Poly polymer gels

The principal classes of high performance fibers are derived from rigid-rod polymers, gel spun fibers, modified carbon fibers, synthetic vitreous fibers, and poly(phenyiene sulfide) fibers. 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Polymer gels In response to pH changes in their enviromnent, materials derived from poly(acrylonitrile) will swell or shrink in a slow analogy to muscle action, thought to have robotic applications. 

Polymer gels and ionomers. Another class of polymer electrolytes are those in which the ion transport is conditioned by the presence of a low-molecular-weight solvent in the polymer. The most simple case is the so-called gel polymer electrolyte, in which the intrinsically insulating polymer (agar, poly(vinylchloride), poly(vinylidene fluoride), etc.) is swollen with an aqueous or aprotic liquid electrolyte solution. The polymer host acts here only as a passive support of the liquid electrolyte solution, i.e. ions are transported essentially in a liquid medium. Swelling of the polymer by the solvent is described by the volume fraction of the pure polymer in the gel (Fp). The diffusion coefficient of ions in the gel (Dp) is related to that in the pure solvent (D0) according to the equation ... 

BG Kabra, MK Akhtar, SH Gehrke. Volume change kinetics of temperature-sensitive poly(vinylmethylether) gel. Polymer 33 990-995, 1992. 

R Kishi, O Hirasa, H Ichijo. Fast responsive poly(N-isopropylacrylamide) hydrogels prepared by gamma-ray irradiation. Polym Gels Networks 5 145-151, 1997. 

Concerning drug delivery, electrically erodible polymer gels for controlled release of drugs have been prepared, and a measured release rate of insulin has been observed under electrical stimulus [69]. A suspension of zinc insulin in a mixed solution of poly(ethyloxazoline) and PMAA was formed into a gel by decreasing the pH of the suspension. The obtained complex gel with 0.5 wt% of insulin was attached to a woven platinum wire cathode which was 1 cm away from the anode and immersed in 0.9% saline solution. When a stepped function of electrical current of 5 mA was applied to the insulin-loaded gel matrix, insulin was released in a stepwise manner up to a release of 70%. The insulin rate measured was 0.10 mg/h. 

Note 3 An example of covalent polymer gels is nei-poly(A-isopropylacrylamide) swollen in water, which shows volume phase transition during heating. 

Note 4 Examples of physically aggregated polymer gels are poly(vinyl alcohol) gel and agarose gel, which show reversible sol-gel transitions. 

After Little s proposal, many researchers have pursued such an exciting system in vain. Even metallic behavior was rarely seen in doped organic polymers, gels, and actuators. As mentioned in Sect. 3.4.4, MCso with linearly polymerized Ceo" exhibited one-dimensional (M = Rb, Cs) or three-dimensional (M = K) metallic behavior [144]. Recently a doped poly aniline was reported to exhibit a metallic temperature dependence for a crystalline polymer chemical oxidation of monomers grew crystallite polyaniline [329] early doping studies on polypyrrole (PFg) and poly(3,4-ethylene-dioxythiophene)X (X = PFg, BF4, and CF3SO3) prepared by electrooxidation at low temperatures also showed a metallic temperature dependence below 10-20 K (Scheme 16) [330, 331]. 

Polymer bound tris-(2,2 -bipyridyl)-ruthenium-(II)-derivatives were synthesized by reaction of 4-(3-chloroformyl-propyl)-4 -methyl-2,2 -bipyridyl with crosslinked amino-groups containing poly(styrene) gel or crosslinked sucrose-methacrylate gels, and by... 

Stress-strain properties and structure of poly (dimethylsiloxane) networks. Microsymposium on macromolecules Polymer gels and concentrated solutions. Inst, of Macromolecular Chemistry, Prague 1967, E6. 

The dependence of the friction coefficient of the poly(acrylamide) gel on the total concentration of polymers of the gel, including both the main constituent and cross-linker, has been studied under the experimental conditions of a constant molar concentration of the cross-linker at 1 mol%. The total concentration was changed from 400 mM to 2.8 M which corresponds to a concentration from about 3 to 20 wt.%. The temperature was fixed at 20 0.1 °C. 

The density of the polymer network of the gel fluctuates with time and space in microscopic scale. Such fluctuations are frozen in the gel under certain gelation conditions. As a result of the frozen density fluctuations, opacity develops in the gel. Although quantitative studies have not been made so far, the qualitative studies of the opacity development in poly(acrylamide) gel have been reported... 

AA AAm Con A DSS DSS-gel LCST MAPTAC MBA MP MP-gel NIPA ONPG PVMA SSPG Tc TMED acrylic acid acrylamide concanavalin A dextran sulfate sodium gel containing Con A/DSS complex lower critical solution temperature [(methacrylamide)propyl]trimethylammonium chloride /V,/V -methylenebis(acrylamide) a-methyl-D-mannopyranoside gel containing Con A/MP complex /V-isopropylacrylamide O-nitrophenyl-P-D-galactopyranoside poly(vinyl methyl ether) stimulus-sensitive polymer gel transition temperature /V,/V,/V, /V -tetramethylethylenediamine... 

In poly(AAm-co-BMA)/PAAc IPNs (BMA is butyl methacrylate), the synthetic procedure applied was the sequential polymerization technique shown in Fig. 10. A monomer or set of comonomers is polymerized into a polymer gel. A second monomer is introduced and subsequently polymerized and crosslinked within the initial gel (AAm-co-BMA) matrix to form the IPN. 

Many recent studies on polymer gels are related to volume phase transition phenomena of poly(acrylamide) PAAm gel [7] and poly(N-isopropyl acrylamide) PNIPAAm gel [8, 9]. The volume phase transition in gels was extensively studied by Tanaka and his coworkers [10, 11]. 

More recently, Sugiura et al.11 developed a fully functional microvalve based on this photoresponsive behavior, which was composed of poly(/V-isopropylacrylamide) functionalized with the chromophore spirobenzopyran (pSPNIPAAm). The microvalve was fabricated in a polydimethylsiloxane (PDMS) microchannel by in situ photopolymerization. Blue light irradiation (18 to 30 s) to the gel induced photoisomerization of the spirobenzopyran chromophore which resulted in shrinkage due to dehydration of the gel, thus causing the microvalves to open, as seen in Figure 23.7. In this example, localized irradiation enabled independent control of three photoresponsive polymer gel microvalves, which had been fabricated on a single microchip. 

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