Cross-linked copolymer

The performance of several Sephacryl gel combinations is illustrated by results achieved for glucans from different types of starch granules. The applied Sephacryl gels of Pharmacia Biotech (15) are cross-linked copolymers of allyl dextran and N,N -methylene bisacrylamide. The hydrophilic matrix minimizes nonspecific adsorption and thus guarantees maximum recovery. Depending on the pore size of the beads, ranging between 25 and 75 im in diameter, aqueous dissolved biopolymers up to particle diameters of 400 nm can be handled. 

Cross-link density, 10 415-416, 417-418 direct measurement of, 10 426 427 Cross-linked copolymers, 7 6 lOt Cross-linked high amylose starch, 13 742 Cross-linked hydrogels, 13 729-730 Cross-linked polymers, internal stresses and, 10 423 424 Cross-linked starches, 4 721 Cross-linked thermoset polymer structure, 10 418... 

Derivatized silica gel that is used for size-exclusion HPLC contains a proprietary bonded phase that is defined as hydrophilic to minimize nonspecific hydrophobic and ionic interactions. Polymeric supports consist of highly cross-linked agarose beads, with or without bonded dextran or cross-linked copolymers of allyl dextran and AyV -methylenebisacryl-amide. All supports are available with a variety of particle and pore sizes and distribution. 

Cross-linked copolymers of hydroxyethyl methacrylate and methyl methacrylate are slightly swollen by water and are used as soft contact lenses. 

Polystyrene and its divinylbenzene cross-linked copolymer have been most widely exploited as the polymer support for anchoring metal complexes. A large variety of ligands containing N, P or S have been anchored on the polystyrene-divinylbenzene matrix either by the bromination-lithiation pathway or by direct interaction of the ligand with C1-, Br- or CN-methylated polystyrene-divinyl-benzene network [14] (Fig. 7). 

The second example used visible light absorption that increased the temperature locally within the thermosensitive gel [39]. The gel consisted of a covalently cross-linked copolymer network of N-isopropylacrylamide and chloro-phyllin, a combination of a thermo-sensitive gel and a chromophore. In the absence of light, the gel volume changed sharply but continuously as the temperature was varied. Upon illumination the transition temperature was lowered, and beyond a certain irradiation threshold the volume transition became discontinuous. The phase transition was presumably induced by local heating of polymer chains due to the absorption and subsequent thermal dissipation of light energy by the chromophore. The details will be discussed in a later section. 

Cross-linked copolymers of polystyrene and divinylbenzene are usually used. These polymers are hard enough to resist pressure in the column and are made of small spheres with a diameter of a few micrometres (Fig. 4.2). 

The reason for the selective adsorption of a colloidal particle of parent size is explained by the typical snapshots in Figs. 45b and c. We see that the particle of parent or smaller size (a < central cavity (Fig. 45b), because the corresponding fitting was ensured by the sequence design procedure (Fig. 10b). On the other hand, a particle of larger size (a > ap) turns out to be too big for a central cavity (Fig. 45c), and thus the complex formed does not saturate all the possibilities for the attraction of red units to the surface of the particle. As to small particles, they easily penetrate inside the molecular dispenser, but the complex formed is not stable (especially at high temperature) because of the small surface of such particles. All these factors explain the peak in P(T,a) observed at a ap for moderately cross-linked copolymer envelopes (Fig. 45a). 

The macroporous or macroreticular resins2 are rigid highly cross-linked copolymers containing large pores and large effective surface. They provide another possible... 

It was demonstrated481 that preliminary modification of cotton fabrics by grafting with AN, butyl acrylate (BA) or lauryl methacrylate enhances the efficiency of cross-linking by dimethyloldihydroxyethylurea, i.e. increases the tear resistance, abrasion resitance and the wrinkle recovery angle of the cross-linked fabric. Fabrics based on cross-linked copolymers of cotton with poly(methacrylie acid) proved less susceptible to contamination and showed easier oil and soil release than the cloths obtained from non-modified cross-linked cotton. 

The process of producing an ion-sensing polymer includes the following steps (i) selection and preparation of ligand monomers, (ii) synthesis of ion complexes of the monomers or linear copolymers of the complexing monomers, (iii) preparation of cross-linked copolymers with the monomeric complexes or linear copolymer complexes, (iv) the testing of the polymers for ion selectivity, (v) optimisation of polymer ionic selectivity and (vi) the use of the polymers in the construction of ion-selective electrodes (ISEs) and optical sensors. 

In a related study, preparation of the Pd(0) complex of the cross-linked copolymer (183) [prepared via (181) and (182)] and its catalytic activity have been investigated and compared with the small molecule model (184). The polymeric Pd complex appeared to be effective in heterogeneous catalysis of the Heck arylation reaction. Recycling of the catalyst is possible without significant loss of activity. ... 

According to literary data, the following mixtures of aromatic/aliphatic-aromatic hydrocarbons were separated toluene/ n-hexane, toluene/n-heptane, toluene/n-octane, toluene/f-octane, benzene/w-hexane, benzene/w-heptane, benzene/toluene, and styrene/ethylbenzene [10,82,83,109-129]. As membrane media, various polymers were used polyetherurethane, poly-esterurethane, polyetherimide, sulfonyl-containing polyimide, ionicaUy cross-linked copolymers of methyl, ethyl, n-butyl acrylate with acrilic acid. For example, when a composite polyetherimide-based membrane was used to separate a toluene (50 wt%)/n-octane mixture, the flux Q of 10 kg pm/m h and the separation factor of 70 were achieved [121]. When a composite mebrane based on sulfonyl-containing polyimide was used to separate a toluene (1 wt%)/ -octane mixture, the flux 2 of 1.1 kg pm/m h and the separation factor of 155 were achieved [10]. When a composite membrane based on ionically cross-linked copolymers of methyl, ethyl, w-butyl acrylate with acrilic acid was used to separate toluene (50 wt%)//-octane mixture, the flux Q of 20-1000 kg pm/m h and the separation factor of 2.5-13 were achieved [126,127]. 

SIO A highly polar cross-linked copolymer of acrylonitrite and divinylbenzene. 

It is claimed that the cross-linked copolymer resin prepared from tetraethylene-pentamine and toluene diisocyanate having a much greater affinity for transition metal ions than for alkaline earth ions is superior to Chelex-100 for the extraction of nickel (Cu, Zn) from sea water. At the natural pH of sea water a nearly quantitative recovery of metal ions seems to be feasible 79). 

Styrene-divinylbenzene cross-linked copolymer resins constitute one sort of resin with good adsorbing ability phenolic resins have also been tested. Other types with improved qualities may be developed. 

The synthesis of cross-linked copolymers of styrene and divinylbenzene has been studied intensively and is well documented. The starting monomer is styrene, and divinylbenzene (DVB) is used as cross-linker. The amount of DVB can reach up to 55 wt.%. At 55% DVB, the copolymer shows practically no swelling and possesses a permanent porosity. Figure 3.21 illustrates the network structure of poly(styrenedivi-nylbenzene) (St-DVB). 

Another SPE method was developed with the use of cross-linked copolymer styrene-divinylbenzene cartridges (ENV+), to perform the recovery of the analyte with ethyl acetate after removing ethanol from wine under vacuum and using 13C15N-labeled EC as an internal standard (Jagerdeo et al., 2002). 

Polystyrene-divinylbenzene cross-linked copolymer adsorbent resins removed effectively both limonin and naringin from citrus juices (44). Over 85% of limonin was adsorbed from about 50 bed volume juices of grapefruit, navel orange, lemon and tangerine. Up to 70% of naringin was also removed from grapefruit juice. 

---