Poly(urethane-norbornene) Aerogels via Ring Opening Metathesis Polymerization of Dendritic Urethane-Norbornene Monomers: Structure-Property Relationships as a Function of an Aliphatic Versus an Aromatic Core and the Number of Peripheral Norbornene Moieties

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Μονάδα:
Τμήμα Χημείας
Τίτλος:
Poly(urethane-norbornene) Aerogels via Ring Opening Metathesis Polymerization of Dendritic Urethane-Norbornene Monomers: Structure-Property Relationships as a Function of an Aliphatic Versus an Aromatic Core and the Number of Peripheral Norbornene Moieties
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
We report the synthesis and characterization of synthetic polymer aerogels based on
dendritic-type urethane-norbornene monomers. The core of those monomers is based either on
an aromatic/rigid (TIPM/Desmodur RE), or an aliphatic/flexible (Desmodur N3300) triisocyanate.
The terminal norbornene groups (three at the tip of each of the three branches) were polymerized via
ROMP using the inexpensive 1st generation Grubbs catalyst. The polymerization/gelation conditions
were optimized by varying the amount of the catalyst. The resulting wet-gels were dried either
from pentane under ambient pressure at 50 oC, or from t-butanol via freeze-drying, or by using
supercritical fluid (SCF) CO2. Monomers were characterized with high resolution mass spectrometry
(HRMS), 1H- and solid-state 13C-NMR. Aerogels were characterized with ATR-FTIR and solid-state
13C-NMR. The porous network was probed with N2-sorption and SEM. The thermal stability of
monomers and aerogels was studied with TGA, which also provides evidence for the number of
norbornene groups that reacted via ROMP. At low densities (<0.1 g cm-3) all aerogels were highly
porous (porosity > 90%), mostly macroporous materials; aerogels based on the aliphatic/flexible core
were fragile, whereas aerogels containing the aromatic/rigid core were plastic, and at even lower
densities (0.03 g cm-3) foamy. At higher densities (0.2–0.7 g cm-3) all materials were stiff, strong,
and hard. At low monomer concentrations all aerogels consisted of discrete primary particles that
formed spherical secondary aggregates. At higher monomer concentrations the structure consisted of
fused particles with the size of the previous secondary aggregates, due to the low solubility of the
developing polymer, which phase-separated and formed a primary particle network. Same-size fused
aggregates were observed for both aliphatic and aromatic triisocyanate-derived aerogels, leading to
the conclusion that it is not the aliphatic or aromatic core that determines phase separation, but rather
the solubility of the polymeric backbone (polynorbornene) that is in both cases the same. The material
properties were compared to those of analogous aerogels bearing only one norbornene moiety at the
tip of each branch deriving from the same cores.
Έτος δημοσίευσης:
2018-01-01
Συγγραφείς:
Aspasia Kanellou
George C. Anyfantis
Despoina Chriti
Grigorios Raptopoulos
Marinos Pitsikalis
Patrina Paraskevopoulou
Περιοδικό:
Molecules: A Journal of Synthetic Organic Chemistry and Natural Product Chemistry
Εκδότης:
MDPI
Τόμος:
23
Αριθμός / τεύχος:
5
Σελίδες:
1007
Λέξεις-κλειδιά:
aerogels, dendritic monomers, ring opening metathesis polymerization (ROMP), polymeric materials, ruthenium
Κύρια θεματική κατηγορία:
Θετικές Επιστήμες
Επίσημο URL (Εκδότης):
Στοιχεία έργου:
This project has received funding from the European Union’s Horizon 2020 research and
innovation programme under grant agreement No. 685648.
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