Discipline: Chemistry and Chemical Sciences
Subcategory: Materials Science
Usmaan Siddiqui - University of South Florida
Co-Author(s): Daniel Sunday, National Insitute of Standards and Technology, Gaithersburg, MD
Supramolecular polymers are unique compared to traditional polymers in that they are composed of key reversible and directional secondary bonding. Secondary bonds, most notably hydrogen bonds, can be fine-tuned and can consequentially alter the polymer’s material properties. Studies on self-assembly of linear chains with sidechain pendants (approximating the structure of graft polymer) typically use short small molecules for hydrogen bonding, yet it is unclear how well short polymers (<5K Daltons) will assemble. To study the impact of how sidechain length impacts supramolecular assembly, hydroxyl terminated polystyrene (PSOH) side chains were blended on to a poly-4-vinyl pyridine (P4VP) backbone. P4VP was chosen as the backbone due to the strength of the pyridine groups as an H-bond acceptor while PSOH of varying molecular weights were used as the pendant chains. Fourier transform infrared spectroscopy (FTIR) was primarily used to investigate the hydrogen bonding occurring in the blended samples. Employing FTIR methods provides fundamental results in analyzing the amount of the pyridine groups in P4VP that are participating in supramolecular self-assembly. Small angle neutron scattering (SANS) located at the NIST Center for Neutron Research (NCNR) was also used to track the mesoscopic solution structure. Final results from the FITR showed that a single hydrogen bond (OH-P4VP) appeared to be insufficient to drive self-assembly for even oligomeric polymer chains. These findings contrast from SANS results on a lauryl gallate (surfactant) polymer blends. These findings show promise in supramolecular graft polymer being based on the multiple hydrogen bonding sites. References: Rathgeber et al., J. Chem. Phys. 2005, 122, 124904 Vatankhah-Varnosfaderani et al, Science 2018, 359, 1509 Wei et al.,Science, 2015. 350, 6256, 72-75 Lee et al., Macromolecules 1988, 21, 4, 954-960 Ikkala et al., Marcomolecules 1995, 28, 7088-7094 Kuila et al., Marcomolecules 2010, 43, 7713-7721 Tung et al., Marcomolecules 2008, 41, 6453-6462
Funder Acknowledgement(s): National Institute of Standards and Technology Summer Undergraduate Research Fellowship (NIST-SURF)
Faculty Advisor: Dr. Daniel Sunday, firstname.lastname@example.org
Role: I performed elastic neutron scattering measurements on polymers at research reactor site. I collected spectroscopy data. I reduced and analyzed scattering data. I programmed a deconvolution algorithm that removed interferant noise from sample data. I prepared varied polymer samples for testing.