Excimer fluorescence as a probe of mobility in bulk poly(dimethyl-siloxanes)

Intramolecular excimer formation of 10,10′-diphenyl-bs-9-anthrylmethyloxide (diphant) in bulk poly(dimethylsiloxanes) has been investigated from ?40°C to 160°C. The excimer/monomer fluorescence ratio, as well as the activation energy for excimer formation appear to be independent of host matrix molecular weight. The results are consistent with high local mobility of the macromolecular chains.     

Laser from the dimer state of a conjugated polymer (PFO) in solution

The spectral and laser properties of the conjugated polymer poly (9,9-dioctylfluorenyl-2, 7-diyl) (PFO) in benzene have been studied and presented in this paper. The absorption spectra of PFO in benzene under low concentration showed that there was only one peak at 390 nm. When the concentration was increased, a new peak at 437 nm appeared additionally, indicating dimer formation at higher concentration of PFO in benzene. The fluorescence spectra for low concentration showed two peaks at 422 nm and 444 nm, which could be attributed to the monomer and the excimer. At the longer wavelength side of these spectra, there was a hump at 465 nm. This hump became dominant for higher concentrations and in low temperatures, while the other peaks became weaker. So, this new peak at 465 nm may be due to the dimer. For still higher concentrations, the peaks at 422 nm and 444 nm vanished and there was a dominant peak only at 465 nm. Under suitable concentration and pump power excitation of Nd: YAG laser (355 nm) the amplified spontaneous emission (ASE) spectra were obtained. It could be seen that there were three ASE peaks at 422, 444 and 470 nm. These peaks could be attributed to the monomer, excimer and dimer respectively. This is perhaps the first report on ASE from dimers of the conjugated polymer, PFO in liquid solution.     

N-(2-Anthracene)methacrylamide: a new fluorogenic probe molecule for monitoring in situ the radiation-induced polymerization of methyl methacrylate in bulk and in solution

This paper introduces the fluorogenic molecule N-(2-anthracene)methacrylamide, AnMA, employed as a probe for monitoring radiation-induced polymerization in situ. The relative reactivity of AnMA during free radical polymerization of methyl methacrylate (MMA) has been determined via fluorescence techniques. The ratio between propagation rate constants for the reaction of an MMA free radical chain-end with AnMA relative to the reaction with MMA is found to be 0.96. It is demonstrated that AnMA can be used for monitoring MMA polymerization quantitatively throughout the entire course of the reaction including the gel effect region. Results are also provided which demonstrate that AnMA can be used for sensitive monitoring of MMA polymerization both in bulk and in solution.     

Effects of annealing on morphology of polymer/polymer (PS/PMMA) blend; a fluorescence study

Steady state fluorescence (SSF) technique conjunction with optical microscopy were used to study the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend upon annealing above glass transition in elevated time intervals. The PS/PMMA blends were prepared from dissolution of pyrene (P) and naphthalene (N) labeled PS and PMMA particles, respectively. Monte Carlo simulations were performed to model the N and P fluorescence intensities (I_N and I_P), using photon diffusion theory. Number of N and P photons (N_N and N_P) emerging from the front surface of the blend are calculated when only N is excited, where N_P photons are combined of photons from radiative (N_PR) and nonradiative (N_PNR) energy transfer processes. Optical microscopy images were taken at each annealing step to support our findings from fluorescence measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2104–2110, 2006     

The influence of polymer concentration on the internal motion — intramolecular pyrene excimer formation — of a low molecular weight probe in solution

Fluorescence decay measurements were used to study the kinetics of end-to-end cyclization of the molecule Py(CH₂)₅Si(Me₂)OSi(Me₂)(CH₂)₅Py (1), where Py=1 ? pyrenyl. Experiments were carried out in toluene at 22°C and in cyclohexane at 35°C, in the absence and in the presence of added polystyrene (PS). Addition of even small amounts (0.01 g/ml) of PS caused the cyclization rate of probe molecule 1 to decrease substantially in cyclohexane, whereas in toluene, a much milder retardation of cyclization rate with increasing PS was observed. These effects are interpreted in terms of a coupling between the chain dyanmics and that of the probe molecule 1, mediated by the solvent. These hydrodynamic screening interactions depend sensitively upon whether the polymer is in a good or a poor solvent.     

Conductivity, charge transfer and transport number—an ac-investigation of the polymer electrolyte LiSCN-poly(ethyleneoxide)

In this paper a series of impedance measurements in the frequency range 10⁻⁴−2 × 10⁵ Hz and in the temperature range 20–170°C is reported for the cell: Li-metal/LiSCN [dissolved in poly (ethyleneoxide)]/Li-metal. On the basis of the measurements a whole range of electrical properties such as the conductivity, the charge transfer resistance, the transport number for the Li⁺-ion, the double layer capacity and the dielectric constant were determined for the polymer complex. The most important findings were (1) two regions with linear log σ vs 1/T plots and a transition temperature between the regions of 80°C and (2) the fact that both ions were mobile in the polymer complex with the Li⁺-ion having a transport number of 0.54 independent of temperature.     

Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

A set of hydrodynamic methods in extremely dilute solutions (determination of intrinsic viscosity [η ], translational diffusion D and flotation in a centrifugal field s ) was used in the studies of conformational properties, dimensions and equilibrium rigidity of individual molecules of a series of samples of poly(3‐hexylthiophene). Absolute molecular masses M _sD were determined. The Mark–Kuhn–Houwink equations for the range of M _sD from 2240 to 15 300 g mol^?1 are given. For the first time, an analysis of conformational properties and equilibrium flexibility of poly(3‐hexylthiophene) molecules was carried out using the model of a statistical segment containing a twisted polymer chain. © 2017 Society of Chemical Industry     

A characterisation of the surface properties of an ultra fine fly ash (UFFA) used in the polymer industry

Fly ash is the residue from the combustion of pulverised coal in thermal power stations. It consists of a variety of particle sizes of hollow silica-alumina spheres, which can be utilised as a custom made filler material in a number of industries, e.g. plastics, rubber, paint, refractories, etc. The 5 μm average particle size fraction is popular for its application in plastic products. In order to comply with the requirements for application in plastics, it is essential to understand and characterise the surface of the ultrafine glass spheres coming into contact and interacting with the organic phase of the final composite. This contribution describes the use of a number of techniques, such as EPMA (Electron probe micro-analysis), Raman spectrometry, zeta potential measurements and ICP-OES (Inductively coupled plasma optical emission spectroscopy) to investigate the surface composition and behaviour of the ultrafine fly ash particles.     

The length of a transfer unit (LTU) for polymer devolatilization processes in screw extruders

In this paper we introduce the concept of the length of a transfer unit (LTU) for polymer devolatilization and show that the LTU is an appropriate measure of the effectiveness of the process unit in which the devolatilization operation is conducted. The utility of the concept is demonstrated for the case when the process unit is a twin screw extruder for which values of the LTU were determined from experimentally measured values of devolatilization rates. Values of the LTU were found to depend solely on the fluid mechanics in the extruder as expected and were in good agreement with the predictions of a theoretical expression developed for the system that was studied. Finally, we discuss the implications of the LTU concept in relation to the engineering design and analysis of polymer devolatilization processes.     

A new copper(II) selective fluorescence probe based on naphthalimide: Synthesis,mechanism and application in living cells

A new fluorescence probe L based on naphthalimide has been synthesized for selective and quantitative detection of Cu^2 + in CH₃CN:H₂O (4:1, v/v) solution. L exhibited a strong green fluorescence. Upon addition of 2 equiv. of Cu^2 +, the fluorescence emission shows a steady and smooth decrease until a plateau is reached with a 30-fold quenching of fluorescence intensity. In the presence of Cu^2 +, the absorbance peak of L maximum at 466 nm decreased, and a new absorption band at 600 nm appeared. Under the identical conditions, other physiological and environmental important metal ions induced negligible spectroscopic changes. The 1:2 stoichiometry binding mode of L with Cu^2 + was supported by the Benesi–Hildebrand analysis and ESI-MS spectra studies. The detection limit for Cu^2 + was estimated to be 64 ppb. Fluorescence microscopy experiments showed that L has practical application in living cells.     

Fluorescence and molecular dynamics to study the intramolecular energy transfer in N-vinyl carbazole/styrene copolymers of different molar compositions

Emission spectra, fluorescence polarization, quenching and lifetime measurements were performed on dilute solutions of poly(N-vinyl carbazole) and N-vinyl carbazole/styrene copolymers to study the intramolecular energy transfer between carbazole groups along the polymer chain. Fluorescence anisotropy values for the samples dissolved in a PMMA solid matrix and quenching measurements in toluene by CCl₄ were used to estimate the efficiency of energy transfer as a function of the monomer molar composition. Analysis of the experiments suggests that the copolymer with the highest carbazole content, which corresponds to the highest amount of carbazole excimers, does not show the highest energy transfer efficiency. Intramolecular excimers which strongly increase with the carbazole content and that are mainly due to carbazole-carbazole monomer sequence interactions undoubtedly act as energy transfer traps. Molecular dynamics simulations on isotactic and syndiotactic copolymer fragments were used for obtaining different parameters related to the energy transfer process as a function of the number of styrene monomer units between vinyl carbazole ones.     

A novel solid state battery based on a polymer proton conductor: poly(propargyl alcohol) doped with perchloric acid

A battery was constructed by including a polymer proton conductor, poly(propargyl alcohol) doped with perchloric acid, between electrodes of magnesium and gold. The characteristics of the cell, showing an open circuit voltage of 2.0–2.2V, were studied as the function of the relative humidity. It was found that the system behaves as a fuel cell and that the discharge current of the battery is due to magnesium oxidation at the anode and proton reduction at the cathode.     

A new method to measure the high-shear bulk properties of pressure sensitive adhesives used in LCD devices

The wide application of pressure sensitive adhesives (PSAs) in thin film transistor liquid crystal display (TFT-LCD) devices is based on their advantages that PSAs provide sufficient bond strength and also are cleanly removable upon debonding. These two essential requirements are not obtainable without a proper understanding of the substrate as well as the rheological properties of the PSA. Unlike other substrates, the polarizer, the core unit of an LCD device, may exhibit a considerable dimension change with temperature and humidity. This imposes a large residual stress on the PSA layer, which often generates serious defects such as partial delamination. To overcome this problem, an accurate control of the rheological properties is required in the design of the PSA. In this study a new method is devised to measure the rheological behavior of thin film PSAs under high shear deformation. This method provided us with important information regarding the effects of molar mass and the level of crosslinking on the rheological behavior of the PSA. These findings along with the new method should be applicable not only to the LCD industry but also to other fields where an accurate control of PSA rheology is required.     

Conformation of isotactic polystyrene (IPS) in the bulk crystallized state as revealed by small-angle neutron scattering

Neutron scattering experiments have been performed on isotactic polystyrene (IPS) samples in the bulk crystallized state (T_{crystallization} = 185°C). The determination of the conformation of tagged chains ranging from 2.5 × 10⁵ to 7 × 10⁵ has been undertaken on two different hydrogenated IPS matrices. A matrix of usual molecular weight (M_w = 4 × 10⁵) leads to results which do not agree with Flory's model. In this case, measurements on radius of gyration R_g show on the one hand an important increase of this parameter (40%) with increasing crystallinity for the highest molecular weight tagged chains and on the other hand a variation with molecular weight like M^0.78. These results are interpreted with a schematic model involving a long crystalline sequence incorporated in the monocrystal along the 110 plane and two amorphous wings. Such an assumption is confirmed by the scattering behaviours in the intermediate range. On the other hand, by using an IPSH matrix of very high molecular weight (M_w = 1.75 × 10⁶), and the same tagged chains previously considered, a very weak variation of R_g with increasing crystallinity is observed. This leads to consider in this case Flory's conformation which is corroborated by data obtained in the intermediate range.     

化学添加剂与三元复合驱用破乳剂的配伍性研究

通过对三元复合驱用破乳剂的性能评价及与消泡剂、防垢剂、抗沉积剂的配伍性研究,确定了破乳剂的最佳反应条件,即质量浓度30mg/L、温度50℃,并探讨了其他化学添加剂对破乳剂脱水性能的影响规律。     

A chelating resin as a probe for the copper(II) distribution in grape wines

Presented hereafter is the pilot-study of the applicability of resin titration (RT) to mixed solvents in regard to the studies of metal distribution in wines – a beverage that has attracted great attention and that has been extensively studied in the recent years.The RT method of studying the distribution of species is based on the determination of the concentration of metal ions sorbed on the iminodiacetic resin Chelex 100 at different V/w (solution volume/mass of resin). The total metal ion present in the considered solution and the free metal ion are estimated from the titration curves. The method, already applied for water solutions, was tested here in mixed solvent media, at the pH around 3, with known amounts of copper(II) and ligands with different complexing properties. Satisfactory results have been obtained and commented critically.In the application of the RT method, the protonation and the exchange reactions of copper(II) with the considered sorbent were investigated in 12% ethanol, in KCl 0.1 and 1.0 M solutions, according to a well established procedure.Finally, a white grape wine (Riesling) from a winery in Oltrepò Pavese was analyzed with RTs. In the sample obtained before processing the wine, 50% of the total Cu(II) (∼18 μM) was combined with ligands with log α_M equal to 3.3; in the final product, the total Cu(II) was 4 μM, almost totally complexed. According to these findings, the ligands accountable for the copper complexation were not the major components in the wine, as they formed considerably weaker complexes.     

Calculation of the molecular weight distribution of the polymer produced in a cascade of reactors with allowance for chain transfer to the polymer

Molecular weight distributions for the polymer produced in a cascade of well-stirred reactors are constructed using the Mathematica software package for symbol mathematical operations. It is shown that the rate of chain transfer to polymer affects the distributions of macromolecules over the degree of polymerization and the number of active sites.     

A study of the binding of the biologically important hematin molecule to a novel imidazole containing poly(N-isopropylacrylamide) microgel

The influence of two different comonomers incorporated separately at 1 %w/w into a poly(N-isopropylacrylamide) microgel is investigated by photon correlation spectroscopy, transmission electron microscopy and high sensitivity differential scanning calorimetry. The synthesis, characterisation and subsequent binding affinity of iron protoporphyrin IX to the microgels was also investigated. Mössbauer and electronic absorbance spectroscopies were used to characterise the resulting protoporphyrin IX iron(III) polymer complexes. Co-polymer microgels containing either sulfide or imidazole residues acted as a matrix for the binding of haems to form soluble molecular structures containing multiple iron centres.