Calorimetric characterization of nanoconfined melts, glasses and reactive monomers

Date

2019-12

Journal Title

Journal ISSN

Volume Title

Publisher

Abstract

Nanoconfined materials exhibit altered and interesting behavior different from the bulk. Understanding the behavior of nanoconfined materials is of great importance to both nanoscience and nanotechnology communities. The work in this dissertation aims to elucidate the effects of nanoconfinement on melting, the glass transition and associated structural relaxation kinetics, and reactivity using Flash and conventional differential scanning calorimetry. The feasibility of anodic aluminum oxide nanopores (AAO) as a form of 2D nanoconfinement on the Flash DSC is investigated by studying the melting behavior of n-hexadecane and n-nonadecane. Depressed melting and solid-solid transition temperatures are observed in the AAO nanopores, validating the use of AAO nanopores as a nanoconfinement matrix on the Flash DSC. The results suggest an abnormal melting behavior in the AAO nanopores which is investigated using X-ray diffraction. The glass transition behavior of 20, 55, and 350 nm AAO supported and stacked polystyrene (PS) nanorods is studied using Flash DSC. The results indicate that the glass transition temperatures are depressed for stacked PS nanorods which are less than 100 nm diameter; on the other hand, bulk-like behavior is observed for AAO supported PS nanorods irrespective of rod diameter. The effect of spatial dimensionality on glass transition behavior is also investigated. The structural recovery kinetics of 20 and 350 nm stacked PS nanorods is investigated using Flash differential scanning calorimetry. The results indicate an enhanced overall structural recovery rate for 20 nm stacked PS rods when compared to 350 nm stacked PS rods. The importance of comparing structural recovery rates at same distances from their respective glass transition temperature is also highlighted. In addition, the effect of spatial dimensionality on structural recovery is also discussed using a relaxation time map of average relaxation times, induction times, and time to reach equilibrium. The reaction kinetics of step-growth linear epoxy polymerization is studied in CPG nanopores using conventional DSC. The results indicate an enhanced reaction in the nanopores. The glass transition behavior of cured linear epoxy polymer in CPG nanopores is also studied. In addition to the nanoconfinement effects, the current controversies regarding the mechanisms of structural recovery are also investigated using Flash differential scanning calorimetry.

Description

Keywords

Flash differential scanning calorimetry, Nanoconfinement

Citation