Trimeric surfactant

Polymerizable surfactants capable of working as transfer agents include thiosulfonates, thioalkoxylates and methyl methacrylate dimer/trimer surfactants. Thioalkoxylates with 17-90 ethylene oxide units were produced from ethoxylated 11 bromo-undecanol by replacing the bromine with a thiol group via the thiazonium salt route [8]. In the presence of water-soluble azo initiator the thio ended Transurfs (used at a concentration above the CMC) gave monodispersed latex particles in emulsion polymerization of styrene. However, the incorporation of the Transurf remained low, irrespective of the process used for the polymerization (batch, semibatch, seeded). The stability of the lattices when the surfactant and the transfer function were incorporated in the same molecule was better than when they were decoupled. 

Table XIII. Aqueous-Solution Surface Tension ((Tsoin) of Qrganosilicon Trimer Surfactants...

Danino D, Talmon Y, Levy H, Beinert G and Zana R 1995 Branched threadlike micelles in an aqueous solution of a trimeric surfactant Science 269 1420-1... 

Hickling TP, Bright H, Wing K et al. A recombinant trimeric surfactant protein D carbohydrate recognition domain inhibits respiratory syncytial vims infection in vitro and in vivo. Eur J Immunol 1999 29(ll) 3478-84. 

The concept of Gemini surfactants has currently been extended to more complex homologues including the trimeric surfactants made up of three surfactant-like moieties connected by two spacer groups and tetrameric surfactants, and so forth. The new Gemini and oligomeric surfactants that will be synthesized in the future are anticipated to possess novel and unexpected properties. [34]... 

The issue of water in reverse micellar cores is important because water swollen reverse micelles (reverse microemulsions) provide means for carrying almost any water-soluble component into a predominantly oil-continuous solution (see discussions of microemulsions and micellar catalysis below). In tire absence of water it appears tliat premicellar aggregates (pairs, trimers etc.) are commonly found in surfactant-in-oil solutions [47]. Critical micelle concentrations do exist (witli some exceptions). 

Alkylphenol Ethoxylates (APE). The hydrophobes of most commercial APE are made by reacting phenol with either propylene trimer or diisobutylene to form nonylphenol or octylphenol. These products contain an aromatic moiety and extensive branching in their alkyl chains. It has been shown that APE biodegrade more slowly and less extensively than LPAE (3.15-20). The difference is more pronounced when the treatment system is operating under stress conditions such as low temperatures and high surfactant loadings. 

The variation of n with concentration expresses the fact that in Region 2 complete removal of each CH2 group of the surfactant from water is only possible at a monolayer. In bulk systems the analogous processes are the pre-association into dimers, trimers, etc. just below the critical micelle concentration. 

More than two surfactants can be put together to form tri,- tetra- or polymeric surfactants. Trimeric or even tetrameric surfactants show properties often superior to monomeric surfactants. Besides, they are intermediate between conventional surfactants and polymeric surfactants. In a normal polymeric surfactant each monomer unit is amphiphilic. Another type of polymeric surfactant, called block copolymer [522], consists of at least two parts. One part is made of monomer type A, the other part is made of monomer B. If A is polar and B nonpolar, the blockcopolymer will be strongly surface active and show many properties of a conventional surfactant. If there are two different blocks we talk about a diblock copolymer. In the following part of this chapter we concentrate on conventional surfactants. 

Fig. 9. Formation of trimeric aggregates of 1,1-ionic surfactants with sulfonate groups. (Hydration and intermolecular interaction. New York Academic 1969]...

Alkylphenol. Alkylphenol is a common surfactant intermediate used to produce alkylphenol ethoxylates. Phenol reacts with an olefin thermally without a catalyst but with relatively poor yields. Catalysts for the reaction include sulfuric acid p-toluene sulfonic acid (PTSA), strong acid resins, and boron trifluoride (BF3). Of these, strong acid resins and BF3 are mostly widely used for the production of surfactant-grade alkylphenols. The most common alkylphenols are octylphenol, nonylphenol, and dodecylphe-nol. Mono nonylphenol (MNP) is by far the most common hydrophobe. It is produced by the alkylation of phenol with nonene under acid conditions. All commercially produced MNP is made with nonene based on propylene trimer. Because of the skeletal rearrangements that occur during propylene oligomerization, MNP is a complex mixture of branched isomers. 

ANEDCO AC-163 is a versatile basic intermediate which can be further modified by reacting with dimer-trimer acids to obtain an excellent film persistent-corrosion inhibitor. Various surfactants may be added to obtain improved water dispersibility. ANEDCO AC-163 may be reacted with a short chain organic acid such as acetic acid, hydroxy acetic acid, etc. to form a water-soluble corrosion inhibitor. 

An outline of the ideas is as follows [62-65]. It suffices to assert that a dilute solution of surfactant molecules can be considered to consist of water plus monomers, dimers, trimers, and larger allowed aggregates (micelles, vesicles, liposomes,. ..). The concentration is assumed to be so low that aggregates can be considered to be non-interacting. The probability distribution of aggregates, is then determined from the law of mass action... 

Crude TDI has an average functionality of more than 2 because it contains TDl-dimer, TDI-trimer, and carbodiimide-containing compounds. The NCO percent of crude TDI is about 40%, which is lower than pure TDI but is higher than crude MDI as well as TDI-based semiprepolymers, both of which have about 30% fi ee NCO. Accordingly, the kinds and amount of catalysts and surfactants for the one-shot, crude-TDI process are slightly different fi om those of TDI-based semiprepolymers. 

Urethane-Modified Isocyanurate Foams. Urethane-modified isocyanurate foams are prepared by the trimerization of a polyisocyanate in the presence of a polyol, a trimerization catalyst, a blowing agent, and a surfactant. The foams have high flame and temperature resistance. The combined use of an isocyanurate foam and glass fiber not only improves the physical properties, e.g., flexural strength, friability, etc. but it also improves the flame resistance because the char formed from the foam acts as thermal barrier and protects it from flame and heat. This type of composite, therefore, is widely used for buUding applications in the U.S.A. Urethane-modified isocyanurate foam systems have also been used in the SRIM process (26, 36, 37). 

Dimers, trimers, etc. are practically absent in surfactant solutions. Spherical micelles are relatively monodispersed, and increase in the surfactant concentration leads to increase in the number of aggregates, but not in their size. The aggregation number N is characteristic for given surfactant (N increases with the tail length in a series of analogs, and decreases in a scries of nonionic surfactants with the same tail length, when the number of ethylene oxide units increases), and it depends on the experimental conditions. The factors depressing the CMC usually induce an increase in N. 

Trimeric and oligomeric surfactants have also been prepared (Zana, 1995 Sumida, 1998 In, 2000 Onitsuka, 2001). Their CMC values are even smaller than those of the analogous geminis. As the number of hydrophobic groups per molecule increases for gemini quaternary C12 ammonium compounds with polymethylene -(CH2) j spacers, their surface layers become more dense, their micellar microviscosity increases, and their micellar shape changes from spherical to wormlike, to... 

Fig. 41a-d. Examples of oligomeric surfactants a bola dimer [426-428] b gemini dimer [435, 445, 448] c cyclic hexamer of tail end type [419] d star-shaped trimer of tail end type [420]... 

Virtually all examples reported for higher oligomeric surfactants than dimer belong to the tail end type , preventing an analysis of the evolution of geometric effects. This is the more true, as the majority of the tail end structures represents stars [416, 417, 420, 422,425, 449] rather than linear or cyclic oligomers [418,419,423], Most attempts to produce head-type trimers suffer from the poor water solubility of the products [450], but recently some water-soluble examples have been reported [427]. 

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