Cellulose nanocrystals (CNCs) have been exploited due to their natural assembly to helicoidal structures that have potential applications in advanced materials. However, the persistent layer of water surrounding CNC rods hinder effective interfacial adhesion between CNCs and polymer systems, compromising efficient stress transfer between the two components. Understanding the interplay between water and local polymer dynamics at the CNC-polymer interface is paramount to optimizing macroscopic mechanical performance. Therefore, we designed a series of CNC composites with poly(diethylene glycol methyl methacrylate) (PMEO2MA), a thermoresponsive polymer with lower critical solution temperature of 26 oC in water. By incorporating a water sensitive dye (RhB) into the thermoresponsive polymer, we were able to use fluorescence lifetime imaging microscopy (FLIM) to probe the local dynamics in response to water. Nanocomposite films containing 5% to 100% weight percent of blended and grafted PMEO2MARhB were prepared via controlled evaporation-induced self-assembly. In blended PMEO2MARhB-CNC system, the fraction of confined polymers at the CNCs interface decreases with increasing polymer loading, resulting in shorter fluorescence lifetimes. On the contrary, longer fluorescence lifetimes were observed for grafted PMEO2MARhB-CNC due to polymer chains being restricted to the CNC rods’ surface. Observation of transient polymer dynamics was performed by exposing the nanocomposite films to variation of relative humidity.

Dynamics of blended versus grafted thermo-responsive polymers in cellulose nanocrystal nanocomposites

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.