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RAFT and Other Processes

RAFT and Other Processes. Ryan Gunckel 4/19/2012 Mentor Program – Iowa State University. RAFT Overview. Reversible Addition-Fragmentation chain Transfer Often referred to as ‘living radical polymerization’ because of its absence of a termination process.

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RAFT and Other Processes

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  1. RAFT and Other Processes Ryan Gunckel 4/19/2012 Mentor Program – Iowa State University

  2. RAFT Overview • Reversible Addition-Fragmentation chain Transfer • Often referred to as ‘living radical polymerization’ because of its absence of a termination process. • Allows for easy control of the molecular weight and composition of the polymer produced.

  3. RAFT Process • During RAFT polymerization, a propagating polymeris introduced to a thiocarbonylthio compound and two species are formed: a dormant chain and a new propagating chain. • This new radical reacts with a monomer to produce another propagating radical. • The two propagating radicals undergo rapid equilibrium along with the polymeric thiocarbonylthio compounds to produce chains in equilibrium.

  4. RAFT Process (cont.) • By controlling the amount of monomer, thiocarbonylthio compounds, and radicals that react, the molecular weight and structure of the polymer produced can be easily controlled. • Very cost effective and does not require overly-hazardous materials or conditions in order to undergo the reaction.

  5. Other Processes • Aside from RAFT, there are other lab procedures that I used throughout the Mentor Program, such as: • Cleaning Styrene/ Soybean Oil • Degasing Styrene • Using the ‘RotoVap’ machine • NMR machine • Initiator Crystalization

  6. Cleaning Styrene/Soybean Oil • Used to remove any contaminants& water from the fluid. • When cleaning Styrene, filling the filter tube with alumina . • Soybean Oil, however, requires the alternation of alumina and inhibitor removal (hydroquinone). • Argon is pumped through to help speed the process.

  7. RotoVap • Used to remove a liquid from a mixture of two liquids. • Difference in boiling points. • In our case, the removal of THF from the soybean oil after it has been cleaned. • Condenses it back into liquid form using liquid nitrogen, and then lets it drip into the flask at the bottom.

  8. Degasing Styrene • Set up and maintained the vacuum pump (using liquid nitrogen). • Used alteration of freezing and thawing under vacuum to remove any oxygen from the styrene

  9. AIBN • Azobisisobutyronitrile • It decomposes into two 2-cyanoprop-2-yl molecules (and nitrogen), that can each grow chains from their radicals.

  10. Initiator Crystallization • Simple process of dissolving the initiator (AIBN) in ethanol (at 40 degrees Celsius) for 15 minutes and then cooling rapidly to form a crystalline structure of the initiator. The ethanol is then filtered out so that just the initiator is left. • The crystalized AIBN produced is then used in the RAFT polymerization process.

  11. All Together… • After the soybean oil/styrene has been cleaned and RotoVap-ed, a pre-determined amount is dissolved in dioxane. • A pre-determined amount of AIBN (initiator) and CTA (radical) is also added. • The mixture is then heated and stirred for a given amount of time in order for the reaction to proceed and the desired molecular weight is reached.

  12. All Together…(cont.) • After the reaction is complete, a small sample is evaluated by GPC to determine the molecular weight of certain blocks within the entire molecule. • Polymer is precipitated in Methanol and Water and vacuum oven dried. • The dried polymer is redissolved and the second monomer is added with initiator and allowed to react. • Repeat!

  13. Results • Diblocks and Triblocks were synthesized with different molecular weights and different styrene/soy bean concentrations.

  14. NMR Machine • Uses magnetic field and the spin states of the nucleus (when introduced to a magnetic field) to determine the molecular weight of the compound and its structure. • Can also be used to determine the molecular weight of different compounds. • Dissolved a miniscule amount of substance into chloroform and then inserted it into top of machine.

  15. NMR (Continued) • When observing the graph output of the NMR machine, certain peaks (indicating presence of hydrogen molecules) are visible. • The integral of these peaks is equal to the molecular weight (as determined by a GPC machine) of a certain section of the molecule.

  16. Thanks! I would like to thank Dr. Cochran for giving me this opportunity to work for him and give me experience working in a lab. It has always been a dream of mine to go into research and discover new things and formulate new ideas. Also, I would like to personally thank Nacu for guiding me and showing me what it is like to work in a lab!

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