Precision heat capacity measurements for the characterization of two-phase polymers

Harmonic and Anharmonic Lattice Thermal Capacities of Molecular Wires and 0001-Oriented Cylindrical ZnO Nano-Wires

“…Features of the temperature dependencies of the harmonic and anharmonic components of the specific (volumetric) thermal capacity of low-dimensional solids become subject of theoretical and experimental studies several decades ago [1][2][3][4][5][6]. In particular, it was recognized, that the low-temperature C p (T) function(s) of linear macromolecules, layered polymeric structures, and some other polymeric substances apparently do not follow the Debye's law, C p (T) ∝ T 3 , which was well established experimentally and theoretically for the bulk crystalline and amorphous solids at relatively low temperatures [1][2][3]7]. Soon thereafter, so-called 'Quantum Dots' (QDs), Nano-Wires (NWs), and other nanostructured solids and devices, become subject(s) of intense studies in semiconductor physics and technology due to their unique optical, electrical and photoelectrical properties [8][9][10][11][12].…”

“…Theoretical description(s) of thermal properties of those bulk, spatially non-homogeneous, low-dimensional, and nano-structured solids is traditionally based on the static plane-wave basis (of an infinite and/or finite -confined -spatial extents) for the acoustic thermal waves (acoustic phonons), pioneered by Peter Debye for bulk solids elsewhere in ref [7]. This approximations works fairly well for those bulk, polycrystalline and nano-crystalline solids of cubic (parallelepiped), square (rectangular) and linear wire-like morphologies (just to mention few), but it apparently has to be replaced with more appropriate choice of the basis functions for the cylindrical NWs (with the morphology 'sketched' in Figure 1 below), spherical QDs, 'conical' nano-structures, etc [1][2][3]16,17]. In particular, the time-independent (static) eigenfunctions set based on the Bessel functions of the first and second kinds of the integer order(s) are used customarily at simulations on vibrational spectra, as well as on thermal and optical properties of nano-structured solids of the cylindrical and spherical morphologies [18][19][20][21].…”

Rigid Amorphous Fraction as an Indicator for Polymer-Polymer Interactions in Highly Filled Plastics

“…One possible approach is to further refine semi-crystalline polymers into a two-phase model with subdivision into amorphous and crystalline phases (crystalline fraction, CF), as shown in Figure 2 , far left. Wunderlich [ 8 , 9 ] and Schick [ 10 ] show the extension to a three-phase model. Here, the amorphous phase is divided into a mobile amorphous fraction (MAF) and a rigid amorphous fraction (RAF).…”

“…The consideration that the RAF softens only when the crystalline areas melt is part of the theory and was also already so included in the considerations of the tie molecules. Although Wunderlich first reported this phenomenon in 1985 [ 8 ], it has come back into focus in recent years, partly due to improved measurement technology. Proof of the method is the subject of current literature.…”