Toluene polymerization behaviors

Based on this approach Schouten et al. [254] attached a silane-functionalized styrene derivative (4-trichlorosilylstyrene) on colloidal silica as well as on flat glass substrates and silicon wafers and added a five-fold excess BuLi to create the active surface sites for LASIP in toluene as the solvent. With THF as the reaction medium, the BuLi was found to react not only with the vinyl groups of the styrene derivative but also with the siloxane groups of the substrate. It was found that even under optimized reaction conditions, LASIP from silica and especially from flat surfaces could not be performed in a reproducible manner. Free silanol groups at the surface as well as the ever-present impurities adsorbed on silica, impaired the anionic polymerization. However, living anionic polymerization behavior was found and the polymer load increased linearly with the polymerization time. Polystyrene homopolymer brushes as well as block copolymers of poly(styrene-f)lock-MMA) and poly(styrene-block-isoprene) could be prepared. 

Unbridged, bridged, substituted, and half-sandwich complexes have been used as metallocenes for ethylene polymerization (Figs. 1 and 2). To compare the activities and molecular masses, the polymerizations are carried out under the same conditions (30°C, 2 bar ethylene pressure, with toluene as a solvent) (105). Table IV shows the polymerization behavior of various met-allocene/alumoxane catalysts. Generally, zirconium-containing catalysts are... 

Tables. Polymerization behavior of metallocenes based on bridged biscyclopentadienyl compounds. All polymerizations were performed at 30 °C in 500 ml toluene at 3 bar. Al/M = 10 0(X), [M] = 0.002mmol, t = 2h...

Table 20. Polymerization behavior of silica-fixed metallocene catalysts at 40°C in toluene...

In addition to monomers and the initiator, an inert liquid (diluent) must be added to the monomer phase to influence the pore structure and swelling behavior of the beaded resin. The monomer diluent is usually a hydrophobic liquid such as toluene, heptane, or pentanol. It is noteworthy that the namre and the percentage of the monomer diluent also influence the rate of polymerization. This may be mainly a concentration or precipitation effect, depending on whether the diluent is a solvent or precipitant for the polymer. For example, when the diluent is a good solvent such as toluene to polystyrene, the polymerizations proceed at a correspondingly slow rate, whereas with a nonsolvent such as pentanol to polystyrene the opposite is true. 

In comparison to Ba-Mg-Al polymerizations, the preparation of block copolymers and functionally terminated polymers has not been successful with Ba-Li initiators. Chain transfer to toluene in Ba-Li systems is considered to be responsible for this behavior. 

The catalyst 4b/borate was tested under similar conditions as in the case of 4a (toluene solution and liquid propylene) in propylene polymerization experiments after preactivation with TIBA (Table 1). According to the data from Table 1, the catalytic properties of 4b are inferior to those of 4a. The behavior of 4b is similar to that of asymmetric catalysts with a forward orientation of the 4-substituted indene unit [10]. The effect of the substitution position is remarkable. While the 5,7-substituted hafnocene 4a shows higher activities (up to 3.2 x 105 kg PP mol 1 Hf h 1 at 40 °C) with increasing temperatures, substantially lower or almost no activities were found for the 4,6-substituted hafnocene 4b at the same temperature (Fig. 13). 

Behavior of VC in emulsion-seeded polymerization is quite different from that of other vinyl monomer such as styrene and vinyl toluene. For instance, in styrene-seeded polymerization, Vanderhoff (11) did not observe any anomalous seed growing. He reports uniform growing for a mixture of two seeds with a < = 2640 and 5570 A., respectively, by seeding 0.193 X 1012 particles/ml. H20, whose surface per ml. of water is, according to our calculations, equal to 0.121 X 1020 sq. A. 

The improved properties of modified CNTs achieved by polymerization technique, e.g. better polymer-CNT interaction, can be also detected by other techniques. As an example, we present here behavior of solutions of the prepared composites. Figure 8.8 represents photomicrographs of two different SWCNT/PS samples dissolved in toluene (right parts) and optical transmission microscopy of casted PS thin films from two different dispersions. The first one (a) represents PS solution in toluene where raw SWCNTs were only added and dispersed by ultasonication for two hours. The second (b) is... 

The polymers were fractioned into 8-14 components by coacervate extraction from the benzene - methanol system. For fractions and nonfractioned polymers, characteristic viscosities [t ], were me-asured. Because that was the first example of studying conformations of macromolecules of this ty-pe in diluted solutions, authors of the work [56] paid much attention to selection of an equation, which would adequately describe hydrodynamic behavior of polymeric chains. Figure 10 shows de-pendencies of [q] on molecular mass (MM), represented in double logarithmic coordinates. Parame-ters of the Mark-Kuhn-Hauvink equation for toluene medium at 25°C were determined from the slo-pe and disposition of the straight lines. 

In dichloromethane,the polymerization of propylene under higher pressure yields an isotactic polypropylene with a small number of stereodefects, while in toluene a mixture of isotactic and atactic products was obtained. This fact can testify about the presence of two different active catalytic species. The nature of the intermediate responsible for the formation of the atactic fraction has not been fully elucidated yet. On the basis of NMR experiments, it seems that in toluene one of the benzamidinate ligations opens to an rf coordination, and the solvent occupies the vacant site. It was shown that similar heteroallylic ligations (alkoxysilyl-imido) have exhibited dynamic behaviors [64,65]. 

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