Polymer phase

MBS polymers are prepared by grafting methyl methacrylate and styrene onto a styrene—butadiene mbber in an emulsion process. The product is a two-phase polymer useful as an impact modifier for rigid poly(vinyl chloride). 

There are five North American manufacturers of EPDM Unhoyal Chemical, Exxon, DuPont, DSM, and Bayer. In addition. Union Carbide and Dow are manufacturing the new gas-phase polymers. A new joint agreement between Dow and DuPont will offer these two companies some competitive advantages in this market. Trade names of commercial ethylene—propylene polymers include Bayer s Epsyn, Exxon s Vistalon, DuPont s Nordel, and Unhoyal s Royalene. 

In the suspension polymerization of PVC, droplets of monomer 30—150 p.m in diameter are dispersed in water by agitation. A thin membrane is formed at the water—monomer interface by dispersants such as poly(vinyl alcohol) or methyl cellulose. This membrane, isolated by dissolving the PVC in tetrahydrofuran and measured at 0.01—0.02-p.m thick, has been found to be a graft copolymer of polyvinyl chloride and poly(vinyl alcohol) (4,5). Early in the polymerization, particles of PVC deposit onto the membrane from both the monomer and the water sides, forming a skin 0.5—5-p.m thick that can be observed on grains sectioned after polymerization (4,6). Primary particles, 1 p.m in diameter, deposit onto the membrane from the monomer side (Pig. 1), whereas water-phase polymer, 0.1 p.m in diameter, deposits onto the skin from the water side of the membrane (Pig. 2) (4). These domain-sized water-phase particles may be one source of the observed domain stmcture (7). 

Fig. 24.2. A two-phase polymer alloy, mode by co-polymerising styrene and butadiene in polystyrene. The precipitates ore a polystyrene-butadiene copolymer.

Blending the glassy phase polymer with another polymer of higher Tg such as a polycarbonate. 

It should also be pointed out that the Tg of the soft blocks, which consist of fairly short polymer chains, will be somewhat lower than for a corresponding homopolymer of high molecular weight, for the reasons given in Section 4.2. This effect may, however, be more than compensated by the loss of molecular freedom due to the presence of and interaction with the hard phase polymer present. 

Column Mobile phase Polymer PEO standard MW Polydispersity... 

A need for single-phase polymers in some applications, e.g., polytetrafluoroethylene, VHMWPE, light-sensitive polymers, etc. 

Figure 7. Structures of dual-phase polymer electrolytes. Reprinted from T. Ichino, M. Matsumoto, Y. Take-shita, J. S. Rutt, S. Nishi, Electrochim. Acta. 40, 2265-2268, Copyright 1995, with kind permission of Elsevier Science Ltd. The Boulevard, Langford Lane, Kindlington 0X5 1GB, UK.

These two-phase polymers are generated in an optimized single-stage process using a corotating, close-intermeshing, twin-screw extruder. 

Fritz H.G., Boel U., and Cai Q., Innovative TPV two-phase polymers Formulation, morphology formation, property profiles and processing characteristics, Polym. Eng. Sci., 39, 1087, 1999. 

Protective colloids or polymeric materials can be adsorbed onto the surface of the dispersed phase. Polymer adsorption can be accomplished simply by... 

Several attempts have been made to superimpose creep and stress-relaxation data obtained at different temperatures on styrcne-butadiene-styrene block polymers. Shen and Kaelble (258) found that Williams-Landel-Ferry (WLF) (27) shift factors held around each of the glass transition temperatures of the polystyrene and the poly butadiene, but at intermediate temperatures a different type of shift factor had to be used to make a master curve. However, on very similar block polymers, Lim et ai. (25 )) found that a WLF shift factor held only below 15°C in the region between the glass transitions, and at higher temperatures an Arrhenius type of shift factor held. The reason for this difference in the shift factors is not known. Master curves have been made from creep and stress-relaxation data on partially miscible graft polymers of poly(ethyl acrylate) and poly(mcthyl methacrylate) (260). WLF shift factors held approximately, but the master curves covered 20 to 25 decades of time rather than the 10 to 15 decades for normal one-phase polymers. 

Scheme 9.1 Comparison of one-phase and two-phase polymer-supported synthesis of oligosaccharides. Continued next page.

Scheme 9.15 Further examples of oligosaccharides prepared using one-phase polymer-supported design.

Type 2 Soft matrix 4- hard dispersed phase Polymer filled Elastomers... 

One of the main assumptions of the Donnan partition model is that two well-defined phases (polymer and solution) exist and the electrostatic potential presents a sharp transition between them. This approximation is fulfilled when the typical decay length of the electrostatic potential (Debye length) is much shorter than the film thickness. The other limiting situation is that where all the redox sites are located in a plane and thus the Debye length is larger than the film thickness. This situation can be described by the surface potential model ... 

For the synthesis of perfectly dendronized sohd-phase polymers (Fig. 7.4) various dendritic structures were prepared based on amide connections [6]. For example, the naturally occurring amino acid lysine was used as a building block in creating a dendritic scaffold [33]. The synthesis of symmetrical tri-branching den-drimers on aminomethyl polystyrene macrobeads was also described in literature [34]. Recently, aryl ether dendrimers were prepared on hydroxymethyl polystyrene using a Mitsunobu reaction with 3,5-bis(acetoxymethyl)phenol [35]. 

The phenomenon of aqueous two-phase polymer systems has been known since the 19th century. However, the utilization of aqueous two-phase systems as a separation method for biological materials was explored much later by Albertsson in the mid-1950s. Albertsson performed an extensive investigation on the ability of different water-soluble polymers to form aqueous two-phase systems and how biological macromolecules and cell particles partitioned in these phase systems [27]. 

An important issue to be addressed in industrial applications of two-phase polymer systems for enzyme recovery is the economic or product quality requirement that the phase-forming polymers and salts be recycled. 

Double-layer forces are commonly used to induce repulsive interactions in colloidal systems. However, the range of electrostatic forces is strongly reduced by increasing the ionic strength of the continuous phase. Also, electrostatic effects are strong only in polar solvents, which is a severe restriction. An alternative way to create long-range repulsion is to adsorb macromolecules at the interface between the dispersed and the continuous phase. Polymer chains may be densely adsorbed on surfaces where they form loops and tails with a very broad distribution of sizes... 

Two-Phase Polymer Systems, L. A. Utracki, ed., Hanser, New York, 1991. 

Figure 5.73 Toughness, elongation at break, Et, yield strength, ay, and tensile strength cr, as a function of composition for a PC/PMMA blend. Reprinted, by permission, from T. Kyu, J. M. Saldanha, and M. J. Kiesel, in Two-Phase Polymer Systems, L. A. Utracki, ed., p. 271. Copyright 1991 by Carl Hanser Verlag.

---