Stimuli-Responsive Macromolecular Architecture by Butler Cyclopolymerizations: Synthesis and Applications.

This article reviews the synthesis of polyzwitterions (PZs) (poly-carboxybetaines, -phosphonobetaines, and -sulfobetaines) having multiple pH-responsive centers. The synthesis follows the Butler cyclopolymerization protocol involving a multitude of diallylammonium salts and their copolymerization with SO2 and maleic acid. The PZs have been transformed into cationic-, anionic-polyelectrolytes, and polyampholytes under the influence of pH. Particular attention is given to the application of these polymers as antiscalants, mild steel corrosion inhibitors, components in constructing Aqueous Two-Phase Systems (ATPSs), and membrane modifiers. The ATPSs could be used to separate various biomolecules, including proteins. Many amphiphilic polymers incorporating a few mol % hydrophobic monomers have shown enhanced viscosities and could be suitable for applications in oil fields. The progress of applying Butler cyclopolymerization in reversible addition-fragmentation chain transfer (RAFT) chemistry has been discussed. Future works are expected to focus on RAFT cyclopolymerization to construct block copolymers.

Polymer nanoparticles containing 2,4,6-triiodophenol: a potential contrast medium for medical imaging.

Contrast agents have been utilized for x-ray imaging to visualize blood vessels. Triiodobenzene derivatives are known contrast agents yet have not been formulated in a nanoparticle form for the purpose of enhancing the contrast of cancer tissues. In this study, experiments to encapsulate 2,4,6-triiodophenol in a polymer matrix were designed. Spherical NPs made of PLA, PLGA, PLA-TPGS, PLGA-TPGS and TPGS-FOL, were synthesized and characterized. Using the oil-in-water single-emulsion technique, the effect of several experimental parameters such as sonication power, ratio of 2,4,6-triiodophenol/polymer, type and concentration of emulsifier, and polymer type has been studied. A good morphology of polymer NPs with entrapped 2,4,6-triiodophenol was successfully obtained however the encapsulated iodine was in the range of 5 to 26%.

A resin containing motifs of maleic acid and glycine: a super-adsorbent for adsorptive removal of basic dye pararosaniline hydrochloride and Cd(II) from water.

The cyclocopolymerization of N,N-diallylglycine hydrochloride, maleic acid and 1,1,4,4-tetraallylpiperazinium dichloride afforded a cross-linked polyzwitterionic acid, which, upon treatment with NaOH, gave the corresponding cross-linked anionic polyelectrolyte (CAPE) in quantitative yield. The pH-responsive resins contained a high density of CO2 - motifs as well as the chelating motifs of glycine residues. The resin CAPE was found to be a super-adsorbent for the removal of pararosaniline hydrochloride (PRH); having a q max of 1534 mg/g. The adsorption process followed pseudo-second-order kinetics and was found to be a nearly irreversible process as suggested by the parameters obtained from Elovich kinetic model. The resin demonstrated excellent adsorption/desorption efficiencies, thereby ensuring its recycling and reuse in potent applications like remediation of industrial dye-waste water. The resin's chelating motifs were also efficient in the adsorptive removal of Cd(II) ions with a q max of 248 mg/g. It was also employed for the simultaneous and effective trapping of Cd(II) and the dye from industrial wastewater. The resin's impressive performance accords it a prestigious place among many sorbents in recent works.

Fast removal of methylene blue and Hg(II) from aqueous solution using a novel super-adsorbent containing residues of glycine and maleic acid.

The alternate cyclo-copolymerization of diallylammonioethanoate [(CH2=CHCH2)2NCH2CO2-] and maleic acid in the presence of a cross-linker afforded a novel pH-responsive resin (90% yield). The resin has turned out to be a super-adsorbent for methylene blue (MB) removal with a qMax of 2101 mg g-1. The adsorption of the dye followed pseudo second-order kinetics with an energy of activation (Ea) of 31.5 kJ mol-1. The process showed an extraordinarily fast adsorption rate owing to faster film diffusion; the resin (250 mg) was able to trap 78 and 99.4% MB from its 3000 mg L-1 solution (100 mL) within 3 and 30 min, respectively. Equilibrium constants from Langmuir nonlinear isotherm model in the range 288-328 K gave ΔGo ΔHo, and ΔSo values of ≈ -25 kJ, -13 kJ and 39.5 J mol-1 K-1, respectively. Immobilization mechanism was discussed using FTIR, SEM, and Elovich kinetic model. The presence of the chelating glycine residues was exploited for the removal of Hg(II) ions; the qHg was determined to be 263 mg g-1. The resin also removed MB and Hg(II) simultaneously from industrial wastewater with remarkable efficacy. The very impressive performance along with efficient recycling conferred the resin a top position among many sorbents.

Scope of sulfur dioxide incorporation into alkyldiallylamine-maleic acid-SO2 tercyclopolymer.

Alternate copolymerization of diallylamine derivatives [(CH2CH[double bond, length as m-dash]CH2)2NR; R = Me, (CH2)3PO(OEt)2, and CH2PO(OEt)2] (I)-maleic acid (MA) and (I·HCl)-SO2 pairs have been carried out thermally using ammonium persulfate initiator as well as UV radiation at a λ of 365 nm. The reactivity ratios of ≈0 for the monomers in each pair I-MA and I·HCl-SO2 ensured their alternation in each copolymer. However, numerous attempted terpolymerizations of I-MA-SO2 failed to entice MA to participate to any meaningful extent. In contrast to reported literature, only 1-2 mol% of MA was incorporated into the polymer chain mainly consisting of poly(I-alt-SO2). Quaternary diallyldialkylammonium chloride [(CH2[double bond, length as m-dash]CH-CH2)2N+R2Cl-; R = Me, Et] (II) also, did not participate in II-MA-SO2 terpolymerizations. Poly((I, R = Me)-alt-SO2) III is a stimuli-responsive polyampholyte; its transformation under pH-induced changes to cationic, polyampholyte-anionic, and dianionic polyelectrolytes has been examined by viscosity measurements. The pK a of two carboxylic acid groups and NH+ in III has been determined to be 2.62, 5.59, and 10.1. PA III, evaluated as a potential antiscalant in reverse osmosis plants, at the concentrations of 5 and 20 ppm, imparted ≈100% efficiency for CaSO4 scale inhibition from its supersaturated solution for over 50 and 500 min, respectively, at 40 °C. The synthesis of PA III in excellent yields from cheap starting materials and its very impressive performance may grant PA III a prestigious place as an environment-friendly phosphate-free antiscalant.