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Short Range Order in Polymers within Neutrons' Eyeshot

100%
Acta Physica Polonica A
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2009
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vol. 115
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issue 2
594-598
EN
The paper presents a short review of neutron scattering results obtained during investigation of short range order in bulk polymers. Neutron scattering proves exceptionally powerful in this type of study through (i) large penetration depth of bulk samples, (ii) isotope sensitivity, and (iii) the use of spin polarization technique. The examples provided deliver results that can hardly be obtained from e.g. X-ray diffraction.
2
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How Random Is a Random Polymer Coil?

100%
Acta Physica Polonica A
|
2012
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vol. 121
|
issue 2
464-467
EN
Short range order within amorphous, random polymer structures is a well known and widely studied property of disordered systems. An aggregate of five random atactic chains, each comprising 400 building units was computer-generated and then used to calculate neutron coherent scattering intensity for 0.01 < Q < 30 nm^{-1} (0.001 < Q < 3 Å^{-1}). The latter was compared with experimental data within the diffuse scattering range. On the grounds of quantum chemical calculations for an atactic polystyrene tetramer and the above information it is concluded that interactions among phenyl rings are responsible for the onset of the local order in this polymer.
EN
We report the properties of a novel mesogen with high temperature cholesteric mesophase, which belongs to an unexplored as yet series of cholesteric esters. This compound is cholesteryl 4-(4-nonyloxybenzoylthio) benzoate (C_9H_{19}OC_6H_4COSC_6H_4COOch, where ch = cholesteryl), hereafter named 9OSBch. The chemical structure and purity of 9OSBch was established by ^1H NMR, ^{13}C NMR and FT-IR spectroscopy, and its mesomorphism was characterised by differential scanning calorimetry, polarizing optical microscopy, and transmitted light intensity. Differential scanning calorimetry measurements showed that substance is stable up to 270C and partially decomposes above this temperature. Observation under polarizing optical microscope revealed oily streak texture of cholesteric phase (Ch). The chemical structure of an isolated molecule was optimized by the density functional theory method. Energetically most favourable configuration is that of hockey stick geometry. At the same time this is the conformation best suited for the formation of highly ordered condensed phases.
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