Introduction | Polymer Properties | Connectivity Indices | Properties Calculated in MOE | SVL Functions | Future directions
The 1997.09 release of MOE includes the new polymer property predictions. The polymer utilities a predictions panel which calculates and displays over 50 polymer properties. A polymerize function is available to easily create MOE polymers from a given monomer repeat unit. Methods for creating report files containing the output of the polymer calculations are provided as well as a utility for performing the property predictions on a database of polymers. A selection function allowing the user to visually inspect the backbone of the polymer repeat unit is also provided.
The ability to predict polymer properties computationally is an important tool, enabling the research chemist to eliminate certain polymer structures prior to the costly process of synthesizing the polymer. In the past the main method of predicting the polymer properties was to break down the polymer into substituent groups and to use look up tables to determine the experimental values of these groups and then to add the partial results together. This of course required that the experimental values were available. A fairly new technique is under investigation by Jozef Bicerano in his monologue "Prediction of Polymer Properties", Marcel Dekker Inc., 1996. This method utilizes the graph theoretical properties, the connectivity indices, of the polymer's repeat unit. Since all the properties are based on the graph of the polymer, the properties can be predicted for any polymer entered into MOE with no need for any database to be maintained for look up and no threat that the polymers substituent group properties will not be available. The polymer properties in MOE are all calculated using the techniques found in Bicerno's book.
MOE defines a polymer as a repeat unit contained within a single residue, flanked on either side by identical copies of the monomer with bonds attaching the residues at the repeat unit endcaps. MOE provides the Polymerize[] function to perform the copy operation and the bonding between the residues. The user is prompted for the endcap atoms or, if running in MOEBatch, the atoms may be given as atom keys.
The polymer predictions panel is simple to use. On opening, the panel displays an empty list. When the Predict button is pressed, the polymer properties are calculated for all polymers currently within the MOE system and the results are displayed in the list. The list shows the scalar properties for the polymer displayed in the Polymer option menu.
The Plot option menu shows a list of available plots. When the Plot button is pressed the property selected is plotted for all the polymers in the system. This gives the user a way to visually compare the property between polymers.
The output of the predictions can be sent to a file and stored for further reference. A text field is supplied for the file name, however, if no file name is given then the output is sent to the CLI.
The SVL command MOE_Polymer_MDB[] allows the chemist to calculate all the properties listed in the predictions panel on an entire database of polymers. For each polymer in a given database, the polymer properties are calculated and the results are entered in a database field whose names matches the Tag in the output vector. The results can then be plotted using the database plot facility and polymer entries may be selected based on output values within the plot area.
where
| Atom | Hyb | Nh | Delta | DeltaV | Atom | Hyb | Nh | Delta | DeltaV | |
|---|---|---|---|---|---|---|---|---|---|---|
| C | sp3 | 3 | 1 | 1 | O | sp3 | 1 | 1 | 5 | |
| 2 | 2 | 2 | 0 | 2 | 6 | |||||
| 1 | 3 | 3 | sp2 | 0 | 1 | 6 | ||||
| 0 | 4 | 4 | F | --- | 0 | 1 | 7 | |||
| sp2 | 2 | 1 | 2 | |||||||
| 1 | 2 | 3 | 0 | 4 | ||||||
| 0 | 3 | 4 | P | sp3 | 2 | 1 | ||||
| sp | 1 | 1 | 3 | 1 | 2 | |||||
| 0 | 2 | 4 | 0 | 3 | ||||||
| N | sp3 | 2 | 1 | 3 | S | sp3 | 1 | 1 | ||
| 1 | 2 | 4 | 0 | 2 | ||||||
| 0 | 3 | 5 | 0 | 4 | ||||||
| sp2 | 1 | 1 | 4 | Se | sp3 | 0 | 2 | |||
| 0 | 2 | 5 | Cl | --- | 0 | 1 | ||||
| sp | 0 | 1 | 5 | Br | --- | 0 | 1 | 7/27 | ||
| 0 | 3 | 6 | I | --- | 0 | 1 | 7/47 |
The exceptions outlined in the above table are built in to the MOE prediction routines. In general, a polymer property is predicted through a formula that uses some of the Chi values with additional correction indices added in. A common correction term is one that involves simply the number of atoms of a certain element type. For more information on the correction terms used for each property, we refer you to Bicerno's book, which explains in detail each term used in the prediction formulas.
| Tag | Description | UNITS |
|---|---|---|
| M | Molecular Weight of Repeat Unit | g/mol |
| Me | Entaglement Molecular Weight | g/mol |
| lm | Length of Extended Repeat Unit | A |
| V298 | Amorphous Molar Volume | cc/mol |
| Vvdw | Van der Waals Volume | cc/mol |
| p298 | Amorphous Density | g/cc |
| Ecoh1 | Cohesive energy (Fedors) | J/mol |
| Ecoh2 | Cohesive energy (van Krevelen) | J/mol |
| sol_Ecoh1 | Solubility Parameter (Fedors) | (J/cc)**0.5 |
| sol_Ecoh2 | Solubility Parameter (van Krevelen) | (J/cc)**0.5 |
| Tg | Glass Transition Temperature | K |
| a298 | Volumetric thermal expansion | 10**-6../TD> |
| C298 | Heat Capacity | J/molK |
| DeltaCpTg | Heat Capacity Jump at Tg | J/molK |
| g298_Ecoh1 | Surface Tension (Fedors) | dyn/cm |
| g298_Ecoh2 | Surface Tension (van Krevelen) | dyn/cm |
| g298 | Surface Tension (molar parachor) | dyn/cm |
| n298 | Refractive Index | - |
| RLL | Molar Refraction | cc/mol |
| dipole | Effective Dipole Moment | debyes |
| PLL | Molar Polarization | cc/mole |
| eps298 | Dielectric Constant | - |
| vr298 | Volume Resistivity (log10) | ohm cm |
| mag | Magnetic Susceptibility | 1e-6 ../TD> |
| sigma | Steric Hindrance Parameter | - |
| Cinf | Characteristic Ratio | - |
| viscosity | Intrinsic Viscosity (molar stiffness) | - |
| Mcr | Critical Molecular Weight | g/mol |
| Eact | Activation Energy for Viscous Flow | J/mol |
| l298 | Thermal Conductivity | J/Kms |
| pO2 | Permeability to O2 | Dow Units |
| pN2 | Permeability to N2 | Dow Units |
| pCO2 | Permeability to CO2 | Dow Units |
| Eact_d | Activation Energy of Decomposition | kJ/mol |
| T0_d | Temperature of Initial Decomposition | K |
| T_d | Temperature of Half Decomposition | K |
| Tmax_d | Temperature of Maximum Decomposition | K |
| Y_d | Molar Thermal Decomposition Function | kgK/mol |
| Fd | Dispersion Component of Molar Attraction | - |
The following values are plots as a function of temperature. The temperature range calculated is 0-500K for all properties.
| TAG | Description | UNITS |
|---|---|---|
| V(T) | Molar Volume | cc/mol |
| p(T) | Amorphous Density | g/cc |
| C(T) | Heat Capacity | J/molK |
| g(T) | Surface Tension | dyn/cm |
| n(T) | Refractive Index | - |
| B(T) | Bulk Modulus | MPa |
| v(T) | Poisson's Ratio | - |
| E(T) | Young's Modulus | MPa |
| G(T) | Shear Modulus | MPa |
| F(T) | Brittle Fracture Stress | Mpa |
| Y(T) | Shear Yield Stress | Mpa |
| l(T) | Thermal Conductivity | J/Kms |