Glassy Dynamics in Condensed Isolated Polymer Chains

Abstract

In the course of miniaturization down to the nanometer scale, much remains unknown concerning how and to what extent the properties of materials are changed. To learn more about the dynamics of condensed isolated polymer chains, we used broadband dielectric spectroscopy and a capacitor with nanostructured electrodes separated by 35 nanometers. We measured the dynamic glass transition of poly(2-vinylpyridine) and found it to be bulk-like; only segments closer than 0.5 nanometer to the substrate were weakly slowed. Our approach paves the way for numerous experiments on the dynamics of isolated molecules.

Calorimetric evidence for a mobile surface layer in ultrathin polymeric films: poly(2-vinyl pyridine)

“…A corresponding broadening was observed by dielectric spectroscopy employing nanostructured electrodes. 20 A closer inspection of the data for the 10 nm thick film reveals that there is a small shoulder at T À T Max = 28 K (T = 424 K). This shoulder is found at the same temperature frequency position, where for the nanocomposites of P2VP with silica nanoparticles, discussed in ref.…”

“…The selected polymer here is similar to the material used in ref. 20 and allows therefore a direct comparison of the dielectric data. For the AC-chip calorimetry, the sensors were first mounted on the spincoater, a few drops of chloroform were added in the center, and then spin coated to rinse dust and organic contaminations.…”

“…In a recent perspective discussion by Ediger et al, 11 the progress made in the last years was discussed (see for instance ref. [12][13][14][15][16][17][18][19][20].…”

Humidity-dependent compression-induced glass transition of the air–water interfacial Langmuir films of poly(d,l-lactic acid-ran-glycolic acid) (PLGA)

“…With water acting as a plasticizer for the PLGA material, the diffusion of water molecules through the PLGA film appears to be the key factor determining the glass transformation property and thus the mechanical response of the PLGA film against lateral compression. Based on our combined results, we hypothesize the following mechanism for the compression-induced glass transformation of the Langmuir PLGA film; (1) initially, a humidified/non-glassy PLGA film is formed in the full surface-coverage region (where the surface pressure shows a plateau) during compression; (2) further compression leads to the collapse of the PLGA chains and the formation of new surfaces on the air side of the film, and this newly formed top layer of the PLGA film is transiently glassy in character because the water evaporation rate in the top surface region is momentarily faster than the humidification rate (due to the initial roughness of the newly formed surface); (3) after some period of time, the top layer itself becomes humidified through diffusion (formed by polymers possessing "amphiphilic" character) transforms into a multi molecular layer. 3 Using the Langmuir film balance technique, the surface/interfacial tension of a Langmuir polymer monolayer can be measured as a function of monolayer area.…”

New insight into relaxation dynamics of an epoxy/hydroxy functionalized polybutadiene from dielectric and mechanical spectroscopy studies

“…In particular, information sourced from a variety of experimental methods seems to be helpful in categorizing and understanding these relaxation mechanisms. Among other methods, dielectric spectroscopy is systematically used to study the dynamics of polymer melts because of a broad range of accessible frequencies and a high sensitivity, both of which enable very accurate measurements [3, 4]. Multiple relaxation peaks can usually be distinguished in the dielectric spectra of dipolar polymers [5–7].…”