Comprehensive study on the formation of polyelectrolyte complexes from (quaternized) poly[2‐(dimethylamino)ethyl methacrylate] and poly(2‐acrylamido‐2‐methylpropane sodium sulfonate)

Polyelectrolyte complexes (PECs) have been prepared from well‐defined (quaternized) poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) and high molecular weight poly(2‐acrylamido‐2‐methylpropane sodium sulfonate) (PAMPSNa) after a thorough study of their viscometric properties. The effect of pH and quaternization degree of PDMAEMA on PECs stoichiometry has been examined. PEC‐based materials have been characterized in terms of thermal stability, equilibrium swelling degree, and free/bound water composition. The stoichiometry and swellability of the physically crosslinked hydrogels obtained from fully quaternized PDMAEMA/PAMPSNa complexes do not depend on pH. In contrast, PECs made of non quaternized PDMAEMA and PAMPSNa are highly affected by pH, and could reversibly disintegrate at pH ≥ 9. Partially quaternized PDMAEMA/PAMPSNa PECs exhibit intermediate properties and form stable loose structures in the whole investigated pH range. Finally, stable dispersions of PECs nanoparticles have been successfully produced from dilute solutions of the complementary polyelectrolytes. The nanoparticle average diameter as determined by dynamic light scattering proved to depend on the molar fraction of DMAEMA‐based subunits and on the initial polyelectrolyte concentration. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5468–5479, 2006     

Polymérisation anionique amorcée par les composés lamellaires du graphite et du lithium

In the present work, we use the binary insertion compound LiC₁₂ to polymerize styrene, methyl methacrylate, butadiene, isoprene, and to copolymerize isoprene and styrene in various hydrocarbon solvents (aromatics and aliphatic) and etheral solvents. We show that the styrene polymerization in aromatic solvents gives better yields than in the etheral solvents, the polymer being atactic. Methyl methacrylate does not polymerize in toluene but does so completely in DME. More generally, the yields of polymerization are better with KC₃₇ than with LiC₁₂ because of the different capacities of the monomer to get into the carbon layers. The polymerization of dienes with LiC₁₂ shows that the microstructures of the polymer obtained in π-or n-donor solvents are similar to the ones obtained by homogenous polymerization with Li cation in such solvents. However, for isoprene in cyclohexane, the results are different. The isoprene styrene copolymers are statistical ones and the mean length of styrene blocks is less than 5. The monomer interaction with the insertion compound and the growing chain geometry between the carbon layers are the facts which control either the stereospecificity of the polymerization or the selectivity of the copolymerization.     

Anionic polymerization of lactones initiated by alkali graphitides. III. Polymerization of δ-valerolactone initiated by KC24

The anionic polymerization of δ-valerolactone initiated by KC₂₄ in xylene or tetrahydrofuran was investigated. The influence of the polymerization conditions on the amount and composition of the oligomers fraction and high polymers formed was tested. Experiments were done with a potassium mirror and benzophenone-potassium as initiators of the polymerization to check the influence of the layered structure of the initiator. It was found that the amount of the oligomers formed under comparable conditions increases in the order KC₂₄ (9%), potassium mirror (22%), benzophenone-potassium (56%). The highest yields of poly(δ-valerolactone) (over 90%) and highest intrinsic viscosities (1.0 dL/g and more) were achieved by the KC₂₄-initiated polymerizations in xylene.     

Anionic polymerization of lactones initiated by alkali graphitides. IV. Copolymerization of ε-caprolactone initiated by KC24

The copolymerization of ε-caprolactone (ε-CL) with octamethylcyclotetrasiloxane (D₄) and styrene (St) under the action of the second-stage potassium graphitide KC₂₄ was investigated. The copolymerizations were carried out in bulk or in xylene at 20°C. The content of the block copolymer ε-CL/D₄ in the polymerization mixture was 60–95%, the molecular weight ranging between 150,000 and 300,000. The data for the copolymers' composition obtained by ¹H-NMR and GPC showed 14–20% of D₄-units in the copolymer. The amount of the block copolymer ε-CL/St in the polymerization products was 0–87%, and the molecular weights in the case of copolymer formation were between 100,000 and 500,000. The content of St-units in the copolymers was from 10 to 75% as shown by GPC and ¹H-NMR. The mechanism of action of the initiator is discussed.     

Potassium-graphite intercalation compounds as initiators for ethylene oxide polymerization in benzene and tetrahydrofuran

The ability of alkali graphitides KC₂₄ and LiC₁₂ to initiate the polymerization of ethylene oxide in benzene and THF has been studied. Polymerization by LiC₁₂ leads to small quantities of oligomers; KC₂₄ causes quantitative polymerization. Initiation and chain growth take place in the interlayer space and the solvent nature does not affect the polymerization. The orders of the polymerization with respect to monomer and initiator have been determined. The polymerization rate is constant up to high conversion and initiator efficiency increases with the yield.     

An investigation into the initial degradation steps of four major dye chromophores: study of their one-electron oxidation and reduction by EPR, ENDOR, cyclic voltammetry, and theoretical calculations

The degradation of dyes is frequently initiated by one-electron oxidation or reduction; however, relatively little is known about the initially formed radicals. Acid Green 25 (AG25), Crystal Violet (CVI), Methylene Blue (MB), and Acid Orange 7 (AO7), representing paradigms of four types of commercial organic dyes, were therefore investigated in terms of their redox behavior. Their redox potentials in MeCN and buffered aqueous solutions were determined by cyclic voltammetry. The structures of the one-electron reduced and oxidized dyes were established by EPR spectroscopy and by theoretical calculations on the density functional level of theory.     

Über die Reduktionsformen einiger nichtenolisierenden aromatischer Ketone und Chinone,welche die Vinylpolymerisation zu initiieren vermögen

It is known that the reduction forms of aromatic carbonyl compounds (ACC) initiate anionic polymerization of vinyl monomers. The ability of the reduction forms to transfer an electron to the interacting molecules is defined also by the electron affinity of the partners. To obtain data about the electron affinity the half-wave potentials of polarographic reduction were measured and compared with the values of the lowest antibonding molecular orbital, according to theHückel's method. A linear correlation between the potentials of polarographic reduction and the energy of the lowest antibonding molecular orbit was found. The results prove the correctness of the previously determined electroaffinity defined by electron transfers between the reduction forms and neutral molecules. From the data of quantum chemical calculation and the polarographic reduction ofACC the changes of the free energy, enthalpy and the equilibrum constant for electron transfer reaction were calculated. The initiation ability of the reduction forms ofACC and the elctron affinity discussed.     

Preparation, characterization and biological activity of Schiff base compounds derived from 8-hydroxyquinoline-2-carboxaldehyde and Jeffamines ED

Polyethers with 8-hydroxyquinolin-2-yl end groups (HOQCHN-POE-NCHQOH) were prepared by reaction between polyethers having amino end groups (Jeffamines ED^®) and 8-hydroxyquinoline-2-carboxaldehyde. The HOQCHN-POE-NCHQOH polymers were characterized by size-exclusion chromatography, UV, IR, 1H and 13C NMR spectroscopy, and MALDI-TOF mass spectrometry. The complexation between HOQCHN-POE-NCHQOH and Fe³⁺ was studied by UV, IR spectroscopy and differential scanning calorimetry. The UV-irradiation of the complexes caused photodegradation of the polyether chains. It was shown that HOQCHN-POE-NCHQOH had high efficacy on remedying iron-deficient maize plants and exhibited very low-antibacterial activity towards non-pathogenic soil bacteria (B. subtilis).     

Functionalized electrospun mats from styrene-maleic anhydride copolymers for immobilization of acetylcholinesterase

A series of electrospun mats of styrene-maleic anhydride copolymers has been functionalized by modification with two types of spacers - a polymer with a flexible hydrophilic polyether chain (Jeffamine® ED) and a rigid low-molecular-weight spacer (р-phenylenediamine). The successful modification of the microfibrous mats with these bifunctional compounds has been proved by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analyses. In a further step, acetylcholinesterase (AChE) has been covalently immobilized onto the modified mats using glutaraldehyde as a binding agent. The amount of bound protein and the specific activity of the immobilized AChE have been determined. The highest activity has been displayed by AChE covalently bound to Jeffamine-modified microfibrous mats. Moreover, the immobilized AChE is characterized by enhanced thermal and storage stability as compared to the free enzyme.     

Electrospun Mats from Styrene/Maleic Anhydride Copolymers: Modification with Amines and Assessment of Antimicrobial Activity

New antimicrobial microfibrous electrospun mats from styrene/maleic anhydride copolymers were prepared. Two approaches were applied: (i) grafting of poly(propylene glycol) monoamine (Jeffamine® M‐600) on the mats followed by formation of complex with iodine; (ii) modification of the mats with amines of 8‐hydroxyquinoline or biguanide type with antimicrobial activity. Microbiological screening against S. aureus, E. coli and C. albicans revealed that both the formation of complex with iodine and the covalent attachment of 5‐amino‐8‐hydroxyquinoline or of chlorhexidine impart high antimicrobial activity to the mats. In addition, S. aureus bacteria did not adhere to modified mats.