Journal
POLYMER
Volume 230, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.polymer.2021.124042
Keywords
Polyurethane; POSS; Diels-alder reactions; Shape memory properties; Reprocessing properties
Categories
Funding
- Natural Science Foundation of China [21774078, 51973113, 51133003, 10sr0260, 10sr0126]
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A novel organic-inorganic polyurethane thermoset crosslinked with a difunctional polyhedral oligomeric silsesquioxanes (POSS) was synthesized via Diels-Alder (DA) reaction. The resulting DAPU-DDSQs displayed improved thermomechanical properties and shape memory properties with increasing 3,13-dimaleimido DDSQ incorporation. The reprocessing properties of the DAPU-DDSQs at the temperature of retro DA reaction allow for the re-editing of the original shapes of shape memory PUs.
In this work, a novel organic-inorganic polyurethane thermoset crosslinked with a difunctional polyhedral oligomeric silsesquioxanes (POSS) was synthesized via Diels-Alder (DA) reaction. First, a linear multi-segmented polyurethane with furan rings in the main chain (PU-F) was synthesized via the step-growth polymerization of 4,4'-diphenylmethane diisocyanate (MDI) with poly(tetramethylene ether glycol) (PTMEG) and 2,5-furandimethanol. Second, 3,13-dimaleimido octaphenyl double decker silsesquioxane (3,13-dimaleimido DDSQ) was synthesized and used as the crosslinker of the linear PU-F. By adjusting the feed ratio of the difunctional POSS macromer (i.e., 3,13-dimaleimido DDSQ) to PU-F, the organic-inorganic PU thermosets (denoted DAPU-DDSQs) with variable densities of crosslinking were obtained. It was found that the DAPU-DDSQs were microphaseseparated and that POSS cages were aggregated into the spherical microdomains, the sizes of which were 20-40 nm in diameter. It was demonstrated that the crosslinking in the DAPU-DDSQs had two aspects of contribution: i) the chemical crosslinking with D-A adducts between 3,13-dimaleimido DDSQ and PU-F and ii) the physical crosslinking with POSS microdomains via the aggregation of POSS cages. The DAPU-DDSQs displayed the improved thermomechanical properties with increasing 3,13-dimaleimido DDSQ incorporation. Owing to the formation of crosslinked structures, the DAPU-DDSQs displayed excellent shape memory properties. More importantly, the DAPU-DDSQs displayed the reprocessing (or recycling) properties at the temperature of retro DA reaction. The reprocessing properties of the DAPU-DDSQs can be utilized to re-edit the original shapes of shape memory PUs.
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