In Situ Electron Microscopy of Poly(ethylene glycol) Crystals Grown in Thin Ionic Liquids Films. Issue 3 (7th January 2020)

• Record Type: Journal Article
• Authors: Srivastava, Satyam; Ribbe, Alexander E.; Russell, Thomas P.; Hoagland, David A.
• Is Part Of: Journal of polymer science. Volume 58:Issue 3(2020)
• Page Start: 478
• Page End: 486
• Publication Date: 2020-01-07
• Subjects: crystallization -- electron microscopy -- gels -- ionic liquids; Polymers -- Periodicals; Polymerization -- Periodicals; Polymerization; Polymers; Periodicals; 547.7
• DOI: 10.1002/pol.20190120
• Languages: English
• ISSNs: 2642-4150

Abstract

ABSTRACT: Crystals of poly(ethylene glycol) grown in thin films of the room temperature ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium ethyl sulfate were examined by electron microscopy as a first step toward exploiting nonvolatile liquids for nanoscale imaging of solvated/dissolved polymeric materials. The crystals were generated by cooling supported (over surfaces of varied polarity) and freestanding solution films to room temperature. This "open, " that is, without liquid cell, microscopy was performed on unstained, as‐grown crystals in the presence of the IL. A variety of nearly two‐dimensional crystal morphologies were observed, including rods, fibers, spherulites, compact faceted single crystals, and interconnected networks, with characteristic sizes ranging from tens of nanometers to tens of microns. Electron diffraction patterns for the rods and fibers revealed single crystal‐like long‐range order. The nature of the IL support little affected the morphology, but film thickness and cooling rate proved important. To assess the role of solvent polarity, crystals were also grown from 1‐ethyl‐3‐methylimidazolium ethyl sulfate mixed with the second IL, the less polar ethyl‐tributyl‐phosphonium diethyl phosphate; here, although the morphologies were similar to those made with pure IL, fibrillar morphologies were more prevalent. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 478–486 Abstract : Poly(ethylene glycol) crystals were grown in thin ionic liquid (IL) films and observed in the transmission electron microscope in the absence of a liquid cell. A variety of crystalline morphologies including rod‐like, spherulitic, fiber‐like, and network‐like were observed. A predominant transition to fiber‐like morphology was observed in a binary mixture of ILs.