Molecular and Charge Mobility of a Poloxamer in the Bulk and as Soft Component in Polyurethanes

Publication date: Available online 18 September 2019Source: PolymerAuthor(s): Konstantinos N. Raftopoulos, Izabela Łukaszewska, Panagiotis Α. Klonos, Edyta Hebda, Artur Bukowczan, Apostolos Kyritsis, Krzysztof PielichowskiAbstractAn amphiphilic PEO-b-PPO-b-PEO copolymer (poloxamer) is used as the soft phase of a biocompatible polyurethane matrix. The molecular and charge transport dynamics of the polyurethanes and the copolymer is studied in detail by broadband dielectric spectroscopy and differential scanning calorimetry. Various fitting techniques and formalisms are used for the extraction of data from the obtained dielectric spectra. As a result of incomplete phase separation, the glass transition of the polyurethanes occurs 10 K higher than that of the copolymer. The dynamic glass transition of the copolymer (α relaxation) is accompanied by a normal mode relaxation. When the poloxamer is constrained as part of the polyurethane chain, a process slower than α is observed and is likely associated with the normal mode relaxation despite a very significant spectral broadening. The dynamics of the α relaxation and this process does not depend significantly on the soft:hard segment ratio suggesting only minor differences in the consistency of the soft phases. The charge transport mechanism is similar to that of the neat copolymer for high soft segment contents, whereas for the 50 wt% material it changes, presumably as a result of a radical change in morphology.Graphical abs...

Source: Polymer - September 19, 2019 Category: Chemistry Source Type: research