Macroporous copolymers

A macroporous polystyrene-divinylbenzene copolymer, produced by copolymerizing a mixture of styrene and divinylbenzene, is dissolved in an organic liquid such as t-amyl alcohol or isooctane, which is a solvent for monomers. This solvent is unable to substantially swell the resulting copolymer. Macroporous cation-exchange beads are also produced from these macroporous copolymers (25,26). 

Solid-Phase Extractions Using XAD Resins. The Amberlite XAD series (Rohm and Haas Co., Philadelphia, PA, USA) have been most often used for isolation of marine DOM by SPE. XAD resins are nonionic macroporous copolymers that differ in pore size, surface area, and polarity. Their generally large specific surface areas and more-or-less reversible adsorption of organic solutes from aqueous solution have made them well-suited for isolation of selected fractions of DOM from natural waters. Even though XAD resins have been used far more often to... 

In addition to the silica-based materials mentioned above, modem polymers are widely used for TTA and QTA sample preparation allowing SPE not impaired by undesirable silanol activities. HLB Oasis (Waters) is the tradename for a hydrophilic-lipophilic balance reversed-phase sorbent enabling lipophilic interaction to benzene moieties and hydrophilic interactions to pyrrolidone groups as present in the macroporous copolymer of poly(divinylbenzene-co-iV-vinylpyrrolidone). Elution of analytes is often performed with solvents containing MeOH or ACN. Applying this adsorbent TA such as atropine and scopolamine were extracted from human viscera [15], human serum [97-99], human urine [12] as well as from rat plasma and brain microdialysate [77], Furthermore, this hydrophilic-lipophilic balance phase was also suitable for extraction of the QTA trospium from human and rat plasma [77, 84] and methyl scopolamie from rat plasma [77] (Table 4). 

The growing popularity of reversed phase chromatography in particular has prompted polymer manufacturers to investigate the use of polymeric media for this mode of operation. Macroporous copolymers of styrene and divinylbenzene have similar properties to silica based stationary phases bonded with alkyl chains. However, the absence of leachables and stability at high pH can offer advantages under certain circumstances. High quality, mechanically stable macroporous polymeries are now manufactured at much larger scales than the... 

O. Okay, Macroporous copolymer network. Progress in Polymer Science 25,711-779 (2000). 

Oh KS, Oh JS, Choi HS, Bae YC (1998) Effect of crosslinking density on the swelling behavior of NIPA gel particles. Macromolecules 31 7328-7335 Okay O (2000) Macroporous copolymer networks. Prog Polym Sci 25 711-779 Okay O, Gundogan N (2002) Volume phase transition of polymer networks in polymeric solvents. Macromol Theory Simul 11 287-292... 

In 1996, a new hydrophilic-lipopophilic balance (HLB) adsorbent was introduced. Oasis HLB (Waters Corporation, Millford, MA). This macroporous copolymer (poly[divinylbenzene-co-A-vinylpyrrolidone]) exhibits hydrophilic and lipophilic retention characteristics, its major features being the abilities to remain wetted with water and to retain a wide spectrum of polar and nonpolar compounds, among which are OCPs. ... 

Formation of macroporous copolymers in the presence of precipitating diiuents... 

Figure 3.3 Dependence of inner surface area on the volume fraction of diluent for the macroporous copolymers of styrene with fech-DVB prepared in the presence of (3-7) f)-heptane and (1,2) isooctane, the concentration of DVB, % (1,4) 20, (2,5) 30, (3) 8, (6) 40, (7) 60. After [271],...

Figure 33 Pore size distribution for (1) dry conventional styrene-6% tech-DVB copolymer and macroporous copolymers prepared in the presence of (2) n-heptane, (3) isooctane, and (4-7) buthyl alcohol the concentration of DVB % (4) 2, (1-3,6) 6, (7) 20. After [282].

Figure 3.9b shows the same boundaries confining the macroporous domain II for real styrene-DVB copolymers prepared in the presence of 2-ethyl-1-hexanoic acid, benzyl alcohol, heptane, or pentanol [314]. Judging from the shape of the plots, 2-ethyl-1-hexanoic acid and benzyl alcohol generate macroporous copolymers with cauliflower texture and high surface area in a wider range of crosslinking densities and dilutions compared with heptane or pentanol diluents. 

Kolarz [347] synthesized macroporous copolymers in the presence of a mixture of polystyrene with xylene as the solvating diluent (Tables 3.5 and 3.6). As found, at a constant dilution, the increase of DVB concentration from 8 to 12% involves a noticeable increase in the porosity of the copolymers, while further increase of crosshnking density does not change anymore the parameters of the porous structure. The highest porosity was characteristic of samples prepared in the presence of approximately equal amounts of polystyrene and xylene. Similar to the copolymers prepared with polystyrene alone, it was observed that pore size... 

Table 3.7 Permeability of macroporous and conventional polystyrene sulfonates for methylene blue [356] (the macroporous copolymers were prepared in the presence of 100 %-wt n-heptane)...

Figure 7.18 Kinetics of swelling in toluene of macroporous copolymers (1) styrene-15% DVB copolymer prepared in the presence of 60wt% n-hexane, (2) polydivinylbenzene prepared in the presence of 60wt% toluene, (3) polydivinylbenzene prepared in the presence of 60 wt% n-hexane. (After [159]).

Summarizing our experience with hypercrosslinked polystyrene networks, as well as with conventional gel-type and macroporous copolymers, we beheve that the topology of the network was undeservedly neglected by all theoretical treatments. By this we particularly mean that a network must be considered as an ensemble of interconnected and interpenetrating meshes or cycles, rather than as a combination of chains and junctions. 

In contrast to the main tendencies known for truly macroporous copolymers, the dilution of initial linear polystyrene solutions was observed to have no dramatic influence on the apparent inner surface area of hypercrosslinked polymers. The surface area rather shows a tendency to decrease with dilution, contrary to the pore volume (Table 7.9). 

Other types of hypercrosslinked sorbents, namely commercial Lewatit EP63, laboratory samples obtained by post-crosslinking styrene-DVB copolymer with CCI4 [55], by self-crosslinking macroporous copolymer of vinylbenzyl chloride with 20% DVB via Friedel-Crafts reaction [56], or by bridging preliminary chloromethylated macroporous styrene-DVB copolymer [57, 58], are all superior to XAD-2, XAD-4, and activated carbon Ambersorb XE340 with respect to phenol and nitrophenol removal. Material [20%-VBC(F.C.)] retains 2,4-dichlorophenol much stronger than unsubstituted phenol, and, therefore, the presence of phenol in the solution does not impact the retention of the chlorinated phenol. On the contrary, the sorption of phenol from the binary solution depends heavily on the concentration of 2,4-dichlorophenol. 

Jefabek et al. [79] reported the adsorption of furfural onto the hypercrosslinked sorbents prepared by post-crosslinking both chloro-methylated gel-type styrene-5% DVB copolymer and chloromethylated macroporous copolymer of styrene with 8% DVB via Friedel-Crafts... 

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