Polymers in Aqueous Media - American Chemical Society

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on February 10, 2016 | http://pubs.acs.org Publication Date: May 5, 1989 | doi: 10.1021/ba-1989-0223.ch009

9 Copolymers of N-Vinylpyrrolidone and Sulfonate Monomers Synthesis and Solution Properties 1

2

1

D . N . Schulz , K . Kitano , J. A . Danik , and J. J. Kaladas Exxon Research and Engineering Company, Corporate Research Science Laboratories, Route 22 East, Annandale, N J 08801

This chapter describes the synthesis, kinetics, and solution properties for copolymers of N-vinylpyrrolidone

(NVP) with sulfonate ionic and

zwitterionic monomers. Examples of the sulfonate ionic monomers are sodium styrenesulfonate ylpropanesulfonate sulfonate

monomer

ammonium monomer

inner pair

(NaSS) and sodium

(NaAMPS); is

salt,

acrylamido-2-meth-

an example of the zwitterionic

(2-hydroxyethyl)dimethyl(3-sulfopropyl)--

methacrylate

was exceptional,

(SPE).

showing

The

NVP-NaAMPS

evidence for

donor--

acceptor character and an alternating tendency in copolymerization. The NVP copolymers (e.g., NaAMPS)

containing simple sulfonate ionic monomers

showed polyelectrolyte

the other hand, the NVP copolymers

solution properties. with zwitterionic

monomers showed "antipolyelectrolyte" solution

On

sulfonate

behavior.

N E W SULFONATE MONOMERS, both the simple ionic [e.g., sodium styrenesulfonate

(NaSS) and sodium

acrylamido-2-methylpropanesulfonate

(NaAMPS) (1)], and zwitterionic [e.g., (2-hydroxyethyl)dimethyl(3-sulfopropyl)ammonium, inner salt, methacrylate (SPE) (2)] types, have recently become available. Homopolymers of such simple sulfonate monomers are characterized by good thermal and hydrolytic stability; however, their soCurrent address: Exxon Chemical Company, P.O. Box 45, Linden, NJ 07036 Current address: Tonen Petrochemical Ltd., Tokyo 104, Japan

1 2

0065-2393/89/0223-0165$06.00/0 © 1989 American Chemical Society

In Polymers in Aqueous Media; Glass, J. Edward; Advances in Chemistry; American Chemical Society: Washington, DC, 1989.

166

POLYMERS IN A Q U E O U S M E D I A


lutions lose viscosity in the presence of added salts because of their polyelectrolytic character. In contrast, poly(sulfo zwitterions) exhibit "antipolyelectrolytic" solution behavior (3-6). Poly(N-vinylpyrrolidone), P(NVP), is a nonionic, water-soluble polymer with high thermal and hydrolytic stability (7-9). Copolymers of N-vinylpyrrolidone (NVP) with various carboxylate and carboxylate-precursor monomers (e.g., acrylic acid, sodium acrylate, crotonic acid, itaconic acid, and maleic anhydride) are also well-known (JO). In addition, the homo- and copolymerization kinetics of these monomers are well-established. O n the other hand, reports of copolymerizations of N V P with sulfonate monomers are sparse (11, 12). This chapter describes the synthesis, kinetics, and reactivity ratios for the copolymerization of N V P and some of the newer sulfonate monomers. A comparison of some of the solution properties for such copolymers is also included.

Experimental Details Materials. NVP was received from Aldrich Chemical Company and purified by vacuum distillation (bp 88 °C at 5 mmHg; literature value, bp 96 °C at 14 mmHg). Sodium styrenesulfonate (NaSS) was obtainedfromAirco; sodium acrylamido-2-methylpropanesulfonate (NaAMPS) was obtained from Lubrizol; SPE, (3-methacrylamidopropyl)dimethyl(3-sulfopropyl)ammonium, inner salt (SPP), and l-(3-sulfopropyl)2-vinylpyridinium, inner salt (SPV) were obtained from Raschig (Germany) via its American distributor, Howard Hall International (Cos Cob, CT). SPE, SPP, and SPV were rectified by recrystallization.

Copolymer Characterization. Copolymer compositions were determined by elemental analysis and thermal gravimetric analysis. A Perkin-Elmer TGS-2 thermogravimetrie analyzer, programmed from ambient to 800 °C in N and air, was used. Spectroscopic analysis of the copolymers was not as useful as elemental analysis and thermal gravimetric analysis measurements for analyzing these copolymers. Viscometric measurements were made in a solution of water and NaCl with a Contraves low-shear viscometer. Molecular weight and second virial coefficient (A ) measurements were made on a KMX-6 fixed low-angle light-scattering (LALLS) spectrometer at 25 °C. The refractive index increments (dn/dc) in 2% NaCl were 0.163 for NVP/NaAMPS (50/50), 0.136 for NVP/SPE (50/50), 0.159 for NVP/SPE (80/20), and 0.139 for NVP/SPE (10/90), as measured on a KMX-16 differential refractometer at 25 °C. Quasi-elastic light scattering measurements were made on a Brookhaven apparatus. 2

2

Copolymerization Procedures. The copolymerization kinetics runs were made using azobis(isobutyronitrile) (AIBN) as the initiator, at [M][I] = 15, a total monomer concentration of 14 wt % in water, at 60 °C under N . Polymers were isolated by precipitation in acetone. The initial rate of polymerization (R ) was determined by measuring the initial slope of time vs. conversion plots. Analysis of reactivity ratio data was performed by using the Kelen-Tudôs method (13, 14). 1/2

2

p


9.

SCHULZ ET AL.

Copolymers of N-Vinylpyrrolidone-Sulfonate Monomers 167


Results and Discussion In this chapter, we describe the synthesis, kinetics, and solution properties of poly(N-vinylpyrrolidone-co-sodium styrenesulfonate) [poly(NVP-coNaSS)], poly(IV-vinylpyrrolidone-co-sodium acrylamido-2-methylpropanesulfonate [poly(N VP-eo-NaAM PS)], poly(N-vinylpyrrolidone-co-IV,iV-dimethyl-N-methacroyloxyethylam [poly(NVP-co-SPE)], poly(N-vinylpyrrolidone-co-N,N-dimethyl-N-methacroylamidopropylammoniopropanesulfonate [poly(NVP-co-SPP)], and poly(N-vinylpyrrolidoneco-2-vinylpyridiniopropanesulfonate [poly(NVP-co-SPV)]. Radical copolymerizations were carried out in water solutions with A I B N initiator at elevated temperature (e.g., 60 °C), (see reactions 1-5). The rates of polymerization (R ) for the copolymerization of N V P and the various sulfonate monomers (simple ionic and zwitterionic) as a function of sulfonate content are shown in Figure 1. The R for the copolymerization of N V P with the sulfonate monomers is p

p

NaAMPS »

SPP ~ S P E ~ NaS »

SPV

The R of the copolymerization of N V P with N a A M P S is not only several p

-{C^-çm-fCHa-ÇH-^

S0 "Na

NVP

3

+

S0 Na 3

+

poly(NVP-co-NaSS)

Ji^sP

\ 1

\

1

NVP

*

î~ NH

? C-CHaSOgNa*

0

H a

CH3

AIBN 7·+· 6

0

C

NaAMPS —(CHoCH) (CH2 — I f i

CIBI y NH

Ç-C^^Na* CH3

poly(NVPco "NaAMPS)


(2)

168


Ji.

^

^

Q

AIBN^

CH3 NVP

SPE -t-CHaÇHWC^-ÇHH^ C=0


N^O Γ

CH3

0(CH )2N(CH ) S0 -

I

2

2

3

3

CHg poly(NVPco-SPE)

a ,

τ

NVP

υ

C=0

CH,

AIBN

NH(CH ) N(CH ) S0 CHg 2

3

2

3

3

6

0

«

C

SPP -eCHjjCH-fj-fCHaCH-i-y

et Ν

Λ

CHq

C—O

NH(CH ) N(CH ) S0 2

3

2

3

3

CH3

poly ( N V P c o "SPP) AIBN N-(CHo) SO3

•

^

1

NVP

3

•

60 °C

SPV

poly ( N V P c o - S P V ) orders of magnitude faster than that of SPP, S P E , and NaSS, but it also shows a maximum in the R vs. sulfonate curve near the 1:1 NVP-sulfonate charge ratio. This result suggests some donor-acceptor ( D - A ) character for this monomer pair (15). Also, consistent with the involvement of donoracceptor complexes (16), the N V P - N a A M P S monomer pair polymerizes in p



9.

SCHULZ ET AL.


100 % Sulfonate In the Feed Figure 1. Rates of copolymerization of NVP with sulfonate monomers. Key: ·, NVP/NaAMPS; A , NVP/NaSS; O, NVP/SPE; NVP/SPP; NVPiSPV. the absence of initiator at room temperature in water or salt solution, whereas N a A M P S itself does not. The NVP-zwitterion monomers S P E and SPP can also autopolymerize, but for a different reason (17). In contrast, N V P and SPV do not copolymerize under either the catalyzed or uncatalyzed conditions used in this study. Presumably, the reactivity of the l-(3-sulfopropyl)2-vinylpyridinium inner salt is depressed for steric reasons. N V P is a mildly electron-donating monomer, and the various sulfonates are mildly electron-accepting monomers. Reactivity ratios were determined for the copolymerization of N V P with the simple and zwitterionic sulfonate monomers and are presented in Table I. Such data indicate that N V P and N a A M P S have a tendency to alternate (i.e., r = 0.13, r = 0.66, and r r = 0.086), The level of alternating tendency is similar to that exhibited by N V P - m e t h y l methacrylate and NVP-acrylamide but less than that for NVP-acrylonitrile. The N V P - N a A M P S comonomer pair also has an azeotropic composition at 70 mol % sulfonate (Figure 2). Such data are also consistent with some donor-acceptor involvement for this monomer pair (16). As expected, there is little drift in the copolymer composition with conversion near the azeotropic composition (Figure 3). N V P

N V P

N a A M P S

N a A M P S

In contrast, the other simple ionic sulfonate monomer, NaSS, copolymerizes with N V P with preferential incorporation of NaSS ( r — 0.084, Nass 7.19) (Table I and Figure 2). Furthermore, there is significant drift in copolymer composition with conversion for this polymer (Figure 4). The zwitterionic sulfonates (sulfobetaine monomers) also show a higher NVP

r

=


170


Table I. Reactivity Ratios for Copolymerization of NVP with Sulfonate Monomers


Sulfonate Monomer Simple ionic NaAMPS NaSS Zwitterionic (sulfobetaines) SPP SPE Footnote a AN MMA MA AM ST

2

R2R2

1/Rj

0.13 0.84

0.66 7.2

0.086 0.60

7.7 12

0.11 0.066

2.60 6.50

0.29 0.43

9.0 15

0.06 0.020 0.041 0.17 0.45

0.18 5.0 0.27 0.66 15

0.010 0.10 0.11 0.11 0.76

17 50 24 5.8 22

Ri

R

NOTE: All copolymerizations were with NVP. Ratios were determined by the Kelen-Tudos method (13-14) at average conversions of 15-18% for NaSS, NaAMPS, and SPE copolymers and 28% for the SPP copolymer. No data were obtained for the copolymerization of NVP and SPV. "V-Pyrol, N-Vmyl-2-pyrrolidone", technical bulletin, GAF Corporation, New York.

e

0

0.5

1.0

Sulfonate Composition in Feed Figure 2. NVP/sulfonate monomer copolymerization curves. Key: •, NVP/SPE; ·, NVP/NaSS; A , NVP/SPP; O, NVP/NaAMPS. relative reactivity of sulfonate monomer compared to N V P (Figure 2). O n the basis of r ^ " values, the order of sulfonate monomer reactivities toward the the N V P radical is 1

S P E > NaSS > SPP > N a A M P S »

SPV


9.

SCHULZ ET AL.


Φ

Ε >· "δ

&


Ο

s ο

I< IB

100 Yield (Χ) Figure 3. NVP/NaAMPS: yield vs. copolymer composition curves. Key: f 20/80 NVP/NaAMPS; 50/50 NVP/NaAMPS; A , 80/20 NVP/NaAMPS.

50

100

Yield (%) Figure 4. NVP/NaSS: yield vs. copolymer composition curves. Key: · , 20/80 NVP/NaSS; • , 50/50 NVP/NaSS; A , 80/20 NVP/NaSS. N V P - s i m p l e ionic sulfonate polymers (e.g., N V P - N a A M P S ) are typical polyelectrolytes in solution. Thus, such polymers show enhanced viscosities in H 0 (0% NaCl) but exhibit lower viscosities at higher salt concentra tions. In contrast, NVP-zwitterion sulfonate copolymers (e.g., N V P - S P E ) actually show a slight increase in viscosity with increasing salt concentration (Figure 5). 2



172

POLYMERS IN A Q U E O U S

MEDIA

NaCl Figure 5. Salt effect on intrinsic viscosity at 25 °C. Key: O , NVP/NaAMPS (50/50); • , NVP/SPE (50/50).

These macroscopic viscosity measurements have been confirmed at the molecular level. For example, dynamic light-scattering methods show an average hydrodynamic diameter (D J of about 370 A for a 50/50 copolymer of N V P / S P E in low salt (

Polymers in Aqueous Media - American Chemical Society

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