Paramagnetic conjugated polymers with stable radicals in side groups

Summary Poly(1,3-dihydroxy-2-(4-ethynylphenyl)-4,4,5,5-tetramethylimidazolidine), poly(2-(4-ethynylphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-oxide), poly(4-(4-ethynylbenzylideneamino)-2,2,6,6-tetramethylpiperidine) and poly(4-(4-ethynylbenzylideneamino)-2,2,6,6-tetramethylpiperidine-1-oxyl) were prepared from poly(4-ethynyl-benzaldehyde). The products were characterized spectroscopically (IR, UV, ¹H and ¹³C NMR) and with respect to the magnetic susceptibility. The polyradicals (1-oxyl compounds) showed paramagnetic properties obeying Curie's law.     

Electrode reactions of nitroxide radicals at platinum in acetonitrile

Electrode reactions of 2,2,6,6-tetramethylpiperidinenitroxide (TMPNO) and di-tert-butylnitroxide (DTBNO) at platinum in acetonitrile solution were investigated by means of linear sweep voltammetry and controlled potential coulometry. In the case of TMPNO, the voltammetric resuls were satisfied with diagnostic criteria for reversible charge transfer, and those of esr and coulometry led to one electron transfer. In the case of DTBNO, the coulometric results in which apparent number of electron was $\text{1}\text{3}$ times the real one led to a mechanism with interesting series of reactions. This was also confirmed by esr.     

Microstructure in solid polymers

Electron microscopy can only yield information about polymers in the solid state. Preparative methods have been developed which consisted of replica techniques; thin films stained with uranyl acetate, sodium tungstate or phosphotungstic acid; and extraction replicas. Results suggest an ordered sequence of structures from: (i) the stereochemically defined chain molecule which tends to form; (ii) a folded structure to minimise free energy; (iii) a structure which can be resolved in the electron microscope and is roughly spherical in shape-this structure is dependent on molecular weight up to a certain figure after which it is independent as is a constant for the material; and (iv) aggregates of structure (iii), either in the form of chains resembling a string of pearls or a pile of aggregated spheres.     

Carbon radicals generated by solid polymers: Electron spin resonance spectroscopy for detection of species in water

Radicals generated in plastic medical devices (solid phase) by γ-rays or electron-beam irradiation during sterilization are known to cause oxidation of protein drugs, resulting in a loss or reduction in drug efficacy. The generation of radical species in water by the radical species in solid polymers has not been proved. Using electron spin resonance (ESR) spectroscopy, we confirm the generation of new radicals in water by γ-ray irradiated cyclic olefin polymers (COP). ESR measurements are obtained using 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) as a spin probe and 5-(2,2-dimethyl-1,3-propoxycyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO) as a spin trap, in which the irradiated COP was immersed. The ESR signals indicate the TEMPOL radicals decline over time, suggesting the generation of new radicals. Conversely, the characteristic ESR signals of the adduct formed by the reaction between CYPMPO and the hydroxyl radical are observed. Thus, hydroxyl radicals are generated because of the migration of the radicals from COP to water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48604.     

NIT-Ph-p-BEN氮氧自由基的制备及催化降解性

以对醛基苯甲酸为原料，通过醛酸与2,3-二甲基-2,3-二羟胺基丁烷缩合，再经NaIO4氧化最终制得4-(4,4,5,5-四甲基-1,3-二氧化物)咪唑基-1-苯甲酸（NIT-Ph-p-BEN氮氧自由基）。采用FTIR、UV、ERP（电子顺磁共振波谱仪）和元素分析等对其结构进行表征；通过催化降解废水中有机染料甲基橙、甲基蓝和罗丹明B对其催化活性进行了评估。结果表明，当甲基橙、甲基蓝和罗丹明B浓度为15 mg/L，NIT-Ph-p-BEN质量浓度为0.15 g/L，H2O2浓度为30 mmol/L时，NIT-Ph-p-BEN对甲基橙有更好的催化降解性，仅在1 h内甲基橙的降解率达到94.26%。此外，反应机理表明，H2O2有助于实现NIT-Ph-p-BEN自由基的再生和循环利用。     

Ferromagnetic interactions in zinc(II) coordination complex containing nitronyl nitroxide radicals

A novel complex Zn(NIT2-py)₃(ClO₄)₂(NIT2-py = 2-(2′-pyridyl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl-3-oxide) (1) has been synthesized and characterized structurally and magnetically. The metal coordination sphere is fully occupied by three chelating nitroxide ligands, showing a distorted octahedral geometry. Temperature dependence of susceptibility measurements shows a weak ferromagnetic coupling between NIT2-py radicals with J = 2.13 cm⁻¹. The field dependence of the magnetization further confirms that the ground state of the compound S = 3/2 results from ferromagnetic interactions within the complex 1.     

Study of rotational mobility of a polar molecule in polystyrene by the thermally stimulated depolarization method

The rotational mobility of paranitroparadimethylamino azobenzene in polystyrene has been studied by a thermally stimulated depolarization (TSD) method at temperatures less than T_g. The frequencies and activation energies of the rotation of particles, as well as the parameters characteristic of the distribution over rotational relaxation times, and their temperature dependence have been studied.     

Heterogeneous photooxidation of solid polymers

Photooxidation of polymer can undergo heterogeneous effects, a complication which impacts attempts to extrapolate artificial accelerated tests to natural outdoor exposures. The main cause of heterogeneous degradation results from oxygen diffusion-limited effects. Several experimental techniques can be used to monitor macroscopic heterogeneous oxidation in polymers. These techniques are based on i.r. spectroscopy: micro FTi. r. spectroscopy permits to determine oxidation profiles in polymer materials till a resolution around 10 microns and photoacoustic (PAS) -FTi. r. spectroscopy is an interesting method for analyzing the oxidation of the surface layers.     

Electrochemical study of stable N-alkoxyarylaminyl radicals

The electrochemical study of N-tert-butoxy-2,4-diphenyl-6-tert-butylphenylaminyl (1a), N-tert-butoxy-2,4-bis(4-chlorophenyl)-6-tert-butylphenylaminyl (1b), N-[2-(methoxycarbonyl)-2-propyl]-2,4-diphenyl-6-tert-butylphenylaminyl (2), and N-tert-butoxy-2,4,6-tris(4-chlorophenyl)phenylaminyl radicals (3) was performed by cyclic voltammetry using acetonitrile as the solvent and Bu₄NPF₆ as the supporting electrolyte. On cathodic scan (100 mV/s), all the radicals gave chemically reversible cyclic voltammograms, and the were determined to be −1.405 V (1a), −1.310 V (2a), −1.282 V (2b), and −1.195 V (3) (versus Fc⁺/Fc), respectively. On anodic scan (100 mV/s), on the other hand, 1a, 1b and 2 showed chemically reversible cyclic voltammograms, but 3 exhibited a partially reversible couple even on a scan rate of 500 mV/s, indicating that the cation species of 3 was less stable. The determined for 1a, 1b, 2 and 3 were 0.220, 0.280, 0.318 and 0.294 V (versus Fc⁺/Fc), respectively. The electrochemical data were compared with those of thioaminyl radicals, the corresponding sulfur analogues of 1-3.     

格列美脲分子印迹聚合物应用于固相萃取的研究

以降血糖药物格列美脲为模板分子,ɑ-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EDMA)为交联剂,偶氮二异丁腈(AIBN)为引发剂,采用本体聚合法制备了格列美脲分子印迹聚合物(MIP),用于血浆样品前处理,建立了对加标兔血浆中格列美脲含量的固相萃取检测方法,通过高效液相色谱法测定,分子印迹固相萃取柱的回收率可达80%以上,有效地减少了基体中蛋白质等杂质对目标物检测的干扰,适用于生物样品中模板分子的富集和纯化。     

Bubble dissolution in molten polymers and its role in rotational molding

The presence of bubbles is inherent in the rotational molding process and can often cause poor quality in rotomolded parts. In an effort to gain a fundamental understanding of bubble removal in polymer melts, a model that includes diffusion, surface tension, and viscosity effects has been implemented. This work has been complemented with experiments performed in a heated chamber, which enabled the visualization of the bubble formation and removal process. It was concluded that bubble removal is mainly diffusion controlled and is not influenced significantly by melt viscosity when the latter lies within ranges typical for rotational molding resins. Air concentration in the bulk of the polymer melt and initial bubble size were found to be of great importance. The application of pressure after the polymer has melted accelerates the dissolution rate, owing to an increased driving force for diffusion.     

Distribution in correlation times for rotational diffusion of spin probes in polymers

Electron spin resonance spectra of poly(vinyl acetate) (PVAc) and plasticised PVAc doped with nitroxide spin probes show a double-peak feature at temperatures immediately below T_{50 G}. This can be explained on the basis that probe tumbling occurs with a distribution of correlation times τ_R arising from a distribution of free volume within the polymeric matrix. The two-component e.s.r. spectra arise because the distribution in τ_R of the probes straddles the value (c. 3 × 10^?9 s) which marks the change-over from fast- to slow-motion spectra. The implications of the existence of a distribution of τ_R values for calculations based on the assumption of a single value are examined. It is concluded that when probe tumbling is slow the error in τ_R could be significant, but for rapid tumbling (motionally narrowed spectra) the error is likely to be insignificant.     

Extracellular polymers in activated sludge and stable foams

The hydrophobicity and surface polymer extracellular polymer characteristics of a range of foams and mixed liquor samples were examined and the species involved studied. The results show that, for samples dominated by Microthrix parvicella, the hydrophobicity of the solids was linearly related to the uronic acid content of the extracellular polymer polysaccharide. The stability of foams was increased significantly with the addition of polyvalent metal ions to the mixed liquors producing the foams.     

Controlling mobility and birefringence of azo chromophores in epoxy polymers

Polymers containing azobenzene units are of special interest due to the reversibility of their photo‐orientation. Applications of these materials are in the fields of optical information storage, information processing, optical switching devices and others. In the work reported, we synthesized, characterized and compared the optical behaviour of azo‐modified epoxy polymers. With this goal in mind, Disperse Red 13 was selected as azo chromophore and two different amines, N,N‐benzyldimethylamine and 4‐(dimethylamine)pyridine, as initiators of the epoxy homopolymerization. The influence of the degree of union between azo chromophore and matrix in crosslinked polymers, and, in consequence, the azo mobility, on the optical behaviour (birefringence and dichroism) of resulting films was evaluated. An analysis of the dynamics of the writing and relaxation processes was also carried out. When the azo chromophore was covalently linked to the network, the maximum birefringence was reached three times faster. Also, two completely different optical behaviours were observed taking into account the occurrence or not of covalent bonding between the chromophore and the matrix. A remnant birefringence of around 60% was retained in the first case; an on‐off optical behaviour was observed in the second case. Copyright © 2011 Society of Chemical Industry     

Thermodynamic behavior of solid polymers in uniaxial deformation

The heat and work of uniaxial deformation were measured for two commercial polyurethane elastomers and a low density polyethylene using a new deformation calorimeter. Internal energy changes in the materials resulting from deformation were calculated from the difference between the heat and work according to the first law of thermodynamics. The elastomers were found to exhibit complete reversibility for small and large strain deformation cycles as determined from the absence of a permanent internal energy change, even though one of these undergoes strain-induced crystallization and melting. The low density polyethylene behaves irreversibly even at small strains, and will store 30 percent of the deformation work as internal energy during drawing at room temperature.     

Experimental and numerical investigation of warpage of semicrystalline polymers in rotational molding

Warpage of various semicrystalline polyethylenes (linear low density polyethylene [LLDPE]) has been investigated under typical rotational molding conditions, which means slow cooling from only one side. We have developed an experimental technique that is able to quickly rate different materials with respect to warpage under typical process conditions. We have also developed a numerical model simulating the experiments assuming a thermoelastic material including crystallization. As has been observed in practical rotational molding, it has been found in both experiments and simulations that materials with high crystallinity have in general higher warpage. The simulations also showed that the crystallization kinetics has implications on the warpage because the crystallinity gradient during solidification depends on the rate of crystallization. POLYM. ENG. SCI., 45:945–952, 2005. © 2005 Society of Plastics Engineers     

Recent progress in negative-working photosensitive and thermally stable polymers

The production of semiconductors, especially for semiconductor large-scale integration (LSI), has been definitely supported by photolithographic technologies using photosensitive polymers in the micro-electronic device industry. Among them, photosensitive and thermally-stable polymers (PSTSPs) provide simpler resist system than the conventional one, in which the resist materials stays after forming a pattern and function as thermally resisting insulators in integrated circuits (ICs) and multi-chip packages (MCPs), eliminating the extra process of resist removal. Recently, negative-working chemical amplification photoresists have started to receive much attention as quite simple and direct network formation systems in polymer films. The recent progress in negative-working PSTSPs based on the chemical amplification system is summarized in this review article, which includes low dielectric constant polymers for LSI, high refractive index polymers for microlens materials in complementary metal oxide semiconductor image sensors, novolac resists for indium tin oxide patterning, and poly(3-hexylthiophene) for organic field-effect transistors.