Design, synthesis, and characterization of reactive aromatic polymers.

Abstract

The research presented in this manuscript is aimed towards the design and synthesis of reactive aromatic precursor polymers. These precursor polymers have been designed to contain latently reactive functional groups that can be activated for ladder and network formation to lock in the desired physical form. Ladder polymers have been based on a polyaminoketone (B) backbone that can be formed through thermal ring closure of a polyarylketone precursor polymer (A). Thermosetting polymers were based on extended-chain and engineered thermoplastic polymers. Specifically, aramid and arylate materials have been synthesized from a crosslinkable monomer XTA, which can be thermally activated for network formation. These novel synthetic methods were designed to address the insolubility and intractability that is common to ladder and thermosetting materials. The scope of a new polymerization reaction for polyarylketones was investigated and the information gained from this study was used in the design and synthesis of polyaminoketone ladder materials. This new polymerization reaction was based on palladium catalyzed cross-coupling of aromatic diacid chlorides and bis(trimethylstannane) monomers. Several high molecular weight, soluble polyketones having good thermal stability were synthesized using this polymerization reaction. It has been found that aromatic tin monomers substituted with electron withdrawing groups have low molecular weights where electron releasing groups have increased molecular weights. Results from a model compound study into the feasibility of the synthesis of polyaminoketone ladder polymers using this new polymerization reaction indicates that a new design may be necessary. A model compound study on derivatives of the new crosslinkable monomer, XTA was performed to determine the operating window for polymerization and processing of polymeric materials containing this structural unit. Excellent stability towards strong protonic acids was observed when benzocyclobutene small molecule derivatives were substituted with electron withdrawing groups. This is in contrast to the case of the parent hydrocarbon and derivatives substituted with electron donating groups and is consistent with acid degradation resulting from electrophilic aromatic substitution chemistry. Exothermic reaction maxima are typically around 350$\sp\circ$C. ftn* Please refer to dissertation for diagrams.