Surfactant Side Chains

Considering hydrocarbon tails, it seems that the minimal length to produce polysoap properties is about C8 [52, 191, 199, 200], Polysoap behaviour was reported even for some shorter chains, but then additional hydrophobic units in the backbone must be present (see below). Also, hydrophobic counterions such as tetrabutylammonium [252] or alkyltrimethylammonium ions [186,204] may induce hydrophobic aggregation for short chain polysoaps , but in such cases it 

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The length of surfactant side chain determines dimensions of the hydrophobic domain and consequently unit cell of a liquid crystal. Pores of different diameter can be obtained by changing surfactant size. This initially allowed MCM-41 pore adjustment from about 20 A up to 50-60 A. Further expansion was possible based on another phenomenon, i.e. micelle swelling by solubilized organic compounds. MCM-41 with pores up to 120 A was obtained with mesitylene as an auxiliary organic (expander) in a hexadecyltrimethylammonium tcmplated preparation [4]. Triblock copolymers were found to afford hexagonal structure, SBA-15, with a pore diameter up to 300 A [33]. Pore dimensions can also be tailored by adjusting the synthesis temperature and post-synthesis treatment with amines 118]. 

The geometrical constraints of vinyl polymers are the consequence of the excessive density of surfactant side chains. The problem is a general one encountered in functionalized polymers, and can be overcome by reducing the density by the incorporation of spacer groups. In the case of main chain... 

Fig. 29a-c. Schematic polarity profile in the surfactant side chains of polysoaps a tail end geometry b mid tail geometry c head geometry. (Reprinted with kind permission from [78]. Copyright 1993 Huthig Wepf, Basel)... 

An intermediate situation between these extremes is found in the model of the regional micelle (Fig. 33b) [78, 203, 217]. Here the aggregation of a few neighbouring surfactant side chains is superposed by the aggregation of individual segments of the polymer. The resulting properties would be similar to the ones of the local micelle , except that the severe geometric restrictions of the... 

Fig. 43 AFM pictures and analysis of results for the complexes (spincast on freshly cleaved mica) between cylindrical brushes with PSS-surfactant side chains and with PEI-PEO side chains with increasing mass fraction w of cylindrical brushes with PEI-PEO side chains (a) w = 0. (b) w = 0.33, (c) w = 0.7, and (d) w = 0.87. From [152]...

We have shown that surfactants associate with oppositely charged polyelectrolytes preadsorbed onto surfaces having the same charge as the surfactant. The association is, just like in bulk solution, a cooperative process driven by the hydrophobic interaction between the surfactant side chains and made more favorable by the presence of polyelectrolytes acting as counterions to the surfactant aggregates. It is possible to define a critical association... 

The pioneering work on amphiphilic polyelectrolytes goes back to 1951, when Strauss et al. [25] first synthesized amphiphilic polycations by quaternization of poly(2-vinylpyridine) with n-dodecyl bromide. They revealed that the long alkyl side chains attached to partially quaternized poly(vinylpyridine)s tended to aggregate in aqueous solution so that the polymers assumed a compact conformation when the mole fraction of the hydrophobic side chains exceeded a certain critical value. Thus, Strauss et al. became the first to show experimentally the intramolecular micellation of amphiphilic polymers and the existence of a critical content of hydrophobic residues which may be compared to the critical micelle concentration of ordinary surfactants. They called such amphiphilic polyelectrolytes polysoaps [25],... 

The oligomerization leads to a mixture of a-olefins. In the first step the a-olefins are isolated by distillation. These a-olefins are of a suitable side chain for use in the manufacture of surfactants (starting material for alcohols and deriva-... 

As the length of the side chain increases the CMC decreases. The general rule for ionic surfactants is applicable to alcohol sulfates. This rule establishes... 

The sulfated alkylbenzenesulfonamides (no. 7-8) and alkylaroylsulfo-propionates (no. 9) were found to be efficient lime soap dispersants [27]. Although the nonionics (nos. 10-11) had low LSDR values they did not potentiate the detergency of soap and exhibited some antagonism. Amphoteric surfactants with alkyl side chains from C12 to C18 (nos. 12-13) possessed the lowest LSDR values, ranging from 2 to 4. The amine oxide derived from an aromatic sulfonamide had a low LSDR of 5 close to that of amphoterics. 

Di Corcia A, Costantino A, Crescenzi C, Marinoni E, Samperi R (1998) Characterization of recalcitrant intermediates from biotransformation of the branched alkyl side chain of nonylphenol ethoxylate surfactants. Environ Sci Technol 32 2401-2409... 

The electrostatic and steric effects can be combined to stabilize nanoparticles in solution. This type of stabilization is generally provided by means of ionic surfactants such as alkylammonium cations (Scheme 9.3). These compounds bear both a polar head group which is able to generate an electrical double layer, and a lipophilic side chain which is able to provide steric repulsion [14, 15]. 

Another aspect of polysorbates is that they are inherently susceptible to oxidative degradation. Often, as raw materials, they contain sufficient quantities of peroxides to cause oxidation of protein residue side chains, especially methionine (59). The potential for oxidative damage arising from the addition of stabilizer emphasizes the point that the lowest effective concentrations of excipients should be used in formulations. For surfactants, the effective concentration for a given protein will depend on the mechanism of stabilization. It has been postulated that if the mechanism of surfactant stabilization is related to preventing surface-denaturation, the effective concentration will be around the detergent s critical micellar concentration. Conversely, if the mechanism of stabilization is associated with specific protein-detergent interactions, the effective surfactant concentration will be related to the protein concentration and the stoichiometry of the interaction (39). 

The effects of cationic head groups on the alkaline hydrolysis of the quinoxaline (192) to give (193) have been looked at using the surfactants (194 R = Me, Et, n-Pr, n-Bu X = Cl, OH).164 The reactivity increases with increasing head-group size and is related to the disruption of the hydration of the HO ion. An earlier paper from the same group describes the synthesis of (192) and some micellar effects on its basic hydrolysis.165 A novel site-selection functionalization reaction is facilitated by histidine side-chains in helical structures which can catalyse the acylation by mono-p-nitrophenyl... 

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