Extended molecular chain length

Fig. 10. Schematic structure models of the bulk-crystallized polyethylene samples. 1, II, and 111 indicate the crystalline, interfacial, and interzonal regions, respectively. Models A, B, C, D, and E express the molecular crystal, unpeeled crystal, disheveled unpeeled crystal, and lamellar crystals for medium and large molecular weight samples, respectively66), f and x designate the lamellar thickness and the extended molecular chain length, respectively...

The spectrum for samples with a very low molecular weight, ie., lower than about 1000, is fairly independent of the mode of crystallization, whether from the melt or from dilute solution. The spectrum is characterized by a very large broad component (wb 0.95) and a medium component with a large second moment, but no narrow component. In such samples the extended molecular chain length will be comparable to or slightly larger than the lamella thickness. The conformation of molecular chains to form the lamellar crystallites will be similar to that depicted schematically in Fig. 10 (B), independent of the crystallization mode. 

The c axis corresponds to both the short axis of the crystal and the axis along the molecular chain. The observed repeat distance in the c direction is what would be expected between successive substituents on a fully extended hydrocarbon chain with normal bond lengths and angles (see Sec. 1.2). 

Quite large elastic strains are possible with minimal stress in TPEs these are the synthetic rubbers. TPEs have two specific characteristics their glass transition temperature (7 ) is below that at which they are commonly used, and their molecules are highly kinked as in natural TS rubber (isoprene). When a stress is applied, the molecular chain uncoils and the end-to-end length can be extended several hundred percent, with minimum stresses. Some TPEs have an initial modulus of elasticity of less than 10 MPa (1,500 psi) once the molecules are extended, the modulus increases. 

We may note in passing that the intrinsic viscosity of a fully extended rod molecule, for which is proportional to the square of the length, should depend on the square of the molecular weight, in the free-draining approximation. In a more accurate treatment which avoids this approximation, the simple dependence on is moderated by a factor which depends on the effective thickness of the chain (or bead density along the chain) compared with the chain length. 

To provide further insight into the nature of multiple conduction states observed experimentally, DFT-based calculations of alkanedithiols coupled to Au electrodes were carried out. Calculations were performed for different configurations of an extended molecule composed of an n-alkanedithiol with variable chain length (n = 4... 10) bridged between two pyramids of 45-55 Au atoms (Fig. 15a-c). These clusters mimic the contact region of the gold electrodes. Molecular... 

As described above, the arrangement of the various functional moieties was controlled spatially across the films at molecular dimensions in the form of LB films. In a series of folded type of sensitizer (S) and electron-donor (D) dyads in a previous work, however, the dyad molecules in the LB films can take many conformations due to flexibility of the longer alkyl chain of the dyads so that clear dependence of the photoinduced electron transfer rate on the alkyl chain length, i.e. S-D distance, was not observed [2], By this reason, we are studying the chain length dependence by using a series of linear type S-D dyads, in which the S and D moieties were linked by a single alkyl chain. In the closely packed LB films, the alkyl chain was considered to be extended and the distance between S and D to be... 

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