The synthesis of unsaturated Friedel - Crafts polymers

A study has been undertaken to establish whether it is possible to introduce unsaturation into Friedel - Crafts ( F/C) polymers, so that they can be cured free - radically via the unsaturation. It was hoped that the hydrocarbon - only nature of the polymer backbone, and the absence of hydrophilic cure catalysts would produce a material of low water absorption. The introduction of unsaturation has been approached in two ways. The first was to synthesize Friedel - Crafts prepolymers with ethyl side - chains. The side - chains were then tb be chlorinated, and then dehydrochlorinated to produce vinyl unsaturation. The introduction of vinyl unsaturation by this method was concluded to be unsatisfactory, due to the ease of premature crosslinking of the vinyl polymer during dehydrochlorination. The second method of introducing unsaturation was to include an allyl aromatic monomer in a F/C polymerisation. Such allyl F/C prepolymers were successfully prepared, characterised, and crosslinked. The need for a high cure temperature, and the consequent ease of oxidation make the radical cure of the allyl polymers inconvenient. They may be cured at lower temperatures, without oxidation, by cross linking them via a cationic mechanism. A study of the 13 C NMR spectrum of an F/C polymer has yielded new information on the branched structure and on the routes by which the polymer is built from monomer units.