Monomer and polymer densities

Monomer and Polymer Densities. Liquid density values at the relevant taiperature have been used (L5) a constant value for the polymer density, Pp, is assumed, indepandent of polymer c qposltlon and correspondent to the average of the homopalymer density values. 

Negleding the difference in the monomer and polymer densities gives an explicit expression for the conversion versus time ... 

This procedure is based on the measurement of the contraction of volume that results from the different densities of the monomer and polymer. The conversion of the volume contraction to the yield of polymer can be made by means of a gravimetrically determined calibration curve or by calculation from the specific volumes (see Example 3-6). 

Marchand, A.P. (1986) Synthesis of new high energy/high density monomers and polymers synthesis of D3-Hexanitrotrishomocubane. Proc. Naval Workshop on Energetic Crystalline Materials, Office of Naval Research, MD. 

Drijvers and Goethals 52) have reported that excess sulphide functions (monomer and polymer) and diethyl ether have no detectable effect on the dissociation of two sulphonium tetrafluoroborate salts in methylene chloride and nitrobenzene, when present in similar proportions to those in corresponding polymerisation reactions. In contrast to this, however, Jones and Plesch 51) have shown that the dissociation constant of triethyloxonium hexafluorophos-phate in methylene chloride at 0°C increases by a factor of - 2 when small quantities of tetrahydrofuran are added. The latter molecule has a lower dielectric constant than methylene chloride and might therefore be expected to reduce dissociation. These workers have interpreted their results in terms of specific solvation of the cation by ether molecules, with subsequent reduction in the effective charge density of the positive ion and hence in the coulombic force favouring ion pairing, e.g. 

Besides other intriguing properties, such as inherent planar chirality, metallocenes are of interest due to their considerable Lewis basicity. Their direct or conjugative attachment to a polymer chain should enhance the electron density along the main chain and therefore lower the HOMO-LUMO band gap. In addition, organometallic compounds and metallocene-based monomers and polymers represent interesting potential nonlinear optical materials, useful for frequency doubling, modulation, and switching, for three reasons ... 

If the monomer and polymer are not mutually soluble, the bulk reaction mixture will be heterogeneous. The high pressure free radical process for the manufacture of low density polyethylene is an example of such reactions. This polyethylene is branched because of self-branching processes illustrated in reaction (6-89). Branches longer than methyls cannot fit into the polyethylene crystal lattice, and the solid polymer is therefore less crystalline and rigid than higher density (0.935-0.96 g cm ) species that are made by coordination polymerization (Section 9.5). 

Tang et al. (2004) presented a cure model that captures transient, thermal and chemical effects that are ignored in typical threshold-based models. This new model incorporates as inputs photoinitiation rates, reaction rates, diffusion and temperature distributions, and is able to determine the spatial and temporal distributions of monomer and polymer concentrations, molar masses, crosslink densities and degree of cure. 

The kinetic aspect of the polymerization process has been studied only for the gaseous phase polymerization (6, 7). Smith (6), by following polymer optical density at 370 nm, and Blake (2), by monitoring the fall in monomer pressure, found the polymerization to be first order with respect to both monomer and polymer. They observed an induction period when no polymer was initially present, and that the polymer, once formed, served as the substrate for the growth of more polymer. Smith proposed that C2O, formed by the thermal decomposition of C3O2, is responsible for formation of the initial polymer structure. 

Table 8.9. Shrinkage accompanying polymerization calculated from bulk densities of monomer and polymer 4>...

The polymerization is accompanied by approximately 6% shrinkage (calculated from densities of monomer and polymer at 25 °C). Upon heating the polymer solution in the presence of trifluoromethanesulfonic acid the substituted 1,3-dioxolane ring opens and linear polymer is formed. This is accompanied by a 9.7% expansion in volume. 

The corresponding H-NMR spectra are shown in Fig. 8.5. The volume changes during polymerizations, as calculated from densities of monomer and polymers, are given in the Table 8.11 47). 

Table 8.12. Densities of monomer and polymer of 3,9-dimethylene-l,5,7,l 1-te traoxaspi ro 5.5 lundecane and the calculated volume change during polymerization 541...

Calculate the total polymer mass production, and the percentage increase in polymer production achieved in the second operation. You may assume an ideal mixture the densities of monomer and polymer are pm - 800 kg/m, pp 1100 kg/m. The monomer molecular weight is Mm 100 kgAmoI, and the rate constant is k 0.1 min" h... 

Electronic properties related to the semiconductivity of monomers and polymers of phthalocyanoruthenium with bidentate bridging ligands, [PcRu(L2)] and [PcRu(L)] , have been investigated using density functional calculations (L = pyrazine, triazine, tetrazine, etc.) <2001JMT(579)169>. The electronic structures of one-dimensional... 

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