Extended chain length

The relation between head-group area and extended chain length and volume of the apolar groups favors formation of vesicles or bilayers from these twin-tailed surfactants. However, it seems that DDDAOH forms vesicles only in dilute solution, because the solution becomes viscous with increasing [surfactant] which is incompatible with the presence of approximately spherical vesicles. It appears that the solution then contains long, non-vesicular aggregates (Ninham et al., 1983). 

It is clear that the quenched material has lamellae that are both thinner in the chain direction and smaller in lateral extent. Both these parameters increase with slower rates of cooling. So, too, does density. The microstructure of PTFE prepared this way may be likened to a pack of rods (the helical polymer chains), which in turn comprise lamellar crystals. Consider a hexagonal poker chip as a macroscopic analogue of one lamella. The diameter of die poker chip is the lamellar breadth and its thin dimension is the lamellar thickness. The fully extended chain length of a 10-million-MW PTFE macromolecule would be ca. 26 pm while our thickest observed lamellae are ca. 0.5 pm thick. It therefore... 

Q-Factor (Extended Chain Length—Retention Volume Calibration)... 

Table I. Molecular Weight Averages of Cellulose by Viscometric and GPC Weight Average Methods Using Extended Chain Length Model (Q Factor)...

The gel permeation chromatographs were obtained by eluting a 2% solution of copolymer in a 104 A column manufactured by Water Associates. The calibration curve used to determine the molecular weights was obtained by plotting elution volumes against projected extended chain lengths of polystyrene. 

If a polymer molecule in solution behaves as a random coil, its average end-to-end distance is proportional to the square root of its extended chain length (see page 25) - i.e. proportional to Ai 5, where Mr is the relative molecular mass. The average solvated volume of the polymer molecule is, therefore, proportional to M 5 and, since the unsolvated volume is proportional to A/r, the average solvation factor is proportional to (i.e. Af 5). The intrinsic viscosity of... 

Fig. 11 Nascent radiation initiated PTFE dispersion particles. The polymerization conditions were (a) 0% emulsifier, 90 min, (b) 0.5% emulsifier, 60 min, (c) 1% emulsifier, 60 min, (d) 2% emulsifier, 90 min, all for essentially the same radiation dose rate at 25 °C in water (with 1.3% hexadecane and ammonium perfluorooctanoate emulsifier) at 30-kg/cm2 pressure. The measured molecular weights, the corresponding extended chain lengths (eel) the and dimensional characteristics are, respectively, (a) Mn = 230 x 104, edn = 6.0 pm, particle volume approximately 7 x 108 Da (b) Mn = 50 x 104, eel = 1.3 pm, rod diameter approximately 100 molecules (c) Mn = 20 x 104, ed = 0.52 pm rod length (d) Mn=2xl04, ed = 520A. (Reprinted from Ref. [14] with permission from Wiley-Interscience)...

Ungar and Zeng [33] have comprehensively summarized the research on strictly monodisperse materials from their first synthesis in 1985 until 2001. From the earliest studies it became apparent that, due to the monodisper-sity of the materials, the thickness of the lamellar crystals formed is always an integer fraction of the extended chain length (allowing for any chain tilt), such that the polymers always crystallize in the extended chain form or fold exactly in half (once-folded), or in three (twice-folded), etc. This behavior means that, when the alkanes are crystallized at a particular temperature, the entire lamellar population has very closely the same thickness and stability. The use of such an ultra-pure system to study the impact of thickness on lattice parameters removes many of the problems inherent to polymers, whilst maintaining the most important characteristic of chain length. 

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