Hydrophilic surface characteristics

The hydrophilic surface characteristics and the chemical nature of the polymer backbone in Toyopearl HW resins are the same as for packings in TSK-GEL PW HPLC columns. Consequently, Toyopearl HW packings are ideal scaleup resins for analytical separation methods developed with TSK-GEL HPLC columns. Eigure 4.44 shows a protein mixture first analyzed on TSK-GEL G3000 SWxl and TSK-GEL G3000 PWxl columns, then purified with the same mobile-phase conditions in a preparative Toyopearl HW-55 column. The elution profile and resolution remained similar from the analytical separation on the TSK-GEL G3000 PWxl column to the process-scale Toyopearl column. Scaleup from TSK-GEL PW columns can be direct and more predictable with Toyopearl HW resins. 

The term "bioenertness" is a relative one since few if any synthetic polymers are totally biocompatible with living tissues. The terra is used here on the basis of preUminary in vitro and in vivo tests, together with chemical evaluations based on analogies with other well-tested systems. Two different types of polyphosphazenes are of interest as bioinert materials those with strongly hydrophobic surface characteristics and those with hydrophilic surfaces. These will be considered in turn. 

Figure 13.4 APTS-modified surfaces may be further derivatized with amine-reactive crosslinkers to create additional surface characteristics and reactivity. Modification with NHS-PEG4-azide forms a hydrophilic PEG spacer terminating in an azido group that can be used in a click chemistry or Staudinger ligation reaction to couple other molecules.

Also the surface of hydrophilic SiO substrate was confirmed to be smooth and amorphous, based on morphological and ED studies, respectively. Therefore, the crystallographic study of the monolayer and the surface characteristics of the substrate indicate that the hydrophilic SiO substrate is suitable for the electron microscopic morphological and structural investigations on the monolayer on the water surface. Then, the monolayer was transferred onto the hydrophilic SiO substrate by the upward drawing method[3,15] at a transfer rate of 60 mm-min 1 at various TSps and pressures, except at the surface pressure of 0 mN-nr1. The monolayer at 0 mN-nr1 can be transferred only by a horizontal lifting methodf 16). 

Heats of immersion of two solids with widely different surface characteristics 39) are given in Table IV. Rutile (TiOz) is a heteropolar hydrophilic solid, and Graphon is homopolar and hydrophobic. A homologous series of alcohols and hydrocarbons and several n-butyl derivatives are the wetting liquids. Water is included for comparison. 

There are other desirable properties for the powder, such as exhibiting a hydrophilic surface, but these are related to tablet performance, to product stability (antioxidant), or to esthetic characteristics (e.g., colors, flavors). 

XAD-2 resin is a styrene-divinylbenzene copolymer that has a highly aromatic structure. It has a surface area of about 300 m2/g, an average pore diameter of 90 A, and a maximum pore diameter of 290 A. XAD-8 resin is a methyl methacrylate copolymer and has a slightly more hydrophilic surface than XAD-2. It has a surface area of about 140 m2/g, an average pore diameter of 250 A, and a maximum pore diameter of 375-840 A. Each exhibits different adsorption characteristics because of structural and surface chemistry differences. Both XAD resins have a significant number of micropores <25 A in diameter. The adsorption area is distributed biomodally in XAD-8 and has maximums at 22.5 A or less and at 375 A. XAD-2 has a maximum at 22.5 A or less and a slight increase at 240 A (11). This result indicates that XAD-2 adsorption is initially more diffusion-limited than XAD-8. 

Adsorption the drug/particulate adsorbs to the phagocytic cell surface. This process may be facilitated by serum proteins knows as opsonins, which cover the particulate and promote adsorption and ingestion. The extent and pattern of opsonization depends highly on antigen surface characteristics such as charge and hydrophilicity. 

The diversity of pore sizes coupled with the essentially cation-free framework make AlPOi, molecular sieves potentially applicable in separations of molecules and other adsorption applications. A broad screening program in air drying has shown many AlPOi, molecular sieves with performance characteristics similar to those of Linde Type A and X. The hydrophilic surface character has also been demonstrated in the selective removal of Hz0 from solutions of 2-butanone containing 4 vol.% HzO. The hydroxyl infrared region (4000-3400 cm-1) for several AlPO molecular sieves contains weak VqH absorptions at 3680 cm- attributed by Peri (14)... 

The film surface characteristics were also dramatically changed due to oxygen addition as was seen in the change in contact angle with water, at the peak weight increase at 70 C, films all showed water contact angle reduction of about 20 to 30 percent indicating a drastic reduction of hydrophobicity with the surface formation of carbonyl functionality (see below) which enhanced hydrophilicity. 

---