Molecular chains lengths

Like PEO-LiCl04, a 6 1 crystalline compound is formed but, in this instance, the weakened interactions between polymer chains [18] contributes to the lowest melting point for any PEO-salt crystalline complex. A eutectic with composition 0 Li = 11 1 forms, provided the PEO molecular chain length is beyond the entanglement threshold [31]. For lower molecular weights, the 6 1 compound dose not crystallize in the presence of excess PEO and a crystallinity gap exists over the range 6 l < 0 Li < 12 1 [26]. 

In order to reduce the immersing time and to examine the influence of the chain length of the adsorbed molecules on the formation of SAMs, Hu et al. [26,34] has investigated the properties of the SAMs of FPTS, FOTS, and FDTS, which have a different molecular chain length as shown in Table 1. 

The variations of film thickness and the contact angle value of FDTS SAM are also closely related to the immersing time as shown in Fig. 22. The film thickness of FDTS SAM increases to about 20 A within 2 h, which is close to the molecular chain length of FDTS, and then the thickness in-... 

The property is hardly influenced by the molecular chain length, the film layers, and the surface roughness, but the uniformity of a FATS SAM was important considering that decreases when the immersing time was less than 50 min. 

Empirically established relationships between molecular chain lengths in various polymer series and their intrinsic viscosities have been summarized by Goldfinger, Hohenstein, and Mark. ... 

An important feature of surfactant monolayers is their transferability from the air-water interface to clean, smooth, solid supports such as glass or metal surfaces. Blodgett and Langmuir (67) developed this technique and employed it for building up multilayers whose thickness was that of a known number of molecular chain lengths. Recently, there has been considerable interest in the application of this technique to prepare organized multilayers for the study of optical, electrical, and catalytic properties of very thin films of known composition (47,53-55). 

Figure 10.1 Dependence of molecular chain length, and hence viscosity, of molten sulfur on temperature.

Tyrrell and Watkiss [58] showed that the numerical coefficient for 2-methylpentan-2,4-diol solvent is not 6 or 4 but nearer 1—3 depending on the solute molecular size and shape and temperature, being smaller for smaller and planar molecules. In a study of normal alkanes, Amu [59] found that this numerical factor decreased as the molecular chain length increased. Indeed, if the solute molecules are significantly different from a spherical shape, the diffusion coefficient should be regarded as (a tensor) having different values in different directions. Usage of the microfriction factor mentioned in Sect. 5.2 is an improvement, but still rather unsatisfactory (Alwatter et al. [43]). 

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 parabens are most effective against molds and yeasts, but less active against bacteria, particularly gram-negative bacteria. The antimicrobial activity of the parabens is directly related to the molecular chain length (methyl is weakest butyl is strongest). However, the solubility... 

Much of the work with labelled initiators in radical polymerizations is quite independent of determinations of molecular weights, attention being focussed on kinetic chain lengths instead of on molecular chain lengths (10). In a sensitized polymerization, the rate of initiation is identified with the rate at which initiator fragments are incorporated in the polymer to calculate the rate of initiation, it is necessary only to determine the empirical formula shown previously for the recovered polymer and the overall rate of polymerization. No assumptions are required concerning the mechanism of termination or the frequency of transfer processes involving monomer, solvent or polymer. Errors can arise from three causes ... 

This expression is independent of molecular chain length and so is suitable for use with polymers of mixed molecular weight. The turn molecular rotation contribution can be obtained from either of the models for optical rotation we have presented 12-14), either as a sum of contributions from four-atom units or by use of helical conductor equation (Eq. 1) ... 

Fig. 10. Molecular chain lengths of four types of organosilane molecules calculated by using ab initio molecular orbital theory. The -Si(OCH3)3 was converted to the -SiH3 for the model molecules used in the calculation using GAUSSIAN 98.

Since the dose rate exponent of both the rate of polymerization and the average molecular chain length, as well as the over-all temperature coefficient, vary so markedly between the dry and the wet conditions, and the latter are accepted as being indicative of a free radical process, it becomes tempting to describe the dry process as being non-radical, and, by logical exclusion, ionic. Both the extreme sensitivity to water, ammonia, and amines and the data from the copolymerization with a-methylstyrene further support this thesis. 

A second possibility was that the increasing viscosity of the solution and/or increasing molecular chain length reduced the reaction rate by lowering the diffusion of reactants. However, if this were happening, it would reduce the rate at high conversions rather than at the beginning of the polymerization when only monomers and very short chains are present. 

It is a well-known fact that the length of folds in crystal lamellae increases with temperature. Since the melting temperature (=solidification temperature) goes up as a result of the high pressure, also the fold length will increase (with the full molecular chain length as the limit). 

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