Dynamics of Entangled cis-1,4-Polyisoprene Confined to Nanoporous Alumina
Autor(en): | Politidis, Christos Alexandris, Stelios Sakellariou, Georgios Steinhart, Martin Floudas, George |
Stichwörter: | ANODIC POROUS ALUMINA; CHAIN DYNAMICS; DEPENDENCE; DIBLOCK COPOLYMER; DIELECTRIC-RELAXATION; GLASS-TRANSITION TEMPERATURE; INTERFACIAL ENERGY; MOBILITY; POLYISOPRENE; Polymer Science; THIN POLYMER-FILMS | Erscheinungsdatum: | 2019 | Herausgeber: | AMER CHEMICAL SOC | Journal: | MACROMOLECULES | Volumen: | 52 | Ausgabe: | 11 | Startseite: | 4185 | Seitenende: | 4195 | Zusammenfassung: | The dynamics of a series of entangled cis-1,4-polyisoprenes located within self-ordered nanoporous alumina templates are studied as a function of the degree of confinement, 2R(g)/d (R-g is the radius of gyration and d is the pore diameter) with dielectric spectroscopy and temperature-modulated differential scanning calorimetry. For the higher molecular weights, the segmental dynamics obtained on cooling speed-up under confinement resulting in a lower glass temperature, T-g, with respect to the bulk, scaling as Delta T-g = -62 X (2R(g)/d). This effect is discussed in terms of the proposed relation of the glass temperature to the interfacial energy. Under confinement, a new process appears with an Arrhenius temperature dependence and with a dielectric strength that increases linearly with the increasing degree of confinement. This mode is discussed in terms of the adsorption/desorption kinetics of segments in the vicinity of the pore walls. The particular geometry employed here with the electric field being parallel to the polymer/surface interface maximizes the contribution of adsorbed segments. Moreover, with temperature-modulated differential scanning calorimetry and dielectric spectroscopy, we address the origin of the dual glass temperature, T-g, found on the heating traces. By employing several temperature/annealing protocols, we show that the higher T-g is conditional; it appears only when the lower T-g is crossed on the previous cooling run. These findings could suggest that the lower T-g is the one closer to equilibrium. |
ISSN: | 00249297 | DOI: | 10.1021/acs.macromol.9b00523 |
Zur Langanzeige
Seitenaufrufe
2
Letzte Woche
0
0
Letzter Monat
0
0
geprüft am 20.05.2024