Crosslinking polyacrylamides

Hj erten (1983) reported the use of crosslinked polyacrylamide gels for the capillary electrophoretic separation of proteins. However, crosslinked polymers are quite rigid, and the capillary has a short lifetime. 

Crosslinked polyacrylamide gels were obtained by free radical... 

Figure 4. Variation of the linewidth of the parallel signal for Cu(ll) in crosslinked polyacrylamide gels of pore diameter 0.7 nm as a function of the microwave frequency, for mj = -3/2 and -1/2. The solid line is calculated from the values of aH, 6A and 6g given in Table I. Measured values are indicated.

Crosslinked polyacrylamide latexes encapsulating microparticles of silica and alumina have also been prepared by this method [179], Three steps are involved a) formation of a stable colloidal dispersion of the inorganic particles in an aqueous solution containing acrylamide, crosslinker, dispersant, and initiator b) HIPE preparation with this aqueous solution as the dispersed phase and c) polymerisation. The latex particles are polyhedral in shape, shown clearly by excellent scanning electron micrographs, and have sizes of between 1 and 5 pm. 

Figure 1. Effect of pH on the swelling of a 5% crosslinked polyacrylamide gel with 40 % DMAEM. The percent increase in disk diameter vs time at various pH values.

Figure 3. Effect of amine concentration on swelling. Percent increase in diameter as a function of time after exposure to a pH 2.6 phosphate/citrate buffer for 1% crosslinked polyacrylamide gels with 10, 20 and 40% DMAEM.

Figure 5. Effect of glucose on the swelling of a 3.3% crosslinked polyacrylamide gel with 32% DMAEM. Percent increase in diameter as a function of glucose concentration vs. time.

In the methodology developed by us [24], the incompatibility of the two polymers was exploited in a positive way. The composites were obtained using a two-step method. In the first step, hydrophilic (hydrophobic) polymer latex particles were prepared using the concentrated emulsion method. The monomer-precursor of the continuous phase of the composite or water, when that monomer was hydrophilic, was selected as the continuous phase of the emulsion. In the second step, the emulsion whose dispersed phase was polymerized was dispersed in the continuous-phase monomer of the composite or its solution in water when the monomer was hydrophilic, after a suitable initiator was introduced in the continuous phase. The submicrometer size hydrophilic (hydrophobic) latexes were thus dispersed in the hydrophobic (hydrophilic) continuous phase without the addition of a dispersant. The experimental observations indicated that the above colloidal dispersions remained stable. The stability is due to both the dispersant introduced in the first step and the presence of the films of the continuous phase of the concentrated emulsion around the latex particles. These films consist of either the monomer-precursor of the continuous phase of the composite or water when the monomer-precursor is hydrophilic. This ensured the compatibility of the particles with the continuous phase. The preparation of poly(styrenesulfonic acid) salt latexes dispersed in cross-linked polystyrene matrices as well as of polystyrene latexes dispersed in crosslinked polyacrylamide matrices is described below. The two-step method is compared to the single-step ones based on concentrated emulsions or microemulsions. 

Figure 44 presents a scanning electron micrograph of a capsule in which alumina particles are encapsulated in crosslinked polyacrylamide. Table 20 lists under PLA1 the amounts of the components involved in the preparation of these capsules. The capsules have a polyhedral shape and their sizes are larger (around 5 pm) and more uniform than the polymer latexes free of solid particles. Some of the cells of the gel coalesce during polymerization, forming bulk phases. As a result, some unencapsulated solid particles were also observed. 

HF. 44. Scanning electron micrographs at two magnifications of capsules of alumina particles encapsulated in crosslinked polyacrylamide with the composition PLA1 (Table 20)... 

Heiger DN, Cohen AS, Karger BL (1990) Separation of DNA restriction fragments by high performance capillary electrophoresis with low and zero crosslinked polyacrylamide using continuous and pulsed electric fields. J Chromatogr 516 33-48. 

Deyl Z, MikSik I (1995) Separation of collagen type I chain polymers by electrophoresis in non-crosslinked polyacrylamide filled capillaries J Chromatogr A 698 369-373. 

Fig. 3. Kinetics of liquid sorption in 10 replications using samples cut from the same microporous sheet. The sorbent particles were comminuted crosslinked polyacrylamide (approx. 80% by weight) enmeshed in PTFE microfibers...

Hydrogels are fascinating polymeric structures (an open porous network containing sometimes > 90% water by weight) that are ideally suited for electrochemistry. Crosslinked polyacrylamides (Figure 7.5) and agarose gels are two commonly used examples. 

Figure 4.48. Some examples of separations by hpce. (a) CZE BSA peptide map. Conditions 20 mM phosphate, pH 7, V - 25 kV, i 16/tA, 1 50 cm, L > 57 cm, id B 50/im with 3X extended pathlength detection cell, 2 - 200 nm. (b) MECC separation of cold-relief medicine constituents. Conditions 20 mM phosphate-borate, lOOmM SDS, pH 9, V - 20kV, L - 65cm, i.d, = 50/im, X - 210nm. (c) CGE of 1 kbp ladder using minimally crosslinked polyacrylamide. Conditions Bis-crosslinked polyacrylamide (3%T, 0.5%C), lOOmM Tris-borate, pH 8.3, E = 250V/cm, i = 12.5/

PMAA- or citrate-coated magnetite [160] or citrate-coated maghemite [162] nanoparticles could successftiUy be encapsulated in a crosslinked polyacrylamide matrix using an inverse miniemulsion process. Here an inert hydrocarbon (cyclohexane or dodecane) was used as continuous phase and SpanSO as stabilizer. 

Enzyme activity has a certain dependence on temperature, and the general enzyme has an optimal temperature, and immobilized enzyme is no exception. Compared to the solution enzyme, the optimum temperature of immobilized enzyme shows ups and downs. The study found that the aminoacylase was bound to DEAE-cellulose and DEAE-dextran using ion-binding, or embedded in crosslinked polyacrylamide gel. Thus, the immobihzed enzyme was prepared, and its optimum temperature was somewhat higher than that before the immobilization. When aminoacylase was immobilized by iodine acetyl cellulose with covalent binding, its optimum temperature was somewhat lower than that before the immobilization. When the glucose isomerase was boimd to porous resin with covalent binding. 

Poliak A, Blumenfeld H, Wax M, Baughn RL, Whitesides GM. Enzyme immobilization by condensation copolymerization into crosslinked polyacrylamide gels. Journal of the American Chemical Society. 1980 102(20) 6324-6336. 

Enzyme immobilization is a well developed area of chemistry and numerous methods are available (18). We have prepared a variety of enzyme based biosensors using the following immobilization procedures 1) entrapment in crosslinked polyacrylamide (J7), 2) glutaraldehyde... 

This system is not in itself useful because the polymer is brominated and the reagents expensive but such a system has been used to generate periodic self-assembly of aggregates of acrylonitrile-derivatized gold nanocrystals (43). Kalyshyn et al. reported macroscopic patterns in crosslinked polyacrylamide with BZ waves (44). 

Tokita et al. [160], using small-molecule probes having molecular weights of 18-342 Da in crosslinked polyacrylamide, report that Dp of the probes ftdls as a stretched exponential in probe molecular weight and matrix concentration. They interpret the dependence on P as a dependence on the probe radius R, namely exp(—Matsukawa and Ando [159], studying polyethylene glycol probe polymers in crosslinked poly-(N,N-dimethylacrylamide) with P up to 20 kDa, find the very similar Dp/Dpp = exp(—... 

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