Effect of Molecular Weight on Thermal Behavior and Processability of Oligomeric Phthalonitrile Resins

Abstract

A series of phthalonitrile end-capped oligomers having controlled molecular weights were prepared by the reaction between aromatic diols, dichloro compounds and 4(4’-aminophenoxy) phthalonitrile. The average molecular weight of the oligomers can be controlled by varying the stoichiometric ratio of diols and dichloro compounds used. The structure of the prepared compounds was characterized by FT-IR and NMR spectral techniques. The average molecular weights (Mn & Mw) and polydispersity index (PDI) values of the oligomers were determined by Gel permeation chromatographic (GPC) analysis. Differential scanning calorimetric (DSC) analysis was used to follow the cure behavior of the oligomeric phthalonitrile with 4,4’-oxydianiline (ODA) curing agent mixtures. The oligomeric phthalonitriles were converted into cross-linked network structure by three step curing process at elevated temperatures. As the average molecular weight of the oligoimides increases, enhancement of thermal stability was observed. Such oligomeric system is expected to be quite useful for the advanced composite applications that need high temperature capabilities.