Dr. Jean Ruehl (née Waldbieser)
Nitroxide mediated radical polymerization (NMRP) utilizes alkoxyamine initiators to form polymers with well-controlled chain lengths and low polydispersities. This thesis is a study of the synthesis and polymerization kinetics of several novel alkoxyamines and their use in forming new materials.
Inside-out bidirectional alkoxyamine initiator 2.2 was synthesized and used in the polymerization of styrene, n-butyl acrylate, t-butyl acrylate, isoprene, and dimethylacrylamide. Symmetrical amphiphilic ABA triblock copolymers were prepared; addition of 2,2’-(ethylenedioxy)bis(ethylamine) resulted in AFM images of self-assembled structures.
A hybrid double-headed initiator containing an α-bromoester moiety and an alkoxyamine moiety was synthesized. Atom-transfer radical polymerization formed a poly(methyl methacrylate) macroinitiator. The polymerization kinetics of this macroinitiator compared to small molecule initiator TIPNO-St showed no significant difference.
Several outside-in bidirectional alkoxyamines with distal nitroxides were synthesized. The polymerization kinetics were identical to those of monodirectional initiator TIPNO-St. In contrast, outside-in bidirectional alkoxyamine 3.1 exhibited much faster polymerization rates. Low temperature EPR studies of the bisnitroxide 4.1 revealed an unusually strong radical-radical interaction, suggesting that the near proximity of the nitroxide moieties is responsible for the faster rate of polymerization. In comparing bisalkoxyamine 3.1 to TIPNO-St near 120°C, EPR measurements showed a dissociation rate constant approximately twice as large, whereas 1H-NMR investigations of the decomposition revealed a faster rate of decomposition. EPR decomposition studies at 120 ºC showed that bisnitroxide 4.1 decomposes much more quickly than TIPNO. The increased rates of dissociation and decomposition can be attributed to an intramolecular interaction between the proximal nitroxide moieties.
Carboxylic acid-functionalized alkoxyamine 5.17 and alcohol-functionalized alkoxyamine 5.18 were synthesized and used as initiators in NMRP. Post-polymer coupling of the end groups to pyrene dyes verified end group functionalization of greater than 90% by UV absorption. Poly(dimethylacrylamide) formed from initiator 5.17 was covalently linked to lysozyme to form a protein-polymer conjugate.
A 17-membered cyclic alkoxyamine 6.37 was synthesized and used to polymerize styrene. Polymerization with 6.37 resulted in a macropolymer in which multiple polymer chains are linked through NO-C bonds. EPR homolysis experiments showed that alkoxyamine 6.37 dissociates to form nitroxide, but its rate of dissociation is much slower than parent alkoxyamine TIPNO-St.
Ph.D. 2008: Alkoxyamine Initiators for Nitroxide Mediated Radical Polymerization: Synthesis, Characterization, and Applications
2004 NSF Graduate Fellowship
BS Chemical Engineering Cornell
Teach for America between undergrad and grad school
Jean is a professor at Diablo Valley College
Publications with the Braslau Group:
J. Ruehl, N. L. Hill, E. D. Walter, G. Millhauser, R. Braslau* “A Proximal Bisnitroxide Initiator: Studies in Low-temperature Nitroxide-Mediated Polymerizations” Macromolecules, 2008, 41, 1972-1982.doi: 10.1021/ma702358c http://tinyurl.com/cmbupv.
J. Ruehl, N. Ningnuek, T. Thongpaisanwong, R. Braslau* “Cyclic Alkoxyamines for Nitroxide Mediated Radical Polymerization,” Journal of Polymer Science Part A: Polymer Chemistry, 2008, 49, 8049-8069. doi: 10.1002/pola.23103.
J. Ruehl, C. Morimoto, D. J. Stevens, G. Millhauser, R. Braslau* “Carboxylic Acid and Hydroxy-Functionalized Alkoxyamine Initiators for Nitroxide Mediated Radical Polymerization,” Reactive & Functional Polymers 2008, 68, 1563-1577. doi:10.1016/j.reactfunctpolym.2008.08.010.
J. Ruehl; A. Nilsen; S. Born; P. Thoniyot; L. Xu; S. Chen; R. Braslau* “Nitroxide-Mediated Polymerization to Form Symmetrical ABA Triblock Copolymers from a Bidirectional Alkoxyamine Initiator” Polymer 2007, 48(9), 2564-2571.
J. Ruehl; R. Braslau* “A Bidirectional ATRP-NMRP Initiator: The Effect of Nitroxide Size on the Rate of Nitroxide-Mediated Polymerization” Journal of Polymer Science Part A: Polymer Chemistry, 2007, 45, 2015-2025. http://tinyurl.com/cjx4s4
R. Braslau,* G. O'Bryan, A. Nilsen, J. Henise, T. Thongpaisanwong, E. Murphy, L. Mueller, J. Ruehl “The Synthesis and Evaluation of New αll α-Hydrogen Nitroxides for "Living" Free Radical Polymerization” Synthesis, 2005, 9, 1496-1506. http://tinyurl.com/cm8ytr