Porous polymer matrix

WA Ritchel, A Sabouni, SH Gehrke, ST Hwang. Permeability of [3H]water across a porous polymer matrix used as a rate-limiting shell in compression-coated tablets. J Controlled Release 12 97-102, 1990. 

We have studied the oxygenation of ferroheme bound to a polymer ligand in the solid state98. The profiles of oxygen uptake by powders of polymer-heme complexes were measured by volumetry, as shown in Fig. 22. The heme complex embedded in the porous polymer matrix or in the poly(electrolyte) aggregate takes up... 

PtOEP is widely used as a PSP probe among the metalloporphyrins. The absorption and emission maximum of PtOEP are 381 and 535, and 646 nm, respectively. For examples of PSPs based on the OEP metal complexes in silicone polymer films, PSPs based on the platinum or palladium OEP immobilized in poly(TMSP) film have been reported. Oxygen permeability of poly(l-trimethylsily-l-propyne) (poly(TMSP)) film is about ten times larger than that of poly(dimethylsiloxane) (poly(DMS)) film, and provides a tough and thin film [14,15]. The poly(TMSP) film is a porous polymer matrix with a high oxygen permeability and diffusion, indicating that the probe... 

Porous polymer matrix Release of remaining entrapped drug (booster release)... 

Redmon, M.P. Physicochemical Characteristics of a Porous Polymer Matrix for Drug Dehvery. Ph.D. thesis. University of Kentucky Lexington, KY, 1989. Brannon-Peppas, L. Design and mathematical analysis of controlled release from microsphere-containing polymeric implants. J. Contr. Rel. 1992, 20, 201-207. 

The effective diffusion coefficient accounts for the rate of diffusion of the protein through the complex, porous polymer matrix. Incorporation of an effective diffusion coefficient is necessary because protein molecules do not diffuse through the pure polymer phase, but must find a path out of the slab by diffusing through a tortuous, water-filled network of pores. Z>eff is assumed to be independent of position in the slab Equation 9-14 is justified in this case by local averaging over a volume that is large compared to a single pore. Characteristic desorption or protein release curves are represented by Equation 9-18, with substitution of Dgn- for Z),.p ... 

The stationary phase is a porous polymer matrix whose pores are completely filled with the solvent to be used as the mobile phase. The pore size is highly critical, since the basis of the separation is that molecules above a certain size are totally excluded from the pores, and the interior of the pores is accessible, partly or wholly, to smaller molecules. 

At the time Tiof setting the pendulum into motion the electrode potential of the tray AU shifts to the positive side (Fig. 4.26). This is because of the mechanochemical activation of metals and damage to the film of the products of electrochemical reactions on the tray surface. At time T2 the pendulum stops. Time At, during which the potential returns to its initial value (before actuation), is seen to reduce with increasing liquid phase in the composite. This regularity is attributed to structural features of the studied composites, which is characterized by a porous polymer matrix filled by the liquid phase liberating from the material in the process of syneresis. 

Kumakura M, Kaetsu I (1984) Immobilization of cellnlase using porous polymer matrix. J Appl Polym Sci 29 2713-2718... 

Percolation theory can be used to describe diffusion in a porous polymer matrix (Saltzman and Danger, 1989 Siegel et a/., 1989 Saltzman, 1990). As a simple example of a percolation process, consider a porous material represented as a two-dimensional square lattice (Fig. 5). In this simple model, the squares are called sites and the edges of the squares are bonds. A certain number of the sites are assumed to represent pores in the polymer (black squares in Fig. 5), and the remaining sites represent the backbone material or polymer (white squares). In site percolation, the porosity of the material is equal to the probability, p that a given site will be a pore. A percolation lattice for simulating a material of porosity p is created by randomly assigning each site in the lattice as pore or polymer, based on this probability. For each lattice there exists a critical probability. 

GPEs can be classified into two categories according to their structures as follows One is a homogeneous GPE in which a polymer matrix and solvent or plasticizer are uniformly mixed to form a single phasecomposite. The other is a GPE with phase separation in which a solvent is maintained in a porous polymer matrix. 

Truly porous, synthetic ion exchangers are also available. These materials retain their porosity even after removal of the solvent and have measurable surface areas and pore size. The term macroreticular is commonly used for resins prepared from a phase separation technique, where the polymer matrix is prepared with the addition of a hq-uid that is a good solvent for the monomers, but in which the polymer is insoluble. Matrices prepared in this way usually have the appearance of a conglomerate of gel-type microspheres held together to... 

All VGCF was graphitized prior to composite consolidation. Composites were molded in steel molds lined with fiberglass reinforced, non-porous Teflon release sheets. The finished composite panels were trimmed of resin flash and weighed to determine the fiber fraction. Thermal conductivity and thermal expansion measurements of the various polymer matrix composites are given in Table 6. Table 7 gives results from mechanical property measurements. 

Similarly, a composite of hydroxyapatite and a network formed via cross-linking of chitosan and gelatin with glutaraldehyde was developed by Yin et al. [ 169]. A porous material, with similar organic-inorganic constituents to that of natural bone, was made by the sol-gel method. The presence of hydroxyapatite did not retard the formation of the chitosan-gelatin network. On the other hand, the polymer matrix had hardly any influence on the high crystallinity of hydroxyapatite. 

Given that the primary step in the formation of NPSs is the infiltration of macromolecules into the porous silica matrix, the polymer size is an important parameter. Low molecular weight PEs are preferred for infiltration into the pores of the APTS-BMS spheres, and this process can be promoted by tuning the adsorption... 

A method was recently developed to deliver plasmid DNA locally to cells involved in wound repair (Bonadio et al., 1999 Fang et al., 1996 Shea et al., 1999). The technique involves the introduction of a porous, biodegradable polymer matrix into the wound site (Bonadio et al., 1998). The scaffold (a gene activated matrix, or GAM), in its simplest form comprises plasmid DNA and the polymer matrix (Bonadio, 2000). Naked... 

Chirica and Remcho first created the outlet frit, packed the column with ODS beads, and then fabricated the inlet frit. The column was filled with aqueous solution of a silicate (Kasil) and the entrapment achieved by heating the column to 160 °C [105,106]. The monolithic column afforded considerably reduced retention times compared to the packed-only counterpart most likely due to a partial blocking of the pores with the silicate solution. This approach was recently extended to the immobilization of silica beads in a porous organic polymer matrix [107]. 

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