Well, it has certainly been an informative and productive first day of polymer research! Arrived on the third floor of Milliken at precisely 9:13 this morning to meet with my advisor - the great Dr. Bass - and determine my group's goals for the immediate future. Though we certainly have a plan of what we hope will transpire over the course of the month of January, we also realize that our schedule will need to be flexible based on the success of our syntheses and reaction mechanisms.
Fortunately, there are a few things that we can say right off the bat.
So let's begin with...definitions!
- Polymer: Taken from the Greek polus ("many") and meros ("parts"), a chemical compound consisting of repeating structural units. Examples include rubber, cellulose, nylon, PVC, and silicone.
- Monomer: The structural unit.
- Polymerization: The process of linking monomers to make a polymer.
Those were hopefully fairly straightforward, but the remaining definitions are very specific and technical.
- Ester: An organic compound characterized by one carbon connected to a carbon and an oxygen by single bonds and another oxygen by a double bond.
- Lactone: A cyclic ester.
- Caprolactone: A lactone formed from caproic acid (also known as hexanoic acid). Contains six carbons in its backbone.
- Ring-opening polymerization: The polymerization process facilitated by opening the cyclic structure and connecting monomers at the break point.
- Substituent: An additional group attached to the primary compound.
At this point in the process, it would be beneficial to mention how these vocabulary terms are connected. The goal of this project is to synthesize four substituted caprolactones and separately polymerize them. According to current research being conducted at College of Charleston under Dr. Van Horn and other publicized studies (see below), rate of polymerization - and polymerization in general - could be impacted by the bulkiness of the substituent on the ring. Essentially, the bigger the lactone, the slower the rate of polymerization. In order to test this hypothesis, each member of my group will be synthesizing one of these four monomers.
The monomer I will be investigating is 7-benzyloxepan-2-one. In order to synthesize this molecule, I will begin with simple cyclohexanone and lithium diisopropylamide (LDA). The important thing to know about these reagents is that an incredibly strong base will form as a result, which will react quite nicely with the compound chlorotoluene (more commonly, benzyl chloride). The desired monomer, minus the additional oxygen that makes it a lactone, should result.
From there, a reaction called the Baeyer-Villager oxidation will be employed to convert 2-benzylhexanone into 7-benzyloxepan-2-one, and a catalyst will be added to the reaction vessel to begin the polymerization process.
In later entries, I will detail the techniques and apparatuses that my group uses to carry out these reactions. Tomorrow, we plan to learn how to operate the infrared radiation (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy instruments that will be used to characterize our compounds as we go along. Until next time!
Publications:
Martello, Mark T., Adam Burns, and Marc Hillmyer. "Bulk Ring-Opening Transesterification Polymerization of the Renewable δ-Decalactone Using an Organocatalyst." ACS Macro Letters 1 (2012): 131-134.
Wang, Cui, Yan Xiao, Andreas Heise, and Meidong Lang. "Organometallic and Enzymatic Catalysis for Ring Opening Copolymerization of ε-Caprolactone and 4-methyl-ε-Caprolactone." Journal of Polymer Science 49 (2011): 5293-5300.
Peeters, Joris W., Oscar van Leeuwen, Anja R. A. Palmans, and E. W. Meijer. "Lipase-Catalyzed Ring-Opening Polymerizations of 4-Substituted ε-Caprolactones: Mechanistic Considerations." Macromolecules 38 (2005): 5587-5592.
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