Conductometric and Light Scattering Studies on the Complexation between Cationic Polyelectrolyte Nanogel and Anionic Polyion

Abstract

This work aims to provide a basic understanding of the water dispersibility of a 1:1 stoichiometric polyelectrolyte complex (SPEC) in water in the absence of low-molecular-weight salts. We studied the complexation of a linear polyanion, potassium poly(vinyl alcohol sulfate) (KPVS), with a cationic polyelectrolyte nanogel (CPENG) composed of a lightly cross-linked copolymer of N-isopropylacrylamide and 1-vinylimidazole, in an aqueous salt-free solution (pH 3 and 25 °C), as a function of the molar mixing ratio (Mmr) of anionic to cationic groups. Also studied for comparison was the complexation of KPVS with poly(diallyldimethylammonium chloride) (PDDA), which is a standard reaction in colloid titration. Turbidimetric and conductometric measurements were used in combination of dynamic light scattering (DLS). An abrupt increase of turbidity curve and a break of conductivity curve were observed at Mmr =1 when KPVS was added to the CPENG or PDDA solution, indicating the formation of SPEC. All the complexes formed at Mmr ≤ 1 were water-dispersible and hence characterized by DLS. The CONTIN analysis of DLS data showed that (i) an increase of Mmr causes a decrease of the hydrodynamic radius (R(h)) of the nanogel complex particle but (ii) the R(h) of the PDDA complex remains unchanged at Mmr < 0.8. Taking these into account, we discussed the conductometric results in terms of the random model (RM) and all-or-none model (AONM) in polyelectrolyte complex formations. It was found that KPVS and PDDA yield a water-dispersible SPEC particle at each Mmr, accompanying the uptake of counterions (K(+) and Cl(-)) by the complex. This uptake amount was about 7% of the stoichiometric release of the counterions. In the nanogel system, a complete release of the counterions was observed at Mmr < 0.2 at which one or two KPVS chains were bound to a CPENG particle, but further KPVS binding led to about 20% of the counterion uptake to maintain electroneutrality. Thus, we suggest that the counterion uptake becomes a key factor to understand the water dispersibility of SPEC particles.

Cationic Polymer Nanoparticles and Nanogels: From Synthesis to Biotechnological Applications

“…More recently, the same group analyzed the water dispersibility of complexes formed between cationic polyelectrolyte nanogels and anionic polyions and their complexation by conductometric and light scattering studies, respectively. , …”

“…Recently, Kokufuta and Doi , reported a study on the water dispersibility of a 1/1 stoichiometric complex between a cationic nanogel and linear polyanion (SPENC) composed of a cross-linked (using MBA as the cross-linker) copolymer of 1-vinylimidazole and NIPAM and discussed in terms of the association–dissociation reactions between both of the polyelectrolyte components. The results indicated that the whole and a part (segment) of the complexed polyanions undergo dissociation–association reactions on the surface of a SPENC particle, depending on the ionization state of the cationic gel component.…”

“…More recently, the same group analyzed the water dispersibility of complexes formed between cationic polyelectrolyte nanogels and anionic polyions and their complexation by conductometric and light scattering studies, respectively. 380,381 In addition, Hu et al 382 published the synthesis and physicochemical properties of cationic microgels based on PNIPMAM. Microgels were synthesized by surfactant-free radical precipitation polymerization of NIPMAM and the cationic comonomer N-(3-aminopropyl)methacrylate hydrochloride (APMH).…”

Molecular interactions in N-[(2-hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride-sodium alginate polyelectrolyte complexes

“…Sodium alginate (SA), extracted from sea weeds having (1,4)-linked β-Dmannuronate(M) and α-L-glucuronate (G) residues is widely used in the food packaging (Oliveira Filho, Rodrigues, Valadares, Almeida, Lima, Takeuchi, et al, 2019;Yao, Zhou, Chen, Ma, Li, & Chen, 2018), drug delivery (Agüero, Zaldivar-Silva, Peña, & Dias, 2017), textile (Li, He, & Huang, 2017), and cosmetic fields (Bae, Nam, & Park, 2019), among others. Owing to its polyanionic nature, SA can form PECs with positively charged polymers in the absence of organic solvents (Doi & Kokufuta, 2011;Paques, van der Linden, van Rijn, & Sagis, 2014). Based on these advantages, SAbased PECs are commonly used as bone tissue engineering scaffolds, drug packaging/controlled release agents, and functional food additive carriers (Mirpoor, Hosseini, & Yousefi, 2017;Xiao, Yu, & Yang, 2011;Zimet & Livney, 2009).…”