Candan Erbil

Effects of synthesis‐solvent composition and initiator concentration on the swelling behaviour of poly(N‐isopropylacrylamide) P(NIPAAM), poly(NIPAAM‐co‐dimethyl itaconate), and poly(NIPAAM‐co itaconic acid) gels

The effects of synthesis-solvent composition, initiator concentration, comonomer type and monomer purity on the volume swelling ratios, and polymer-solvent interaction parameter χ have been investigated as a function of temperature. Non-ionic N-isopropylacrylamide (NIPAAM) homopolymer gels, poly[NIPAAM-co-(dimethyl itaconate)] (P(NIPAAM-co-DMI)) and poly[NIPAAM-co-(itaconic acid)] (P(NIPAAM-co-IA)) gels containing hydrophobic (DMI) and hydrophilic (IA) comonomers were prepared by free radical polymerization using potassium persulfate (KPS) –N, N, N′, N′-tetramethyl ethylene diamine (TEMED) (redox initiator) in the presence of an N, N′-methylene bis(acrylamide) (MBAAM) cross-linking agent. The synthesis-solvent composition (40/60 mixture of water/methanol and water) and initiator concentration employed significantly affected the properties of the NIPAAM gels. The transition temperatures of P(NIPAAM-co-IA) gels synthesized in water/methanol mixture were higher than that of the gel obtained in water. Furthermore, χ values of the NIPAAM homopolymer gel prepared with higher KPS content was an increasing function of temperature, while χ values of the sample obtained with lower initiator concentration changed around a critical solubility value 0.50. The results obtained also show that the interactions between monomer and solvent molecules in the reaction media (ie composition of the pregel solution) have an important effect on the formation and properties of the network structure (ie pore sizes of the gels). © 2000 Society of Chemical Industry

Polypyrrole synthezited with oxidative cerium(IV) ions

SummaryThe chemical oxidation of pyrrole by Ce(IV) salts in aqueous solutions or water-acetonitrile system has been studied. Products were characterized by elementel analyses, FT-IR and conductivity measurements. Conductivity values of polypyrrole complexes synthesized in aqueous solutions are comparable with those in acetonitrile-water, if suitable oxidant/monomer ratio and [H+] are selected.

Description of the turbidity measurements near the phase transition temperature of poly(N-isopropyl acrylamide) copolymers: the effect of pH, concentration, hydrophilic and hydrophobic content on the turbidity

Abstract Absorbance values between 300 and 800 nm of aqueous solutions of poly(N-isopropyl acrylamide-co-itaconic acid-9.80), poly(N-isopropyl acrylamide-co-itaconic acid-52.05) and poly(N-isopropyl acrylamide)s containing Tegomer H–Si 2111 end groups and/or blocks were measured using a Shimadzu 160-A UV–visible spectrometer. Turbidities obtained from these absorbance values were used to interpret the macromolecular phase transition from a hydrophilic to a hydrophobic structure of the polymers. The effects of comonomer type and content, concentration of the solutions, pH and temperature on the coil–globule transition were discussed in terms of turbidity form factor, β related to size and shapes of particles and calculated by using the simplified form of Debye equation. The results presented in this work show that the presence of Tegomer H–Si 2111 (Si containing end groups and/or blocks) or high amount of itaconic acid (IA) in the chains prevent a collapse transition from hydrated extended coils to hydrophobic globules, which aggregate and form a separate phase (β 2). This stage of the transition corresponds to macroscopic phase separation after an intramolecular process.

Determination of the monomer reactivity ratios for copolymerization of itaconic acid and acrylamide by conductometric titration method

Abstract Compositions of low conversion itaconic acid-acrylamide (IA-AAm) copolymers synthesized with solution polymerization in aqueous medium by using potassium persulfate under nitrogen atmosphere were determined by conductometric titration method. The results were evaluated by various linear and nonlinear methods. The monomer reactivity ratios were found to be r IA =1.47±0.03, r AAm =0.76±0.02 with Fineman–Ross, r IA =1.25±0.10, r AAm =0.67±0.05 with Kelen–Tudos, r IA =1.65±0.21, r AAm =0.88±0.08 with Tidwell–Mortimer methods. For this system, the analysis of results show that IA is a more reactive monomer in IA-AAm copolymerization.

Conductometric determination of the end group ionization in acrylamide and acrylonitrile polymers initiated by carboxylic acids

Abstract The end group analysis both for polyacrylamides and polyacrylonitriles initiated by Ce(IV)-malonic acid, tartaric acid and citric acid redox systems was carried out by using conductometric titration. Carboxyl end groups of these polymers are determined by dissolving polyacrylamides in water, polyacrylonitriles in dimethylformamide and ethylene carbonate-propylene carbonate (80/20 by weight) at 25° and titrating with aqueous sodium hydroxide, alcoholic sodium hydroxide and tetrabutylammonium hydroxide, respectively. The number average molecular weight results are compared with the viscometric ones. It was found that these are in good agreement with each other. In addition to the experiments with conductometric titrations, calculations were made to find the ionization constant of carboxylic acid end groups in acrylamide and acrylonitrile polymers. For this purpose the Ostwald dilution law was used.

Monomer reactivity ratios of itaconic acid and acrylamide copolymers determined by using potentiometric titration method

Abstract Itaconic acid (methylene succinic acid)–acrylamide (IA–AAm) copolymers were synthesised with solution polymerisation by using potassium persulphate. The potentiometric titration method was used to determine the copolymer compositions. The results were evaluated by various methods. The monomer reactivity ratios were found to be r IA =0.99±0.04, r AAm =0.58±0.02 with the Fineman–Ross, r IA =1.05±0.10, r AAm =0.62±0.06 with the Kelen–Tudos, and r IA =1.36±0.11, r AAm =0.77±0.06 with the Tidwell–Mortimer methods. As expected, IA is found to be the more reactive monomer in IA–AAm copolymers.

Potentiometric determination of the molecular weight of polymers

SummaryThe determination of acid end-groups of acrylamide and acrylonitrile polymers initiated by cerium (IV)-malonic acid, cerium (IV)-tartaric acid and cerium (IV)-citric acid redox initiators systems was made in aqueous and nonaqueous media potentiometrically. The effect of solvent, titrant and electrode system on the half-neutralization potentials and number-average molecular weights,

Structural definitions for soluble portions of polyacrylamides synthesized with Ce(IV)–chelating agent redox systems

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