Monomers Properties

Monomer Properties. Some physical properties of the lower homologues of vinyl ether are presented in Table 1. 

For copolymerizations between non protie monomers solvent effects are less marked. Indeed, early work concluded that the reactivity ratios in copolymerizations involving only non-protic monomers (eg. S, MMA, AN, VAe, etc.) should show no solvent dependence.100101 More recent studies on these and other systems (e.g. AN-S,102-105 E-VAc,106 MAN-S,107 MMA-S,10s "° MMA-VAc1" ) indicate small yet significant solvent effects (some recent data for AN-S copolymerization are shown in Table 8.5). However, the origin of the solvent effect in these cases is not clear. There have been various attempts to rationalize solvent effects on copolymerization by establishing correlations between radical reactivity and various solvent and monomer properties.71,72 97 99 None has been entirely successful. 

From these monomer properties alone it is not quite clear how the trends in the interaction strength with a fixed given acceptor B will develop. For the X2 molecules the polarizabilities rise in the series F2, CI2, and Br2. The dipole moments of the interhalogens XY decrease in the series C1F, BrF, and BrCl, whereas the polarizabilities increase in this series. 

Apart from the question of linear scaling methods, we may employ the so-constructed orbitals for studying weakly interacting complexes. Of course, usual functionals do not include the important dispersion terms, but such an approach remains effective to study induction in large assemblies of molecules and, as we will see, for extracting monomer properties and interaction-induced changes of these. 

In parallel to the properties of H-bonded complexes (Section 5.2), the monomer properties in the CT complex of Fig. 5.42 are strongly altered by n-7t stabilization. Tables 5.23 and 5.24 summarize geometrical and NBO descriptors of the H3N- -NO+ complex that illustrate these changes. 

Many authors [8-10] have demonstrated that the CP method undercorrects the BSSE. Moreover, Karlstrom and Sadlej [11] pointed out that addition of the partner orbitals to the basis set of a molecule not only lowers its energy, in accordance with the variation principle, but also affects the monomer properties (multipole moments and polarizabilities). Latajka and Scheiner [12] found that in a model ion-neutral system such as Li" -OH2, this secondary BSSE can be comparable in magnitude to the primary effect at both SCF and MP2 levels. The same authors also underlined the strong anisotropy of secondary error [13]. 

Some unusual monomer properties and major characteristics of polymerizing systems involving lactones. There are at least two features of... 

TABLE I, PHYSICAL PROPERTIES OF STYRENE MONOMER Property Value... 

The polarization and exchange energies through the second order have an appealing physical interpretation. Except for the second-order exchange terms they can also be rigorously related to monomer properties which considerably facilitates their practical evaluation. 

Electron correlation introduces basically two effects into ab initio calculations on intermolecular forces. Hartree-Fock calculations do not account for dispersion forces and hence the dispersion energy is included only in Cl calculations. A second contribution comes from a correction of monomer properties through electron correlation effects. Again, the correlation correction of the electric dipole moment is the most important contribution. In the case of (HF)2 these two effects are of opposite sign and hence the influence of electron correlation on the calculated results is rather small (Table 3). 

Table 1. List of typical monomers, properties they enhance, and viscosity. ... 

Table 3 Anisotropic Atom—Atom Models for the Intermolecular Pair Potential, Which Can Be Quantified Using Ab Initio Monomer Properties, and Lead References... 

Goepferich, A. Langer, R. The influence of microstructure and monomer properties on the erosion mechanism of a class of polyanhydrides. J. Polym. Sci. A Polym. Chem. 1993, 31, 2445-2458. 

Type of complex Typical A , , (phartree) at equilibrium geometry Example Relative importance of long-range terms Acceptable relative errors (%) in monomer properties" /I D a. 

It is possible to apply the multipole expansion and perturbation theory in order to derive long range expressions for T (R), thus relating this quantity to monomer properties. A simple example of such a procedure can be found in the appendix of ref. , where the induction contribution to the dipole moment (J = 1) of an arbitrary Van der Waals dimer has been evaluated. 

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