Structural Insights into Polymethacrylamide-Based LCST Polymers in Solution: A Small-Angle Neutron Scattering Study

Copolymerization is a powerful method that offers access to new polymer materials with a tailored response to external stimuli like temperature and pH. Polymers with a lower critical solution temperature are well known to undergo a coil-to-globule transition when the temperature is raised above the transition temperature. In particular, for copolymers, complex inter- and intrachain interactions may complicate this simple picture of a single-chain phase transition. In this work, we study the phase transition of poly­((methylacrylamide)-stat-(N-cyclohexylacrylamide)) copolymers at different concentrations in heavy water by using small-angle neutron scattering. Measurements are performed well below and above the respective cloud points of polymers with two different molecular weights. We show that interchain interactions are already present below the cloud point even in the dilute regime. Above the cloud point, polymer–polymer interactions become more prominent and polydisperse aggregates form.