.447
0.003 0.001
0.493
0.364
0.001
0.410
0.002
0.445
0.521
0.001
0.498
0.001
avg dev
avg dev
Figure 4. Experimental activities a1 of benzene (1) in PMMA, PBMA, and PMMA-PBMA copolymers (2) as a function of benzene weight fraction w1 at 323.15 K. ⧫ = PMMA, ■ = PMMA/PBMA (75:25), ▲ = PMMA/PBMA (40:60), ● = PBMA. Solid curves are from the fits of eq 10.
a
avg dev is the average deviation between experimental values of w1 and those calculated from eq 10. Also shown are the parameter and resulting average deviation for A = B = χ.
experimental and calculated values of weight fraction w1. Comparisons of experimental activities with those computed from eq 10 are shown in Figures 4−6. The representation of weight fraction is to within experimental uncertainty in all cases. It can be seen from Figures 4−6 that the weight fractions of solvents in the copolymers are typically between those in the two homopolymers at equal activity. An exception occurs for dichloromethane in that the solvent weight fractions in PMMA/PBMA 40:60 are almost identical to those in the PBMA homopolymer. We have also fit the experimental activities to the Flory− Huggins equation, which is obtained from eq 10 by setting A = B and calling the single parameter χ. Values of χ are provided in Table 6 along with resulting average deviations and indicate that solutions of PMMA-PBMA with 2-butanone very nearly follow the Flory−Huggins model. However, solutions with benzene and dichloromethane, particularly for homopolymer PMMA, are not
Figure 5. Experimental activities a1 of dichloromethane (1) in PMMA, PBMA, and PMMA-PBMA copolymers (2) as a function of dichloromethane weight fraction w1 at 323.15 K. ⧫ = PMMA, ■ = PMMA/ PBMA (75:25), ▲ = PMMA/PBMA (40:60), and ● = PBMA. Solid curves are from the fits of eq 10.
as well described by the Flory−Huggins model, and a number of data cannot be fit to within experimental error. An indication of this is given by the representation in Figure 3 of dichloromethane and PBMA by the Flory−Huggins model, where it can be seen that a value of χ that provides a good representation of activity E
DOI: 10.1021/acs.jced.6b00612 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
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Article
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Wong, H. C.; Campbell, S. W.; Bhethanabotla, V. R. Sorption of Benzene, Toluene and Chloroform by Poly(styrene) at 298.15 and 323.15 K using a Quartz Crystal Balance. Fluid Phase Equilib. 1997, 139, 371−389. (2) Wong, H. C.; Campbell, S. W.; Bhethanabotla, V. R. Sorption of Benzene, Tetrahydrofuran and 2-Butanone by Poly(vinyl acetate) at 323.15 K using a Quartz Crystal Balance. Fluid Phase Equilib. 2001, 179, 181−191. (3) Wong, H. C.; Campbell, S. W.; Bhethanabotla, V. R. Sorption of Benzene, Dichloromethane, n-Propyl Acetate, and 2-Butanone by Poly(methyl methacrylate), Poly(ethyl methacrylate) and their Copolymers at 323.15 K Using a Quartz Crystal Balance. J. Chem. Eng. Data 2011, 56, 4772−4777. (4) Tait, P. J. T.; Abushihada, A. M. Comparative Studies on the Use of Gas Chromatographic and Vapour Pressure Techniques for the Determination of Interaction Energy Parameter. Polymer 1977, 18, 810−816. (5) Sé, R.A. G.; Aznar, M. Vapor-Liquid Equilibrium of Polymer + Solvent Systems: Experimental Data and Thermodynamic Modeling. Polymer 2007, 48, 5646−5652. (6) Wohlfarth, C. Vapour-Liquid Equilibrium Data of Binary Polymer Solutions: Vapour Pressures, Henry-Constants and Segment-Molar Excess Gibbs Free Energies; Physical Science Data 44; Elsevier: Amsterdam, 1994. (7) Wibawa, G.; Takahashi, M.; Sato, Y.; Takishima, S.; Masuoka, H. Solubility of Seven Nonpolar Organic Solvents in Four Polymers Using the Piezoelectric-Quartz Sorption Method. J. Chem. Eng. Data 2002, 47, 518−524. (8) Wibawa, G.; Hatano, R.; Sato, Y.; Takishima, S.; Masuoka, H. Solubility of 11 Polar Organic Solvents in Four Polymers Using the Piezoelectric-Quartz Sorption Method. J. Chem. Eng. Data 2002, 47, 1022−1029. (9) Wibawa, G.; Khoiroh, I.; Afrizal, D.; Suki, G. Solubilities of Dichloromethane, Diethyl Ether, Ethyl Acetate, and Nitrobenzene in Three Polymers Using the Piezoelectric Quartz Sorption Method. J. Chem. Eng. Data 2010, 55, 5581−5586. (10) Tochigi, K.; Kurita, S.; Okitsu, Y.; Kurihara, K.; Ochi, K. Measurement and Prediction of Activity Coefficients of Solvents in Polymer Solutions using Gas Chromatography and a Cubic-Perturbed Equation of State with Group Contribution. Fluid Phase Equilib. 2005, 228−229, 527−533. (11) Hao, W.; Elbro, H. S.; Alessi, P. Polymer Solution Data Collection; Chemistry Data Series; DECHEMA: Frankfurt, Germany, 1992; Vol. 14, Part 2. (12) Eser, H.; Tihminlioglu, F. Solubility and diffusivity of solvents and nonsolvents in poly(methyl methacrylate co butyl methacrylate). Fluid Phase Equilib. 2005, 237, 68−76. (13) Bhetanabotla, V. R.; Campbell, S. W. P-x Measurements for Ethanol - n-Heptane - Isobutanol at 303.15 K. Fluid Phase Equilib. 1991, 62, 239−258. (14) Tsonopoulos, C. An Empirical Correlation of Second Virial Coefficients. AIChE J. 1974, 20, 263−272. (15) Reid, R. C.; Prausnitz, J. M.; Poling, B. W. The Properties of Gases and Liquids, 4th ed.; McGraw-Hill: New York, 1987. (16) Brandrup, J., Immergut, E. H., Eds. Polymer Handbook, 3rd ed., Wiley Interscience: New York, 1989. (17) Spencer, C. F.; Danner, R. P. Improved Equation for Prediction of Saturated Liquid Density. J. Chem. Eng. Data 1972, 17, 236−241.
Figure 6. Experimental activities a1 of 2-butanone (1) in PMMA, PBMA, and PMMA-PBMA copolymers (2) as a function of 2-butanone weight fraction w1 at 323.15 K. ⧫ = PMMA, ■ = PMMA/PBMA (75:25), ▲ = PMMA/PBMA (40:60), and ● = PBMA. Solid curves are from the fits of eq 10.
behavior at low solvent composition does not do so at the higher solvent compositions.
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CONCLUSIONS The solvent weight fraction as a function of solvent activity at 323.15 K is reported for benzene, dichloromethane, and 2butanone in poly(methyl methacrylate), poly(butyl methacrylate), and two different poly(methyl methacrylate)-poly(butyl methacrylate) copolymers. The data are represented by a modified Flory−Huggins model to within experimental uncertainties. Agreement with literature data for solvent activities in the two homopolymers is generally good, and trends in solvent solubility with copolymer composition are evident. In particular, for PMMA-PBMA with benzene and with dichloromethane, the activities of solvents in the copolymers are much closer (at the same weight fraction) to the activities of the solvents in the PBMA homopolymer (and further from those in the PMMA homopolymer) than would be expected simply by considering the copolymer composition. On the other hand, the variation of solvent activity of 2-butanone with copolymer composition is more closely proportional. This mirrors behavior reported earlier3 for the activities of these solvents in PMMA-PEMA copolymers. The data reported here comprise the fourth of five studies in this series of publications. The first two papers1,2 reported solubilities of solvents in single homopolymers, and the third3 and fourth reported solubilities of solvents in copolymers of various composition and in their corresponding homopolymers. We plan to present results for the solubilities of benzene, dichloromethane, and n-propyl acetate in PMMA, polystyrene, and their copolymers in the near future. All measurements in the series were obtained using the static apparatus described here. Other solvent−copolymer systems are currently being investigated in our laboratory using a flow apparatus. F
DOI: 10.1021/acs.jced.6b00612 J. Chem. Eng. Data XXXX, XXX, XXX−XXX
