Effect of polymeric surfactants

Descriptions of both emulsion and dispersion polymerisation are given below, with particular reference to the control of their particle size and colloid stabiHty, which is greatly influenced by the emulsifier or dispersant used. Particular emphasis will be placed on the effects of polymeric surfactants that have been recently appHed to the preparation of emulsion polymers. 

A macromolecular picture of the effectiveness of polymeric surfactants in oil displacement from porous rock can be understood from the fact that polymers normally assume the coiled Gaussian chain configuration (Rodriguez et al., 2003). Under the shear field of a flow situation within the pores, the polymeric macromolecules assume an elongated configuration and would tend to lodge themselves onto the oil adjacent to the rock surfaces. 

Figure 3 The architectural diversity, combinatorial effect, of polymeric surfactants as illustrated for block copolymers. The design parameters include the relative and absolute size of the blocks (a-c), their number (d, e), topology (f-i), the chemical nature of the blocks (j), their rigidity or crystallinity (k, 1) and their charge (m, n).

Effect of Polymeric Surfactants on the Behavior of PolycrystaUine Materials with Special Reference to Ammonium Nitrate... 

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. 

Another class of surfactants that are used in cosmetics and personal care products is the phosphoric acid esters. These molecules are similar to the phospholipids that are the building blocks of the stratum corneum (the top layer of the skin, which is the main barrier for water loss). Glycerine esters, in particular, triglycerides, are also frequently used. Macromolecular surfactants of the A-B-A block type [where A is PEO and B is polypropylene oxide (PPO)] are also frequently used in cosmetics. Another important naturally occurring class of polymeric surfactants is the proteins, which can be used effectively as emulsifiers. 

In a study by Consani and Smith, over 140 commercial and commonly available surfactants have been screened for application in CO2 resulting in only a handful with, at best, minute C02-solublilityl2. Recent research in various laboratories, including our own, has developed more soluble surfactants active in CO2 based on the incorporation of C02-philic fluorinated and silicone materialsTT 13-15 Herein we describe the effects of various surfactant and stabilizer systems as they apply to polymerizations in C02-... 

There are an enormous variety of commercial emulsifiers that are employed in emulsion polymerization. Emulsifiers are generally categorized into four major classes anionic, cationic, nonionic and zwitterionic (amphoteric). The anionic and nonionic emulsifiers are the most widely used. In addition, mixtures of emulsifiers are also often used. Since the effects of the molecular structme and chemical and physical properties of an emulsifier on particle formation are still far from being well understood, numerous experimental investigations on particle formation have been carried out to date with various nonionic emulsifiers [99-102], mixed emulsifiers (ionic and nonionic emulsifiers) [18,103-106] and reactive surfactants [33, 107-110]. Recently, polymeric surfactants have become widely used and studied in emulsion polymerizations [111-116]. A general review of polymeric surfactants was published in 1992 by Piirma [117]. Recently, emulsion polymerization stabilized by nonionic and mixed (ionic and nonionic) emulsifiers was reviewed by Capek [118]. 

Figure 1. Effect of mixed surfactant composition on polymerization rate (SLS-BC 840...

Figure 2. Effect of total surfactant concentration with varying surfactant ratio on polymerization rate...

Incorporation of long-chain hydrocarbon hydrophobes into a cellulose ether backbone leads to an interesting new class of polymeric surfactants. Their enhanced solution viscosity can be explained in terms of intermolecular associations via the hydrophobe moieties. Entropic forces cause the polymer hydrophobes to cluster to minimize the disruption of water structure. The same thermodynamic principles that are used to explain the micellization of surfactants can be applied to explain the solution behavior of HMHEC. HMHECs interact with surfactants that modify their solution viscosities. The chemical nature and the concentration of the surfactant dictate its effect on HMHEC solution behavior. The unique rheological properties of HMHEC can be exploited to meet industrial demands for specific formulations and applications. 

Chem C-S, Liou Y-C (1998) Effects of mixed surfactants on the styrene miniemulsion polymerization in the presence of an alkyl methacrylate. Macromol Chem Phys 199 2051-2061... 

It is seen that the effect of the surfactant on the adhesion strength of polymer is related not only to the surface hut also to the hulk properties of siufactant. Let us now pass to considering the details of smfac-tant behavior in oligomeric and polymeric solutions. 

NVP-HRAM). We examined both synthetic variables and the aqueous (brine) viscometry of the products. The NVP-RAM polymers were synthesized by terpolymerization of acrylamide (AM)f N-octylacrylaxnide (RAM), and N-vinylpyrrolidone (NVP) in water with AIBN initiator and SDS surfactant. Since NVP is a moderately good solvent for N-octyl acrylamide, only low levels of SDS are required. The effects of polymerization variables on product solution properties was studied. 

However, in the context of polymeric surfactants, type III behavior is promoted by decrease in the polarity of the hydrophilic part of the surfactant relative to that of the hydrophobic part. While the polarity level of the hydrophobic part could be much higher than that of a hydrocarbon, the relatively large size of the hydrophilic part promotes type III behavior. Therefore, the relatively high polarity of the hydrophobic part is crucial to the effectiveness of these multifunctional multipolymeric surfactants, as long as the hydrophilic part is either ionic or has a high enough polarity if it is nonionic. 

As will be discussed later, one of the main features of effective steric stabilization is strong adsorption (anchoring) of the chains to the interface. This anchoring is produced by the use of polymeric surfactants, the main topic of this chapter. These materials have attracted considerable attention in recent years for stabilization of many o/w and w/o emulsions. Apart from their effectiveness in prevention of flocculation and coalescence of the droplets, they are also expected to cause no skin irritation. The high molecular weight of the surfactants prevents their penetration through the skin and hence they do not cause any disruption of the stratum corneum. 

Another approach to overcome MDR involves the use of polymeric surfactants, such as Pluronic block copolymers, as chemosensitizing agents. The affect of Pluronic block copolymers on MDR cells has two components first, the polymers alter membrane micro viscosity and, second, they cause ATP depletion selectively in MDR cells Both effects... 

Silicone-based materials are an important class of polymeric surfactants that are commonly used in the cosmetic industry. They consist of poly(dimethyl siloxane) (PDMS) that is modified by incorporation of specific groups for special applications. For example, dimethicone copolyol (used as emulsifier or dispersant) is typically a copolymer of PDMS and polyoxyalkylene ether. Aminofunctional silicones provide excellent hair-conditioning benefit. Polyether-modified silicones, including terpolymers containing an alkyl or polyglucoside moiety, are very effective emulsifiers for water-silicone emulsions. These silicone surfactants act as defoamers, depending on the amount and type of glycol modification. They are also used to reduce skin irritation. 

Renken A, Hunkeler, D. Effect of the surfactant blend composition on the properties of polymerizing acrylamide-based inverse-emulsions characterization by small-angle neutron scattering and quasi-elastic light scattering. Polymer 1999 40 3545-3554. 

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