Intrachain order

Both increased temperature and increased acyl chain unsaturation introduce disorder in phospholipid acyl chain packing thus, their effects on bilayer properties are often compared and discussed as being equivalent perturbations on the bilayer structure. However, detailed studies of the effect of these two factors on both intrachain order and acyl chain packing reveal significant differences. The difference between temperature-induced disorder and sn-2 unsaturafion-induced disorder of the saturated sn-1 acyl chain is illustrated in Fig. 2 A. The difference in NMR order-parameter data is plotted for each methyl group of the saturated 18 0 sn-1 acyl chain. The two difference curves show that the disorder caused by exchanging 18 ln-9 at the sn-2 position for 22 6n-3, occurs mainly... 

Among the polyphenylene-based materials highly emissive PFs have received particular attention due to their extraordinary properties in device applications as originally demonstrated by Bradley [74,76-78]. In addition to the wide variety of synthetic routes allowing for the synthesis of differently substituted homopolymers as well as copolymers, PFs display attractive optical and electronic properties which make them ideal model systems for studying relevant structure to property relations in conjugated polymers as shown by Cadby et al. [77,116]. For this reason different properties which are related to the molecular structure as well as to intrachain order effects of the polymer shall be discussed in the following. 

The photoluminescence spectrum of MeLPPP as depicted in Figure 5.8 is characterized by a steep onset at 2.69 eV and by the well-resolved vibrationally split maxima which are homologous to the excitation spectrum. The dominant photoluminescence maximum is only very slightly Stokes-shifted by -35 meV, which is due to the ladder-type structure of the polymer hindering geometrical relaxations. The steep onset of the absorption spectrum reflects the high intrachain order of MeLPPP in the film. 

Aiyar AR, Hong J-I, Reichmanis E (2012) Regioregularity and intrachain ordering impact on the nanostructure and charge transport in two-dimensional assemblies of poly (3-hexylthiophene). Chem Mater 24 2845-2853... 

The Spano model provides an easy approach for estimating the aggregate content and intrachain order in P3HT thin films by simply exploiting the absorption spectrum, as shown in Fig. 10b. The model can be further used to follow crystallization of P3HT from solution, distinguishing between well-dissolved chains and chains incorporated in crystalline nanocrystals (compare with Sect. 3). 

Thus while trajectory measurements are insensitive to these large scale local fluctuations in intrachain order, those flucmations have a marked impact on the wide angle x-ray scattering intensity curve. A similar sensitivity has been recorded in the x-ray study of polydimethylsiloxane. 2 The chain segment of natural rubber is thus highly disordered, its regularity extended over no more than the monomer length, and hence its aspect ratio is close to unity. 

The other two polymer systems considered, namely, poly(a-methylstyrene) and the phenylene based polymers, also yielded to an analysis of their intrachain order. However, in... 

The effective method for increasing thermal oxidation stability of polymers is control of the physical structure [7], The additive effect on the physical structure of PI film was studied with the help of X-ray structural analysis. The film possesses mesomorphous regularity, of which the presence of an intrachain order in the absence of interchain packing regulation is typical. As shown on the diffraction pattern, such structure manifests itself by a single narrow peak of the intrachain order (5-6 deg) and wide amorphous halo (Figure 19). Diffraction patterns show high intrachain orderliness of the stabilized sample. This difference is... 

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