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Determination of intrinsic viscosity for some cationic polyelectrolytes by Fedors method
Eur. Polym. J. Vol. 34, No. I, pp. 13-16, 1998 1997 Elsevier Science Ltd. All rights reserved
Q
Pergamon
Printed in Great Britain 0014-3057/97 $17.00 + 0.00
PII: SOOW3057(97)00072-4
DETERMINATION OF INTRINSIC VISCOSITY FOR SOME CATIONIC POLYELECTROLYTES BY FEDORS METHOD LUMINITA “Petru
Poni”
Institute
GHIMICI*
of Macromolecular
and FLORIN
POPESCU
Chemistry, Aleea Grigore Romania
Ghica
Voda 41A, RO-6600
(Received 30 October 199k; accepted in final form I I December
Ia$i,
1996)
Abstract-The viscosity of some cationic polyelectrolyte solutions was determined over a wide concentration range, in the absence of low-molecular weight electrolytes. The experimental data were plotted in terms of Fuoss, Korecz et al. and Fedors equations. Straight lines were obtained in all cases, allowing the calculation of intrinsic viscosity values. The obtained values showed a satisfactory agreement between the three methods. This indicates the applicability of Fedors equation for describing the viscosity of polyelectrolyte solutions. 0 1997 Elsevier Science Ltd
INTRODUCTION
MATERIALS AND METHODS
The properties of polyelectrolyte solutions have been the subject of intensive studies for a long time, both from theoretical and experimental purposes. Due to electrostatic interactions between the charged groups along the chain, the polyelectrolyte solutions show quite different behaviour compared with neutral polymers regarding colligative properties (activity coefficients, osmotic coefficients), as well as transport properties (viscosity, diffusion, etc.). Thus, it is well known that in the case of pure solutions of ionic polymer or in the presence of low amounts of low-molecular weight electrolytes, the rlSp/C-C curves are asymptotically against the ordinate [l-3] or show a maximum [&8]. These q.,/C-C curves cannot be extrapolated to zero polyelectrolyte concentration for intrinsic viscosity determination. This problem can be solved in two ways: (1) by means of empirical equation; (2) through screening of charges by addition of low-molecular weight salts. The literature presents equations, such as Fedors equation [9-l 11, which can sometimes describe the viscosity of uncharged polymer solutions over the whole concentration range. Up to date, there are no data, as we are aware, on the application of this equation to the intrinsic viscosity determination of polyelectrolyte solutions. The aim of this paper is to apply the Fedors equation in order to linearize viscometric data obtained in the case of some cationic polyelectrolytes. The intrinsic viscosity values determined by this method are compared with those obtained by the Fuoss and Korecz et al. equations.
Polyelectrolytes used in this study were cationic polymers with quaternary N atoms and/or tertiary amine N atoms in the main chain. They were prepared either by condensation polymerization of epichlorohydrin (ECH) with dimethylamine (DMA) and NJ-dimethyl-1,3-diaminopropane (DMDAP)-polymer type A or by polyaddition of PEG diglicidylethers with DMDAP-polymer type PEGA. The structures of these polymers are presented overleaf. The syntheses of these polymers have been described in detail elsewhere [2, 31. The samples of cationic polyelectrolyte type A were carefully purified by dialysis against distilled water until the absence of Cl- in the external water; the diluted solutions were concentrated by gentle heat in vacuum to -50% w/w and then precipitated with acetona p.a. The samples were dried in vacuum over P205, at room temperature, and were characterized by: [S]I MN~C,= 0.680 dL/g for A,, [q], MN~CI= 0.335 dL/g for A2 and [q], MW = 0.550 dL/g for A,. Viscometric measurements of the aqueous polyelectrolyte solutions were carried out at 25°C using an Ubbelohde viscometer with internal dilution. The concentration range was 2 x 1O-4 to 1.3 x lO~*g/cm’.
*To whom
all correspondence
should
RESULTS AND DISCUSSION
The reduced viscosity increases with the decrease in the polymer concentration for polymers under study, a behaviour which corresponds to polyelectrolyte solutions, as shown in Figs l(a) and (b). The expansion begins at the concentration < 1 x lo-* gcrne3 for the A, polymer and the concentration <5 x lo-’ g cm-’ for AZ and A, polymers [Fig. l(a)]; a higher polyfunctional amine (DMDAP) content in A2 and AJ polymers leads probably to a higher branching degree and consequently, to a limited expansion of the chain.
be addressed. 13
L. Ghimici
and F. Popescu
CH3
[~~~~H,-~H-CH,~~-CH*-~H-CH~~]” OH
CHs
(SH2)s N: HCl /\ CHs CHs Cationic
OH
polyelectrolyte
Where A, p = 0.95;
A
A2 p = 0.80;
As p = 0.66
f-O+CH2-CH2-0tCH2-~H-CH+CH2-~H-CH+ OH (SH2)s N:
OH
C/H&H, Cationic Where PEGA,:
Mnpno = 400;
polyelectrolyte PEGAl:
In the case of PEGA-type cationic polyelectrolytes the reduced viscosity values are related to the charged density of polyelectrolyte [Fig. l(b)]. For the same polymer concentration, the values of the reduced viscosity decrease in the following order: PEG, > PEG2 > PEG3, so with the decrease of the charge density of the ionic polymer. A greater distance between the ionic groups determines a decrease of the electrostatic repulsion and, consequently, the expansion of the chain. The curves shown in Figs l(a) and I(b) can be linearized applying the Fuoss [2, 121 (1) and Korecz et al. [13] (2) equations:
PEGA
Mnpao = 600;
PEGAs: Mnpno = 4000
r/,/c = A/l where A = the intrinsic
+ B.P,
viscosity;
(1)
B = constant
rJ.,/c = (ao f a,.C).C?‘,
(2)
where aa = the intrinsic viscosity; k = the slope of the In ?JJC vs In C curves; it was obtained by the least-squares method. The curves obtained by calculating the viscometric data for the ionic polymer, in terms of the Fuoss and Korecz equations, are presented in Figs 2(a), 2(b), 3(a) and 3(b), respectively. As may be seen, straight
(4 (b) 0.8 r
I
I 1.0
I 0.5
0
C (g/d0
C Wdl)
Fig. 1. (a) Variation of the reduced viscosity (qSp/C) vs concentration (c) of the polyelectrolyte in H20 at 25°C: (0) A,; ( x ) AI; (a) A1. (b) Variation of the reduced viscosity (nsp/C) vs concentration (c) of the polyelectrolyte in Hz0 at 25°C: (0) PEGA,; (0) PEGAX; (V) PEGA>.
Determination of intrinsic viscosity
(4 0.20
15
(a> __----
1
xXX-X-X-X
---x7
____-/
0.15
c 9 3
i
1
< 0.10 _________-oL~-~_O
u
0.05
t 0
I
I
I
0.5
‘0
fi
0
I
I
0.5
1.0 C (g/d])
(gldl) (b)
____n
0.2
I
____n
0.1 I
t
0.5 0
fi(g/dl) Fig. 2. (a) Representation of the Fuoss equation for: (0) AI; ( x ) AX; (A) A,. (b) Representation of the Fuoss equation for: (0) PEGA,; (0) PEGAl; (V) PEGAI.
lines are obtained for all samples over the whole studied concentration range. Fedors [9] suggested an equation applicable to describing the viscosity of diluted to moderately concentrated neutral polymer solution, given by equation (3):
1/wrl:‘2- 111= 1lhl.C - l/hl~G,
(3)
where C, = a polymer concentration parameter. Ioan et al. [IO] applied this equation to their experimental data obtained on poly(butylmethacrylate) of various molecular weights in methyl ethyl ketone at 25°C. Rao [I l] reexamined the Fedors Table I. Intrinsic viscosity values obtained by Fedors, Fuoss and Korecz er al. methods
Al Al A3 PEGA, PEGAx PEGA,
EPJ 34/l
[VlFCd.=
MF”0S
@L/g)
@L/g)
ltll...= @L/g)
‘0.6’ 5 5.41 0.67 0.26 0.19
11.1’ 5.3’ 6.15 0.76 0.33 0.30
9.10 4.90 5.60 0.49 0.22 0.15
I
I
I
0.5
1.0 C (g/d0
3. (a) Representation of the Korecz et al. equation for: (0) A,; ( x ) AZ; (A) A,; k~l = 0.8438; kA* = 0.970; kA, = 0.955. (b) Representation of the Korecz et al. equation for: (0) PEGA,; (0) PEGA2; (V) PEGA,; kPEC,,l= 0.870; /(mm = 0.939; kmA3 = 0.919. Fig.
equation, taking into account the polymer swelling behaviour and polymer-solvent interaction. We have found that the equation proposed by Fedors can be also used to describe the viscosity of some polyelectrolyte solutions over a wide concentration range. As Figs 4(a) and 4(b) illustrate the plotting 1/[2(~1’~- l)] vs l/C, according to equation (3), straight lines were obtained for all samples over the studied concentration range. It can be also observed that, by the Fedors method, a better fitting of viscometric data was obtained over a greater concentration range than by the Fuoss and Korecz et al. methods. The results obtained by fitting the Fedors, Fuoss and Korecz et al. equations to the viscosity data of the cationic polyelectrolytes are listed in Table 1. The analysis of these data shows a satisfactory agreement between the intrinsic viscosity values obtained by the three methods. This indicates the applicability of Fedors equation for describing the viscosity of polyelectrolyte solutions.
L. Ghimici
16
and F. Popescu
(4 (b) I
1
7 Y
-B E r-4
0
5
I 5
10
l/C (d&g)
l/C (dllg)
Fig. 4. (a) Representation
of the Fedors equation for: (0) AI; ( x 1 AI; (A) A,. @I Representation the Fedors equation for: (0) PEGA,; (0) PEGAl; (VI PEGA).
REFERENCES 1. Contois, L. L. and Trementozz, Q. A., J. Polym. Sci., 1955, 18, 479. 2. Dragan, S. and Ghimici, L., Angew Makromol. Chem., 1991, 192, 199. 3. Dragan, S. and Ghimici, L., Angew. Makromol. Chem., 1994, 215, 107. 4. Vink, H., Makromol. Chem., 1970, 131, 133. 5. Cohen, J. and Priel, Z., Polym. Commun., 1988,29,235. 6. Cohen, J., Priel, Z. and Rabin, Y., J. Chem. Phys., 1988, 88, 7111. 7. Yamanaka, J., Araie, M., Masuoko, H., Kitano, H.,
I
IO
8.
9. 10. 11. 12. 13.
of
Ise, N., Yamaguki, T., Saeki, S. and Tsubokava, M., Macromolecules, 1991, 24, 6156. Malovikova, A., Milas, MC., Borsali, R. and Rinaudo, M., Polym. Prepr. (Am. Sot. Div. Polym. Chem.), 1993, 34, 1011. Fedors, R. F., Polymer, 1979, 20, 225. Ioan, S., Simionescu, B., Neamtu, I. and Simionescu, C. I., Polymer Commun., 1986, 27, 113. Rao, M. V. S., Polymer, 1993, 34, 592. Casson, D. and Rembaum, A., Macromolecules, 1972, 5, 75. Korecz, L., Csacvari, E. and Tudos, F., Polym. Bull., 1988, 19, 493.
Q
Pergamon
Printed in Great Britain 0014-3057/97 $17.00 + 0.00
PII: SOOW3057(97)00072-4
DETERMINATION OF INTRINSIC VISCOSITY FOR SOME CATIONIC POLYELECTROLYTES BY FEDORS METHOD LUMINITA “Petru
Poni”
Institute
GHIMICI*
of Macromolecular
and FLORIN
POPESCU
Chemistry, Aleea Grigore Romania
Ghica
Voda 41A, RO-6600
(Received 30 October 199k; accepted in final form I I December
Ia$i,
1996)
Abstract-The viscosity of some cationic polyelectrolyte solutions was determined over a wide concentration range, in the absence of low-molecular weight electrolytes. The experimental data were plotted in terms of Fuoss, Korecz et al. and Fedors equations. Straight lines were obtained in all cases, allowing the calculation of intrinsic viscosity values. The obtained values showed a satisfactory agreement between the three methods. This indicates the applicability of Fedors equation for describing the viscosity of polyelectrolyte solutions. 0 1997 Elsevier Science Ltd
INTRODUCTION
MATERIALS AND METHODS
The properties of polyelectrolyte solutions have been the subject of intensive studies for a long time, both from theoretical and experimental purposes. Due to electrostatic interactions between the charged groups along the chain, the polyelectrolyte solutions show quite different behaviour compared with neutral polymers regarding colligative properties (activity coefficients, osmotic coefficients), as well as transport properties (viscosity, diffusion, etc.). Thus, it is well known that in the case of pure solutions of ionic polymer or in the presence of low amounts of low-molecular weight electrolytes, the rlSp/C-C curves are asymptotically against the ordinate [l-3] or show a maximum [&8]. These q.,/C-C curves cannot be extrapolated to zero polyelectrolyte concentration for intrinsic viscosity determination. This problem can be solved in two ways: (1) by means of empirical equation; (2) through screening of charges by addition of low-molecular weight salts. The literature presents equations, such as Fedors equation [9-l 11, which can sometimes describe the viscosity of uncharged polymer solutions over the whole concentration range. Up to date, there are no data, as we are aware, on the application of this equation to the intrinsic viscosity determination of polyelectrolyte solutions. The aim of this paper is to apply the Fedors equation in order to linearize viscometric data obtained in the case of some cationic polyelectrolytes. The intrinsic viscosity values determined by this method are compared with those obtained by the Fuoss and Korecz et al. equations.
Polyelectrolytes used in this study were cationic polymers with quaternary N atoms and/or tertiary amine N atoms in the main chain. They were prepared either by condensation polymerization of epichlorohydrin (ECH) with dimethylamine (DMA) and NJ-dimethyl-1,3-diaminopropane (DMDAP)-polymer type A or by polyaddition of PEG diglicidylethers with DMDAP-polymer type PEGA. The structures of these polymers are presented overleaf. The syntheses of these polymers have been described in detail elsewhere [2, 31. The samples of cationic polyelectrolyte type A were carefully purified by dialysis against distilled water until the absence of Cl- in the external water; the diluted solutions were concentrated by gentle heat in vacuum to -50% w/w and then precipitated with acetona p.a. The samples were dried in vacuum over P205, at room temperature, and were characterized by: [S]I MN~C,= 0.680 dL/g for A,, [q], MN~CI= 0.335 dL/g for A2 and [q], MW = 0.550 dL/g for A,. Viscometric measurements of the aqueous polyelectrolyte solutions were carried out at 25°C using an Ubbelohde viscometer with internal dilution. The concentration range was 2 x 1O-4 to 1.3 x lO~*g/cm’.
*To whom
all correspondence
should
RESULTS AND DISCUSSION
The reduced viscosity increases with the decrease in the polymer concentration for polymers under study, a behaviour which corresponds to polyelectrolyte solutions, as shown in Figs l(a) and (b). The expansion begins at the concentration < 1 x lo-* gcrne3 for the A, polymer and the concentration <5 x lo-’ g cm-’ for AZ and A, polymers [Fig. l(a)]; a higher polyfunctional amine (DMDAP) content in A2 and AJ polymers leads probably to a higher branching degree and consequently, to a limited expansion of the chain.
be addressed. 13
L. Ghimici
and F. Popescu
CH3
[~~~~H,-~H-CH,~~-CH*-~H-CH~~]” OH
CHs
(SH2)s N: HCl /\ CHs CHs Cationic
OH
polyelectrolyte
Where A, p = 0.95;
A
A2 p = 0.80;
As p = 0.66
f-O+CH2-CH2-0tCH2-~H-CH+CH2-~H-CH+ OH (SH2)s N:
OH
C/H&H, Cationic Where PEGA,:
Mnpno = 400;
polyelectrolyte PEGAl:
In the case of PEGA-type cationic polyelectrolytes the reduced viscosity values are related to the charged density of polyelectrolyte [Fig. l(b)]. For the same polymer concentration, the values of the reduced viscosity decrease in the following order: PEG, > PEG2 > PEG3, so with the decrease of the charge density of the ionic polymer. A greater distance between the ionic groups determines a decrease of the electrostatic repulsion and, consequently, the expansion of the chain. The curves shown in Figs l(a) and I(b) can be linearized applying the Fuoss [2, 121 (1) and Korecz et al. [13] (2) equations:
PEGA
Mnpao = 600;
PEGAs: Mnpno = 4000
r/,/c = A/l where A = the intrinsic
+ B.P,
viscosity;
(1)
B = constant
rJ.,/c = (ao f a,.C).C?‘,
(2)
where aa = the intrinsic viscosity; k = the slope of the In ?JJC vs In C curves; it was obtained by the least-squares method. The curves obtained by calculating the viscometric data for the ionic polymer, in terms of the Fuoss and Korecz equations, are presented in Figs 2(a), 2(b), 3(a) and 3(b), respectively. As may be seen, straight
(4 (b) 0.8 r
I
I 1.0
I 0.5
0
C (g/d0
C Wdl)
Fig. 1. (a) Variation of the reduced viscosity (qSp/C) vs concentration (c) of the polyelectrolyte in H20 at 25°C: (0) A,; ( x ) AI; (a) A1. (b) Variation of the reduced viscosity (nsp/C) vs concentration (c) of the polyelectrolyte in Hz0 at 25°C: (0) PEGA,; (0) PEGAX; (V) PEGA>.
Determination of intrinsic viscosity
(4 0.20
15
(a> __----
1
xXX-X-X-X
---x7
____-/
0.15
c 9 3
i
1
< 0.10 _________-oL~-~_O
u
0.05
t 0
I
I
I
0.5
‘0
fi
0
I
I
0.5
1.0 C (g/d])
(gldl) (b)
____n
0.2
I
____n
0.1 I
t
0.5 0
fi(g/dl) Fig. 2. (a) Representation of the Fuoss equation for: (0) AI; ( x ) AX; (A) A,. (b) Representation of the Fuoss equation for: (0) PEGA,; (0) PEGAl; (V) PEGAI.
lines are obtained for all samples over the whole studied concentration range. Fedors [9] suggested an equation applicable to describing the viscosity of diluted to moderately concentrated neutral polymer solution, given by equation (3):
1/wrl:‘2- 111= 1lhl.C - l/hl~G,
(3)
where C, = a polymer concentration parameter. Ioan et al. [IO] applied this equation to their experimental data obtained on poly(butylmethacrylate) of various molecular weights in methyl ethyl ketone at 25°C. Rao [I l] reexamined the Fedors Table I. Intrinsic viscosity values obtained by Fedors, Fuoss and Korecz er al. methods
Al Al A3 PEGA, PEGAx PEGA,
EPJ 34/l
[VlFCd.=
MF”0S
@L/g)
@L/g)
ltll...= @L/g)
‘0.6’ 5 5.41 0.67 0.26 0.19
11.1’ 5.3’ 6.15 0.76 0.33 0.30
9.10 4.90 5.60 0.49 0.22 0.15
I
I
I
0.5
1.0 C (g/d0
3. (a) Representation of the Korecz et al. equation for: (0) A,; ( x ) AZ; (A) A,; k~l = 0.8438; kA* = 0.970; kA, = 0.955. (b) Representation of the Korecz et al. equation for: (0) PEGA,; (0) PEGA2; (V) PEGA,; kPEC,,l= 0.870; /(mm = 0.939; kmA3 = 0.919. Fig.
equation, taking into account the polymer swelling behaviour and polymer-solvent interaction. We have found that the equation proposed by Fedors can be also used to describe the viscosity of some polyelectrolyte solutions over a wide concentration range. As Figs 4(a) and 4(b) illustrate the plotting 1/[2(~1’~- l)] vs l/C, according to equation (3), straight lines were obtained for all samples over the studied concentration range. It can be also observed that, by the Fedors method, a better fitting of viscometric data was obtained over a greater concentration range than by the Fuoss and Korecz et al. methods. The results obtained by fitting the Fedors, Fuoss and Korecz et al. equations to the viscosity data of the cationic polyelectrolytes are listed in Table 1. The analysis of these data shows a satisfactory agreement between the intrinsic viscosity values obtained by the three methods. This indicates the applicability of Fedors equation for describing the viscosity of polyelectrolyte solutions.
L. Ghimici
16
and F. Popescu
(4 (b) I
1
7 Y
-B E r-4
0
5
I 5
10
l/C (d&g)
l/C (dllg)
Fig. 4. (a) Representation
of the Fedors equation for: (0) AI; ( x 1 AI; (A) A,. @I Representation the Fedors equation for: (0) PEGA,; (0) PEGAl; (VI PEGA).
REFERENCES 1. Contois, L. L. and Trementozz, Q. A., J. Polym. Sci., 1955, 18, 479. 2. Dragan, S. and Ghimici, L., Angew Makromol. Chem., 1991, 192, 199. 3. Dragan, S. and Ghimici, L., Angew. Makromol. Chem., 1994, 215, 107. 4. Vink, H., Makromol. Chem., 1970, 131, 133. 5. Cohen, J. and Priel, Z., Polym. Commun., 1988,29,235. 6. Cohen, J., Priel, Z. and Rabin, Y., J. Chem. Phys., 1988, 88, 7111. 7. Yamanaka, J., Araie, M., Masuoko, H., Kitano, H.,
I
IO
8.
9. 10. 11. 12. 13.
of
Ise, N., Yamaguki, T., Saeki, S. and Tsubokava, M., Macromolecules, 1991, 24, 6156. Malovikova, A., Milas, MC., Borsali, R. and Rinaudo, M., Polym. Prepr. (Am. Sot. Div. Polym. Chem.), 1993, 34, 1011. Fedors, R. F., Polymer, 1979, 20, 225. Ioan, S., Simionescu, B., Neamtu, I. and Simionescu, C. I., Polymer Commun., 1986, 27, 113. Rao, M. V. S., Polymer, 1993, 34, 592. Casson, D. and Rembaum, A., Macromolecules, 1972, 5, 75. Korecz, L., Csacvari, E. and Tudos, F., Polym. Bull., 1988, 19, 493.