Surfactants, polymeric

Barnes and co-workers have studied mixed-monolayer systems [278,281,283,284] and found some striking nonidealities. Mixed films of octadecanol and cholesterol, for example, show little evaporation resistance if only 10% cholesterol is present [278] apparently due to an uneven granular microstructure in films with cholesterol [284]. Another study of cellulose decanoate films showed no correlation between holes in the monolayer and permeation rate [285]. Polymerized surfactants make relatively poor water evaporation retarders when compared to octadecanol [286]. There are problems in obtaining reproducible values for r [287] due to impurities in the monolayer material or in the spreading solvent. 

Patterns of ordered molecular islands surrounded by disordered molecules are common in Langmuir layers, where even in zero surface pressure molecules self-organize at the air—water interface. The difference between the two systems is that in SAMs of trichlorosilanes the island is comprised of polymerized surfactants, and therefore the mobihty of individual molecules is restricted. This lack of mobihty is probably the principal reason why SAMs of alkyltrichlorosilanes are less ordered than, for example, fatty acids on AgO, or thiols on gold. The coupling of polymerization and surface anchoring is a primary source of the reproducibihty problems. Small differences in water content and in surface Si—OH group concentration may result in a significant difference in monolayer quahty. Alkyl silanes remain, however, ideal materials for surface modification and functionalization apphcations, eg, as adhesion promoters (166—168) and boundary lubricants (169—171). 

D. M. Anderson. A new technique for studying microstructures NMR band-shapes of polymerized surfactants and counterions in microstructures described by minimal surfaces. J Physique Colloque 57 1-18, 1990. 

W. Gozdz, R. Holyst. Distribution functions for H nuclear magnetic resonance band shapes for polymerized surfactant molecules forming triply periodic surfaces. J Chem Phys 706 9305-9312, 1997. 

Piirma, Polymeric Surfactants, Marcel Dekker, New York (1992). 

Tethering may be a reversible or an irreversible process. Irreversible grafting is typically accomplished by chemical bonding. The number of grafted chains is controlled by the number of grafting sites and their functionality, and then ultimately by the extent of the chemical reaction. The reaction kinetics may reflect the potential barrier confronting reactive chains which try to penetrate the tethered layer. Reversible grafting is accomplished via the self-assembly of polymeric surfactants and end-functionalized polymers [59]. In this case, the surface density and all other characteristic dimensions of the structure are controlled by thermodynamic equilibrium, albeit with possible kinetic effects. In this instance, the equilibrium condition involves the penalties due to the deformation of tethered chains. 

Block copolymers containing polysiloxane segments are of great interest as polymeric surfactants and elastomers. Polycondensation and polyaddition reactions of functionally ended prepolymers are usually employed to prepare well-defined block copolymers. The living polystyrene anion reacts with a,co-dichloropoly(dimethyl-siloxane) to form multiblock copolymers398. ... 

ThF Tadros. Polymeric surfactants , stabilization of emulsions and dispersions. In E Desmond Goddard, JV Gruber, eds. Principles of Polymer Science and Technology in Cosmetics and Personal Care. New York Marcel Dekker, 1999, pp 73-112. 

Y Sela, S Magdassi, N Garti. Release of markers from the inner water phase of W/O/W emulsions stabilized by silicone based polymeric surfactants. J Control Release 33(1) 1-12, 1995. 

In order to determine whether these surfactant vesicles were of polymerized vesicle forms, a 25% V/V ethanol (standard grade) was added to the three year old sample solution. Alcohols are known (34) to destroy surfactant vesicles derived from natural phospholipids, however, synthetically prepared polymerized vesicles are stable in as much as 25% (V/V) alcohol addition. Photomicrographs shown in Figures 7c and 7d indicate that these vesicles partially retain their stability (being mesomorphic) and therefore are suspected to be polymerized surfactants. Whether surfactant molecules of these vesicles are single or multipla bonds in tail, or in head groups remains to be seen. 

I Piirma, Polymeric surfactants (New York Marcel Dekker 1992). 

Fig. 8 Preparation of biodegradable microspheres entrapping proteins using amphiphilic PDP-b-PLA block copolymers as biodegradable polymeric surfactants, and SEM images of their cross-sections. Reprinted from [182] with permission...

Pt-catalysed reduction of methylene blue and 10-methyl-5-deazoisoalloxazine -3-propanesulfonic acid Polymerized surfactant vesicles. Catalytic efficiencies high in these systems Kurihara and Fendler, 1983... 

Polymeric surfactants, 24 153, 154, 159 Polymeric system, smart, 13 742 Polymeric titanate esters, 25 79 Polymer industry, organic peroxides in, 18 495... 

Piirma I (ed) (1992) Polymeric surfactants. In Surfactant science series, vol 42. Marcel Dekker, New York... 

The 4,4 -dibromobiphenyl was used as the starting material The strategy taken for the synthesis of the organosilica was to carry out Grignard-type reaction to incorporate tetraethyl orthosilicate (TEOS) to 4,4 -dibromobiphei5rl to create 4,4 -Bis(triethoxysilyl)biphenyl. Materials from this procedure had been subjected to polymerization surfactant-mediated polymerization. The product obtained was a white powder aggregate. Shown in Table 47.1 are the formulations used for the samples and the heat treatment. 

When micelles are used, the CE technique becomes a micellar elec-trokinetic chromatography (MEKC) one. Natural surfactants, such as bile salts, digitonin and saponins, optically active synthetic surfactants, e.g., amino-acid derived ones, alkylglycoside-, tartaric acid- and steroidal glucoside-based surfactants, and high-molecular mass or polymerized surfactants, have been used as chiral selectors in In the lat-... 

Open-tubular Polymeric surfactants Neutral hydrophilic layer, e.g.,... 

Zhu et al. coupled OT-CEC to ESI/MS for the analysis of /i-blockers and benzodiazepines. The authors described the use of a polymeric surfactant as a stationary-phase coating that enabled minimal surfactant introduction in the MS compared to MEKC—ESI/MS, thus avoiding interferences from non-voIatile micelles in ESI/MS. ... 

Zhu, X., Kamande, M. W, Thiam, S., Kapnissi, C. P., Mwongela, S. M., and Warner, I. M. (2004). Open-tubular capillary electrochromatography/electrospray ionization-mass spectrometry using polymeric surfactant as a stationary phase coating. Electrophoresis 25, 562-568. 

Y. Sela, Y. Magdassi, and N. Garti Polymeric Surfactants Based on PolysUoxanes-Graft-Poly(Oxyethylene) for Stabilization of Multiple Emulsions. Colloids Surfaces 83, 143 (1993). 

Synthesis of New Polymeric Surfactants and Dispersants Via Atom Transfer Radical Polymerisation at Ambient Temperature... 

Exploiting ATRP as an enabling technology, we have recently synthesised a wide range of new, controlled-structure copolymers. These include (1) branched analogues of Pluronic non-ionic surfactants (2) schizophrenic polymeric surfactants which can form two types of micelles in aqueous solution (3) novel sulfate-based copolymers for use as crystal habit modifiers (4) zwitterionic diblock copolymers, which may prove to be interesting pigment dispersants. Each of these systems is discussed in turn below. 

---