AbstractsChemistry

Abstract

I introduce and demonstrate a novel detector for characterization of lower critical solution temperature (LCST) behavior during synthesis. This new detector acts in concert with Automatic Continuous Online Monitoring of Polymerization (ACOMP) to correlate LCST behavior with other properties of the polymer system. As a result, the new detector system is called “Second generation ACOMP” (SGA). This allows me to observe, for the first time ever, LCST behavior of a polymer during synthesis. ACOMP works by extracting a small stream of sample from a polymerization reaction, diluting it, and passing it through several detectors. This allows rapid characterization of molecular weight (Mw), radius of gyration (Rg), second virial coefficient (A2), and viscosity. For copolymers, ACOMP also characterizes the comonomer composition and comonomer composition drift. The SGA detectors consist of three temperature-controlled single-angle light scattering flow cells. These allow the characterization of polymer aggregation due to LCST effects. The onset and temperature of this effect can be correlated to the more basic properties (primarily composition) of the polymer. I use this detector to characterize the composition dependence of the LCST of poly(N-isopropyl acrylamide) (pNIPAM). I copolymerize NIPAM with the neutral, hydrophilic comonomer Acrylamide (Am), the anionic comonomer styrene sulfonate (SS), and the cationic comonomer [2-(acryloyloxy)ethyl]-trimethylammonium chloride (Q9). The effect of each of these comonomers on the LCST is compared. In addition, I compare the effect of ionic strength on the LCST of each of the copolymer systems.