Identifying the Role of Primary and Secondary Interactions on the Mechanical Properties and Healing of Densely Branched Polyimides.

We present a systematic study of the role of the aromatic dianhydride structure on the self-healing behavior of dimer diamine-based polyimides. By means of solid-state NMR and rheology, we studied the molecular and microscale dynamics of four polyimides comprising the same aliphatic branched diamine yet with variable dianhydride rigidities and correlated these to their macroscopic healing kinetics measured by tensile testing. Following the two-step kinetics of the healing process, we were able to differentiate and quantify the extent of mechanical strength recovery in each of the healing stages separately.

Understanding the Effect of the Dianhydride Structure on the Properties of Semiaromatic Polyimides Containing a Biobased Fatty Diamine.

In this work we report the effect of the hard block dianhydride structure on the overall properties of partially biobased semiaromatic polyimides. For the study, four polyimides were synthesized using aliphatic fatty dimer diamine (DD1) as the soft block and four different commercially available aromatic dianhydrides as the hard block: 4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic anhydride) (BPADA), 4,4'-oxidiphthalic anhydride (ODPA), 4,4'-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA), and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA). The polymers synthesized were fully organo-soluble thermoplastic branched polyimides with glass transition temperatures close to room temperature.

Imaging the Molecular Motions of Autonomous Repair in a Self-Healing Polymer.

Self-healing polymers can significantly extend the service life of materials and structures by autonomously repairing damage. Intrinsic healing holds great promise as a design strategy to mitigate the risks of damage by delaying or preventing catastrophic failure. However, experimentally resolving the microscopic mechanisms of intrinsic repair has proven highly challenging.