Triptycene-based polymers of intrinsic microporosity for membrane applications
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Date
29/11/2016Author
Rose, Ian James
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Abstract
This project was focused on the synthesis of novel Polymers of Intrinsic
Microporosity (PIMs) that are soluble in common low boiling point solvents so that self-standing
films can be prepared for gas permeability measurements. The common building
unit of these novel PIMs was triptycene and its derivatives. Modification of these
triptycene compounds enabled the alteration of the polymeric backbone, so that we could
tune the gas permeability properties. Modifications included the substitution of different
functional groups (e.g. addition of methyl groups) and also the extension via
benzoannulation of the triptycene structure.
The synthesis of the PIMs was based around three different polymerisation
techniques. The first one involved the formation of triptycene-based polyimides (PIs) using
a triptycene based dianhydride, prepared in a multistep synthesis. Shorter and cheaper
synthetic routes were attempted, but all to no avail. The resulting triptycene monomer was
reacted with a variety of commercial and non-commercial bisanilines for the formation of
several PIM-PIs, all exhibiting different performances. Robust self-standing films were
obtained for two of these PIM polyimides.
In addition to the formation of polyimides, the synthesis of Tröger’s Base (TB)
polymers, also based on triptycene components, were achieved. This type of
polymerisation involves the reaction between a “bisaniline” monomer and a source of
“formaldehyde”, such as dimethoxymethane (DMM), in a strong acid media, typically
trifluoroacetic acid (TFA). Modification of these triptycene-based bisanilines has led to the
formation of TB-PIMs, all with distinctive gas permeation properties. TB-PIM copolymers
(reaction between two different bisaniline monomers with DMM and TFA) were
synthesised in an attempt to further tune the performance of the polymers.
Finally, the preparation of polybenzodioxan polymers based around extended
triptycene monomers (i.e. benzotriptycenes) was studied. By using a variety of substituted
benzotriptycene biscatechol monomers and performing the polymerisation using
tetrafluoroterephthalonitrile, in the presence of K2CO3, the synthesis of a series of
substituted benzotriptycene polybenzodioxane polymers was successfully achieved and the
polymers showed enhanced gas permeation properties.