Conformation Transitions of Thermoresponsive Dendronized Polymers across the Lower Critical Solution Temperature

Abstract

Thermoresponsive dendronized polymers, displaying remarkable phase behavior, are currently being studied for their potential exploitation as polymeric sensors and biomaterials. Understanding the conformational transitions occurring at the LCST is essential for improved design and translation of these polymers. The combination of NMR and molecular dynamics simulations opens a unique window onto the thermal behavior, showing that the peripheries of the dendrons, while driving the thermal properties, largely retain mobility above the critical temperature. The cores of the dendrons and the polymeric main chain are highly rigid below the thermal transition and increasingly so above the LCST. Both the experimental and computational studies reveal stretching of the interior segments of the dendrons with associated changes in spatial arrangements of the structural units. Furthermore, diffusion-ordered NMR and DLS below and above the LCST show a further hierarchy of dynamics within different size aggregates. The combination of the detailed experimental study and molecular dynamics simulations provides a detailed understanding of thermoresponsive behavior of these dendronized polymers.