Polyurethane block copolymer, hydrophobic

The hydrophobic polyurethane block copolymer was chosen because phase-separated samples had been shown by an in vitro assay to exhibit a greater platelet adhesion from human blood than samples having a mixed, nonphase-separated structure (7). The hydrophobic styrene-butadiene-styrene (SBS) block copolymer was chosen because of the ease with which the morphology could be controlled (8). The block copolymer having hydrophilic blocks of poly(ethylene oxide) and hydrophobic polystyrene blocks (PS-PEO) was chosen to examine the effect of the more hydrophilic blocks on the protein interaction. 

The polyurethane in the phase-separated state (ANN), however, behaved in a manner similar to certain other hydrophobic surfaces (3), including siliconized glass, in that platelet adhesion was independent of the time of exposure to plasma, that is, no difference between 3 s and 3 min existed. The hydrophobic SBS block copolymer, on the other hand, attached significantly (P < 0.025) less platelets at 3 min of plasma exposure. The effect was relatively more predominant in the mixed state as the percent decrease in platelets attached at 3 min (conversion) was 56 compared with 34 for the phase-separated state (Table II). The conversion, however, was far less than the 99% observed on the hydrophilic glass. 

A variety of stabihzers, including reactive diol containing two primary hydroxyl groups with a long hydrophobic moiety (e.g., PLMA) (Fig. 5.3a), an amphiphilic block copolymer (Fig. 5.3b) and graft copolymer (Fig. 5.3c) have been used in the preparation of polyurethane microspheres or microcapsules in nonaqueous medium [15-17,19-24]. 

In general two types of adhesives are used for the manufacture of baby diapers, feminine-hygiene, and incontinence products. For simple construction purposes, hot-melt adhesives based on amorphous poly(alpha-olefins) (APAOs) are used. High-quality constructions are produced with adhesives based on styrenic block copolymers. For bonding of elastic materials such as polyurethane foam, lycra and natural rubber strands, and hydrophilic and hydrophobic of nonwovens, pressure-sensitive adhesives (PSAs) based on styrenic block copolymers are used. Hot-melt adhesives are the most common types of adhesive. The most widely used synthetic block copolymers are styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), and styrene-ethylene-butadiene-styrene (SEES) with different styrene contents. 

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