Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

The overall goal of this procedure is to set up a high throughput polymerization and assess the ability of a catalyst to undergo chain transfer through detailed characterization and kinetic analysis of the resultant polymer. This method helps answer key questions in polymerization catalysis linked into newly designed catalysts, which can exploit chain transfer to produce efficient routes to a variety of polymers. The main advantage of this technique is that high throughput polymerizations allow for efficient catalyst screening and direct comparisons of catalysts over a large range of reaction conditions.

Demonstrating this technique will be Dr.Ryan Hugh, a postdoc in my laboratory. First dissolve one milliliter of two three butane Dion and 2.8 milliliters of two six dimethyl annin in 20 milliliters of methanol in a 100 milliliter round bottom flask. After adding 0.4 milliliters of formic acid, stir the reaction at room temperature until the diamine precipitates, which is typically one to two hours.

Following this, filter the reaction mixture with a glass frit and filter flask and wash the yellow solid with 20 milliliters of cold methanol. Then dry the solid in vao. In a glove box, combine one gram of dim eth nickel bromide, and 1.1 grams of biz.

Two six dimethyl phenyl, two three butane Dion in a 50 milliliter round bottom flask, add 20 milliliters of di chloro methane and stir overnight at room temperature. On the next day, filter the reaction mixture with a glass frit and filter flask. Wash the brown solid with 75 milliliters of chloro methane and dry in vao.

Prepare a 0.001 molar catalyst stock solution by adding 0.0041 grams of the previously prepared nickel bromide catalyst into a vial with 7.5 milliliters of toluene to the stir nickel suspension. Add 0.5 milliliters of 30%methyl luane in toluene. Stir for one minute, changing the reaction mixture from a brown suspension to a solution.

Next, prepare a 1.2 molar dathyl zinc solution by dissolving 0.25 milliliters of dathyl zinc in 1.75. Milliliters of toluene set up all polymerization reactions in a parallel pressure reactor with overhead stirring housed in a nitrogen atmospheric glove box program. The polymerization in the software indicating the total reaction volume as three milliliters.

The purge gas is nitrogen. The reaction gas is ethylene. The pressure as 15 to 150 PSI and the reaction time is one hour.

The setup of the reactor, including adding the reagents and solvents, programming the software and securing the overhead storing assembly is the most critical step. Following this insert glass liner reaction vials into the eight wells. Add the reagents according to table one.

Use the depth tool to ensure the glass liners are at the appropriate height. Then insert the blade impellers into the overhead assembly. After filling the reaction vials and ensuring the O-rings are properly seated in the metal grooves, carefully place the overhead stirring assembly on the base and screw down in an alternating fashion.

Once all screws are sufficiently tightened, press start in the software. Monitor the reaction via gas uptake measurements. After one hour of polymerization, remove the reaction vials from the glove box, precipitate polyethylene with the addition of 5%hydrochloric acid in methanol.

Then remove the solvent and dry the polymer under vacuum. After determining the polymer yield dissolves 0.002 grams of the polymer in two milliliters of 1 2 4 tri chloro benzene at 135 degrees Celsius. Use gel permeation chromatography or GPC to analyze the molecular weight and dispersity index of the dried polyethylene.

This sample is now ready to be placed on a high temperature GPC for analysis. Next dissolve 0.05 to 0.08 grams of the polymer in 0.5 milliliters of derated tetra chloro eth ethane at 130 degrees Celsius. For high temperature carbon NMR spectroscopy analysis for chain transfer polymerization fill the reactor and program the software following the previously described procedures and analysis.

The ethylene gas consumption versus time is presented here for the different ethylene pressures tested. The ethylene gas consumption versus time is shown here for the catalyst alone samples, which is used to calculate the rate of propagation. GPC traces for chain transfer polymerizations with zero to 1000 of ethyl zinc are displayed here.

The GPC is used to calculate the molecular weight and dispersity of the polymer samples. The carbon NMR spectra of the polyethylene samples of the full series and a zoomed in spectrum with the peaks labeled are shown here. The molecular weight data is used to calculate the number of chains initiated and the Mayo plot.

The fit of the Mayo plot is used to calculate the ratio of the rate of chain transfer to the rate of propagation, which is used to calculate the rate of chain transfer Once mastered, this polymerization can be done in two hours if it is performed properly. While attempting this procedure, it is important to accurately dispense the stock solutions into the reaction vials, ensure the reactor is properly configured and the overhead stirring assembly is properly secured in place. After watching this video, you should have a good understanding of how to set up a high throughput polymerization, characterize the resulting polymer, and assess the ability of a catalyst to undergo chain transfer through kinetic analysis.

Don't forget that dathyl, zinc and methyl luminox are pyrophoric and air free. Techniques should always be used when performing this procedure.