Comparison of polymerization

Fig. 20 Comparison of polymerization mechanism of (3-BL with homologous compounds...

For most of the systems reported in the literature, C/K is not known—very often, neither K nor C is known. For two-component initiator-coinitiator systems, C is usually taken to he the initiator concentration [YZ] when the coinitiator is in excess or the coinitiator concentration [I] when the initiator is in excess. C may be lower than [YZ] or [I] due to association that is, only a fraction of [YZ] or [I] may be active in polymerization. This may also he the case for one-component initiators such as triflic acid. It would be prudent to determine the actual value of C in any polymerization system—usually a difficult task and seldom achieved. Experimental difficulties have also limited our knowledge of K values, which are obtained most directly from conductivity measurements or, indirectly, from kinetic data. A comparison of polymerization in the absence and presence of a common ion salt (e.g., tetra-n-butylammonium triflate for the triflic acid initiated polymerization) is useful for ascertaining whether significant amounts of free ions are present in a reaction system. 

A large number of thiocyanate complexes of Mn have been reported with either terminal N-259,263 (see 93) or 1,3- i-bonded231,264 NCS (see 94). Comparison of polymeric (92)219 with analogous (94)231 reveals that in the thiocyanate complex the Mn atom in (94) is 0.12 A out of the plane defined by the four O-donor sites of the acac ligand in the direction of the N (thiocyanate) atom. 

Comparison of Polymeric Micelles with Other Colloidal Drug Carriers. 334... 

Ceramic membranes may overcome some of the disadvantages of polymeric membranes, particularly the chemical resistance. The higher cost of ceramic membranes may be compensated by the significantly higher fluxes, especially at high temperatures. A full comparison of polymeric and ceramic membranes is given in Table 3.3. 

Table 3.3 Comparison of polymeric and ceramic pervaporation membranes.

In both compounds the magnesium atom is tetracoordinated and the Mg-C distances are very similar (2.17 A), but comparison of polymeric Me2Mg and Mc2Mg-TMEDA shows a significantly shorter Mg-C distance in Me2Mg TMEDA . 

To enable a comparison of polymerization of different monomers and of catalysts based on different metals, activities are usually given as turnovers per hour, TO h (TO = mol substrate converted per mol of metal). When comparing activities determined by different authors under strongly varying conditions the values should be taken as an indication of the order of magrtitude. The same holds true for polymer molecular weights. 

HEMA) [212]). Monomer 42 (MFC) spontaneously polymerizes at room temperature in aqueous solution and the choice of the slowest catalyst is therefore justified. Because poly-38 [212] is not soluble in water, the polymerization is run in a 50 50 MeOH water mixture. Consequently, rates are lower than in water (95% conversion requires 3-4 h reaction time at room temperature). A comparison of polymerization rates in aqueous and non-aqueous media reveals strong solvent effects. Polar solvents have been found to increase the polymerization rate, possibly because of the combined effect of an increase of rate constant [213] and a competitive coordination of the solvent and the ligand in the copper species [214]. 

W.J. Dunn, A.C. Bush, A comparison of polymerization by light-emitting diode and halogen-based hght-curing units, J. Am. Dent. Assoc. 133 (2002) 335—341. 

Table 8 Comparison of polymeric and metal oxide surfaces ...

Table P.7 Comparison of Polymerization Systems (Ref BiRmeyer, F.W., Textbook of Polymer Science, Interscience, New York, 1965, p. 339)...

Shen, Y., Shen, Z., Zhang, Y., Hang, Q., 1997a. A comparison of polymerization characteristics and mechanisms of e-caprolactone and trimethylene-carbonate with rare earth halides. Journal of Polymer Science Part A Polymer Chemistry 35, 1339—1352. 

Table I. Comparison of Polymerization of 1 Initiated by CF3SO3H and CF3S03SiMe3+CF3S03H, n-Hexane, 30 C, [l)o = 1.2 mol dm ...

Figure 2.17 Comparison of polymerization kinetics at 85°C, Ethylene concentration 0.55 M without 1-hexene and with 1-hexene at 2.21Mand 1.11 M. Copolymer compositions were 1.7 mol% 0.6 mol% and 0.0 mol% from top to bottom [66],...

Thula, XT., Svedlund, F., Rodriguez, D.E., Podschun, J., Pendi, L., Gower, L.B. Mimicking the nanostructure of bone comparison of polymeric process-directing agents. Polymers 3, 10-35 (2011)... 

TABLE 43 Comparison of Polymerization Results with and without Phenylsilane (20ml, Added to 10ml of Styrene Monomer)... 

Propagation takes place by addition of n molecules of monomer to the alkoxyethanol product to form H-(0CH2CHR) -0C2H5. The rate constant for the reaction relative to ethylene oxide depends on the epoxide or, actually, the substituents on the oxirane ring. For comparisons of polymerization rates for substituted oxiranes, see Table 1. 

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