Polyurethanes with POSS pendent on flexible hard segments: Morphology and glass transition

• Published in: Polymer (Guilford) Vol. 147; pp. 225 - 236
• Main Authors: Koutsoumpis, Stefanos, Ozimek, Jan, Raftopoulos, Konstantinos N., Hebda, Edyta, Klonos, Panagiotis, Papadakis, Christine M., Pielichowski, Krzysztof, Pissis, Polycarpos
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 04.07.2018; Elsevier BV
• Subjects: Copolymers; Diisocyanates; Glass; Glass transition; Hardness testing; Heat measurement; Hexamethylene diisocyanate; Microscopy; Molecular dynamics; Morphology; Polyurethane; Polyurethane resins; POSS; Glass transition; Polyurethane; POSS
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2018.06.012

Polyhedral Oligomeric Silsesquioxanne (POSS) moieties are tethered on a polyurethane chain, as side groups on the hard domains, which are based on the flexible hexamethylene diisocyanate (HDI). Their effect on morphology, and consequently on molecular dynamics, is studied in detail by microscopy, scattering, spectroscopic, thermal, and dielectric techniques. Albeit the PU micromorphology does not change radically, POSS-rich domains are formed. The segmental dynamics is severely slowed down in a continuous manner, i.e. without the emergence of a new, distinct relaxation, as was the case in a similar system based on the aromatic methylene diisocyanate (MDI). Strikingly, the slowed down components do not seem to have any calorimetric footprint, and hence the calorimetric Tg remains practically unaffected. The linear HDI systems have faster dynamics in the soft phase, as compared to the aromatic MDI ones, presumably owing to higher flexibility and better microphase separation. [Display omitted] •POSS moieties, pendent on PU with aliphatic diisocyanate reduce microphase separation.•Glass transition temperature increases weakly with increasing POSS content.•α-relaxation slows down considerably, but its slow components have a weaker thermal response.•No separate slow relaxation is detected contrary to systems with aromatic diisocyanate.