Permeability crosslinked poly

One of the most widely used hydrogels is water-swollen, crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA) which was introduced as a biological material by Wichterle and Urn [33]. The PHEMA structure permits a water content similar to living tissue. The hydrogel is inert to normal biological processes, shows resistance to degradation, is permeable to metabolites, is not absorbed by the body, withstands heat sterilization without damage, and can be prepared In a variety of shapes and forms [34]. 

Through Irradiation Crosslinked Low-Density Poly(ethylene) Permeability Coefficients of Gases Through Irradiation Crosslinked Low-Density Poly(ethylene) Permeability Coefficients of Chemically Crosslinked Poly(oxypropylene)... 

TABLE 8. PERMEABILITY COEFFICIENTS OF CHEMICALLY CROSSLINKED POLY(OXYPROPYLENE) a ... 

Fig. 18 a, b. Typical permeabilities of various hydrogels to water and various solutes (a) Water permeability at pressures less than 7 x 107 dyne/cm2 531 (1) = polyelectrolyte complex of poly-(sodium styrenesulfonate) (NaSS)-poly(4-vinylbenzyltrimethylammonium chloride) (PVBMA), (2) = crosslinked hydrogel of poly(2-hydroxyethyl methacrylate), (3) - cellulose (b) Dialytic permeability of a polyelectrolyte complex composed of NaSS-PVBMA to solutes with various molecular weights541 (1) Water, (2) neutral polyelectrolyte complex (water content = 70%), (3) anionic polyelectrolyte complex (water content = 61%), (4) cellophane and cuprophane (water content = 57%)... 

Nakatsuka S, Andrady LA. Permeability of vitamin-B-12 in chitosan membranes effect of crosslinking and blending with poly(vinyl alcohol) on permeability. ] Appl Polym Sci 1992 44 7-28. 

A system with interesting properties is the poly(ethylene oxide)-Wock-poly[2-(diethylamino) ethyl methacrylalc -.sfa -[3-(trimclhoxysilyl)propyl methacrylate] (PEO-b-P(DEA-sfaf-TMSPMA)) block copolymer. This self-crosslinkable copolymer formed vesicles which demonstrated pH-tunable membrane permeability [223],... 

Physical and thermal properties Polyesters are formed via a condensation reaction. PET and poly(butylene terephthalate) (PBT) are not crosslinked so are thermoplastic, but cured polyesters are crosslinked and thermosets. Polyesters may be reinforced with glass or carbon fibres or particles. Addition of 30% or more carbon fibre induces electrical conductivity in polyesters. Despite its high polarity, PET Is a good electrical insulator at ambient conditions because its Tg is considerably higher than room temperature. Polyesters have good abrasion resistance and are tough. PET is impervious to water but has low permeability to oxygen. 

Fluorescent dyes as markers can also be used to follow particle-cell interactions, via LSM and FACS measurements. Hence, polyure thane/urea capsules were created in inverse miniemulsion that could encapsulate a fluorescent dye with 90% efficiency [129]. In this case, carboxymethylation was carried out on the particle surface, followed by the physical adsorption of poly(2-aminoethylmethacrylate) or polyethylene imine polycations. As expected, the rate of uptake of capsules modified by the polycation was higher than for non-modified capsules. Rosenbauer et al. applied the same synthetic procedure, but in the presence of a surfactant that crosslinked the shell [130]. The commercially available surfactant containing several amine groups reacted with the diioscyanate monomer subsequently, the capsule shell wall was found to be less permeable than capsules synthesized with a non-crosslinkable surfactant. Baier el al. used the above-described synthesis to perform a polymerase chain reaction (PCR) in crosslinked starch nanocapsules [131]. The permeability of the shell was also evaluated using fluorescence spectroscopy. The combination of a cleavable polyurethane [132] with the interfacial polyaddition described above [126] afforded polymer shells that could be opened by ultraviolet (UV) irradiation, or by modifying the temperature or pH [133], In order to determine the release of encapsulated sulforhodamine dye, polyurethanes with... 

Sustained Releose - Fundamental information concerning membrane transport is likely to find ready application in the development of more effective forms of sustained release medication. The permeability of films composed of poly(methylvinylether)-maleic anhydride copolymer crosslinked with polysorbate 20 can be altered by an adjustment of the polysorbate 20 content, by varying the molecular weight oj the polymer, and by selecting the appropriate humidity pretreatment procedure... 

ROMP and PROMP are very useful methods to synthesize a number of novel materials with unique properties. Poly(cyclooctenes), poly(norbornenes) and poly(acetylenes) were discussed in more details and some of their properties like Tg, cristallinity, oxygen permeability, dielectric properties etc. listed. The polymerization of the cycloolefins was done either thermally or photochemically with the "old" Ru(II)-salts and the later developed Ru-phosphines as catalysts, whereas substituted acetylenes were photo-polymerized with W-, Mo- and Ta-catalysts. In addition, polymeranalogous transformations of the double bonds in ROMP polymers, (additions and cyclo-additions, epoxidation, (photo) crosslinking etc.) were discussed. We are convinced that these materials and systems will find useful applications in the near future. 

J.H. Kim, W.J. Koros, D.R. Paul, Effects of CO2 exposure and physical aging on the gas permeability of thin 6FDA-based poly-imide membranes Part 2. With crosslinking, J. Membr. Sci. 282 (1-2) (2006) 32-43. 

The main advantage of copolymerization is in the enormous variability of polymer properties. An almost unlimited number of different polymeric products can be achieved by varying the type and relative amounts of the different employed monomer units [50,51]. New and advanced properties can be obtained in respect to solu-bihty, permeability, greater affinity for dyes, or good oil resistance [52]. In addition, copolymerization can be used for producing three-dimensionaUy crosslinked polymers, as e.g., poly(styrene-cri-divinylbenzene). 

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