Surfactant hydrophobe modified

A class of systems extensively investigated by means of PFG-NMR are colloids. They are usually hydrophobically modified water-soluble polymers, that is, polymers with a water-soluble skeleton bearing one or more hydrophobic units, which allow the self-assembling of the polymer in water solution and the interaction with surfactants.77... 

Another interesting system containing a surface active betaine ester is the dilute aqueous mixture of dodecyl betainate and hydrophobically modified hydroxyethylcellulose (HM-HEC) that has been studied by Karlberg et al. [33]. It is well known that the viscosity of mixtures of HM polymers and surfactants is strongly dependent on the concentration of the amphiphile. By preparing a mixture of a surface active betaine ester and HM-HEC in a solution buffered at a pH where the surfactant is hydrolyzed, it is possible to make a gel with a time-dependent viscosity. 

Hydrophobically modified PNIPAM-seg-St segmented copolymers can be prepared by evenly inserting short styrene segments (stickers) into a PNIPAM chain backbone using the micellar polymerization. In this method, hydrophobic styrene (St) monomers is first solubilized inside small micelles made of surfactant, hexadecyltriethylammonium bromide (CTAB). KPS and TMED can be used to initiate the polymerization of hydrophibc NIPAM monomers dissolved in the continuous aqueous medium. When the free radical end of a growing PNIPAM chain enters a micelle, styrene monomers entrapped inside start to react to form a short hydrophobic segment (sticker). In this way, the coming-in-and-out of different micelles of each free-radical chain end can connect short styrene blocks on a PNIPAM chain. 

In this paper, the results on the Interactions of hydrophobe modified cationic polymer with surfactants Is presented and the results are compared with those for the unmodified polymer. 

SURFACE ACTIVITY. The surface tension results for aqueous solutions of Polymer JR and Oxiatrlsof t are given In Figure 1. The hydrophobe modified polymers clearly show more surface activity than the unmodified polymer. The surface activity of the modified polymers as measured hy the surface tension criterion Is only moderate compared to conventional surfactants which exhibit ultimate surface tension values In the range of 20-40 mN/m. The effect of the molecular changes resulting In this moderate surface activity can, however, be considerable on other properties of the polymer, as will- be shown In subsequent sections. 

Low charge density, hydrophobically modified polybetaines were shown to interact and comicellize with nonionic, anionic, cationic, and amphoteric surfactants [181-183] and many ionic organic dyes [264,265]. The association mechanism of hydrophobically modified polymers and surfactants in dependence on the concentration of interacting components can be modeled by two pathways (Scheme 21) [183]. 

In a novel process, FIPI was also applied to the emulsiflcation of polymer melts in water, thus providing an alternative method to emulsion polymerization for the production of latexes. " " In fact, some thermoplastic melts (such as polyethylene) cannot be obtained through the emulsion polymerization route hence, the present technique is an example of PI providing a novel product form. To achieve the emulsiflcation of thermoplastics, it is necessary to operate near or above 100°C and at elevated pressures, which necessitates the use of polymer processing equipment fitted with a MFCS mixer at the outlet. It was found that molecular surfactants could not be used to obtain the initial (water-in-polymer melt) emulsion. Instead, hydrophobically modified water-soluble polymers were used as the surface active material. After the phase inversion in the MFCS mixer, the resulting emulsion was diluted to the level required. This also freezes the molten latexes. The important attributes of FIPI emulsification include a low level of surfactant use, low temperature processing, production of submicrometer particles with a narrow size distribution, and production of novel products. 

Both of the types of polymer mentioned above can be modified by the incorporation of hydrophobic monomers onto the essentially hydrophilic acrylate backbone. The effect of this is to modify their characteristics by giving them so-called associative properties. These hydrophobes can interact or associate with other hydrophobes in the formulation (e.g., surfactants, oils, or hydrophobic particles) and thus build additional structures in the matrix [3-11]. These associative polymers are termed cross-polymers when they are based on carbomer-type chemistry [12] and hydrophobically modified alkali-soluble emulsions (HASEs) when based on ASE technology. 

Amphiphilic polymers can have a strong impact on the phase behaviour of microemulsions already at very low concentrations. The most drastic consequence is that on the emulsification capacity of surfactants. A first work in this respect was carried out using hydrophobically modified ethyl hydroxyethyl cellulose [ 1 ]. This is a comb-shaped polymer, having a water-soluble backbone functionalised with low molecular weight hydrophobic... 

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