Conditions Leading to Polyelectrolyte Complex Overcharging in Solution: Complexation of Poly(acrylate) Anion with Poly(allylammonium) Cation

Abstract

Complexation between poly­(acrylate) (PA) and poly­(allylammonium) (PAH) macroions at pH = 7.0 was studied by means of electrokinetics, microcalorimetry, and DLS. At low polyelectrolyte concentrations and no electrolyte present strong overcharging of primary nanocomplexes occurred. In contrast, the increase in polyelectrolyte concentration led to flocculation taking place near the equivalence. The nanocomplex charge reversal was also achieved in the high polymer concentration regime by the abrupt instead of stepwise titrant addition. The procedure was successfully used in the case of several other polyion pairs. The presence of electrolyte affected the PAH–PA interpolyelectrolyte neutralization considerably, leading to ion-specific aggregation and extrinsic charge compensation. The complexation energetics was weakly influenced by ionic conditions. To the best of our knowledge, the reported results are the first direct evidence for primary complex overcharging. Their rationalization explains why interpolyelectrolyte neutralization in solution and at surfaces usually results in formation of neutral and charged products, respectively.

High-Resolution Ultrasonic Spectroscopy: Looking at the Interpolyelectrolyte Neutralization from a Different Perspective

“…The herein-described HR-US results confirm the previously reported anion-specific aggregation of PAH/PAA complexes observed by DLS measurements . In that study, aggregation of positive complexes was detected by a large increase in the particle size at molar ratios of 0.6 and 0.8 in the presence of NaClO 4 and NaCl, respectively (Figure 6a in ref ). Moreover, the anion-specific aggregation of PAH/PAA complexes was further explored by titration of positive primary complexes with simple electrolyte solutions.…”

“…Therefore, after the abrupt titrant addition, the ultrasonic velocity increased due to the coexistence of rigid secondary complexes and free PAA molecules in stable colloidal suspension, and the attenuation increases as a consequence of the increase in heterogeneity. In addition to the PAH/PAA pair, the overcharging of primary PECs achieved by abrupt titrant addition in excess was previously observed by DLS and electrophoretic methods in the case of PDADMAC-PSS and PAH-PSS pairs . It, therefore, seems that the phenomenon of charge inversion of primary polyelectrolyte complexes is universal, just like the surface charge inversion that occurs during the deposition of each polyelectrolyte layer in the process of preparing polyelectrolyte multilayers (PEMs). − The described results are the additional strong evidence of the already observed correlation between the process of interpolyelectrolyte complexation in solution and the formation of PEMs on the surface.…”

“…To obtain a better insight into interpolyelectrolyte neutralization processes between poly­(allylammonium) cations and poly­(acrylate) anions, a relatively novel HR-US technique has been applied. The obtained results were compared with the previous study where more traditional methods (such as DLS and calorimetry) were used to examine PEC formation . The results of HR-US measurements have confirmed that PAH/PAA interpolyelectrolyte neutralization in the low salt regime undergoes solid–liquid phase separation and proceeds as described in the pioneering work of Fuoss and Sadek .…”

High-Resolution Ultrasonic Spectroscopy: Looking at the Interpolyelectrolyte Neutralization from a Different Perspective

“…The herein-described HR-US results confirm the previously reported anion-specific aggregation of PAH/PAA complexes observed by DLS measurements . In that study, aggregation of positive complexes was detected by a large increase in the particle size at molar ratios of 0.6 and 0.8 in the presence of NaClO 4 and NaCl, respectively (Figure 6a in ref ). Moreover, the anion-specific aggregation of PAH/PAA complexes was further explored by titration of positive primary complexes with simple electrolyte solutions.…”

“…Therefore, after the abrupt titrant addition, the ultrasonic velocity increased due to the coexistence of rigid secondary complexes and free PAA molecules in stable colloidal suspension, and the attenuation increases as a consequence of the increase in heterogeneity. In addition to the PAH/PAA pair, the overcharging of primary PECs achieved by abrupt titrant addition in excess was previously observed by DLS and electrophoretic methods in the case of PDADMAC-PSS and PAH-PSS pairs . It, therefore, seems that the phenomenon of charge inversion of primary polyelectrolyte complexes is universal, just like the surface charge inversion that occurs during the deposition of each polyelectrolyte layer in the process of preparing polyelectrolyte multilayers (PEMs). − The described results are the additional strong evidence of the already observed correlation between the process of interpolyelectrolyte complexation in solution and the formation of PEMs on the surface.…”

“…To obtain a better insight into interpolyelectrolyte neutralization processes between poly­(allylammonium) cations and poly­(acrylate) anions, a relatively novel HR-US technique has been applied. The obtained results were compared with the previous study where more traditional methods (such as DLS and calorimetry) were used to examine PEC formation . The results of HR-US measurements have confirmed that PAH/PAA interpolyelectrolyte neutralization in the low salt regime undergoes solid–liquid phase separation and proceeds as described in the pioneering work of Fuoss and Sadek .…”

Ion Content of Polyelectrolyte Complex Coacervates and the Donnan Equilibrium

“…In recent ITC studies, Požar and Kovačević were the first to point out that going beyond 1:1 or stoichiometric complexes produces/uses minimal heat . A follow-up study showed that overcompensated PEC resulted in nanoparticles stabilized by the excess polyelectrolyte, confirming Dautzenberg’s model . In other words, taking polyelectrolyte from dilute solution and concentrating it within the PEC are nearly athermal.…”

Polyelectrolyte Multilayers on Silica Surfaces: Effect of Ionic Strength and Sodium Salt Type

“…Our results suggest that, in order to obtain a deeper insight into the interpolyelectrolyte neutralisation at surfaces, a more detailed investigation of ion-specific effects on reactions between PDADMAC and PSS in solution would be very valuable, as done earlier for complexation of poly(acrylate) anion with poly(allylammonium) cation [30]. According to our preliminary unpublished results obtained for polyelectrolyte complexation in solution, counteranion effects on assembly of both negative and positive PDADMAC-PSS complexes or on their aggregation could be observed, too.…”

High-Resolution Ultrasonic Spectroscopy: Looking at the Interpolyelectrolyte Neutralization from a Different Perspective

“…The herein-described HR-US results confirm the previously reported anion-specific aggregation of PAH/PAA complexes observed by DLS measurements . In that study, aggregation of positive complexes was detected by a large increase in the particle size at molar ratios of 0.6 and 0.8 in the presence of NaClO 4 and NaCl, respectively (Figure 6a in ref ). Moreover, the anion-specific aggregation of PAH/PAA complexes was further explored by titration of positive primary complexes with simple electrolyte solutions.…”

“…Therefore, after the abrupt titrant addition, the ultrasonic velocity increased due to the coexistence of rigid secondary complexes and free PAA molecules in stable colloidal suspension, and the attenuation increases as a consequence of the increase in heterogeneity. In addition to the PAH/PAA pair, the overcharging of primary PECs achieved by abrupt titrant addition in excess was previously observed by DLS and electrophoretic methods in the case of PDADMAC-PSS and PAH-PSS pairs . It, therefore, seems that the phenomenon of charge inversion of primary polyelectrolyte complexes is universal, just like the surface charge inversion that occurs during the deposition of each polyelectrolyte layer in the process of preparing polyelectrolyte multilayers (PEMs). − The described results are the additional strong evidence of the already observed correlation between the process of interpolyelectrolyte complexation in solution and the formation of PEMs on the surface.…”

“…To obtain a better insight into interpolyelectrolyte neutralization processes between poly­(allylammonium) cations and poly­(acrylate) anions, a relatively novel HR-US technique has been applied. The obtained results were compared with the previous study where more traditional methods (such as DLS and calorimetry) were used to examine PEC formation . The results of HR-US measurements have confirmed that PAH/PAA interpolyelectrolyte neutralization in the low salt regime undergoes solid–liquid phase separation and proceeds as described in the pioneering work of Fuoss and Sadek .…”

Ion Content of Polyelectrolyte Complex Coacervates and the Donnan Equilibrium

“…In recent ITC studies, Požar and Kovačević were the first to point out that going beyond 1:1 or stoichiometric complexes produces/uses minimal heat . A follow-up study showed that overcompensated PEC resulted in nanoparticles stabilized by the excess polyelectrolyte, confirming Dautzenberg’s model . In other words, taking polyelectrolyte from dilute solution and concentrating it within the PEC are nearly athermal.…”

Polyelectrolyte Multilayers on Silica Surfaces: Effect of Ionic Strength and Sodium Salt Type

“…Our results suggest that, in order to obtain a deeper insight into the interpolyelectrolyte neutralisation at surfaces, a more detailed investigation of ion-specific effects on reactions between PDADMAC and PSS in solution would be very valuable, as done earlier for complexation of poly(acrylate) anion with poly(allylammonium) cation [30]. According to our preliminary unpublished results obtained for polyelectrolyte complexation in solution, counteranion effects on assembly of both negative and positive PDADMAC-PSS complexes or on their aggregation could be observed, too.…”

High-Resolution Ultrasonic Spectroscopy: Looking at the Interpolyelectrolyte Neutralization from a Different Perspective

“…The herein-described HR-US results confirm the previously reported anion-specific aggregation of PAH/PAA complexes observed by DLS measurements . In that study, aggregation of positive complexes was detected by a large increase in the particle size at molar ratios of 0.6 and 0.8 in the presence of NaClO 4 and NaCl, respectively (Figure 6a in ref ). Moreover, the anion-specific aggregation of PAH/PAA complexes was further explored by titration of positive primary complexes with simple electrolyte solutions.…”

“…Therefore, after the abrupt titrant addition, the ultrasonic velocity increased due to the coexistence of rigid secondary complexes and free PAA molecules in stable colloidal suspension, and the attenuation increases as a consequence of the increase in heterogeneity. In addition to the PAH/PAA pair, the overcharging of primary PECs achieved by abrupt titrant addition in excess was previously observed by DLS and electrophoretic methods in the case of PDADMAC-PSS and PAH-PSS pairs . It, therefore, seems that the phenomenon of charge inversion of primary polyelectrolyte complexes is universal, just like the surface charge inversion that occurs during the deposition of each polyelectrolyte layer in the process of preparing polyelectrolyte multilayers (PEMs). − The described results are the additional strong evidence of the already observed correlation between the process of interpolyelectrolyte complexation in solution and the formation of PEMs on the surface.…”

“…To obtain a better insight into interpolyelectrolyte neutralization processes between poly­(allylammonium) cations and poly­(acrylate) anions, a relatively novel HR-US technique has been applied. The obtained results were compared with the previous study where more traditional methods (such as DLS and calorimetry) were used to examine PEC formation . The results of HR-US measurements have confirmed that PAH/PAA interpolyelectrolyte neutralization in the low salt regime undergoes solid–liquid phase separation and proceeds as described in the pioneering work of Fuoss and Sadek .…”

Ion Content of Polyelectrolyte Complex Coacervates and the Donnan Equilibrium

“…In recent ITC studies, Požar and Kovačević were the first to point out that going beyond 1:1 or stoichiometric complexes produces/uses minimal heat . A follow-up study showed that overcompensated PEC resulted in nanoparticles stabilized by the excess polyelectrolyte, confirming Dautzenberg’s model . In other words, taking polyelectrolyte from dilute solution and concentrating it within the PEC are nearly athermal.…”

Polyelectrolyte Multilayers on Silica Surfaces: Effect of Ionic Strength and Sodium Salt Type

“…Our results suggest that, in order to obtain a deeper insight into the interpolyelectrolyte neutralisation at surfaces, a more detailed investigation of ion-specific effects on reactions between PDADMAC and PSS in solution would be very valuable, as done earlier for complexation of poly(acrylate) anion with poly(allylammonium) cation [30]. According to our preliminary unpublished results obtained for polyelectrolyte complexation in solution, counteranion effects on assembly of both negative and positive PDADMAC-PSS complexes or on their aggregation could be observed, too.…”