brominated polystyrene by viscometry

EUROPEAN POLYMER JOURNAL

European Polymer Journal 42 (2006) 311–315

www.elsevier.com/locate/europolj

Miscibility studies on blends of poly(phenylene oxide)/brominated polystyrene by viscometry A.Z. Aroguz a

a,*

, B.M. Baysal

b,c

Department of Chemistry, Faculty of Engineering, Istanbul University, 34850 Avcilar, Istanbul, Turkey b Department of Chemical Engineering, Bogazici University, 80815 Bebek, Istanbul, Turkey c TUBITAK–Marmara Research Center, PK 21, 41470 Gebze, Istanbul, Turkey Received 16 May 2005; received in revised form 8 July 2005; accepted 13 July 2005 Available online 31 August 2005

Abstract The viscosity behavior of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), brominated polystyrene (PBrS) and their blends at several compositions (25/75, 50/50, 75/25, 85/15) has been studied. The miscibility of this polymer system was investigated on the basis of the sign of the criteria Db, a, DK, l, and D[g] determined by viscosity. These investigations indicate that PPO/PBrS is miscible at the compositions of (75/25), (85/15) and completely immiscible at the compositions of (25/75), (50/50) in chloroform at 20
C. Results from viscometry match very well those of DSC results cited in the literature.  2005 Elsevier Ltd. All rights reserved. Keywords: Blends; Poly(phenylene oxide); Brominated polysytrene; Viscometry; Intrinsic viscosity; Miscibility

1. Introduction In recent years, there is growing interest in modifying the existing polymers rather than synthesizing new polymers [1]. These modifications are copolymers, composites, and polymer blends [2–4]. The mixture of two or more polymers depends on the properties of its polymeric components, its compositions and the miscibility of the polymers. Many experimental and theoretical methods have been used to investigate the polymer– polymer miscibility. Some of the most important techniques for polymer–polymer miscibility are thermal

* Corresponding author. Tel.: +90 216 473 70 33; fax: +90 216 473 71 80. E-mail address: [email protected] (A.Z. Aroguz).

analysis [5,6], electron microscopy [7], dynamic mechanical studies [4,8] and viscometric techniques [9,10]. The viscometric measurements provide an effective, quick and inexpensive technique to investigate polymer–polymer interaction. Therefore this technique is used for many polymer pairs to determine their miscibility [3–5, 9–15]. There are many criteria proposed by researches to determine polymer–polymer miscibility by viscometry such as the plot of reduced viscosity vs. composition, interaction parameter l, thermodynamic parameter a [12,13]. In the present work, the miscibility behavior of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), brominated polystyrene (PBrS), and their blends has been studied using a viscometric method. Various criteria and parameters were calculated to discuss the miscibility of these polymers in different compositions. The results

0014-3057/$ - see front matter  2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2005.07.012

312

A.Z. Aroguz, B.M. Baysal / European Polymer Journal 42 (2006) 311–315

obtained by viscometry were compared with our earlier DSC results for this polymeric system [16].

2. Theoretical The plot, the reduced viscosity vs. concentration of polymer follows the linear relationship given by the Huggins equation [17]. gsp =c ¼ ½g
þ bc

ð1Þ

where gsp denotes specific viscosity, and c is mass concentration of solution, [g] is the intrinsic viscosity. b is related to the Huggins coefficient k, reflects the binary interactions between polymer segments. b ¼ k½g
2

ð8Þ

id0 Db0 ¼ bexp 12  b12

ð9Þ

If Db > 0 or Db 0 > 0, there exist attractive intermolecular interactions and miscibility in binary polymeric systems. Whereas Db < 0 or Db 0 < 0 indicates the phase separation. Recently, Sun et al. [13] proposed another criterion, a, for polymer–polymer miscibility in terms of a thermodynamic parameter. The sign of a indicates the attractive (a > 0) or repulsive (a < 0) interaction between polymer segments. The zero value of a indicates no attraction. a ¼ Km 

k 1 w21 ½g
21 þ 2ðk 1 k 2 Þ1=2 w1 w2 ½g
1 ½g
2 þ k 2 w22 ½g
22 ðw1 ½g
1 þ w2 ½g
2 Þ2 ð10Þ

ð2Þ

The values of b and [g] were determined from the slope and intercept of the plots gsp/c vs. c for the polymers and their blend compositions using linear fit. Eqs. (1) and (2) can be adapted to a polymer (1)/polymer (2)/solvent system. gspm =ðc1 þ c2 Þ ¼ ½g
m þ bm ðc1 þ c2 Þ

ð3Þ

bm ¼ k m ½gm
2

ð4Þ

Subscripts 1, 2 and m correspond to polymer 1, 2 and their blends, respectively. Theoretically, bm(c1 + c2) reflects the total molecular interaction. It is composed of three terms: b11 c21 , b22 c22 and 2b12c1c2 corresponding to polymer (1)–solvent, polymer (2)–solvent, polymer (1)–polymer (2) interactions, respectively. As described by Krigbaum and Wall, the information on the intermolecular interaction in binary polymer blends, (polymer 1 and polymer 2) can be obtained from a comparison of experimental interaction coefficient bexp 12 and the theoretical values bid 12 [18]. id Db ¼ bexp 12  b12

ð5Þ

The ideal interaction coefficient, mers can be expressed as 1=2 bid 12 ¼ ðb11 b22 Þ

Experimental equation:

bid0 12 ¼ ðb11 þ b22 Þ=2

bexp 12

bid 12

between two polyð6Þ

values were estimated by the following

exp 2 2 bexp m ¼ w1 b11 þ w2 b22 þ 2w1 w2 b12

ð7Þ

The terms w1, w2 indicate the weight fraction of the components (1) and (2), and b11, b22 are the slopes of viscosity curves for the pure components (1) and (2), respectively. bexp m values were obtained from the slope of Eq. (3). Catsiff and Hewett have proposed to define the ideal value of interaction parameter, bid 12 as the arithmetic mean value [19].

where Km ¼

k 1 w21 ½g
21 þ 2k 12 w1 w2 ½g
1 ½g
2 þ k 2 w22 ½g
22 ðw1 ½g
1 þ w2 ½g
2 Þ2

ð11Þ

By substituting Eq. (11) into Eq. (10), this criterion can be written in the following form [10]: b¼

2DKw1 w2 ½g
1 ½g
2 ðw1 ½g
1 þ w2 ½g
2 Þ2

ð12Þ

where DK ¼ k 12  ðk 1 k 2 Þ1=2

ð13Þ

and k 1 ¼ b11 =½g
21

ð14Þ

k 2 ¼ b22 =½g
22 k 12 ¼ bm =½g
2m

ð15Þ ð16Þ

The parameter b is a function of g, w, and DK. Similarly, b P 0 signifies miscibility whereas b < 0 indicates immiscibility. In addition Garcia et al. have proposed another miscibility criterion which is based on the difference between the experimental and ideal values of [g]m [20]. id D½g
¼ ½g
exp miscible m  ½g
m < 0 and D½g
> 0 is immiscible

ð17Þ

½g
exp m

The value of was obtained from the intercept of the plot according to Eq. (3) and ½g
id m was calculated by the following relation: ½g
id m ¼ ½g
1 w1 þ ½g
2 w2

ð18Þ

Using the value Db 0 given in Eq. (9) a more effective parameter l is obtained to predict polymer–polymer miscibility [21]. l ¼ Db0 =ð½g
1  ½g
2 Þ2

ð19Þ

A.Z. Aroguz, B.M. Baysal / European Polymer Journal 42 (2006) 311–315

313

l P 0 and l < 0 values show miscibility and immiscibility, respectively. 0.60

Two polymers have been used in this work. Poly(2,6dimethyl-1,4-phenylene oxide) (PPO) was purchased from Polysciences, Inc. (Warrington, PA, USA; Mw = 50 · 103 g mol1, Mn = 20 · 103 g mol1; high softening point, 90
C). Brominated polystyrene (PBrS) was also purchased from Polysciences, Inc. Gel permeation results of this polymer were Mw = 63 · 103 g mol1, and Mn = 19 · 103 g mol1. These polymers were used as received without further purification. The blends of PPO/ PBrS of different compositions (25/75), (50/50), (75/25) (85/15) have been prepared by mixing solutions of the polymers in chloroform. The relative viscosity of polymer solutions in chloroform was measured by using the Ubbelohde-type viscometer immersed in a constant temperature bath at 20.0 ± 0.1
C. Stock solutions of each system were prepared and diluted to yield five lower concentrations made by adding appropriate amount of chloroform to the stock solutions. For each measurement 25 ml solution was introduced into viscometer.

4. Results and discussion The plots of reduced viscosity ([g]sp/c) vs. concentration (c) for pure polymers and their blends in different weight fractions are shown in Fig. 1. The linear relationships are observed for the pure polymers and for all of the polymer mixtures (PPO/PBrS) over whole composition range. The bexp m values are calculated from the slopes of the experimental lines in Fig. 1. The parameters Db, Db 0 computed using Eqs. (1)–(9) are given in Table 1. For the compositions of (85/15) and (75/25) of the (PPO/PBrS) blends the interaction constant bexp 12 is greater than ideal values obtained by (b11b22)1/2 (0.0999) or [(b11 + b22)/2] (0.1301) exhibit positive deviation. According to these criteria this system is miscible for these compositions. The values of the miscibility parameters a, DK, and l were calculated by using Eqs. (10), (13) and (19), respectively and given in Table 2. The plots of the above miscibility parameters against weight fraction of PPO in the mixtures are illustrated in Fig. 2. The viscometric studies show that a, DK, and l values are positive for the weight fractions (85/15) and (75/25) of the PPO/PBrS mixtures. Negative values of the above parameters were calculated for (25/75) and (50/50) weight fractions of the mixtures. Based on the experimentally observed [g] for the binary (polymer/solvent) and ternary (polymer1/polymer2/ solvent) systems, the parameters of the compatibility

ηsp/c

3. Experimental

0.40

0.20

0.00 0.00

0.40

0.80

1.20

concentration (g/100ml)

Fig. 1. Reduced viscosity values of pure polymers of PPO and PBrS and their mixtures (PPO/PBrS) against concentrations. (j) 100/0, (*) 85/15, (+) 75/25, (r) 50/50, (m) 25/75 and (d) 0/100.

Table 1 Observed and calculated polymer–polymer interaction coeffi0 cient bexp 12 and parameters Db , Db, for PPO/PBrS blends PPO/PBrs

bexp m

bexp 12

Db

Db 0

Miscibility

100/0 85/15 75/25 50/50 25/75 0/10

0.2135 0.2127 0.1860 0.1136 0.0664 0.0467

– 0.2261 0.1683 0.0971 0.0714 –

– 0.1262 0.0683 0.0028 0.0285 –

– 0.096 0.0382 0.033 0.0587 –

Miscible Miscible Immiscible Immiscible

Table 2 The numerical values of polymer–polymer interaction parameters for PPO/PBrS blends PPO/PBrs

a

DK

l

Miscibility

85/15 75/25 50/50 25/75

0.0153 0.020 0.172 0.207

0.148 0.111 0.454 0.414

1.670 0.6598 0.5699 1.014

Miscible Miscible Immiscible Immiscible

criterion D[g]m proposed by Garcia [20] were computed using Eqs. (17) and (18) and were tabulated in Table 3. Fig. 3 shows the plot of Db 0 , Db, D[g], as a function of weight fraction of PPO for the system PPO/PBrS in chloroform.

314

A.Z. Aroguz, B.M. Baysal / European Polymer Journal 42 (2006) 311–315

These criteria succeed in predicting the miscibility of polymer blend of (PPO/PBrS), and implying that it is suitable to determine polymer–polymer miscibility.

5. Conclusions

Fig. 2. Values of the various parameters as criterion for viscometric miscibility as a function of PPO (r) a, (j) DK and (d) l.

Table 3 A comparison of the experimental and ideal viscosity parameters of the PPO/PBrs blends PPO/PBrs

gexp

gdeal

[Dg]

Miscibility

100/0 85/15 75/25 50/50 25/75 0/100

0.3623 0.2968 0.2797 0.2503 0.1893 0.1216

– 0.3264 0.3021 0.242 0.1818 –

– 0.0294 0.0224 0.0083 0.0075 –

Miscible Miscible Immiscible Immiscible

Fig. 3. Miscibility parameters as a function of weight fraction of PPO (d) D[g], (r) Db and (j) Db 0 .

In this work we have considered three different approaches on the weighted additivity of intrinsic viscosities of polyblends and that of it constituent polymers. Criteria proposed for the miscibility of polymeric blends proved to be valid for the polymeric materials used in this work. Our earlier studies based on the thermal analysis of PPO/PBrS blends show that the blends containing less than 25% PBrS cast from chloroform solution were transparent [16]. The viscosity studies performed in this work were indicated that the blends containing more than 75% PPO in our mixtures are compatible. The agreement on the results of the thermal analysis and viscosity measurements for these polymer blends support the validity of this simple viscometric study. Acknowledgement B.M. Baysal acknowledges support from TUBATurkish Academy of Sciences. References [1] Kruptphun P, Supaphol P. Thermal and crystallization characteristics of poly(trimethylene terephthalate)/poly(ethylene naphthalate) blends. Eur Polym J 2005;41: 1561–68. [2] Lee WJ, Jung HR, Kim C, Lee MS, Kim JH, Yang KS. Preparation of polypyrrole/sulfonated-poly(2,6-dimethyl1,4-phenylene oxide) conducting composites and their electrical properties. Synth Met 2004;143:59–67. [3] Wanchoo RK, Sharma PK. Viscometric study on the compatibility of some water soluble-polymer–polymer mixtures. Eur Polym J 2003;39:1481–90. [4] Lewandowska K. The miscibility of poly(vinyl alcohol)/ poly(N-vinylpyrrolidone) blends investigated in dilute solutions and solids. Eur Polym J 2005;41:55–64. [5] Crispim EG, Rubira AF, Muniz EC. Solvent effects on the miscibility of poly(methyl methacrylate)/poly(vinyl acetate)blends I: Using differential scanning calorimetry and viscometry techniques. Polymer 1999;40:5129–35. [6] Cabanelas JC, Serrano B, Baselga J. Development of cocontinuous morphologies in initially heterogeneous thermosets blended with poly(methyl methacrylate). Macromolecules 2005;38:961–70. [7] Olabisi O, Robeson LM, Shaw MT. Polymer–polymer miscibility. New York: Academic; 1979. [8] Patel M. Viscoelastic properties of polystyrene using dynamic rheometry. Polym Test 2004;23:107–12. [9] Pingping Z. A new criterion of polymer–polymer miscibility detected by viscometry. Eur Polym J 1997;33:411–3.

A.Z. Aroguz, B.M. Baysal / European Polymer Journal 42 (2006) 311–315 [10] Jiang WH, Han S. An improved criterion of polymer– polymer miscibility determined by viscometry. Eur Polym J 1998;34:1579–84. [11] Pan Y, Cheng R, Xue F, Fu W. A new viscometric criterion for polymer–polymer interaction. Eur Polym J 2002;38:1703–8. [12] Chee KK. Determination of polymer–polymer miscibility by viscometry. Eur Polym J 1990;26:423–6. [13] Sun Z, Wang W, Feng Z. Criterion of polymer–polymer miscibility determined by viscometry. Eur Polym J 1992;28:1259–61. [14] Kavlak S, Kaplan Can H, Guner A. Miscibility studies on poly(ethylene glycol)/dextran blends in aqueous solutions by dilute solution viscometry. J Appl Polym Sci 2004;94:453–60. [15] Haiyang Y, Pingping Z, Feng R, Yuanyuan W, Tiao Z. Viscometric investigations on the intermolecular interactions between poly(methyl methacrylate) and poly-

[16]

[17]

[18] [19] [20]

[21]

315

(vinyl acetate) in various solvents. Eur Polym J 2000; 36:21–6. Aroguz AZ, Baysal BM. Thermal, mechanical, and morphological characterization studies of poly(2,6-dimethyl1,4-phenylene oxide)blends with polystyrene and brominated polystyrene. J Appl Polym Sci 2000;75:225–31. Huggins ML. The viscosity of dilute solutions of long chain molecules IV. Dependence on concentration. J Am Chem Soc 1942;64:2716–8. Krigbaum WR, Wall FT. J Polym Sci 1950;5:505–14. Catsiff RHE, Hewett WA. The interaction of two dissimilar polymers in solution. J Appl Polym Sci 1962;6:S30–2. Garcia R, Melad O, Gomez CM, Figueruelo JE, Campos A. Viscometric study on the compatibility of polymer– polymer mixtures in solution. Eur Polym J 1999;35:47–55. Shashidhara GM, Guruprasad KH, Varadarajulu A. Miscibility studies on blends of cellulose acetate and nylon 6. Eur Polym J 2002;38:611–4.