Polyelectrolyte Complex Particles Research Articles

Sizing of PDADMAC/PSS Complex Aggregates by Polyelectrolyte and Salt Concentration and PSS Molecular Weight

Herein we report on the influence of salt and polyelectrolyte (PEL) concentration, molecular weight, and mixing ratio on the size and size distribution of polyelectrolyte complex (PEC) particles composed of cationic poly(diallyldimethylammonium chloride) and anionic poly(styrene sulfonic acid). The unusual salt concentration dependence of PEC particle sizes was observed. This behavior was explained by competition of two processes both related to the charge screening: swelling/shrinking of the outer shell formed by the excess PEL molecules and increasing/decreasing of the aggregation rate of colloidal PEC particles. The results on the size regulation of PEC particles by varying PEL concentration reflect both competitive processes as well. The regulation of the mixing ratio of PEL allows producing PEC particles with different charges, and it does not affect significantly the PEC particle size regulation by salt concentration. The PEC size dependence on the molecular weight of polymer was shown to be power and an exponent value of α ≈ 0.13 was obtained for the spherical PEC particles. This value is lower than one for polymer particles with a compact globular structure with exponent values of α = 0.33. However, the molecular weight of only one polymer component of a two-component PEC particle was varied.

Influence of the comonomer structure and of the initial pH on the characteristics of polyelectrolyte complexes based on maleic acid copolymers

The interaction between some hydrophilic and hydrophobic maleic acid copolymers and a strong polycation, poly(diallyldimethylammonium chloride), at low concentration and different pH, with the formation of polyelectrolyte complex (PEC) dispersions, was the object of this study. Poly(maleic acid–alt–vinyl acetate) was used as hydrophilic copolymer and poly(maleic acid–alt–styrene) and poly(maleic acid–alt–2-vinylnaphthalene) were used as more hydrophobic copolymers. A special attention was given to the in-situ investigation by turbidimetry, potentiometry, and conductometry of the formed PECs and to their characterization after 24 h by optical density, dynamic light scattering and atomic force microscopy. Taking into account that the conformation of the copolymers is influenced by their neutralization degree, related to the solution pH, we had investigated the influence of this parameter on the PEC formation at pH = 6, where around half of the carboxylic groups are neutralized, and at pH = 10, at totally dissociated state. This study focused on the influence of the comonomer hydrophilic/hydrophobic nature, polyions mixing order, and starting pH of the solutions on the ratio of the complementary polyelectrolytes at the titration end-point and on the PEC particles size.

Electrosprayed polyelectrolyte complexes between mucoadhesive N,N,N,-trimethylchitosan-homocysteine thiolactone and alginate/carrageenan for camptothecin delivery

Novel hydrogel polyelectrolyte complexes (PECs) between the N,N,N,-trimethylchitosan-homocysteine thiolactone (TM-HT-chitosan) and two anionic polymers were investigated. The particles of pure thiolated chitosan and its PECs with alginate and carrageenan were fabricated using the electrospray ionization technique. The hydrogel PEC particles were characterized by scanning electron microscopy, dynamic light scattering, Fourier transform infrared microscopy, thermogravimetric analysis, encapsulation efficiency (EE), mucoadhesive property and in vitro drug release behavior. TM-HT-chitosan/alginate particles could be loaded with camptothecin (CPT), employed as a model anti-cancer drug, at an over 70% EE, and revealed both a reduced burst effect and a prolonged release of CPT over 3 days. The resultant TM-HT-chitosan/alginate PEC particles displayed a 5.60-, 1.86- and 1.55-fold stronger mucoadhesive property compared to that of the unmodified chitosan/alginate PEC at pH 1.2, 4.0 and 6.4, respectively, and this was not affected by the CPT loading level.

Metal Ion-Enriched Polyelectrolyte Complexes and Their Utilization in Multilayer Assembly and Catalytic Nanocomposite Films

The mixing of Ag ion-doped poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAA) produced Ag ion-doped polyelectrolyte complex particles (PECs) in solution. Positively charged Ag ion-doped PECs (Ag ion PECs) with a spherical shape were deposited alternatively with PAA to form a multilayer assembly. The multilayered film containing Ag ion PECs was reduced to generate a composite nanostructure. Metal nanoparticle (NP)-enriched nanocomposite films were formed by an additional process of the postadsorption of precursors on PECs within the nanocomposite films, which resulted in the enhancement of the catalytic and electrical properties of the composite films. Because the films contain PECs that are responsive to changes in pH and most of the NPs are embedded in the PECs, interesting catalytic properties, which are unexpected in a particle-type catalyst, were observed upon pH changes. As a result of the reversible structural changes of the films and the immobilization of the NPs within the films, the film-type catalysts showed enhanced performance and stability during catalytic reactions under various pH conditions, compared to particle-type catalysts.

Release of pamidronate from poly(ethyleneimine)/cellulose sulphate complex nanoparticle films: An in situ ATR-FTIR study

In situ ATR-FTIR spectroscopy was used as a screening method to quantify the relative release of pamidronate (PAM) from films of polyelectrolyte (PEL) complex (PEC) particles. Stable colloid PEC particles consisting of poly(ethyleneimine) (PEI) and cellulose sulphate (CS) loaded with PAM were obtained by PEL complexation featuring hydrodynamic radii between 60 and 90 nm and a cationic or anionic surface charge dependent on the mixing ratio n-/n+=0.9 or 1.1, respectively. Respective bare unloaded PEC particles showed smaller hydrodynamic radii. PAM loaded PEC particles were casted from dispersion onto Ge model substrates and dried forming stable films in contact to water. By in situ ATR-FTIR spectroscopy it could be shown, that PAM/PEC particle films contacting to water resulted in a time dependent retarded release of PAM from the PEC matrix, while PAM from a pure drug film was immediately released. Cationic PAM loaded PEC particles of PEI/CS showed smaller initial burst and long term release compared to anionic one at similar PAM/PEI ratios. With increasing PAM/PEI ratio the initial burst could be minimized to around 30% and the residual long term amount of PAM optimized to 50% for PAM/PEC samples casted from 0.002 M dispersions. A further improvement of the release performance was achieved either by prerinsing the dry film in H(2)O or by rising the PEC concentration from 0.002 M to 0.01 M revealing an initial burst of around 5% and long term residual PAM content of around 75%. ATR-FTIR and TRANS-FTIR analysis of the PAM release from equivalent PEC samples revealed similar kinetic courses and parameters justifying the use of the Ritger/Peppas two parameter model. Applying this model PAM/PEC samples casted from 0.002 M dispersions revealed exponent values of b≪0.5 suggesting PAM dissolution in the PEC matrix, while for those casted from 0.01 M b values close to 0.5 were obtained suggesting hindered dissolution and diffusion. A model describing different retention modalities of PAM in PEC particle is suggested.

Influence of the Hydrophobicity of Polyelectrolytes on Polyelectrolyte Complex Formation and Complex Particle Structure and Shape

Polyelectrolyte complexes (PECs) were prepared by structural uniform and strongly charged cationic and anionic modified alternating maleic anhydride copolymers. The hydrophobicity of the polyelectrolytes was changed by the comonomers (ethylene, isobutylene and styrene). Additionally, the n−/n+ ratio of the molar charges of the polyelectrolytes and the procedure of formation were varied. The colloidal stability of the systems and the size, shape, and structure of the PEC particles were investigated by turbidimetry, dynamic light scattering (DLS) and atomic force microscopy (AFM). Dynamic light scattering indicates that beside large PEC particle aggregates distinct smaller particles were formed by the copolymers which have the highest hydrophobicity (styrene). These findings could be proved by AFM. Fractal dimension (D), root mean square (RMS) roughness and the surface profiles of the PEC particles adsorbed on mica allow the following conclusions: the higher the hydrophobicity of the polyelectrolytes, the broader is the particle size distribution and the minor is the swelling of the PEC particles. Hence, the most compact particles are formed with the very hydrophobic copolymer.

Polyelectrolyte complexes from polyethylene imine/acetone formaldehyde sulfite polycondensates: A novel reagent for effective fluid loss control of oil well cement slurries

AbstractWhen used by itself, polyethylene imine (PEI) does not perform well as cement fluid loss additive. Its combination with acetone formaldehyde sulfite (AFS) polycondensate, however, exhibits excellent filtration control. The mechanism underlying this synergistic effect was studied and the conditions producing best results were determined. For optimum performance, PEI and AFS must be reacted with each other to yield a polyelectrolyte complex (PEC) (d ∼ 5–10 μm), which effectively plugs the pores of the cement filter cake. Composition, size, and effectiveness of the PEC are strongly influenced by the anionic charge amount of the AFS dispersant. Ionic interactions between cationic imine functionalities of PEI and anionic sulfonate groups existing in AFS were confirmed by conductivity, infrared, zeta potential, and particle size measurements. For AFS samples possessing different degrees of sulfonation, the largest particle size and hence best fluid loss performance of the PEC was found to occur at a PEI:AFS molar ratio, which corresponds to neutral charge. Occurrence of large PEC particles (d ∼ 5 μm) within the cement filter cake pores was visualized by scanning electron microscopy, and their stability in highly alkaline cement pore solution was confirmed by particle size measurement. Other anionic polyelectrolytes may be used to yield such PECs with PEI to provide effective fluid loss control for cement slurries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

New polyelectrolyte complex particles as colloidal dispersions based on weak synthetic and/or natural polyelectrolytes

This study aims to evidence the formation of stable polyelectrolyte complex particles as colloidal dispersions using some weak polyelectrolytes: chitosan and poly(allylamine hydrochloride) as polycations and poly(acrylic acid) (PAA) and poly(2-acrylamido-2-methylpropanesulfonic acid - co - acrylic acid) (PAMPSAA) as polyanions. Polyelec- trolyte complex particles as colloidal dispersion were prepared by controlled mixing of the oppositely charged polymers, with a constant addition rate. The influences of the polyelectrolytes structure and the molar ratio between ionic charges on the morphology, size, and colloidal stability of the complex particles have been deeply investigated by turbidimetry, dynamic light scattering and atomic force microscopy. A strong influence of polyanion structure on the values of molar ratio n - /n + when neutral complex particles were obtained has been noticed, which shifts from the theoretical value of 1.0, observed when PAA was used, to 0.7 for PAMPSAA based complexes. The polyions chain characteristics influenced the size and shape of the complexes, larger particles being obtained when chitosan was used, for the same polyanion, and when PAMPSAA was used, for the same polycation.

Synthesis of chitosan‐poly(Acrylic Acid) complex particles by dispersion polymerization and their applications in ph buffering and drug release

AbstractThis research prepared polyelectrolyte complex particles of chitosan‐poly(acrylic acid) (CS‐PAA) through polymerization of acrylic acid (AA) in the presence of chitosan (CS). The prepared CS‐PAA complex particles had positive zeta potential and dispersed very well in the aqueous solution. Structure and morphology of complex particles were investigated with the changes in the feeding molar ratio of glucosamine unit in CS to AA monomer. It was found at a molar ratio of 1.0/1.1, a hollow structure in complex particles was observed after polymerization. From solid state 13C‐NMR and FTIR analyses, the results confirmed that CS‐co‐PAA copolymer was also produced during polymerization in addition to the PAA homopolymer, and both constituted in the structure of complex particles. The synthesized complex particles were environmentally sensitive in which their mean diameter could change with the pH value of medium. Moreover, the complex particles showed a continuous release of the encapsulated doxycycline hyclate up to 8 days. These complex particles with environmentally sensitive properties are expected to be utilized in the hydrophilic drug delivery system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Speedy fabrication of free-standing layer-by-layer multilayer films by using polyelectrolyte complex particles as building blocks

A novel method for speedy fabrication of free-standing layer-by-layer (LbL) multilayer films in salt free media, and without the need for a sacrificial sublayer is described by using two different polyelectrolyte complex (PEC) nanoparticles as LbL self-assembly building blocks. Negatively charged polyelectrolyte complex particles (PEC−) consisting of poly(diallyldimethylammonium chloride)/sodium carboxymethyl cellulose (PDDA/CMCNa), and positively charged polyelectrolyte complex particles (PEC+) consisting of PDDA/poly(sodium-p-styrenesulfonate) (PDDA/PSSNa) were prepared and characterized by FT-IR, zeta-potential (ζ potential) and transmission electron microscopy (TEM). The LbL self-assembly of PEC+/PEC− and PDDA/PEC− was followed by quartz crystal microbalance (QCM), optical transmittance, UV-vis absorption spectroscopy and atomic force microscopy (AFM). QCM results show that the thickness growth rate of the PEC+/PEC− pair is 9 times faster than that of the PDDA/PEC− pair and this result is also supported by optical transmittance and UV-vis absorption. A robust free-standing multilayer film of (PEC+/PEC−)25 can be easily peeled off from the substrate after being cross-linked in 3.5 wt% glutaraldehyde (GA) (80 °C, 50mins). Field emission electron scanning microscopy (FESEM) indicates that both the surface and cross-section of the multilayer film display layered structures. Furthermore, multiwall carbon nanotubes (MWCNTs) can also be uniformly incorporated into the free-standing LbL multilayer film by pre-incorporating MWCNTs into PEC− particles. The experimental results show that using oppositely charged PEC particles as LbL assembly components is a speedy and convenient method to fabricate free-standing LbL multilayer films either with or without nanofillers.

Growth of Polyelectrolyte Complex Nanoparticles: Computer Simulations and Experiments

Herein we report on simulation and experimental studies on the formation of monomodal polyelectrolyte complex (PEC) nanoparticles, prepared by mixing two solutions of oppositely charged polyelectrolytes (PELs) under variation of ionic strength and applying centrifugation. This work aims at the better understanding of recently reported experimental studies, which demonstrated that consecutive centrifugation results in the removal of small primary PEC particles in polymodal dispersions and receipt of monomodal PEC dispersions of secondary PEC particles. In order to describe this effect and the possibilities of particle size regulation in PEC dispersions, a novel particle coagulation model, based on the combination of the mean-field theory of Smoluchowski and the Fuchs stability approach including a classical DLVO potential of interparticle interactions, was used in this study. The aggregation process was simulated under variation of the typical colloidal parameters: the Hamaker constant A, the Debye length λ, and the ζ-potential. The influence of these parameters on the mean final size, kinetics, and size distribution function of the colloid particles was studied. In the experimental section we study the system of cationic poly(diallyldimethylammonium chloride) (PDADMAC) mixed with an excess of anionic sodium poly(styrenesulfonate) (PSS) and varying NaCl concentration in the range CNaCl = 0.001–0.05 M. The size of secondary PEC particles as a function of the salt concentration exhibited a pronounced minimum at CNaCl ≈ 0.005 M. The influence of PEL conformation on the PEC particle size and the comparability of simulation and experimental results are discussed.

Destabilization of model silica dispersions by polyelectrolyte complex particles with different charge excess, hydrophobicity, and particle size

AbstractNonstoichiometric polyelectrolyte complex dispersions (PECs) with different charge excess and hydrophobicity as well as different average hydrodynamic particle size were used to induce flocculation of oppositely charged silica dispersions. PECs were formed with poly(diallyldimethylammonium chloride) (PD) as polycation and poly(styrene‐p‐sodium sulfonate) (NaPSS) and poly(acrylamide‐co‐sodium acrylate) (PR2540) as polyanions. PD was used as single polymer flocculant too. Flocculation process was characterized by optical densities of supernatants OD500, by UV/VIS spectrometry, and determination of average floc sizes D(v; 0.5) as well as volume distribution of floc sizes by laser diffraction and determination of sedimentation velocity s by means of LUMiFuge™ 114. It was found that the reaction process between silica and the used flocculants could be divided into three intervals (destabilization, flocculation optimum, and restabilization) as it is known for all other polymer flocculants. For an effective flocculation of a charged substrate, both electrostatic as well as hydrophobic interactions play an important role. The interval up to the beginning of the flocculation optimum is mainly ascertained by electrostatic interactions (the charge density of the flocculant) but the broadness of flocculation optimum depends largely on hydrophobic interactions. Hydrophobic interactions also play an important role for shear stability of the formed flocs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3776–3784, 2007

Monomodal Polyelectrolyte Complex Nanoparticles of PDADMAC/Poly(styrenesulfonate): Preparation and Protein Interaction

The binding of the model proteins HSA, LYZ and MYO to PEC nanoparticles is reported. PEC particles were prepared by mixing solutions of PDADMAC either with PSS or PMA-MS, followed by consecutive centrifugation. Monomodal anionic (PEC-1.50) and cationic (PEC-0.66) PEC particles were obtained using non-stoichiometric mixing ratios. PEC/protein conjugates were prepared by adding charged protein solutions to dispersions of respective like charged PEC particles, followed by one centrifugation step. Mixing proteins and PEC particles under attractive conditions led to flocculation of the dispersion. From CD, DLS and AFM the following trend for protein binding at PEC particles under repulsive conditions was obtained: HSA/PEC-1.50 > MYO/PEC-1.50 > LYZ/PEC-0.66. Protein uptakes up to 0.33 g x g(-1) (protein/PEC) (CD) and particle diameter enlargements up to 13 nm (AFM) were obtained at c(PROT) = 0.091 mg . mL(-1). Furthermore, novel spin coated films of PEC particles were interacted with proteins under both repulsive and attractive conditions. In-situ ATR FT-IR spectroscopy revealed that the adsorbed amount of HSA and LYZ under attractive conditions was significantly higher than under repulsive ones, which is analogous to protein adsorption at polyelectrolyte multilayers terminated either by polycation or polyanion. Similarly to the dispersed PEC/protein conjugates, under repulsive conditions the uptake of HSA was higher compared to LYZ. The shown protein uptake under repulsive conditions is related to concepts of mild enzyme or protein binding at nonbiogenic substrates.

Interpolyelectrolyte Complexes: A Single-Molecule Insight

Polyelectrolyte (PE) complexes (PECs) between long polycation poly(methacryloyloxyethyl dimethylbenzylammonium chloride) and short polyanion polystyrene sulfonic acid adsorbed onto mica were studied by atomic force microscopy. If one component is taken in excess, then a rapid coupling of the oppositely charged polyions first leads to the formation of nonequilibrium structures when collapsed PEC particles coexist with unreacted PEs molecules. The equilibrium PEC particles possess micelle-like core-shell morphology if the short polyion is taken in excess. When long PE is given in excess, equilibrium PECs are stabilized by wrapping the long polyion around hydrophobic segments of the PEC. We propose that transformations of initially formed nonequilibrium aggregates proceed through slow reactions (addition or/and substitution) of primary complexes with unreacted PEs chains, which finally leads to equilibrium PECs with optimized morphology. As expected, the mixing of oppositely charged PEs in a near-stoichiometric ratio leads to highly aggregated water-insoluble PECs.

Comparison of morphology and properties of polyelectrolyte complex particles formed from chitosan and polyanionic biopolymers

AbstractBeads containing a chitosan core and a polyelectrolyte complex (PEC) shell were formed by the dropwise addition of chitosan to solutions containing sodium alginate, gellan, pectin, κ‐carrageenan, or poly(acrylic acid). Hydrogel cores were formed by crosslinking chitosan with genipin, a natural bifunctional crosslinker. The shell thickness was generally only a few molecules thick and was impermeable to the transport of macromolecules but not low molecular weight molecules. Increasing the number of anionic groups and the strength of the chitosan–polyanion interaction through selection of different anionic species increased the mechanical strength of the PEC shell by increasing the number of interaction points in the shell. Because the core and shell swelled differentially, with the shell able to swell much less than the core, increasing the shell strength increasingly constrained the degree of swelling that could be attained for the entire bead. The degree of swelling could therefore be controlled via the mechanical properties of the shell, which could in turn be explained by the molecular structure of the PEC shell. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1581–1593, 2005

Preparation of Monomodal Polyelectrolyte Complex Nanoparticles of PDADMAC/Poly(Maleic Acid-alt-α-methylstyrene) by Consecutive Centrifugation

We report on the refinement of anionic and cationic nanoparticles of nonstoichometric polyelectrolyte complexes (PEC) by consecutive centrifugation, which was studied by dynamic light scattering (DLS), atomic force microscopy (AFM), colloid titration and infrared spectroscopy (IR). PEC dispersions were prepared by mixing poly(diallyldimethylammonium chloride) (PDADMAC) and sodium poly(maleic acid-alt-alpha-methylstyrene) (PMA-MS) at the monomolar mixing ratio of n-/n+ = 1.50 (anionic PEC) and 0.66 (cationic PEC), respectively, and the polymer concentration of c(POL) = 0.002 M. The particle size (Rh), titrable charge amount, and IR spectra were determined for both dispersions in the original state, after the first centrifugation and after the second centrifugation. Freshly prepared PEC dispersions contained two different particle sizes: around 10-25 nm (small particles) and around 100 nm (large particles). Consecutive centrifugation of freshly prepared PEC dispersions resulted in the separation of highly charged excess polyelectrolyte (PEL) and small PEC particles from a low charged coacervate phase of the desired larger PEC particles. After the second centrifugation, the coacervate phase of both dispersions PEC-1.50 and PEC-0.66 consisted of monomodal particles sizing around 100 nm. These results were supported by AFM measurements on the respective dispersions deposited on glass plates. PEC-1.50 particles tended to adopt slightly smaller sizes ( approximately 90 nm) in comparison to PEC-0.66 ones (approximately 110 nm). No significant influence of the PDADMAC molecular weight on the particle size was found. IR spectroscopy showed changes in the environment of the carboxylate groups of PMA-MS by consecutive centrifugation. The centrifuged PEC-1.50 dispersions showed remarkable long-term stability over more than a year. The high macroscopic stability of the studied PEC dispersions is presumably due to repulsive electrostatic interparticle interactions and attractive hydrophobic intraparticle interaction. The introduced monomodal PEC particles might be projected as latex analogues or as nanocarriers for drugs and proteins.

Formation of Polyelectrolyte Complex Particles from Self-Complexation of N-Sulfated Chitosan

This work investigated the elaboration of biocompatible nanoparticles from the pH-induced self-complexation of the amphoteric polysaccharide N-sulfated chitosan. The acidification of aqueous solutions of chitosan having a degree of acetylation of 24% and a degree of sulfation of 34% or 56% was followed stepwise by turbidimetry, dynamic light scattering, and electrophoresis. With the highest sulfated chitosan, no turbidity was recorded between pH = 7.8 and 2.0, traducing a high apparent solubility of the polymer chains in this domain of pH. With the lowest sulfated chitosan, a steady increase in turbidity was monitored from pH = 6.90 to 6.15 followed by the flocculation of the polymer at pH approximately 6.0. In this range of pH, the polymer phase separated to yield particles having hydrodynamic diameters decreasing from 350 to 260 nm and an almost constant negative charge. These particles were assembled by electrostatic interactions between the protonated amino residues and the sulfate functions and stabilized by an excess of surface sulfate groups. The particles could be separated from the reaction medium and concentrated by centrifugation-redispersion cycles without alteration of their structure.

Versatile and efficient formation of colloids of biopolymer-based polyelectrolyte complexes.

The formation of colloids based on polyelectrolyte complexes (PECs) of biopolymers was investigated through the complexation between two charged polysaccharides, chitosan as polycation, and dextran sulfate as polyanion. The slow dropwise addition of components, generally used for the formation of PECs, allowed to elaborate both cationic or anionic particles with an excess of chitosan or dextran sulfate, respectively. The PEC particles featured a core/shell structure, the hydrophobic core resulting from the segregation of complexed segments whereas excess component in the outer shell ensured the colloidal stabilization against further coagulation. Considering the host/guest concept for the formation of PECs, the influence of the molecular weight of components on particles sizes could be well explained by the chain length ratios of the two polymers. As an irreversible flocculation occurred with a dropwise approach for both cationic and anionic PEC particles when the mixing ratio was close to unity, a more versatile, and simpler to setup, method was designed: the one-shot addition of one solution to the other. Because process of addition is faster than the flocculation, cationic or anionic particles could be elaborated irrespective of the order of addition of the reactant. Characterization of these particles by quasielastic light scattering, electrophoresis, and scanning electron microscopy revealed very similar properties to those obtained by a slow dropwise approach. Critical coagulation concentrations of 0.12 and 0.09 M (with sodium chloride) for cationic and anionic particles evidenced a mostly electrostatic stabilization.

Formation and properties of positively charged colloids based on polyelectrolyte complexes of biopolymers.

Formation of colloids based on polyelectrolyte complexes (PECs) was mainly studied with synthetic polyelectrolytes. In this study, we describe the elaboration of positively charged PEC particles at a submicrometer level obtained by the complexation between two charged polysaccharides, chitosan as polycation and dextran sulfate (DS) as polyanion. The complexes were elaborated by dropwise addition of default amounts of DS to excess chitosan. Quasi-elastic light scattering was used to investigate in detail the influence of the characteristics of components (chain length, degree of acetylation) and parameters linked to the reaction of complexation (molar mixing ratio, ionic strength, concentration in polymer) on the sizes and polydispersity of colloids. Chain length of chitosan is the major parameter affecting the dimensions of the complexes, high molar mass chitosans leading to the largest particles. Variations of hydrodynamic diameters of PECs with the molar mass of chitosan are consistent with a mechanism of particle formation through the segregation of the neutral and then hydrophobic blocks of the polyelectrolyte complexed segments. Resulting particles display probably a structure constituted by a neutral core surrounded by a chitosan shell ensuring the colloidal stabilization. Such a structure was evidenced by measurements of electrophoretic mobilities revealing that the positive charge of particles was decreasing with pH, in relation with the neutralization of excess glucosamine hydrochloride moieties.

Complexation of DNA with poly(methacryl oxyethyl trimethylammonium chloride) and Its poly(oxyethylene) grafted analogue.

Intermolecular complexes of genomic polydisperse DNA with synthetic polycations have been studied. Two cationic polymers have been used, a homopolymer poly(methacryl oxyethyl trimethylammonium chloride) (PMOTAC) and its analogue grafted with poly(oxyethylene). The amount of poly(oxyethylene) grafts in the copolymer was 15 mol % and Mw of the graft was 200 g/mol. Salmon DNA (sodium salt) was used. The average molecular weight (Mw) of DNA was 10.4 x 10(6) g/mol. Conductivity, pH, and dynamic light scattering studies were used to characterize the complexes. The size and shape of the polyelectrolyte complex particles have been studied as a function of the cation-to-anion ratio in aqueous solutions of varying ionic strengths. The polyelectrolyte complexes have extremely narrow size distributions taking into account the polydispersity of the polyelectrolytes studied. The poly(oxyethylene) grafts on PMOTAC promote the formation of small colloidally stabile complex particles. Addition of salt shifts the macroscopic phase separation toward lower polycation content; that is, complexes partly phase separate with the mixing ratios far from 1:1. Further addition of salt to the turbid, partly phase separated solution results in the dissociation of complexes and the polycation and DNA dissolve as individual chains.