Polystyrene/divinylbenzene particles

Monosized macroporous polystyrene-divinylbenzene particles have been prepared in a multistep swelling process, in which particles of different sizes... 

A typical scanning electron micrograph of the uniform macroporous polystyrene-divinylbenzene particles is given in Fig. 20. First studies on the synthesis of macroporous uniform particles were started by Ugelstad et al. [109]. They used a two-step activated swelling method to obtain macroporous uniform particles in the... 

For the analysis of organic-soluble and water-soluble synthetic polymers, silica-based packing materials have not become as widely used as was originally envisioned (8). Major improvements in the properties of polymer-based supports have contributed to their increased use in GPC. Columns packed with polystyrene divinylbenzene particles are now as efficient as those filled with silica particles of the same size. Because polymer-based packings can be synthesized with very small (<60 A) and very large (>4000 A) pores, they provide better selectivity than silica columns for the separation of monomers, as well as for very high molecular weight (5-20 million dalton) polymers. 

A macroporous polystyrene-divinylbenzene copolymer is produced by a suspension polymerization of a mixture of monomers in the presence of water as a precipitant. This is substantially immiscible with the monomer mixture but is solubilized with a monomer mixture by micelle-forming mechanisms in the presence of the surfactant sodium bis(2-ethylhexylsulfosuccinate) (22). The porosity of percentage void volume of macroporous resin particles is related to percentage weight of the composite (50% precipitant, 50% solvent) in the monomer mixture. 

A novel cross-linked polystyrene-divinylbenzene copolymer has been produced from suspension polymerization with toluene as a diluent, having an average particle size of 2 to 50 /rm, with an exclusive molecular weight for the polystyrene standard from about 500 to 20,000 in gel-permeation chromatography. A process for preparing the PS-DVB copolymer by suspension polymerization in the presence of at least one free-radical polymerization initiator, such as 2,2 -azo-bis (2,4-dimethylvaleronitrile) with a half-life of about 2 to 60 min at 70°C, has been disclosed (78). 

For organic SEC separations the use of polystyrene/divinylbenzene (PS/ DVB) particles is almost universal throughout the industry. Polymer Laboratories PS/DVB material, PLgel, which is produced in a series of individual pore sizes, formed the basis for the original product line of SEC columns. Developments in the refinement of particle sizing introduced the benefits of smaller particle size and more efficient columns, which significantly reduced SEC analysis time through a reduction in the number of columns required for... 

The nonporous spherical gels for PCHdC are often specially prepared for research purposes. However, nonporous polystyrene/divinylbenzene beads. Solid Bead, can be obtained in various particle sizes from Jordi Associates, Inc. (Bellingham, MA). Columns packed with these gels can be used for HdC of the polymers that are currently analyzed using polystyrene/divinylbenzene SEC columns. Fumed silica nanospheres are offered by Cabot (Tuscola, IL) (17), and nonporous silica (NPS) microspheres are offered by Micra Scientific, Inc. (Northbrook, IL). These nonporous silica gels may also be used for HdC. 

Although the silica-based columns are the most widely used in RP-HPLC separations of peptides, the use of polymeric carriers (polystyrene divinylbenzene) and composite materials (silica particles with a polymeric coating), which are more chemically stable in that they do not break down at pH values higher than 8 as silica does, is gaining currency (54,55). The mobile phase usually consists of a mixture of water and an organic solvent, generally acetonitrile, methanol, or... 

Structure Macroporous polystyrene-divinylbenzene nonpolar adsorbent, 62-177 pm particle size Analytical Properties Used mainly in preparative-scale HPLC stable over entire pH range (1-13) sometimes difficult to achieve column-to-column reproducibility due to packing the irregular particles relatively lower efficiency than alkyl bonded phases particles tend to swell as the organic content of the mobile phase increases Reference 1... 

Comparable experiments were performed with DexP-coated macroporous polystyrene-divinylbenzene (PS-DVB) particles [264] and with DexP, labelled with 4-amino-TEMPO, using EPR spectroscopy to study the conformation of the polymer chains [265]. Low substituted DexP gave thicker layers with lower density than highly substituted derivatives due to the presence of more loops and tails. With increasing DS of DexP, the stiffness of the adsorbed layers and, therefore, the density increases and the non-specific interaction of BSA with the DexP-coated PS-DVB surfaces seems to be restricted to the top of the adsorbed layer. 

In the latter half of the 1990s, porous, highly cross-linked polystyrene divinylbenzene (PS-DVB) resins with smaller, spherical particle sizes more suitable for SPE uses became available (Figure 2.23). The new generation of apolar polymeric resins is produced in more purified form, reducing the level of impurities extracted from the sorbent. Polymeric resins are discussed in more detail by Huck and Bonn [69], Fritz [73], Thurman and Mills [75], and Pesek and Matyska [87],... 

There are two classes of stationary phases in SEC, one type for GFC and the other for GPC. Stationary phases for GFC are hydrophilic and include polydextrans, polyvinyl alcohol gel, and silica gel those for GPC are hydrophobic, typically cross-linked, rigid polystyrene-divinylbenzene gels. Generally, columns of 15 to 50 cm length are used, packed with 7- to 10-/t,m particles and with an internal diameter between 0.6 and 0.8 cm. In SEC, unlike in other chromatographic modes, the stationary phase is the primary factor controlling retention. 

Examples of particle sizing using photon correlation spectroscopy are presented to demonstrate the straight forward uses and difficulties with the technique. Examples include NBS SRM 1691, a crosslinked polystyrene-divinylbenzene, a fractionated sample of polyvinylchloride, "dusty" samples of reference latex, a bimodal mixture of reference latices, a bimodal mixture of rubber particles, and a 2 1 aggregate. 

Hochleitner, E.O. et al. Analysis of isolectins on non-porous particles and monolithic polystyrene divinylbenzene-based stationary phases and electrospray ionization mass spectrometry. Int. J. Mass Spectmm. 2003, 223-224,519-526. 

The dynamic swelling method (DSM) [10] has also been described for the preparation of crosshnked microspheres with free vinyl groups [78]. Therefore, polystyrene seed particles (1.9 pm) prepared by dispersion polymerization are dispersed in ethanol-water (7/3, w/w) containing divinylbenzene (DVB), benzoyl peroxide, and poly(vinyl alcohol) (PVA). The slow drop-wise addition of water to the mixture causes the DVB phase to separate, and it is continuously imbibed by seed particles to produce relatively large swollen particles (4.3 pm), which are then polymerized to afford the respective PS-PDVB composite particles with free vinyl groups. DSM has recently been developed in order to prepare hohow microspheres and various oddly-shaped polymer particles, including a rugby ball, red blood cells, or snowman structures [79-83]. 

In addition to the silica-based, reversed-phase particles, polymeric particles are available that utilize a hydrophobic stationary phase, e.g., cross-linked polystyrene divinylbenzene. In these polymeric stationary phases, the backbone of the particle provides the opportunity for hydrophobic interactions. Although these packing materials are available in high-performance particles, the particles cannot withstand the high pressure that silica particles can and thus are typically used in medium- to low-pressure operations. The polymeric stationary phases usually have a series of aromatic... 

The corresponding AminoPac PA-1 latex anion exchanger consists of a polystyrene/ divinylbenzene substrate with a particle diameter of 10 pm. The synthesis of the latex beads is carried out, however, using dimethylamine instead of divinylbenzene for crosslinking the polymer. Until now, no methods have been available for the separation... 

For accurate work, the sieves may need to be calibrated. Four organizations prepare standard reference materials (SRM s) the National Institute of Standards and Technology (NIST), Bethesda, MD the Community Bureau of Reference (BCR), Brussels Whitehouse Reference Standards Brussels, and Duke Scientific, Palo Alto, CA. NIST uses glass beads and silicon nitride particles BCR uses quartz beads Whitehouse uses soda-lime glass and Duke uses polystyrene-divinylbenzene or glass spheres. NIST and BCR standards are expensive. Figure 37-31, p. 443, shows a set of standards. 

---