Polymeric surfactants polystyrene

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. ... 

Another beneLt of polymeric surfactants over traditional surfactants is the potential for much lower CMCs. Amphiphiles with a high CMC may not be suitable as drug-targeting devices since they are unstable in an aqueous environment and easily dissociate upon dilution (Jones and Ler-oux, 1999). It must be noted that while some polymers exhibit very low CMCs, for instance, the CMC of poly -benzyl-L-aspartate) (PEO-PBLA), poly(N-isopropylacrylamide-polystyrene (PNIPA-PST), and poly(caprolactone) (PEO-PCL) are between 0.00005% and 0.002% (La etal.,... 

Swelling of polystyrene latex particles with styrene. The swelling ratios and the corresponding interfacial tensions for the different-size latexes with added anionic surfactants Aerosol MA and sodium dodecyl sulfate are listed in Table II. Those values obtained with added nonionic surfactant Triton X-100 and polymeric surfactant polyvinyl pyrrolidone are listed in Table III. Figure 1 compares theoretical curves from Model I with all of the experimental data. It is found that a curve corresponding to Xmp = 0.35 fits the data best. Therefore, a semi-empirical... 

Swelling of Polystyrene Latexes with Styrene in the Presence of Nonionic and Polymeric Surfactants... 

Polymerization of the alkoxyallene with macromonomers having a poly (ethyleneglycol) group by [(7r-allyl)Ni(OCOCF3)]2/PPh3 produces a graft copolymer with narrow molecular weight distribution [129]. The products serve as polymeric surfactants in the polymer blend system of polystyrene and poly(methyl methacrylate). 

Harrison KL, daRocha SRP, Yates MZ, Johnston KP, Canelas D, DeSimone JM. Interfacial activity of polymeric surfactants at the polystyrene-carbon dioxide interface. Langmuir 1998 14 6855-6863. 

The condensation method begins with molecular units, and the particles are built-up by a process of nucleation typical example is the preparation of polymer lattices, in which case the monomer (e.g., styrene or methylmethacrylate) is emulsified in water using an anionic or nonionic surfactant (e.g., sodium dodecyl sulphate or alcohol ethoxylate). A polymeric surfactant is also added to ensure the long-term colloid stabiHty of the resulting latex. An initiator such as potassium persulphate is then added and, when the temperature of the system has increased, initiation occurs that results in formation of the latex [polystyrene or poly(methylmethacrylate)]. 

The type of emulsion stabilized by polymeric surfactants, charged or uncharged, was not investigated in detail, although it has long been understood that it was dependent of the structure of the surfactant macromolecules. In a series of papers, Riess and his coworkers [143-145] have investigated the effect of the composition and architecture of PS-PEO-based block copolymers (PS polystyrene PEO polyethylene oxide) on stability and emul-... 

Recently the polymerization of styrene within lamellar and cubic phases of the surfactant DODAB (dioctadecyldimethylammonium bromide) was studied [50]. After polymerization, the polystyrene/water/DODAB system showed the same phase behavior as the binary water/DODAB system, a result suggesting a phase separation during polymerization into a polymer-rich (with M 400,000) and a lyotropic phase. 

Another graft copolymer that could be used for stabilization of suspensions is that based on a polyfructose backbone on which several alkyl groups have been grafted (INUTEC SPl), mentioned earlier for stabilization of emulsions. This polymeric surfactant was used to investigate the stability of polystyrene (PS) and PMMA suspensions in the presence of electrolytes [NaCl, CaClj, and Al2(S04)3l [25]. The polystyrene latex was prepared by emulsion polymerization without surfactant, and it was fairly monodisperse, with a diameter of 210 nm. The PMMA latex was prepared... 

An alternative (and perhaps more efficient) polymeric surfactant is the amphipathic graft copolymer consisting of a polymeric backbone B (polystyrene or polymethylmethacrylate) and several A chains ( teeth ) such as polyethylene oxide. The graft copolymer is referred to as a comb stabilizer—the polymer forms a brush at the solid/liquid interface. The copolymer is usually prepared by grafting a macromonomer such as me-thoxy polyethylene oxide methacrylate with polymethyl methacrylate. In most cases, some polymethacrylic acid is incorporated with the polymethylmethacrylate backbone this leads to reduction of the glass transition of the backbone, which makes the chain more flexible for adsorption at the S/L interface. Typical commercially available graft copolymers are Atlox 4913 and Hypermer CG-6 (ICI). 

Okubo (16) used a similar approach to follow the growth of seeded emulsion polymerizations. When polystyrene was used as the seed particles, followed by the addition of methyl methacrylate, overcoating of the seed particles with a layer of poly(methyl methacrylati was observed. In the reverse situation, however, a distinctly different morphology was produced as indicated by the surfactant adsorption variations with monomer conversion. Instead of overcoating the PMMA seed particles with a uniform layer, the PSTY tended to separate into spherical domains eventually producing a... 

Surfactants — either anionic surfactants such as sodium dodecylsulfate [SDS], or sodium dodecyl benzene sulfate [SDBS], or polysaccharide [Gum Arabic GA] — were first used to disperse, and exfoliate as-produced SWCNTs in water by ultrasonication, and to stabilize the resulting aqueous CNT suspension, see Figure 2.12. The SWCNTs were synthesized by either the AD method [about 30 % of impurities], or by the HiPCO process [having a catalyst particle content of about 5 wt%]. Please note that not only short surfactant molecules, but also polymeric surfactants such as polystyrene sulfonate, or even conductive polymers having a surfactant nature, can also be successfully used to disperse CNTs in water. 

It is noteworthy that a basic assumption made in the derivation of the free radical desorption rate constant is that the adsorbed layer of surfactant or stabilizer surrounding the particle does not act as a barrier against the molecular diffusion of free radicals out of the particle. Nevertheless, a significant reduction (one order of magnitude) in the free radical desorption rate constant can happen in the emulsion polymerization of styrene stabilized by a polymeric surfactant [42]. This can be attributed to the steric barrier established by the adsorbed polymeric surfactant molecules on the particle surface, which retards the desorption of free radicals out of the particle. Coen et al. [70] studied the reaction kinetics of the seeded emulsion polymerization of styrene. The polystyrene seed latex particles were stabilized by the anionic random copolymer of styrene and acrylic acid. For reference, the polystyrene seed latex particles stabilized by a conventional anionic surfactant were also included in this study. The electrosteric effect of the latex particle surface layer containing the polyelectrolyte is the greatly reduced rate of desorption of free radicals out of the particle as compared to the counterpart associated with a simple... 

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