Poly-DVB

A Comparative Study of Three Poly-DVB-supported Ru Carbenes... 

Tab. 11.9 RCM of diethyl diallylmalonate with poly-DVB-supported Ru catalysts (64), (65) and (66). ...

The synthesis of extremely high molecular weight star polymers has been achieved by another method. First divlnyl-benzene is reacted at very low concentration with an anionic Initiator (sec. BuLi) to yield a suspension of poly-DVB nodules fitted with numerous initiating sites. Then styrene Is added, and each Initiating site should give yield to a branch. However, the polydispersity of the samples obtained is very high. 

Swelling data for Sty-co-DVB polymers that have very-narrow-range molecular weight distributions for the poly(styrene) segments between poly(DVB) nodules have been reported by Rempp [141-143] and his coworkers. The size of these nodules and the number of polystyrene segments covalently bonded to a given... 

F gure temp ate with excess water leaves behind an optically clear and flexible poly-DVB membrane. su° Ref [72] reprinted with permission of the American Chemical Society.)... 

Finally, it is interesting to mention that capillary monolithic columns have also started to be used in gas adsorption chromatography [425, 426]. Poly-DVB monohth obtained in the presence of l.Svol of dodecanol-toluene mixtures possesses good separating power however, its efficiency (the theoretical plate height) still yields by a factor of 3-10 to that of traditional open capillary columns. On the other hand, the theoretical plate height for a similar monolith prepared for use in liquid chromatography proved to be comparable with that of conventional capillary silica-packed column [427]. 

The desweUing anomaly is particularly characteristic of the macroporous poly-DVB XAD-4, also containing a significant firaction of meso- and... 

A hypercrosslinked material derived from macroporous chloromethy-lated poly-DVB by additional bridging with isocyanuric acid well absorbs tannin from aqueous solutions [82]. Experimental isotherms are consistent with the empirical Freundlich equation, which is thought to be a sign of an energeticaUy heterogeneous surface. It was suggested that multiple hydrogen bonds, 71-71 interactions, and hydrophobic interactions are responsible for the retention of tannin on the sorbent prepared. 

Another type of materials is poly-DVB, which receives microporous texture if the monomer is polymerized in the presence of an appropriate amount of a thermodynamically good solvent, such as toluene. However, in our ISE experiments, these were inferior to hypercrosslinked polystyrene sorbents. 

In order to test this prediction, 3 mL portions of different aqueous salt solutions were sent through conventional chromatographic columns packed with nanoporous hypercrosslinked polystyrene or poly(DVB). The latter was obtained by suspension polymerization of 80% DVB in the presence of 150% toluene. (The hypercrosslinked nature of the polymer reveals itself in the fact that the volume of dry beads increases in ethanol and water by a factor of 1.5 and 1.4, respectively.) The column effluent was conducted though a flow cell of a pH meter. 

Figure 12.15 K2SO4 resolution on a poly-DVB column. Column, 28 mL probe 3mL of (1) 0.015, (2) 0.025, (3) 0.035, (4) 0.05 M solutions flow rate 1.2mL/min of the 0.015M KCI background electrolyte. (After [181].)...

In closing, we refer to the recent pubHcation [358] in which the synthesis of mesoporous poly-DVB and the characterization of its porous structure were reported. The polymer readily adsorbs another surrogate for P2M. lysozyme of hen egg white with molecular weight of 14 kDa and size of about 4nm, but exhibits a pretty low affinity to human serum albumin. At present, however, it is hard to evaluate whether there is any prospect of real application of the sorbent because no information is available on its hemocompatibihty. 

It has been noted that hypercrosshnked polystyrene does not adsorb proteins to the same extent as do conventional polystyrene or macroporous polystyrene [190]. Most probably, the open-work hypercrosshnked material does not expose a dense hydrophobic surface for the proteins to adsorb. The same is true for the marked inertness of both the new hypercrosshnked mesoporous poly-DVB materials and industrial hypercrosshnked sorbent MN-200 toward whole blood ceUs. Blood (50 mL) spiked with citric acid freely flows through a 5 mL column fiUed with beads of the above sorbents, contrary to many other coated carbon-type and polymeric hemosorbents tested under identical conditions, where blood coagulation and colurrm clotting were found to occur [359]. Indeed, the new mesoporous poly-DVB sorbent, without any additional modification of the surface, was found to be sufficiently biocompatible and not cause any early coagulation effect in a standard plasma recalcification test. 

The excellent sorption capacity of the hypercrosslinked mesoporous poly-DVB with respect to selective removal of P2M from its mixtures with albumin and other semm proteins, combined with superior hemocompat-ibility of the beads surface modified with poly(N-vinyl)pyrrolidone, justified the manufacturing of an experimental batch of the material for initial clinical studies. The polymer was named BetaSorb (RenalTech International, USA) and was used in 300 mL cylindrical polysrdfone devices that were steam-sterilized and filled with normal saline containing 1000 lU heparin. The device was placed in line with the dialysis circuit, upstream of the dialyzer, in order to not affect the pressure drop across the dialyzer membrane. The blood flow was maintained at the customary value of 400 mL/ min, again the optimal flow rate for the dialyzer. The complete setup of the combined hemoperfusion-hemodialysis treatment [361] is displayed in Fig. 15.2. 

No comphcations related to the combined hemoperfusion/hemodialysis sessions were registered. The treatment was well received by the patients. These results speak for themselves. They prove both the high safety and efficiency of the hemoperfusion procedures on hypercrosshnked poly-DVB. 

Hayes ep B Poly-DVB modified with poly (ethyleneimine) 570 0.5 1.2 [409]... 

Fig. 8 NMR spectrum of poly(/ -DVB) obtained from the nanochannel of [Zn2(bdc)2ted] in DMSO- /. The ratio of the peak intensities of a to those of b, c, and d is found to be 2 5...

Figure 18.3 Top schematic drawing of the terrace-like microchannel device. From Ref [2], Bottom SEM images of poly (DVB) beads at different magnifications. From Ref [1].

The proposed mechanism leading to linear poly(DVB) is as follows (Eq. (13) and (14))" First, DVB dimerizes to 12 (Eq. (13)) in the presence of an oxo acid by a mechanism similar to the selective linear dimerization of styrene (Eq. (11)). Either of the two vinyl groups in /2 is then protonated and the resulting dimer cation reacts with the DVB monomer or its polymer having a terminal vinyl group. Subsequent deprotonation from the propagating cation yields a new carbon-carbon double bond in the main chain. Equation (14) shows the reaction between DVB and its unsaturated dimer 12. This protonation-propagation-deprotonation reaction sequence eventually leads to linear poly(DVB) 11. 

The formation of linear polymer 11 requires that deprotonation from the propagating poly(DVB) cation be favored over its addition (propagation) to monomer. As expected from our linear dimerization process, the DVB polymerization by an oxo-acid initiator (ACCIO4) does in fact meet this requirement to form 11 in quantitative yield,... 

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