Selection method for additives in photopolymers

A method for selecting compounds which can be used as plasticizers in photopolymer formulations for the production of light holographic media, wherein the method comprises:

• a) selecting a compound to be tested,
• b) carrying out a conformer analysis of the compound to be tested using a suitable computer programme, c) generating an optimization of the geometry of all conformers with the aid of a force field method and the conformer space is then further reduced with the aid of a similarity analysis,
• d) effecting a quantum chemical optimization of the geometry of the conformers which are energetically most favourable according to the force field optimization with the use of the B-P86 density functional and a triple □ valence basis set, and of the Conductor Like Screening Model (COSMO) in combination with the optimized COSMO radii or, if these do not exist for a given element, with 1.17 times the Bondi valence radius,
• e) calculating the area (A) in Å2 and the enclosed volume (V) in Å3 of the three-dimensional COSMO shielding charge density surfaces of the conformers having the lowest energy, which are obtained as result of the quantum chemical optimization of the geometry,
• f) dividing into segments, the COSMO shielding charge density surfaces of the conformers having the lowest energy with the aid of a suitable software package, the mean surface shielding charge density (□) of these segments are plotted in the form of a frequency distribution P(□) and the second moments (M2) of this distribution, defined according to the equation:
• M
• 2
• =
• 10
• ·
• ∑
• i
• 
• 
• P
• 
• (
• σ
• i
• )
• ·
• σ
• i
• 2
• ·
• Δσ
• are determined, □□ being the interval width of the discrete frequency distribution and the charge densities □ being stated in the unit e/nm2,
• g) averaging the volumes, areas and second moments of all conformers considered according to their weight in the Boltzmann distribution on the basis of the energies obtained from the quantum chemical optimizations of the geometries,
• h) estimating the volatility of the substance according to the computational rule:
• TGA
• 
• 
• 95
• ≈
• 207.015
• ·
• M
• 2
• A
• +
• 41.405
• ·
• V
• 3
• -
• 253.2
• ,
• i) estimating the density of the compound at room temperature with the aid of the equation:
• ρ
• =
• 0.89
• ·
• M
• V
• ·
• N
• A
• -
• 0.2
• ·
• A
• V
• +
• 0.01
• ·
• M
• 2
• □ being the density of the pure substance in g/cm3, M being the molar mass in g/mol, NA being the Avogadro number, A being the COSMO shielding charge density surface in Å2, V being the volume in Å3 enclosed by the surface and M2 being the second moment of the surface shielding charge density frequency distribution,
• j) using the estimated density in order, with the aid of the Lorentz-Lorenz equation:
• n
• D
• =
• 2
• ·
• ρ
• ·
• MP
• M
• +
• 1
• 1
• -
• ρ
• ·
• MP
• M
• ,
• to convert the molar polarizability (MP) estimated according to a QSPR approach as accurately as possible into a refractive index at 589 nm (nD20)
• k) determining whether the volatility of the compound to be tested is >100° C. and the refractive index thereof is ≦1.4600, the compound to be tested being classed as being suitable if both conditions are fulfilled.