Savaş Küçükyavuz

Conductive properties of poly(4-vinylpyridine)-poly(dimethylsiloxane) block copolymers doped with tetracyanoquinodimethane

Abstract Poly(4-vinylpyridine)-poly(dimethylsiloxane) (P4VP-PDMS) block copolymers with various compositions were prepared by anionic polymerization. The 4VP block was quaternized with methyl iodide and reacted with 7,7′,8,8′-tetracyanoquinodimethane (TCNQ), which is in both anion radical (TCNQ − ) and neutral form (TCNQ 0 ). The products were then characterized by 1 H nuclear magnetic resonance and Fourier-transform infra-red spectroscopy, scanning electron microscopy and differential scanning calorimetry techniques. The electrical conductivities of processable and flexible films of these block copolymers were measured with the four-probe method and found to be as high as 10 −2 S cm −1 . The optimal TCNQ 0 doping for which the conductivities are highest were also determined.

Solution properties and unperturbed dimensions of poly(p-tert-butylstyrene)

Abstract The conformational and thermodynamic properties of poly( p -tert-butylstyrene) were investigated by osmometry, intrinsic viscosity, light scattering, gel permeation chromatography and phase equilibria measurements. Polymeric samples were anionically synthesized. 1-Nitropropane was found to be a θ-solvent for this polymer and the θ-temperature was determined as 31°C. Intrinsic viscosity-molecular weight relationships were obtained in a few solvents. Unperturbed dimensions, estimated from both viscosity and light scattering results, led to the characteristic ratio, C α , of 13.4 ± 0.7 at 31°C. Comparison of this value with those for other polystyrene derivatives shows that the characteristic ratio increases with the bulkiness of the side-group due to the steric effect.

Electrically conductive polymers from poly(N-vinylimidazole)

Abstract Poly(N-vinylimidazole) was synthesized by free radical polymerization. It was quaternized with methyl iodide. The samples were doped with iodine and borontrifluoride. Products were characterized by elemental analysis. Fourier transform infra-red spectroscopy and differential scanning calorimetry techniques. The maximum electrical conductivities achieved were 10−4 S cm−1 for BF3-doped and for I2-doped QPVI. The decrease of electrical conductivity in open atmosphere with time was also studied to understand the stability of doped polymers. Temperature dependence of electrical conductivity exhibits a semiconductor behaviour.

Synthesis of block copolymers via anion-to-radical transformation

Abstract Synthesis of (methyl methacrylate)-styrene block copolymers was carried out using anion-to-radical transformation. For this purpose, living polystyryl anion, prepared by using a new anionic difunctional initiator, 1,5-di(2-(3,3-dimethyl butyl-1-lithio)naphthalene, was terminated by the addition of 4,4′-bromomethyl dibenzoyl peroxide. Polystyrene samples having peroxide terminal groups were then used as initiators in the polymerization of methyl methacrylate. Block copolymers were characterized by spectroscopic and fractional precipitation methods.

Conducting properties of iodine-doped poly(4-vinylpyridine)-poly(dimethylsiloxane) block copolymers

Abstract Block copolymers of various compositions, consisting of poly(4-vinylpyridine)(P4VP) and poly(dimethylsiloxane) (PDMS) blocks, were prepared by anionic polymerization. These samples were modified by the addition of various amounts of iodine in solution. The electrical conductivities of the doped materials were measured by the four-probe method and were found to be as high as 10 −5 S cm −1 . The optimum ratio of iodine to pyridine which gave the highest conductivity was determined.

ESR study of radiation resistance of some aza- and thiacrown ethers at 77 K

Gamma-induced intermediates stabilized in “kriptofix-21”, “kriptofix-22”, “kriptand-222” and 18-ane-S6 have been studied by ESR spectroscopy at 77–300 K. Apparently, radicals with H-atom abstraction from methylene group are the main paramagnetic products in diazocrown ethers while formation of both cyclic and uncyclic species is observed in 18-ane-S6 at 77 K. Heating γ-irradiated thiacrown ether up to room temperature mainly results in the cleavage of macrocyclic C−S following by stabilization of uncyclic radicals. 18-ane-S6 has a higher radiation resistance by comparison with oxygen- and aza-containing crown ethers at low temperature γ-radiolysis.

Characterization of p-t-butylstyrene-dimethylsiloxane triblock copolymers in solution

Anionically synthesized poly(p-t-butylstyrene)-b-poly(dimethylsiloxane)-b-poly(p-t-butylstyrene) block copolymers containing about 28% by weight p-t-butylstyrene were characterized by using differential refractometry, light scattering and viscosity methods in a good solvent, benzene, and in a selective solvent, methyl ethyl ketone. The unperturbed chain dimensions were estimated. Results were discussed with regard to the conformation of block copolymers in solution.

Synthesis and characterization of conducting polypyrrole-poly(N-vinylimidazole) composites

Abstract Conducting composite films of Poly(N-vinylimidazole) with Polypyrrole were prepared electrochemically. Composites having different polypyrrole percentages showed conductivites in the range 10−3−10−1 S.cm−1. Characterization of composites was carried out with FTIR and scanning electron microscopy techniques. Temperature dependence of conductivities exhibited reversible behaviour and confirmed the variable range hopping theory.

Thermal stability of conductive charge transfer complexes of poly(4-vinylpyridine)-poly(dimethylsiloxane) block copolymers

SummaryThermal stability of conductive charge transfer complexes of poly(4-vinylpyridine)-poly(dimethylsiloxane) (P4VP-PDMS) block copolymers with tetracyanoquinodimethane (TCNQ) was investigated by using thermal gravimetric analysis (TGA). The results show that both TCNQ simple and complex salts of polymers are thermally stable up to 800°C and depending on the amount of added neutral TCNQ, the residual product increased up to 75%.

Radiation induced chain addition of allylbenzene to 1,4-dioxane

Radiation induced chain addition of allylbenzene to 1,4-dioxane has been studied by IR-, UV-, mass-, NMR- and ESR-spectrometry. Efficiency of the addition depends on the concentration of monomer and it has an optimum atCmonom<0.125M. Apparently, upper concentration limit of the reaction is caused by absorbed energy transfer on the molecule, of monomer followed by energy deactivation. Radiation-chemical yields of the product are 12 and 31 molec./100 eV for 0.125M and 0.07M solution, respectively. The value ofGprod. is an evidence of chain character of the process.