Restricting Molecular Mobility in Polymer Nanocomposites with Self-Assembling Low-Molecular-Weight Gel Additives

Symone L M Alexander; LaShanda T J Korley

doi:10.1021/acsami.8b15112

Restricting Molecular Mobility in Polymer Nanocomposites with Self-Assembling Low-Molecular-Weight Gel Additives

ACS Appl Mater Interfaces. 2018 Dec 12;10(49):43040-43048. doi: 10.1021/acsami.8b15112. Epub 2018 Nov 30.

Authors

Symone L M Alexander¹, LaShanda T J Korley^{1

2}

Affiliations

¹ Department of Materials Science and Engineering , University of Delaware , Newark , Delaware 19716 , United States.
² Department of Chemical and Biomolecular Engineering , University of Delaware , Newark , Delaware 19716 , United States.

PMID: 30499650
DOI: 10.1021/acsami.8b15112

Abstract

Multiscale investigation of molecular gel additives in polymer matrices guides understanding of how solution-state assemblies result in mechanically enhanced, solid-state nanocomposites. Model polymers, poly(ethylene oxide- co-epichlorohydrin) (EO-EPI) and poly(vinyl acetate) (PVAc), were utilized as matrices and reinforced by cholesterol-pyridine (CP) nanofiber networks. The CP nanofillers suppress ethylene oxide segment melting for EO-EPI composites, whereas for PVAc nanocomposites, cause a polymer-gel dissociation transition. Incorporation of crystalline CP fiber networks led to an order of magnitude increase in tensile storage modulus due to restrictions on polymer chain mobility. This decrease in molecular mobility was confirmed by decreased loss moduli for both EO-EPI and PVAc composites. Excitingly, PVAc nanocomposites display an additional relaxation mode caused by release of PVAc chains from the transient molecular gel assembly. For both EO-EPI and PVAc composites, bulk flow can be suppressed to temperatures up to 100 °C by simply increasing the CP concentration.

Keywords: low-molecular-weight gels; molecular gel; nanofibers; polymer nanocomposite; self-assembly.