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The aromatic epoxy isomers triglycidyl p-aminophenol and triglycidyl m-aminophenol were cured with two aromatic diamine isomers 4,4′ diaminodiphenyl sulphone and 3,3′ diaminodiphenyl sulphone, creating four variations of epoxy resin. Dynamic and static mechanical analyses were used to understand the influence of chemical and network structure on the thermal, volumetric and mechanical properties of the epoxy resin. Fracture toughness increases are observed for networks containing meta substituted phenylene ring amines compared to the para equivalents, however no difference is noticed when the meta substituted phenylene ring epoxy is used. Use of meta substituted phenylene rings increases glassy modulus, yield stress, density and strain to failure. Correspondingly, decreases are seen in the glass transition temperature, intensity of the beta transition and the rubbery modulus. The results are entirely consistent with internal antiplasticisation caused by the presence of the meta substituted phenylene rings.

We have developed a novel route for the synthesis of high-performance bio-polyimides (PIs) microbially-derived from photo-responsive aromatic diamine 4,4′-diaminostilbene (DAS) and its reduced counterpart 4, 4′-(ethane-1,2-diyl)dianiline (EDDA). DAS and EDDA were condensed with various commercially-available dianhydrides to obtain a series of poly(amic acid)s (PAAs) and PIs which were characterized in terms of their thermal, mechanical, and photo-functions. These bio-based PAAs showed a very high viscosity of 6.62 dL/g, and the PIs showed ultrahigh thermal resistance with Td10 values over 600 °C, which were higher than that of any bio-based plastic reported thus far. They also showed Tg values above 250 °C, and tensile strength of over 132 MPa, which is higher than that of Kapton™. The PIs also showed photo-functional behavior based on stilbene-based photoreactions.

A novel fluorinated aromatic diamine, bis[4-(4′-aminophenoxy)phenyl]-3,5-bis(trifluoromethyl)phenyl phosphine oxide, was synthesized. A series of new fluorinated polyimides containing phosphine oxide was prepared from the novel diamine with various commercially available aromatic dianhydrides. All the fluorinated polyimides show high glass transition temperatures, excellent thermal stability, and good solubility in common organic solvents.

Some epoxide resins with or without methoxy branches were cured with an aromatic diamine. A well defined relaxation was observed near room temperature for all cured resins with methoxy branches, independent of the epoxide-resin structure. The relaxation was denoted here as the β′-relaxation. It is suggested that the β′-relaxation can be attributed to suppression of the motion of the hydroxy ether group due to the interaction between this group and the methoxy branch. The effect of the β′-relaxation on the fracture toughness of cured epoxide resins was studied by comparing the stress intensity factor K c of a spiro-ring type epoxide resin containing a methoxy branch with that of a bisphenol A type resin. The value of K c in the former system is considerably higher above the β′-relaxation temperature than that of the latter system. This is explained by the increase in the plastic deformation region at the crack front with increase in temperature caused by the presence of the β′-relaxation.