Chains lengths

This termination step stops the subsequent growth of the polymer chain. The period during which the chain length grows, i.e., before termination, is known as the active life of the polymer. Other termination steps are possible. 

This form is obeyed fairly well above x values of 5-10 dyn/cm in Fig. Ill-15c. Limiting areas or a values of about 22 per molecule result, nearly independent of chain length, as would be expected if the molecules assume a final orientation that is perpendicular to the surface. Larger A values are found for longer-chain surfactants, such as sodium dodecyl sulfate, and this has been attributed to the hydrocarbon tails having a variety of conformations [127]. 

Fig. IV-24. Effect of alkyl chain length of n-alcohols on the resistance of water evaporation at 25°C. (From Ref. 275.)...

The tendency to form organized monolayers improves with chain length. This is illustrated in a study of adsorption kinetics in alkanoic acid monolayers on alumina by Chen and Frank [36]. They find that the Langmuir kinetic equation, discussed in Section XVII-3, (see Problem XI-6)... 

Using guest fluorophores, they show that the adsorption energy increases linearly with the alkyl chain length as... 

Fig. XI-14. Effect of hydrocarbon chain length on the f potential of quartz in solutions of alkylammonium acetates and in solutions of ammonium acetate. (From Ref. 183.)...

After reviewing various earlier explanations for an adsorption maximum, Trogus, Schechter, and Wade [244] proposed perhaps the most satisfactory one so far (see also Ref. 243). Qualitatively, an adsorption maximum can occur if the surfactant consists of at least two species (which can be closely related) what is necessary is that species 2 (say) preferentially forms micelles (has a lower CMC) relative to species 1 and also adsorbs more strongly. The adsorbed state may also consist of aggregates or hemi-micelles, and even for a pure component the situation can be complex (see Section XI-6 for recent AFM evidence of surface micelle formation and [246] for polymeric surface micelles). Similar adsorption maxima found in adsorption of nonionic surfactants can be attributed to polydispersity in the surfactant chain lengths [247], Surface-active impuri-... 

An important application of foams arises in foam displacement, another means to aid enhanced oil recovery. The effectiveness of various foams in displacing oil from porous media has been studied by Shah and co-workers [237, 238]. The displacement efficiency depends on numerous physicochemical variables such as surfactant chain length and temperature with the surface properties of the foaming solution being an important determinant of performance. 

Ruths M and Granick S 1998 Rate-dependent adhesion between opposed perfluoropoly (alkyl ether) layers dependence on chain-end functionality and chain length J. Rhys. Chem. B 102 6056-63... 

R N. The exponent v = 0.588 has been calculated using renonnalization group teclmiques [9, 10], enumeration teclmiques for short chain lengths and Monte Carlo simulations [13]. 

Figure B3.6.5. Phase diagram of a ternary polymer blend consisting of two homopolymers, A and B, and a synnnetric AB diblock copolymer as calculated by self-consistent field theory. All species have the same chain length A and the figure displays a cut tlirough the phase prism at%N= 11 (which corresponds to weak segregation). The phase diagram contains two homopolymer-rich phases A and B, a synnnetric lamellar phase L and asynnnetric lamellar phases, which are rich in the A component or rich in the B component ig, respectively. From Janert and Schick [68].

Grassberger P 1997 Pruned-enriched Rosenbluth method simulations of theta polymers of chain length up to 1,000,000 Phys. Rev. E 56 3682... 

Atre S V, Liedberg B and Allara D L 1995 Chain length dependenoe of the struoture and wetting properties in binary oomposition monolayers of OH and CHj-terminated alkanethiolates on gold Langmuir 3882-93... 

A compound is most soluble in that solvent to which il is most closely related in structure. Thus re-hexane, which is sparingly soluble in water, dissolves in three volumes of methyl alcohol, is more soluble in anhydrous ethyl ilcohol, and is completely miscible with re-butyl and higher alcohols. As the chain length increases the compound tends to resemble the hydrocarbon more and more, and hence the solubihty increases. 

Reaction of 57 with dihalogenoalkanes is reported to give not only the expected dithioether (58) but also the bicyclic salt (59) (Scheme 26) (118). This reaction should depend on the alkyl chain length. 

The effect of an o>-phenyl group as a function of the alkyl chain length has been studied in 3-(through-space interaction has been evidenced on the reactivity of the thiocarbonyl group. 

Strictly speaking the term fatty add is restricted to those carboxylic acids that occur naturally in triacylglyc erols Many chemists and biochemists however refer to all unbranched carboxylic acids irrespective of their origin and chain length as fatty acids... 

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