Copolymers membranes

Mass-polymerized PVC also has a skin of compacted PVC primary particles very similar in thickness and appearance to the suspension-polymerized PVC skin, compared in Figure 3. However, mass PVC does not contain the thin-block copolymer membrane (7). 

The hormone-releasing devices have a closer resemblance to standard methods of sustained release because they involve the release of a steroid compound by diffusion [198,199]. The Progestasert, a reservoir system, is shown in Fig. 16. Progesterone, the active ingredient, is dispersed in the inner reservoir, surrounded by an ethylene/vinyl acetate copolymer membrane. The release of progesterone from this system is maintained almost constant for 1 year. The effects of release are local, with none of the systematic side effects observed with orally administered contraceptives [200-207]. 

Figure 6 Permeation profiles of proteins through HEMA-AEMA copolymer membrane at 30°. The arrows represent the UV irradiation to the membrane. (O) Insulin ( ) lysozyme (A) chymotrypsin (A) albumin. (From Ref. 28.)...

Rubatat, L., Shi, Z. Q., Diat, O., Holdcroft, S. and Frisken, B. J. 2006. Structural study of proton-conducting fluorous block copolymer membranes. Macromolecules 39 720-730. 

Fig. 25. Preparation of amphiphilic copolymer membrane with hydrophilic and hydrophobic side chains...

Sulfo group-containing poly(amide imide) semipermeable membrane 35 from trimellitic anhydride sodium 3,5-dicarboxybenzenesulfonate, and 4,4 -diphenyl-methane diisocyanate have been prepared 90>. A 110 p-thick membrane gave water permeation 5601/m2 day and salt rejection 99.0% (0.5% aqueous NaCl solution, 25 °C, 42 kg/cm2), while a trimellitic anhydride-4,4 -diphenylmethanediisocyanate copolymer membrane gave 30 1/m2 day and 98.2%, respectively. 

They prepared also a similar copolymer membrane having pendant sodium sulfonate groups 37 by using disodium 2,2 -benzidinedisulfonate in addition to the above-described materials 96). The water permeability and salt rejection of the latter mem-... 

They fabricated another two kinds of composite membranes through the interfacial reaction of triethylenetetramine 106,107). The one was the (3,(3 -dichloroethylether-triethylenetetramine-isophthaloyl chloride-trimesoyl chloride copolymer membrane, which had the water permeation rate of 2400 1/m2 day and desalination rate of 96.8 %. The other was the adipic-triethylenetetramine-isophthaloyl chloride copolymer membrane, which showed the water flux 95.8 1/m2 day and NaCl rejection 99.8 % on the reverse osmosis of a 0.5% aqueous solution at 25 °C and 42.5 kg/cm2. These characteristics for both membranes did not decrease during the continuous operation for 100 500 hr. 

A system with clearly defined disperse (A) and continuous (B) component phases is afforded by copolymers of styrene (A) grafted onto a polydimethyl siloxane matrix (B)101 Lack of appreciable interaction between the components was indicated by gas solubility and Tg measurements. The permeability coefficient of propane and other paraffins over a composition range vA = 0 — 0.55 followed the trend described by Eqs. (30)—(33) (with PA = 0, in view of the fact that the polystyrene phase is practically impermeable). Of particular relevance to the present discussion is the close agreement with the Bruggeman, and definite deviation from the Bottcher, equations at higher vA (cf. Fig. 11). Corresponding block copolymer membranes with vA = 0.34 also fitted into this pattern, except in one case where the structure was found to be lamellar and P was considerably lower. 

N. Tanihara, N. Umeo, T. Kawabata, K. Tanaka, H. Kita and K. Okamoto, Pervaporation of Organic Liquids Through Poly(etherimide) Segmented Copolymer Membranes, J. Membr. Sci. 104, 181 (1995). 

Using the block copolymer membranes described above, significant selectivi-ties for electrolytes over non-electrolytes have been observed. Some data reported by Hirahara el al. [17] are shown in Table 13.1. The ionizable electrolytes were 100 times more permeable than non-ionized solutes such as glucose and sucrose, suggesting a number of potential applications in which deionization of mixed solutions is desirable. The permeabilities of salts in these membranes are also... 

Tsujita Y, Yoshimura K, Yoshimizu H, Takizawa A, Kinoshita T, Furukawa M, Yamada Y, Wada K (1993) Structure and gas permeability of siloxane-imide block copolymer membranes 1 effect of siloxane content. Polymer 34(12) 2597... 

Rate-controlling ethylene-vinyl acetate copolymer membranes... 

Avramescu ME, Sager WFC, and Wessling M. Functionalised ethylene vinyl alcohol copolymer membranes for affinity protein separation. J. Membr. Sci. 2003 216 177-193. 

In many cases the organic to be dehydrated (e.g., acetic acid) attacks the ether linkage in the PVA membrane. Indeed, the PVA membrane has very limited fife in the presence of most acids. Ray et al. [14] used the concept of copolymer membranes to dehydrate acetic acid over the entire range of concentration from 0% to 100%. These investigators prepared copolymers of acrylonitrile (AN) with different hydrophUic monomers like hydroxy ethyl methacrylate, acrylic acid, methacrylic acid, and itaconic acid. These copolymers have carbon-carbon bonds, which unlike the ether linkage in the cross-hnked PVA membrane are stable to the attack by carboxyhc acids. The acrylonitrile part is not sufficiently hydrophihc but imparts mechanical strength while the other monomers improve the hydrophilicity. The overall result is an efficient yet stable membrane. Variation of the ratio of AN to (the other) monomer allows freedom of adjusting the hydrophUicity of the membrane to achieve certain... 

Acrylamide-acrylic acid copolymer gel prepared in porous of ceramic thin membrane Acrylonitrile-vinyl compounds copolymer membrane... 

Organic-organic and organic compounds/water separation Acrylonitrile-vinyl compounds copolymer membrane a = 1747 for 80% aqueous acetic acid at 70°C [78]... 

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