Polymer membranes molecular designs

It has been demonstrated that a variety of different polyphosphazenes can be developed as biomaterials, membranes or hydrogels, bioactive polymers, and bioerodible polymers. As with most new areas of polymer chemistry and biomaterials science, molecular design forms the basis of most new advances, but the rate-controlling step is the testing and evaluation of the materials in both in vitro and in vivo environments. This is particularly true for polyphosphazenes where the availability of research quantities only has limited the... 

In this paper, we report the development of ISEs that have been designed by using molecular recognition principles. Specific examples include the development of polymer membrane anion-selective electrodes based on hydrophobic vitamin B12 derivatives and a cobalt porphyrin. The selectivity patterns observed with these electrodes can be related to differences in the structure of the various ionophores, and to properties of the polymer film. 

In summary, it has been demonstrated that ISEs can be designed by employing molecular recognition principles. In particular, the feasibility of using hydrophobic vitamin B12 derivatives and electropolymerized porphyrin films in the development of polymer membrane anion-selective electrodes has been demonstrated. The studies indicated that the changes in the selectivity of these ISEs can be explained by the difference in structure of the ionophores. In addition, it was shown that by electropolymerization of a cobalt porphyrin, anion-selective electrodes can be prepared that have extended lifetimes compared with PVC-based ISEs, which use a similar compound as the ionophore. 

Refs. [i] Heitner-Wirguin C (1995) J Membrane Sci 120 1 [ii] Mau-ritz KA, Moore RB (2004) Chem Rev 104 4535 [iii] Murray R (1992) Molecular design of electrode surfaces. Wiley, New York [iv] Inzelt G (1994) Mechanism of charge transport in polymer-modified electrodes. In BardAJ (ed), Electroanalytical chemistry, vol. 18. Marcel Dekker, New... 

We have used apoenzymes as molecular-recognition transporters for binding and selective transportation of molecules without production of unwanted chemical reactions on reactants. Figure 24.10 shows the design of membrane consisting of microporous polymer membrane sandwiched between two thin films of polypyrrole [3]. The apoenzymes are physically trapped within the pores of the membrane and polypyrrole films. More details regarding the fabrication of the membranes, materials, and experimental setup can be found in the Ref. [3]. 

Membranes applications in sensors and microelectromechanical systems (MEMS) are increasing in importance in our society. The development of new device able to give rapid detection of chemical and biological species is central to many areas of life science and industrial production. In particular, conducting polymeric materials show major potentiality in this field, and are replacing classical inorganic semiconductor materials because of their better selectivity and rapid measurements, low cost, and easy manufacture for their preparation as films [39]. Moreover, appropriate molecular design of polymer properties can increase the efficiency of the system. 

Piletsky SA, Butovich IA, Kukhar VP (1992) Design of molecular sensors on the basis of substrate-selective polymer membranes. Zh Anal Khim 47(9) 1681—1684... 

Many compounds have now been used as template molecules in molecular imprinting. Basically, imprinted polymers can be used directly as separation media. Since all separation applications cannot be described here, some studies recently reported are bsted in Table 7.1. In this chapter, only selected topics, including sensor applications, signaling polymers, molecularly imprinted sorbent assays, molecularly imprinted membranes, affinity-based solid phase extraction, in situ preparation of imprinted polymers, and molecularly imprinted catalysts are discussed. For the reader requiring information on other applications, there are many review articles dealing with these, Recent review articles and books are summarized in Table 7.1. For further development of molecular imprinting techniques, newly designed functional monomers would be desirable. Various functional monomers have been reported and many applications have been conducted. These are summarized in Table 7.2. 

Chapter 5 by Ishihara and Fukazawa focuses on polymers obtained from 2-methacryloylo>yethyl phosphorylcholine (MPC) monomer. Indeed, the molecular design of MPC polymers with significant functions for biomedical and medical applications is summarized in detail. It is especially shown that some MPC polymers can provide artificial cell membrane-like structures at the surface as excellent interfaces between artificial systems and biological systems. In the clinical medicine field, MPC polymers have been used for surface modification of medical devices, including long-term implantable artificial organs to improve biocompatibilily. Thus some MPC polymers have been provided commercially for these applications. 

Molecular Design of Phosphonated Polymers for Proton Conducting Membranes... 

One of the significant differences between hydrocarbon ionomers and perfluoro-sulfonic acid polymers is add groups. The pKa value of benzenesulfonic acid (PhSOsH) is 2.5 and that of trifluoromethanesulfonic acid (CF3SO3H) is —13. The pKa value was estimated to be ca. 1 for sulfonated polyether ketone and ca. —6 for Nafion membranes [78]. Therefore, the effective proton concentration and proton mobility should be lower in the hydrocarbon ionomer membranes. Without appropriate molecular design such as multiblock copolymer and sulfonic acid clusters as mentioned above, hydrocarbon ionomer membranes lack well-developed ionic channels due to less pronounced hydrophilic and hydrophobic phase separation, which causes the lower proton conductivity at low humidity. 

Surface modification of the polymeric membranes via molecular design is one of the most versatile means to improve the surface properties without affecting bulk properties. Surface modification of fluoropolymer membranes, especially for fully fluorinated polymer membranes, such as PTFE membranes, has been of particular interest, due to their physical and chemical inertness. Surface modification of fluoropolymer membranes can be classified into two categories surface coating and surface grafting. 

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