Resolving the Difference in Electric Potential within a Charged Macromolecule

Abstract

Aldrich) and palladium on activated carbon powder (Pd/C, 10%, Alfa Aesar) were used as received. Amino end-terminated polystyrene (PS) (M n = 120 × 10 3 g⋅mol −1 , M w /M n = 1.05) and amino end-terminated poly(N-isopropylacrylamide) (PNIPAM, M n = 7.1 × 10 3 g⋅mol −1 , M w /M n = 1.29) were purchased from Polymer Source (Quebéc, Canada). Water was purified with a Millipore system (18.2 MΩ•cm −1 ). All other chemical reagents were analytical grade and used as received without further purification. Spectral Characterizations:1 H nuclear magnetic resonance (NMR) spectra were measured with a Bruker DMX400 spectrometer with CDCl 3 or DMSO-d 6 as the solvent and tetramethylsilane (TMS) as the internal standard. A size exclusive chromatography (SEC) system equipped with a Waters 515 HPLC pump, three Waters Styragel columns (HT2, HT4, and HT5), a Rheodyne 7725i sampler, and a Waters 2414 refractive-index (RI) detector was adopted to determine the average molecular weights and molecular weight distribution of the polystyrene samples. Linear polystyrene standards were used to calibrate the SEC system. The eluent was DMF with 0.02 M LiBr at a flow rate of 1.0 mL⋅min −1 at 50 ºC. The pH value of the polymer solution was measured by a pH meter (Mettler-Toledo, Delta 320).

Local pH and effective pKA of weak polyelectrolytes – insights from computer simulations

“…18 Thanks to the higher molecular weight and star-like nature of the polymer the experimentally observed difference between the middle and the end was more pronounced (about 0.3 units of pH) than in our simulations. However, our present results cannot explain the relation between the local and bulk pH in the strong poly(styrene sulfonate), 17,45 where the ionization is independent of pH and the mechanism behind the local pH variation is presumably different.…”

“…However, investigation of the local pH near polyelectrolyte chain by means of computer simulations is lacking. Since the local pH in polyelectrolyte solutions has been measured in recent experiments, 17,18,45,46 it is timely to investigate it in computer simulations and to contrast the experimental and simulation results. Similarly, the role of polymer concentration has not been investigated in computer simulations, while its influence on the titration behaviour of weak polyelectrolytes is evidenced in experiments.…”

50th Anniversary Perspective: A Perspective on Polyelectrolyte Solutions

“…This fact has been recognized since the early investigations. 2,7,9 The most recent experiments 51 using fluorescence techniques are opening an opportunity to measure polarizability effects on ionic equilibria in polyelectrolyte solutions. Theoretical formulations of this effect in crowded environments are hard and remain as one of the major challenges in polyelectrolyte physics.…”

Future directions in physiochemical modeling of the thermodynamics of polyelectrolyte coacervates

“…112,113 This effect is observed, for example, in the Langevin simulations of Muthukumar and co-workers. 53 Second, it has been experimentally shown that the degree of counterion binding to a PE chain is higher in the middle of chain than near the chain ends, 114 since the middle of chain is more concentrated in PE charged groups than the ends. In addition, these results explain the stronger association of oppositely charged PEs with blockier sequences, which leads to larger coacervation windows in the studies of Sing and Perry, 7 Chan, 5,6 de Pablo, 115 and Fredrickson 9 and their co-workers.…”