Hydrophilic sheath

Surfactant blends of interest will exhibit clouding phenomena in aqueous solutions undergoing a phase transition from a one phase system to a two phase system at a discrete and characteristic temperature, referred to as the Cloud Point (CP). This value indicates the temperature at which sufficient dehydration of the oxyethylene portion of the surfactant molecule has occurred and this results in its "displacement" from solution. The addition of lyotropic salts will depress the CP, presumably due to the promotion of localised ordering of water molecules near the hydrophilic sheath of the surfactant molecule (8). Furthermore, the addition of different oils to surfactant solutions can induce either an elevation or a depression of the recorded CP and can be used to qualitatively predict the PIT (8x9). 

The first two components are the active surfactants, whereas the other components are added for a variety of reasons. The polyphosphate chelate Ca ions which are present (with Mg ions also) in so-called hard waters and prevents them from coagulating the anionic surfactants. Zeolite powders are often used to replace phosphate because of their nutrient properties in river systems. Sodium silicate is added as a corrosion inhibitor for washing machines and also increases the pH. The pH is maintained at about 10 by the sodium carbonate. At lower pH values the acid form of the surfactants are produced and in most cases these are either insoluble or much less soluble than the sodium salt. Sodium sulphate is added to prevent caking and ensures free-flowing powder. The cellulose acts as a protective hydrophilic sheath around dispersed dirt particles and prevents re-deposition on the fabric. Foam stabilizers (non-ionic surfactants) are sometimes added to give a... 

Fig. 4-10 (A). When detergent is added [Fig. 4-10 (B)], the soil hydrophobe either dissolves into the soil or orient along the fibre surface. The largest concentration of detergent is present along the edge of the soil. Because of the hydrophile, the edges tend to associate with water and thus the removal of soil from the fabric starts. Ultimately, the oil disperses as droplets [Fig. 4-10 (C)] and the dirt is held in suspension within the droplets [8]. The suspended soil particles with its sheath of...

The capped allyl polyalkylene oxide can also be based upon propylene oxide or a mixed ethylene oxide-propylene oxide copolymer. The resulting structure is a comb polymer, with pendant capped hydrophilic groups. In aqueous solution, the hydrophilic groups may form a sheath around the hydrophobic silicone backbone to minimize its contact with the water. 

Figure 7 also shows the structure of a tetrakis-arboral-TTF derivative that can be processed by spin-coating to form potentially conductive nanowires [68]. The TTF inner core of these molecules self-assembles into supermolec-ular aggregates possessing a redox-active interior and a hydrophilic exterior sheath [69]. 

In 2010 Cook Medical launched a new three-piece modular device with an 18 Fr hydrophilic braided sheath and a lower-profile polyester woven graft fabric. While it has received its CE mark in Europe, it is still going through clinical trials in the United States. The TX2 is Cook s thoracic stent-graft. It also comes in a low-profile (LP) iteration. 

---