Processing of aromatic polyimides synthesized from traditional diamines and dianhydrides has always been a limiting factor in their widespread use. Decreasing the molecular weight of these polyimides facilitates processing due to higher solubility and lower viscosity which, in turn, improves wetting characteristics. Higher molecular weight polyimides, on the other hand, are usually characterized by better thermomechanical properties compared to their lower molecular weight analogues.
The introduction of reactive functional end-cappers allows for a controlled degree of polymerization where the resultant oligomeric polyimides can be easily processed and the properties associated with high molecular weight structures can be reclaimed upon a subsequent curing process. This elegant way of combining processability and performance, with special emphasis on the use of acetylenic groups in varnish and coating manufacturing, will be described. Case studies featuring various polyimide formulations will be presented to further illustrate these improvements.
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