Temperature Dependent Single-Chain Structure of Poly(3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate) via SANS
Phillip Pickett, Yuanchi Ma, Michael Lueckheide, Yimin Mao, Vivek Prabhu
Responsive polyzwitterionic materials have become important for a range of applications such as environmental remediation and targeted drug delivery. Much is known about the macroscopic phase-behaviors of such materials but how the smaller scale single-chain structure of polyzwitterions respond to external stimuli is not well understood, especially at temperatures close to their phase boundaries. Such chain conformation responses are important in directing larger-scale associative properties. Here, we study the temperature dependent single-chain structure of a model polysulfobetaine, poly(3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate) (pAPAPS), using small angle neutron scattering. In the absence of salt, we find that temperature has a large effect on solvent quality with a decreasing trend from good solvent conditions at 50 °C to poor solvent at 10 °C (a temperature just above the cloud point of 7.6 °C), and an estimated theta temperature of 40 °C. When 100 mM NaCl is present, the solvent quality is good with weak temperature dependence. Without salt present, the polymer chain appears nearly Gaussian coil conformation and the backbone becomes slightly more rigid as the temperature is lowered to the cloud point as determined by the Debye-Local Rod on a Kratky plot. The addition of salt has significant effects on the smaller scale intra-chain correlations in which an increase in chain dimensions to a swollen coil conformation and an increase in chain rigidity is observed at 100 mM NaCl in D2O, however with a weak temperature dependence.
, Ma, Y.
, Lueckheide, M.
, Mao, Y.
and Prabhu, V.
Temperature Dependent Single-Chain Structure of Poly(3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate) via SANS, Journal of Chemical Physics, [online], https://doi.org/10.1063/5.0093158, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=934364
(Accessed December 6, 2023)