Molecular Dynamics of Janus Polynorbornenes: Glass Transitions and Nanophase Separation

Abstract

For the first time, dielectric and calorimetric investigations of a homologous series of Janus polynorbornenes with rigid main backbones and flexible −Si(OR) 3 side groups of differing length alkyl chains (R = propyl, butyl, hexyl, octyl, and decyl) is reported. Generally, this class of polymers has some potential for applications in the field of gas separation membranes. Two dielectrically active processes are observed at low temperatures, denoted as βand α-relaxation. The former can be assigned to localized fluctuations, while the latter is related to the glassy dynamics of the flexible −Si(OR) 3 side groups, creating a nanophase separation in both the alkyl chain-rich and backbone-rich domains. This is confirmed through temperature-modulated differential scanning calorimetry (TMDSC) measurements and X-ray scattering experiments. The glass transition temperatures of the backbone rich domains, which are beyond or near to their degradation temperatures in terms of conventional DSC, are determined for the first time using fast scanning calorimetry employing both fast heating and cooling rates. This is complemented with scattering experiments that show how the size of the alkyl chain-rich domains increases with the side chain length. Alongside these results, a significant conductivity contribution was observed for all poly(tricyclononenes) with −Si(OR) 3 side groups, which is interpreted in terms of a percolation model.

Side Chain Length-Dependent Dynamics and Conductivity in Self-Assembled Ion Channels

“…The appearance of a glass transition indicates a certain disorder present in the material where this disorder in the ILCn is due to nanophase separation between the flexible alkyl side chains and the rigid aromatic cores. Such a nanophase separation has been previously reported for other materials such as homologous series of polymers bearing different alkyl chain length, 29,30 other discotic liquid crystals 31−35 and for recently investigated ILCs. 15 Molecular Mobility.…”

“…(b) d spacing values as function of the alkyl chain length. Spheres: ILC n ; open circles: HATn in the columnar phase taken from ref , Rhombus: Janus polynorbornenes (taken from ref ); up-pointing triangles: poly­( n -alkyl methacrylate); solid line: alkyl chain length in all trans configuration. Data for poly­( n -alkyl methacrylate) and all trans configuration of alkyl chains are taken from ref .…”

Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry

“…9 On the one hand, the former effect leads to nanophase separation, which has been confirmed by X-ray diffraction (XRD) for CLCs including HATn 9,10 as well as for different polymers possessing long n-alkyl side chains in their structure. [11][12][13][14] On the other hand, the favorable π-π interaction results in 1D high charge mobility along the column direction originating from the delocalization of π-electrons in the π-π stacked system of the HATn molecules in the Colh phase, where the flexible alkyl chains fill the intercolumnar area and are disordered among ordered columns of the cores (see Figure 1b). Majority of the studies reported in the literature regarding triphenylene-based DLCs HATn concentrate on the synthesis, the structure, the charge carrier mobility and the phase behavior of these materials.…”

Molecular mobility in high‐performance polynorbornenes: A combined broadband dielectric, advanced calorimetry, and neutron scattering investigation*

“…It was proven that FSC enables to decouple the kinetics of degradation from other effects like melting, [37,38] the glass transition , [39][40][41] or the chain dynamics. [42,43]…”

“…It should be noted that the influence of the polymerization mechanism (addition or metathesis) on the molecular mobility was discussed recently. [27] 2 | MATERIALS AND METHODS…”