Erich E. Kathmann

Water soluble polymers: 69. pH and electrolyte responsive copolymers of acrylamide and the zwitterionic monomer 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate: synthesis and solution behaviour

Abstract A novel carboxybetaine monomer, 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate (AMPDAB), has been synthesized and copolymerized with acrylamide in an aqueous NaBr solution. The feed ratio of AM (M1)/AMPDAB(M2) was varied from 90 10 to 0 100 mol% . Low conversion samples were collected and copolymer compositions were determined with 13C n.m.r. by integration of the carbonyl resonances. Reactivity ratios were determined and the nonlinear least-squares method yielded values of r1 = 1.01 and r2 = 0.99, indicating random incorporation of monomers into the final copolymer. Molecular weights were determined and range from 3.9 to 12.0 × 106 g mol−1. The solution behaviour of the above copolymers was studied as a function of pH and added electrolytes. With the exception of the copolymers containing 60 and 75 mol% AMPDAB, homogeneous solutions were obtained in deionized water. At high pH, the polyzwitterions show an enhancement in viscosity as the concentration of added electrolyte is increased. In deionized water, as the pH of the aqueous media is lowered, the copolymers exhibit a dramatic increase in viscosity as the carboxylate groups are protonated and charge-charge repulsions of the quaternary ammonium groups induce polyelectrolyte behaviour. The solution behaviour is compared to structurally similar sulfobetaines which do not exhibit any responsiveness to changes in pH.

Water-soluble polymers. 72. Synthesis and solution behavior of responsive copolymers of acrylamide and the zwitterionic monomer 6-(2-acrylamido-2-methylpropyldimethylammonio) hexanoate

A novel carboxybetaine monomer, 6-(2-Acrylamido-2-methylpropyldimethylammonio) hexanoate (AMPDAH), has been synthesized and copolymerized with acrylamide in an aqueous NaBr solution. The feed ratio of AM (M1): AMPDAB(M2), was varied from 98.5 : 2.5 to 0 : 100 mol %. The polymerizations were carried out to 20–30% conversion. Copolymer compositions were determined with 13C NMR by integration of the amido carbonyl resonances. Reactivity ratios determined from the nonlinear least-squares method gave values of r1 = 0.98 and r2 = 0.85, indicating random incorporation of the comonomers into the final copolymer. Molecular weights ranged from 7.3 to 4.7 × 106 g/mol. The solubility behavior of the copolymers is dependent on the mol % AMPDAH incorporated into the copolymers. When 25 mol % or more is incorporated, the copolymers are only swellable in aqueous media and attempts to solubilize these systems were unsuccessful. AMPDAH incorporation of 10 mol % or less resulted in copolymers soluble in aqueous media under a variety of conditions. The viscometric properties of copolymers with 10 mol % or less is reported as a function of pH and added electrolytes. At high pH in deionized water, the polyzwitterions show both inter- and intramolecular associations, which are disrupted by the addition of sodium chloride. In deionized water, as the pH of the aqueous medium is lowered, the copolymers exhibit dramatic increases in viscosity as the carboxylate groups are protonated and charge–charge repulsions of the quaternary ammonium groups induce polyelectrolyte behavior.

Water‐soluble polymers. 71. pH responsive behavior of terpolymers of sodium acrylate, acrylamide, and the zwitterionic monomer 4‐(2‐acrylamido‐2‐methylpropanedimethylammonio)butanoate

Terpolymers of sodium acrylate (NaA), acrylamide (AM), and the zwitterionic monomer 4-(2-acrylamido-2-methylpropanedimethylammonio) butanoate (AMPDAB) were prepared by the free radical polymerization in 0.5M NaBr aqueous solution using potassium persulfate as the initiator. The feed ratio of AMPDAB : NaA : AM was varied from 5 : 5 : 90 to 40 : 40 : 20 mol %, with the total monomer concentration held constant at 0.45M. Terpolymer compositions were determined by 13C NMR. Molecular weights varied from 3.0 × 105 to 9.7 × 106 g/mol. All terpolymers were soluble in deionized water and salt solutions at all pH values. The dilute and semidilute solution behavior of the terpolymers was studied as a function of composition, pH, and added electrolytes. Polyelectrolyte behavior was observed for all terpolymers at pH 8.5, as evidenced by high viscosity values at low polymer concentrations and viscosity decrease in the presence of added electrolytes. The reduced viscosity as a function of decreasing pH exhibits a minimum as the terpolymer undergoes a polyanion/polyzwitterion/polycation transition. Comparison of the solution behavior of the terpolymers to terpolymers of 3-(2-acrylamido-2-methylpropane dimethylammonio)-1-propane sulfonate (AMPDAPS), AM, and NaA (AADAPS series) as well as copolymers of AMPDAB and AM (AMPDAB series) have been made.

Water soluble polymers : 70. Effects of methylene versus propylene spacers in the pH and electrolyte responsiveness of zwitterionic copolymers incorporating carboxybetaine monomers

Abstract Water soluble polyzwitterions have been synthesized by free radical copolymerization of acrylamide with the novel carboxybetaine monomer, 2-(2-acrylamido-2-methylpropyldimethylammonio) ethanoate (AMPDAE). Feed ratios of 10 to 100 mol% AMPDAE were employed to give the polyzwitterion series, DAEAM. Copolymer compositions of low conversion samples were determined from 13 C n.m.r. by integration of the carbonyl resonances. Reactivity ratios were determined yielding an r 1 r 2 value of 0.6. Molecular weights range from 6.3 to 10.4 × 10 6 g mol −1 as determined by low angle laser light scattering. Dilute solution properties of the copolymers have been studied as a function of added electrolytes and pH. Intrinsic viscosity behaviour in NaCl solutions is dependent on the mol% of AMPDAE incorporated into the copolymers. Reduced viscosities were also examined as a function of the nature of added electrolytes, displaying higher viscosity values in accord with the Hoffmiester lyotropic series. The copolymers exhibit an enhancement in viscosity as pH is lowered due to protonation of the carboxylate groups which renders the polymer coil cationic due to the presence of quaternary ammonium groups. The solution behaviour of the copolymer containing 25 mol% AMPDAE, which possesses one methylene unit between the quaternary ammonium group and the carboxylate group, is compared to that of a copolymer containing 25 mol% 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate, which possesses three methylene units between the charged centres.