Synthesis of a diallylammonio propanephosphonate‐alt‐(sulfur dioxide) copolymer and its evaluation as an antiscalant in desalination plants

The cationic monomer N,N‐diallyl‐3‐(diethylphosphonato)propylammonium chloride was cyclo‐copolymerized with sulfur dioxide in dimethylsulfoxide using azoisobutyronitrile as initiator to afford a cationic polyelectrolyte (CPE) having a (diethylphosphonato)propyl pendent moiety. The CPE on acidic hydrolysis of the diester groups gave pH‐responsive polyzwitterionic acid (PZA) which on treatment with one and two equivalents of NaOH gave zwitterionic/anionic polyelectrolyte (ZAPE) and dianionic polyelectrolyte (DAPE), respectively. The solution properties of CPE, PZA, ZAPE and DAPE were investigated in detail using a viscometric technique. For comparison, the solution properties of the polymers were correlated with those of the structurally similar polyzwitterion prepared from copolymerization of the corresponding zwitterionic monomer ethyl‐3‐(N,N‐diallylammonio)propanephosphonate and sulfur dioxide. Evaluation of antiscaling properties using concentrated brine solutions revealed that DAPE at a meagre concentration of 10 ppm is very effective in inhibiting the formation of calcium sulfate scale, and as such can be used effectively as an antiscalant in reverse osmosis plants. © 2013 Society of Chemical Industry     

Comparative solution properties of cyclocopolymers having cationic,anionic, zwitterionic and zwitterionic/anionic backbones of similar degree of polymerization

A new class of ionic copolymers containing amine and phosphonate functionalities has been prepared for the first time. N,N-Diallyl-3-(Diethylphosphonato)-methylammonium chloride underwent cyclocopolymerization with SO₂ to give a cationic polyelectrolyte (CPE) in very good yields. Likewise, ethyl 3-(N,N-diallylammonio)methanephosphonate/SO₂ cyclopolymerization afforded the corresponding polyzwitterion-ester (PZE), which on neutralization with NaOH gave the anionic polyelectrolyte (APE). Both CPE and PZE on hydrolysis of the phosphonate ester functionalities gave the same polyzwitterionic acid (PZA). The pH-responsive PZA on treatment with excess NaOH was converted to dianionic polyelectrolyte (DAPE) which on treatment with 1 equivalent HCl afforded the zwitterionic-anionic polyelectrolyte (ZAPE). Solution properties of the CPE, PZE, DAPE, APE and ZAPE having similar degree of polymerization have been studied in some detail. The apparent basicity constants of the amine group in APE have been determined. An aqueous two-phase system of polyethylene glycol-DAPE-H₂O (0.4 N NaCl) has been constructed for its potential application in selective separation of toxic metal ions since polyphosphonates are expected to be effective chelators.     

Bis[3‐(diethoxyphosphoryl)propyl]diallylammonium chloride: Synthesis and use of its cyclopolymer as an antiscalant

A new symmetrically substituted cationic monomer bis[3‐(diethoxyphosphoryl)propyl]diallylammonium chloride has been synthesized and cyclopolymerized to give the corresponding cationic polyelectrolyte (+) (CPE) bearing two identical (diethoxyphosphoryl)propyl penedents on the pyrrolidinium repeating units. The hydrolysis of the phosphonate ester in (+) (CPE) gave a pH‐responsive cationic polyacid (+) (CPA) bearing the motifs of a tetrabasic acid. The (+) (CPA) under pH‐induced transformation was converted into a water‐insoluble polyzwitterion acid (±) (PZA) or water‐soluble polyzwitterion/monoanion (± ?) (PZMAN) or polyzwitterion/dianion (± =) (PZDAN) or polyzwitterion/trianion (± ≡) (PZTAN), all having identical degree of polymerization. The interesting solubility and viscosity behaviors of the polymers have been investigated in some detail. The apparent protonation constants of the anionic centers in (± ≡) (PZTAN) and its corresponding monomer (± ≡) (ZTAN) have been determined. Evaluation of antiscaling properties of the PZA using supersaturated solutions of CaSO₄ revealed ≈100% scale inhibition efficiency at a meager concentration of 10 ppm for a duration over 71 h at 40°C. The PZA has the potential to be an effective antiscalant in Reverse Osmosis plants. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40615.     

Synthesis and solution properties of hydrophobically associating ionic polymers made from diallylammonium salts/sulfur dioxide cyclocopolymerization

Sulfur dioxide, N,N-diallyl-N-carboethoxymethylammonium chloride and the hydrophobic monomers N,N-diallyl-N-dodecylammonium chloride or N,N-diallyl-N-octadecylammonium chloride were cyclocopolymerized in dimethyl sulfoxide using azobisisobutyronitrile (AIBN) as the initiator to afford water-soluble cationic polyelectrolyte (CPE) having five-membered cyclic structure on the polymeric backbone. The CPE on acidic (HCl) hydrolysis of the pendent ester groups gave the corresponding cationic acid salt (CAS) which was converted to the anionic polyelectrolyte (APE) by treatment with sodium hydroxide. The solution properties of the CPE and APE containing varying amount of the hydrophobic monomers in the range 0-10 mol% were investigated by viscometric techniques. The polymers showed that concentration (C^∗_HA) of less than 1 wt% was required for the manifestation of hydrophobic association, and displayed significant hydrophobic association in salt (NaCl)-free as well as salt-added solutions.     

Synthesis and comparative solution properties of a cationic polyelectrolyte and its corresponding polyzwitterion from 1,1‐diallyl‐4‐methoxycarbonylpiperidinium chloride

The quaternary ammonium monomer 1,1‐diallyl‐4‐methoxycarbonylpiperidinium chloride was synthesized in good yield. On polymerization in water using t‐butylhydroperoxide as initiator, a cationic polyelectrolyte (CPE) with a five‐membered cyclic structure on the polymeric backbone was obtained. On acid hydrolysis, followed by basification, the CPE gave the corresponding polybetaine (PB). The solution properties of these polymers were investigated by potentiometric and viscometric techniques. The PB demonstrated “antipolyelectrolyte” behavior. The basicity constant of the carboxylate functionality in the polyzwitterionic polymers was ‘apparent’ in a 0.1 N NaCl solution and followed the modified Henderson‐Hasselbalch equation. It was found that as the degree of protonation (α) of the whole macromolecule increases, the protonation of the amine nitrogen becomes increasingly more difficult. Unlike other polyzwitterions/polybetaines, the PB was soluble in salt‐free water. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effects of zwitterionic and anionic charge densities in polymer chains on the viscosity behavior of a pH‐responsive hydrophobically modified ionic polymer

Sulfur dioxide, N,N‐diallyl‐N‐carboethoxymethylammonium chloride, and the hydrophobic monomer N,N‐diallyl‐N‐octadecylammonium chloride were cyclocopolymerized in dimethyl sulfoxide using azobisisobutyronitrile (AIBN) as the initiator to afford water‐soluble cationic polyelectrolytes (CPE) having a five‐membered cyclic structure on the polymeric backbone. The CPE on acidic hydrolysis of the pendent ester groups gave the corresponding cationic acid salts (CAS), which, on treatment with sodium hydroxide, were converted to polybetaines (PB) and anionic polyelectrolytes (APE), as well as polymers PB/APE containing various proportions of zwitterionic (PB) and anionic fractions (APE) in the polymer chain. The solution properties of the CPE, APE, and PB/APE systems containing varying amounts of the hydrophobic monomers in the range 0–4 mol % were investigated by viscometric techniques. Treating the pH‐responsive CAS polymers 4 with different equivalents of NaOH varied the zwitterionic and anionic charge densities in the polymer chain. It was found that the PB/APE polymer with a ratio of 33 : 67 for the zwitterionic and anionic fractions in the polymer chain, respectively, gave the highest viscosity value. The polymers showed that concentration (C*_HA) of around 1 g/dL was required for the manifestation of significant hydrophobic associations. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1404–1411, 2005     

Synthesis,solution properties and scale‐inhibiting behaviour of a diallylammonium/sulfur dioxide cyclocopolymer bearing phospho‐ and sulfopropyl pendents

Zwitterion (Z) monomer 3‐[diallyl{3‐(diethoxyphosphoryl)propyl}ammonio]propane‐1‐sulfonate underwent cyclocopolymerization with sulfur dioxide to give a new alternating copolymer poly(Z‐alt‐SO₂) in excellent yield (ca 90%). The polyzwitterion (±) (PZ) (i.e. poly(Z‐alt‐SO₂), bearing a diethylphosphonate as well as a sulfonate functionality in each repeat unit, upon ester hydrolysis gave its corresponding pH‐responsive polyzwitterionic acid (±) (PZA). The pH‐induced equilibrations (+) cationic polyelectrolyte ? (±) PZA ? polyzwitterion/anion (± ?) (PZAN) ? polyzwitterion/dianion (± =) (PZDAN) permitted us to examine the effects of charge types and their densities on the interesting solubility and viscosity behaviours. The apparent protonation constants of the basic functionalities &tbond;N^±PO₃^2? in (± =) PZDAN and &tbond;N^±PO₃H^1? in (± ?) PZAN in salt‐free water and 0.1 mol L^?1 NaCl were determined using potentiometric titrations. (±) PZA at a meagre concentration of 20 ppm was found to be an effective antiscalant to inhibit the precipitation of CaSO₄ from its supersaturated solution: after 500 and 800 min, the respective scale inhibitions of 86 and 98% indicated its potential use as an effective antiscalant in reverse osmosis plant. © 2014 Society of Chemical Industry     

Synthesis and solution properties of a new ionic polymer and its behavior in aqueous two-phase polymer systems

The amine salt, N,N-diallyl-N-carboethoxymethylammonium chloride was copolymerized in dimethyl sulfoxide using ammonium persulfate or azo-bis-isobutyronitrile (AIBN) to afford the cationic polyelectrolyte (CPE) having five-membered cyclic structure on the polymeric backbone. The CPE on acidic (HCl) hydrolysis of the pendent ester groups gave the corresponding cationic acid salt (CAS) having the equivalent of chloride salt of N,N-diallylammonio ethanoic acid as monomeric unit. The CAS was converted into an anionic polyelectrolyte (APE) and polybetaine (PB) [having the monomeric unit equivalent of sodium N,N-diallylaminoethanoate and N,N-diallylammonioethanoate] by treatment with two and one equivalent of base, respectively. The solution properties of APE were investigated by potentiometric and viscometric techniques. Basicity constant of the amine functionality in APE is found to be ‘apparent’ and as such follow the modified Henderson-Hasselbalch equation; the protonation of the APE becomes more and more difficult as the degree of protonation (α) of the whole macromolecule increases. The composition and phase diagram of the aqueous two-phase systems of APE and poly(ethyelene glycol) (PEG) has been studied for the first time for this class of ionic polymers. The CAS and PB were found to be virtually insoluble in water.     

Interactions between cationic conjugated polyelectrolyte and DNA and a label‐free method for DNA detection based on conjugated polyelectrolyte complexes

The electrostatic complexes of single‐stranded deoxyribonucleic acid (ssDNA) and a cationic conjugated polyelectrolyte (CPE), poly{9,9‐di[3‐(1‐ethyl‐1,1‐dimethyl ammonio)propyl]‐2,7‐fluorenyl‐alt‐1,4‐phenylene dibromide} (PFN), were investigated. Fluorescence emission of PFN solution (10 μmol/L) can be drastically quenched to about one fourth of its original intensity in the presence of a trace amount (2.6 μmol/L) of ssDNA. The effect of oligonucleotide length on the fluorescence quenching behavior was also investigated. In contrast to single‐stranded DNA with 20 bases (ssDNA‐20), ssDNA with 40 bases (ssDNA‐40) induces a relatively higher quenching efficiency and larger red‐shift of PFN emission maximum. The binding constant of ssDNA‐20 and PFN is estimated to be 1.12 × 10²¹. At extremely low concentration (10 nmol/L), PFN can respond to 0.2 nmol/L (or 2 × 10^?10 mol/L) of ssDNA‐20 by significant enhancement of its emission intensity. The result is contrary to the observation in the relative higher concentration, and its mechanism is postulated. Based on the high binding ability of ssDNA with cationic CPE, a label‐free method for ssDNA detection is designed. It uses an electrostatic complex of cationic PFN and an anionic CPE, which exhibits fluorescence resonance energy transfer (FRET) between the two components. Addition of ssDNA improves the FRET extent, indicated by obvious change of fluorescence spectra of the conjugated polyelectrolyte complex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cyclopolymerization protocol for the synthesis of a poly(zwitterion‐alt‐sulfur dioxide) to investigate the polyzwitterion‐to‐poly(anion‐zwitterion) transition

The zwitterionic monomer, 3‐(N,N‐diallyl,N‐carboethoxymethylammonio)propanesulfonate, on cocyclopolymerization with sulfur dioxide in DMSO using azoisobutyronitrile as the initiator afforded the polyzwitterion (PZ) copolymer in excellent yields. The PZ on acidic hydrolysis of the ester groups led to the corresponding polyzwitterionic acid (PZA). The pH‐responsive PZA on treatment with sodium hydroxide gave the new poly(eletrolyte‐zwitterion) (PEZ). The solubility, viscosity behaviors, and solution properties of the salt‐tolerant PZ, PZA, and PEZ were studied in detail. Like common PZs, PZ was found to be insoluble in salt‐free but soluble in salt‐added water. The apparent basicity constants of the carboxyl group in PEZ have been determined. As the name implies, the PEZ possesses dual type of structural feature common to both conventional anionic polyelectrolytes and PZs, and its aqueous solution behavior is found to be similar to that observed for a typical alternating anionic‐zwitterionic copolymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and solution properties of a new pH-responsive polymer containing amino acid residues

The amine salt, N,N-diallyl-N-carboethoxymethylammonium chloride was cyclopolymerized in water using ammonium persulfate as an initiator to afford a cationic polyelectrolyte which on acidic hydrolysis of the pendant ester groups gave the corresponding cationic acid salt (CAS). The CAS was converted into an anionic polyelectrolyte (APE) and polybetaine (PB). The solution properties of the APE having two basic functionalities were investigated in detail by potentiometric and viscometric techniques. Basicity constants of the amine as well as the carboxylate groups in APE are ‘apparent’ and as such follow the modified Henderson-Hasselbalch equation; as the degree of protonation (α) of the whole macromolecule increases, the protonation of the amine nitrogens and carboxylate groups becomes increasingly more difficult and easier, respectively. While the APE, PB and CAS were found to be soluble in salt-free water, the corresponding PB and CAS of the SO₂ copolymers of the amine salt 1 were found to be insoluble in water.     

Poly(sulfobetaine)s and corresponding cationic polymers. VIII. Synthesis and aqueous solution properties of a cationic poly(methyl iodide quaternized styrene–n,n‐dimethylaminopropyl maleamidic acid) copolymer

A cationic poly(methyl iodide quaternized styrene–N,N‐dimethylaminopropylmaleamidic acid) copolymer was synthesized through amidoacidification reaction of styrene‐maleic anhydride copolymer with N,N‐dimethylaminopropylamine (ring‐opening reaction). Its properties in various aqueous salt solutions and pH solutions were studied by measurements of reduced viscosity and intrinsic viscosity. The results indicated that the reduced viscosity and intrinsic viscosity of this cationic polyelectrolyte were related to the type and concentration of the added salts and the results also showed a contrary tendency in some salts with monovalent acid groups to polyelectrolyte. At the same time, some salt ions were observed to strongly attract the quaternary ammonium group of the cationic polymeric side chain and resulted in agglomeration of the polymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1619–1626, 2001     

Swelling Behavior and Complex Formation Ability of Ternary Amphoteric Gels based on Allylamine Derivatives and Maleic Acid

Summary: The swelling behavior of an amphoteric gel composed of 50 mol‐% of maleic acid (MA), 25 mol‐% of N,N′‐dimethyldiallylammonium chloride (DMDAAC) and 25 mol‐% of diallylamine (DAA) was studied in aqueous and aqueous‐salt solutions. The isoelectric point (IEP) of the MA‐DMDAAC‐DAA gel determined from swelling experiments was about pH 4.6. Considerable gel swelling with increasing ionic strength was observed at the IEP. Dynamic swelling properties of the amphoteric gel in water with and without added salt were measured at various pH values including the IEP. The swelling behavior of the amphoteric gel was found to depend on the ionization state of the functional groups. It can be described by either a relaxation‐controlled or non‐Fickian (anomalous) mechanism. Swelling‐deswelling properties of the amphoteric gel were also studied in mixtures of water and organic solvents. The amphoteric gel was able to complex sodium poly(styrene sulfonate), sodium lauryl sulfate, the cationic drug richlocain, and the bivalent transition metal ions Cu²⁺, Ni²⁺, Co²⁺, and Zn²⁺. The sorption of polyelectrolyte, surfactant, drug, and metal ions by the amphoteric gel is accompanied by the contraction of the gel network. Partial release of the cationic drug molecules entrapped into the gel volume takes place at the IEP of the amphoteric gel with low activation energy, while neither the anionic polyelectrolyte nor the surfactants are released from the gel interior at the IEP. The swelling‐shrinking behavior of gel‐polyelectrolyte and gel‐surfactant complexes in dependence of pH and ionic strength of the outer solution is similar.

     

Modification of cation exchange membrane by grafted poly(4-vinyl-N-methylpyridinium-iodide)

It is well known that cation exchange membranes, having a very thin layer of a cationic polyelectrolyte on the membrane surface, have preferential permselectivity for monovalent cations in a monovelent-divalent cations system. We studied the relationship between preferential permselectivity and molecular structure of the cationic polyelectrolyte. Grafted poly(4-vinyl-N-methylpyridinium-iodide) was used and was compared with poly(4-vinyl-N-methylpyridiniumiodide). The backbone polymers were poly(styrene-co-p-benzylstyrene) and poly(benzyl), onto which 4-vinylpyridine was grafted by anionic polymerization and then quaternized with CH₃I. The grafted poly(4-vinyl-N-methylpyridinium-iodide) is effective in making the cation exchange membrane preferentially permselevtive for Na⁺ - Ca²⁺ system and is more preferable than poly(4-vinyl-N-methylpyridinium-iodide) in terms of electric resistance of the membrane. However, the relationship between the molecular structure of the cationic polyelectrolyte and the durability of the preferential permselectivity is not clear.     

Oligo(ethylene oxide) side‐chain steric screening effects on conductimetric properties of grafted poly(4‐vinylpyridinium) salts in aqueous solutions

A set of poly[N‐oligo(ethylene oxide)yl 4‐vinylpyridinium tosylate] (P4VOEOOTs) has been prepared by spontaneous polymerization of 4‐vinylpyridine. This method gives a grafted polyelectrolyte having a positive charge on every backbone pyridinic moiety. The P4VP15Ts, P4VP164Ts, P4VP350Ts and P4VP750Ts aqueous solution conductivities were determined in the concentration range from 6 × 10^?4 to 10^?2 M at 25 °C. The variation of the conductivity versus concentration of the investigated system exhibits typical polyelectrolyte behaviour. The polyelectrolyte mobility was found to be dependent on the oligo(ethylene oxide) (OEO) side‐chain length. Manning's rod‐like model fails to describe these results. A simple steric effect is proposed to explain the influence of the OEO length. Copyright © 2003 Society of Chemical Industry     

Interactions of a smart cationic polyelectrolyte based on hydroxypropylcellulose with an anionic surfactant

Novel thermosensitive, cationic polyelectrolyte was obtained by grafting N‐vinylformamide onto hydroxypropylcellulose followed by the hydrolysis of the formamide groups to the amine groups. The effect of the ionic strength on the lower critical solution temperature of the polymers was studied. The interactions of the polymers with sodium dodecyl sulfate (SDS) as a model anionic surfactant were studied. It was found by the measurements of the light scattering and fluorescence spectroscopy that the graft copolymers obtained strongly interact with SDS with the formation of polymer‐surfactant complexes. The values of critical association concentration (cac) of these polymer‐surfactant systems were found to be of the order of 10^?5 mol/dm³ at pH = 6.5 and of the order of 10^?6 mol/dm³ at pH = 2.5. The polymer was shown to be potentially useful for the purification of water from anionic surfactants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and viscosity of hydrophobically modified polymers containing dendritic segments

The cycloterpolymerizations of a newly synthesized dendritic quadruple‐tailed hydrophobic diallylammonium chloride with the hydrophilic monomer N,N‐diallyl‐N‐carboethoxymethylammonium chloride and sulfur dioxide afforded a series of water‐soluble cationic polyelectrolytes (CPEs) containing various proportions (0–1 mol %) of the hydrophobe. At a shear rate of 0.36 s^?1 at 30°C, salt‐free water solutions of the CPEs (4 g/dL) containing 0, 0.35, 0.53, 0.65, and 0.93 mol % of the hydrophobe had apparent viscosity values of 140, 1200, 180,000, 308,000, and 858,000 cps, respectively. The study clearly demonstrated an increase in the viscosity values with increasing incorporation of the hydrophobes. The CPEs on acidic hydrolysis of the pendant ester groups gave corresponding pH‐responsive cationic acid salts, which upon treatment with NaOH, were converted to the polybetaines (PBs), anionic polyelectrolytes (APEs), and PB/APEs containing various proportions of PB and APE fractions in the polymer chain. The effects of charge type and charge density on the polymer chain were investigated. Polymer surfactant interactions were investigated with the cationic surfactant cetyltrimethylammonium bromide; a considerable increase in the viscosity values of the CPE was observed in the presence of the surfactant. The superior viscosity behavior for the polymers containing the quadruple‐tailed hydrophobe was attributed to the blocky nature of the comonomer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dilute solution properties of cationic poly(dimethyl sulfate quaternized dimethylaminoethyl methacrylate)

The dilute solution properties of a cationic polyelectrolyte, poly(dimethyl sulfate quaternized dimethylaminoethyl methacrylate) [poly(DMAEM · C₂H₆SO₄)], are studied by measurements of intrinsic viscosity, degree of binding, and flocculation application. The intrinsic viscosity of this polyelectrolyte is related to the type and concentration of added salt. The intrinsic viscosity behavior for cationic polyelectrolyte resulting from the electrostatic repulsive force of the polymer chain is contrasted with polyampholyte. The polyelectrolyte in the presence of KCl has a lower degree of binding, indicating that the proton ion (H⁺) is relatively difficult to bind to the CH₃SO₄^? at the polymer end. The polymerization of DMAEM · C₂H₆SO₄ in 0.5M KCl aqueous solution proceeded more easily than that of DMAEM · C₂H₆SO₄ in pure water. The polymerization rate of DMAEM · C₂H₆SO₄ is found to pass through an extreme value as a function of pH. Optimum flocculation, corresponding to the complete removal of turbidity in the supernatant, is achieved. Beyond the optimum flocculation, high polymer dosages redisperse the bentonite suspensions.     

Starch Derivatives of High Degree of Functionalization, 8. Synthesis and Flocculation Behavior of Cationic Starch Polyelectrolytes

Water soluble starch derivatives with a high degree of substitution (DS) up to 1 containing quaternary ammonium groups were prepared by reacting starch with 3‐chloro‐2‐hydroxypropyltrimethylammonium chloride (QUAB®188) in ethanol/sodium hydroxide/water or preferably with 2,3‐epoxypropyltrimethylammonium chloride (QUAB®151) in aqueous‐alkaline solution. The DS values of the samples can be controlled by adjusting the molar ratio of cationization agent to anhydroglucose unit and is only slightly dependent on the amylose content of the starting starch material. The structure of the cationic starch derivatives was confirmed by means of NMR spectroscopy. Dewatering experiments with the cationic starch derivatives were conducted on a harbor sediment suspension using a laboratory pressure filtration apparatus. The cationic starches were used alone and in combination with a high‐molar‐mass synthetic polyanion. Both dependence on the DS of the sample and influence of the amylose/amylopectin ratios of the initial native starch were observed. The highest dewatering index of 63 was found for the cationic polyelectrolyte based on the amylopectin‐rich waxy maize starch in monoflocculation. In case of dual flocculation using additionally a poly(acrylamide‐co‐acrylate) a dewatering index of even 85 was attained.     

Ultrasonic atomization and polyelectrolyte complexation to produce gastroresistant shell–core microparticles

In this study ultrasound‐assisted atomization technique was combined with two‐stages polyelectrolyte complexation to produce enteric shell–core microparticles encapsulating a non‐steroidal, anti‐inflammatory gastrolesive active ingredient indomethacin. In particular, a solution of the anionic biopolymer alginate, containing indomethacin, was sprayed in fine droplets which were complexed with a cationic (meth)acrylate copolymer, Eudragit^® E 100, which, in turn, was complexed by the anionic copolymer Eudragit^® L30D‐55. The first complexation stage was applied to achieve a high drug encapsulation efficiency; the second one to assure good gastroresistance feature. The novel protocol has been found more effective in terms of loading, encapsulation efficiency, and enteric properties during in vitro release tests, than conventional procedures which involved alginate cross‐linking by charged ions. Furthermore ultrasonic atomization–polyelectrolytes complexation preparation approach was performed using mild conditions, aqueous solutions, in the absence of organic solvents and chemical cross‐linkers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42976.