Monomer, conversion

Once the primary variables were obtained, numerous secondary variables were also calculated such as overall conversion, monomer A and B conversions, polymer composition from the moles of A and B in the copolymer, and number average molecular weight. The latter was obtained by dividing the mass of monomers A and B in the polymer by the moles of polymer. 

Styrene (see Fig. 3.4 and Example 3-35). Conversely, monomer pairs whose copolymerization behavior is well known can be used to test new initiator systems in order to draw conclusions about the polymerization mechanism. 

In these experiments, monomer droplets disappear after about 25 % conversion. Monomer amounts in the particles increase to a maximum around the point where droplets disappear, and then decrease. 

Initiation with Triphenylmethyl Cation. When tetrahydrofuran (THF) is used to dissolve triphenylmethyl hexachlorantimonate at room temperature, there is almost immediate decomposition of the triphenylmethyl cation (6). On the other hand, solutions of the trityl salt in THF can be prepared and stored as deep yellow solutions if maintained at temperatures around — 80°C. At room temperature the initial decoloration of the catalyst is followed rapidly by polymerization of the monomer to poly(tetramethylene oxide), and the actual percentage conversion depends markedly on the temperature. This behavior is typical of systems exhibiting monomer-polymer equilibria (28), and Table III shows values for the equilibrium conversion of monomeric THF to polymeric THF obtained with a variety of catalysts. As for vinyl ether polymerization, it is most convenient to use the trityl hexachlorantimonate salt however, recourse to Table III shows clearly that above room temperature this anion yields less than the expected equilibrium conversion monomer... 

In all conversion monomer and polymer units form a solid solution. The separation d in chain direction between lattice sites is conversion dependent. 

A typical composition of high-conversion monomer mixtures is as follows ... 

Fig. 6.4 DP vs. time data at low conversion (monomer to dimer) for ADMET of 1,9-decadiene at 45 °C showing the induction period of catalyst 10. (Reprinted with permission from Lehman, Jr., S. E., Wagener, K. B., Macromolecules 2002, 35, 48-53.)...

Fig. 10. Dependence of weight average molecular mass of poly (methacrylonitrile) on conversion. Monomer concentration 1 = 1,2 2 = 2,1 mol/1 [Et3P] = 10 mmol/1...

Catalyst Conversion (%) Monomer selectivity (%) Monomer composition ... 

The calculation of the dipole moment change for the PIC molecule from the obtained value of the Stokes shift in water-ethanol solution gives the value 4 2.56D. The analogous calculation for the PIC dimer was carried out in water at Stokes shift 30 cm-i is taken from (Sato et al., 1989) and gives the value A/m=0.7D. One can see from the values of Afl that the difference of the dipole moments at ground and excited state decreases in 3.66 times with the conversion monomer to J-aggregate form of dye. The calculation of the change at... 

In the radical copolymeiization of styrene and methyl methacrylate the reactivities are about the same, but for anionic initiation of an equimolar mixture of the two monomers the incorporation of methyl methacrylate is much preferred, while for cationic initiation of the same mixture the copolymer contains mostly styrene (see Fig. 3.4 and Example 3.35). Conversely, monomer pairs whose copolymerization behavior is well known can be used to test new initiator systems in order to draw conclusions about the polymerization mechanism. 

On the mechanistic side, emulsion polymerization is very different from suspension polymerization. Reactions do not normally occur in monomer droplets, hut in water phase and polymer particles.Water-solrrhle initiators are used. A typical recipe consists of 100 parts H2O, 50-120 parts monomer, 0.5 part surfactant, 0.5 part initiator, and 0.5 part chain transfer agent. There are three stages in emrrlsion polymerization. In stage I, polymer particles are nucleated from micelles. This stage usually takes a few minutes and is completed at < 10% conversion. Monomer droplets having sizes about tens of miaometers are formed in continuous water phase by agitation and stabilized by surfactant. The added amount of surfactant must be adequate and above its critical micellar concentration (CMC) so that micelles can form. 

Inserting the given rate constants and [/] = [/]o = 0.05 mol/L gives t = 0.141 seconds ( ). From Figure 10.1, the time to reach 50% conversion (monomer half... 

Figure 6.1 Schematic diagram of a plug flow reactor. is the molar flow rate of reactants, is the exit flow rate of the reactants, is the conversion monomer, and is the heat removed by coolants per unit surface area of the reactor.

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