Electron spin resonance (ESR) spectra of nitroxide radicals formed in thermally treated heterophasic propylene−ethylene copolymers (HPEC) containing bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 770) as a hindered amine stabilizer (HAS) were studied in the temperature range 100−433 K; the nitroxides are derived from the HAS and are termed HAS − NO. The results were compared with ESR spectra of the same radicals obtained first by oxidation of Tinuvin 770 and then doped in HPEC and related homopolymers polyethylene (PE) and polypropylene (PP); these nitroxides are termed spin probes. ESR spectra indicated that HAS−NO and the spin probes in HPEC and homopolymers reside in a range of amorphous sites differing in their dynamical properties. Evidence for the various sites was obtained from the ESR line widths, the temperature variation of the extreme separation in the ESR spectra, and the effect of stress on the ratio of the fast and slow components in the spectra of HAS−NO in thermally treated HPEC. The relative population of sites was explained by assuming that the crystalline domains exert a restraining effect on chains located in vicinal amorphous domains; in PE the restraining effect was more pronounced in the polymer with the higher crystallinity (HDPE vs LDPE). Additional support for this assumption was provided by Fourier transform infrared (FTIR) spectra of HPEC and related polymers and by differential scanning calorimetry (DSC). The dynamically restrained chains evidenced by the spin probes are thought to be located in a rigid amorphous phase, which was described in the literature. In HPEC the fast spectral component represents unrestrained ethylene−propylene rubber (EPR) chains, and the slow spectral component represents amorphous PP and EPR chains in the rigid amorphous phase. This study has demonstrated the exceptional sensitivity of ESR spectra from nitroxide radicals to polymer morphology and degree of crystallinity.

Microphase separation in poly(acrylonitrile–butadiene–styrene) (ABS) was studied as a function of the butadiene content and method of preparation with electron spin resonance (ESR) spectra of nitroxide spin probes. Results for the ABS polymers were evaluated by comparison with similar studies of the homopolymers polybutadiene (PB), polystyrene (PS), and polyacrylonitrile (PAN) and the copolymers poly(styrene‐co‐acrylonitrile) (SAN) and poly(styrene‐co‐butadiene) (SB). Two spin probes were selected for this study: 10‐doxylnonadecane (10DND) and 5‐doxyldecane (5DD). The probes varied in size and were selected because their hydrocarbon backbone made them compatible with the polymers studied. The ESR spectra were measured in the temperature range 120–420 K and were analyzed in terms of line shapes, line widths, and hyperfine splitting from the 14N nucleus; the appearance of more than one spectral component was taken as an indication of microphase separation. Only one spectral component was detected for 10DND in PB, PS, and PAN and in the copolymers SAN and SB. In contrast, two spectral components differing in their dynamic properties were detected for both probes in the three types of ABS samples studied and were assigned to spin probes located in butadiene‐rich domains (the fast component) and SAN‐rich domains (the slow component). The behavior of the fast component in ABS prepared by mass polymerization suggested that the low‐Tg (glass‐transition‐temperature) phase was almost pure PB. The corresponding phase in ABS prepared by emulsion grafting also contained styrene and acrylonitrile monomers. A redistribution of the spin probes on heating occurred with heating near the Tg of the SAN phase, suggesting that the ABS polymers as prepared were not in thermodynamic equilibrium. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 415–423, 2002; DOI 10.1002/polb.10109

We recently presented electron spin resonance spectra of poly(acrylonitrile–butadiene–styrene) (ABS) doped with 10‐doxylnonadecane (10DND) and 5‐doxyldecane (5DD) as spin probes. The spectra were measured in three types of ABS that differed in their butadiene contents and methods of preparation. Results for the ABS polymers were evaluated by comparison with similar studies on the homopolymers polybutadiene (PB) and polystyrene (PS) and the copolymers poly(styrene‐co‐acrylonitrile) (SAN) and poly(styrene‐co‐butadiene) (SB). Only one spectral component was detected for 10DND in PB, PS, SAN, and SB. In contrast, two spectral components differing in their dynamic properties were detected in the ABS samples and were assigned to spin probes located in butadiene‐rich domains (the fast component) and SAN‐rich domains (the slow component). The presence of two spectral components was taken as an indication of microphase separation. In this study, we present details on the dynamics and microphase separation by simulating spectra of 10DND in ABS, PB, PS, and SAN. The simulations are based on a dynamic model defined by the components of the rotational diffusion tensor and the diffusion tilt angle between the symmetry axis of the rotational diffusion tensor and the direction of the nitrogen 2pz atomic orbital. The jump diffusion model led to good agreement with experimental spectra. In this model, the spin probe has a fixed orientation for a given time and then jumps instantaneously to a new orientation. The temperature variation of the rotational correlation time in PB and PS consisted of two dynamic regimes, with different activation energies. The transition temperature at which the change in dynamics occurs (Ttr) is 380 K for PS and 205 K for PB, essentially the same as the corresponding glass‐transition temperatures measured by differential scanning calorimetry. We suggest that Ttr is a better indicator of the glass transition than the temperature at which the total spectral width is 50 G, especially for large probes. The simulation program allowed the determination of the relative intensities of the fast and slow spectral components as a function of temperature; this information was used to clarify the redistribution of the probe above the glass transition of the SAN‐rich component in ABS systems. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 424–433, 2002; DOI 10.1002/polb.10110

ESR spectra of three fluorinated nitroxide radicals with different lengths of the fluorinated side chain were measured in neat solvents and in aqueous Nafion solutions and membranes swollen by water. The probes were prepared by condensation of the 3-carboxy-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxyl acid chloride (acid probe, AP) with 1H,1H-perfluoroalkanols, CF3(CF2) n CH2OH, where n = 6, 10, and 16. The corresponding notation for the probes is FP8, FP12, and FP18. The 14N hyperfine splittings (A zz and a N) are sensitive to the local site:  A zz in the range 33.3−36.5 G and a N in the range 13.95−16.48 G were measured for solvents ranging from perfluorinated n-hexane to 10 M LiCl/water solution. The line shapes in the probe solutions at and near 300 K are sensitive to the presence of oxygen; exceptionally narrow signals (peak-to-peak width 0.1 G) were detected in carefully deaerated probe solutions, thus allowing the measurement of small hyperfine splittings (typically 0.24 G) from the methyl protons. ESR spectra of the fluorinated probes in Nafion solutions and membranes suggested the presence of multiple sites where the probes exhibited a range of dynamics. A possible reason for this effect is the location of probes in a range of amorphous phases where the dynamics is restricted by the proximity to crystalline polymer domains. The A zz values for the “slow” component of the probes in Nafion solutions and in membranes swollen by water indicated the location of the nitroxides in polar sites, where the local polarity is similar to that in the 10 M LiCl/water system. Probes with longer fluorinated segments penetrate deeper into the assembled polymer chains, farther away from the interface between the polymer aggregate and the solvent. Structural information that can be deduced from protiated and fluorinated probes intercalated in Nafion systems was compared, based on present results and previous studies.

Background Thyroglossal duct cyst is the most common midline congenital swelling in the head and neck. This anomaly is very rare in elderly. It usually presents as a midline painless neck swelling. In rare cases, it may show abnormal extension into the larynx that manifests with dysphonia and laryngeal obstruction. Case report We report a case of thyroglossal cyst in a sixty five year old patient who presented with difficulty in breathing, and hoarseness of voice. Fiber optic laryngoscopy revealed fullness in the right vallecula and the right piriform fossa. The differential diagnosis on Ultrasound and Computed Tomography was thyroglossal cyst versus laryngocele. After surgical excision, dyspnea resolved and voice improved. Postoperative fiber optic laryngoscope revealed the disappearance of previous fullness. Histopathological examination confirmed the diagnosis of thyroglossal cyst. To the best of our knowledge, very few cases of thyroglossal cyst with laryngeal extension were encountered in literature, and in this study, we are reporting another case of this extremely rare condition.