Spectroscopic and thermal degradation studies of polystyrene grafting onto poly(tetrafluoroethylene-co-hexafluoropropylene) films via electron-beam irradiation

Styrene monomers were grafted onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films by E-beam irradiation, controlling the degree of grafting by varying the radiation dose. In addition, polystyrene sulfonic acid (PSS) grafted FEP films were prepared by treating the polystyrene (PS) grafted FEP films with chlorosulfonic acid. The chemical mechanism of grafting, the substitution positions of the sulfonic acid, and the thermal degradation behaviors of the PS-grafted and PSS-grafted FEP films were investigated using FTIR-ATR spectroscopy, Raman Spectroscopy and TGA. Our results indicated that PS graft formation involved the removal of HF after C–C main chain scission, leading to the formation of an unsaturated structure. When heated, the PS-grafted FEP films underwent two-step thermal degradation, independent of the degree of grafting. The two degradation steps were assigned to the degradation of the PS grafts and the FEP matrix. Sulfonation of the PS-grafted FEP films was found to give rise to para-disubstituted sulfonic acid groups. The PSS-grafted FEP films were found to undergo a three-step thermal degradation, independent of the degree of sulfonation. The three degradation steps were assigned to removal of water molecules hydrogen bonded to the sulfonic acid groups, and the degradation of the PSS grafts and FEP matrix.     

Molecular miscible blend of poly(2-cyano-1,4-phenyleneterephthalamide) and polyvinylpyrrolidone characterized by two-dimensional correlation FTIR and solid state C NMR spectroscopy

Miscibility of blends of poly(2-cyano-1,4-phenyleneterephthalamide/polyvinylpyrrolidone) (CN-PPTA/PVP) was investigated by dilute solution viscometry, two-dimensional (2D) correlation Fourier transformed infrared (FTIR) spectroscopy and solid state ¹³C NMR spectroscopy. It was shown that a large proportion of the PVP, the water-soluble component, could not be removed from CN-PPTA by extraction with water, and even with boiling water for blend films, suggesting that the flexible aliphatic PVP chain forms a blend with the rigid aromatic CN-PPTA chain through strong intermolecular interaction making it too difficult to dissolve even in boiling water. Viscometry on a polymer mixture of dilute solution showed that [η]_exp exhibited larger value than [η]_theo in all mixtures used in this experiment, suggesting occurrence of a strong attractive interaction between the two polymers. 2D correlation FTIR spectroscopy revealed that the carbonyl absorption band of PVP at 1675 cm⁻¹ shifted to a new low frequency absorption band at 1640 cm⁻¹ with a change of 35 cm⁻¹, suggesting strong hydrogen bonding with NH (amide II) proton of CN-PPTA. Another new absorption band at 1685 cm⁻¹ was due to the carbonyl absorption band of CN-PPTA shifting to a higher frequency than that at 1662 cm⁻¹, indicating that some of the carbonyl groups in the CN-PPTA components of the blends were in a free state or in a non-hydrogen bonded state as a consequence of the participation of NH proton of CN-PPTA in hydrogen bonding, resulting in the absorption bands of NH bend deformation of CN-PPTA at 1542 and 1313 cm⁻¹ being shifted to higher wavenumber of 1556 and 1324 cm⁻¹, respectively. Solid state ¹³C NMR spectroscopy revealed a chemical shift for CO of the PVP component in the blend fiber changing down-field (shift to left) at 177.346 ppm with a difference of 1.812 ppm; this was due to a lower electron density around the carbon atom of CO of lactam via hydrogen bonding with NH proton of amide in the CN-PPTA component, suggesting that a homogeneous blend of the CN-PPTA and PVP was produced on a molecular scale via hydrogen bonding.     

Two-dimensional hetero-spectral correlation fluorescence-Raman spectroscopy for a thermotropic liquid-crystalline oligomer

In this paper, 2D fluorescence and 2D hetero-spectral fluorescence-Raman correlation spectroscopies were performed to better understand the dynamic process of liquid crystalline (LC) oligomer, the esterification product of ethyl 4-[4′-oxy-4-biphenyl-carbonyloxy]-4′-biphenylcarboxylate with poly(ethylene oxide)s (PEO) (DP = 12) (designated as 12-4). We found that 2D fluorescence correlation spectroscopy provided much more detailed information on the mechanism of dynamic development of LC oligomer with temperature variation than conventional 1D fluorescence spectroscopy. Furthermore, we investigated the structural change of 12-4 at the molecular level during the phase transitions by using 2D hetero-spectral fluorescence-Raman correlation spectroscopy.     

Reflectionless Solutions for Square Matrix NLS with Vanishing Boundary Conditions

Mathematical Physics, Analysis and Geometry - In this paper we focus on the large time behaviour of momentum support for a Novikov type equation. It is shown that the momentum support can be large...     

Polarized light transfer above a reflecting surface

The existence and uniqueness are established for the solution of the equation of transfer of polarized light in a homogeneous atmosphere of finite optical thickness, assuming reflection by the planetary surface. A general L_p-space formulation is adopted. The boundary value problem is first written as a vector-valued integral equation. Using monotonicity properties of the spectral radii of the integral operators involved as well as recent half-range completeness results for kinetic equations with reflective boundary conditions, the present results follow as a corollary.     

Transport theory inL p-spaces

Integral Equations and Operator Theory - In this article boundary value problems of linear transport theory are studied inL p-spaces (1≤p<+∞). It is shown that the results valid...     

Stationary solutions of the non-linear Boltzmann equation in a bounded spatial domain

A contraction mapping (or, alternatively, an implicit function theory) argument is applied in combination with the Fredholm alternative to prove the existence of a unique stationary solution of the non-linear Boltzmann equation on a bounded spatial domain under a rather general reflection law at the piecewise C¹ boundary. The boundary data are to be small in a weighted L_∞-norm.     

Transport equations with boundary conditions of reverse reflection type

A study is performed of transport equations on arbitrary three-dimensional domains with boundary conditions of reverse reflection type. The existence of the dominant eigenvalue of the criticality problem is proved and its independence of the functional setting and its continuous dependence on a variety of data are established. The corresponding time-dependent problem is shown to be well-posed, also for a conservative boundary. The relationship between the criticality and the time-dependent problem is given explicitly.