Synthesis of helical branched carbodiimide polymers with liquid crystalline properties

ABSTRACT

Carbodiimide polymers are synthetic helical polymers that display unique properties depending on the functional groups attached to the polymer backbone. The amidine groups of the backbone present alternating amine- and imine-like groups. The properties of the polycarbodiimides have been studied by varying the sidechains of the polymer from linear to branched. In previous work, different arenes and straight aliphatic chains substituted polycarbodiimides have been used to evaluate the thermal and liquid crystalline properties of these polymers. In this study, we introduced bulky branched aliphatic and octadecyl side chains to the polymer backbone to generate a branched homopolymer and different branched/linear-chain copolymers. The effect of these side-chain combinations on the solid and solution properties of these polycarbodiimides was studied. It was observed that polycarbodiimides containing octadecyl and branched bulky alkyl groups showed different thermal events in the DSC plot at ~30°C. Also, we observed a decrease in thermal stability in the TGA thermogram as we increase the branched alkyl side chains of the polymers. The lyotropic liquid crystallinity was observed in all the branched copolymers that consist of both branched alkyl side chains and octadecyl functional groups in different ratios.

Graphical abstract

KEYWORDS:

• Polycarbodiimides
• branched polymers
• liquid crystallinity
• lyotropic

Acknowledgments

We wish to acknowledge Dr. Gregory McCandless for the assistance provided with pXRD. Also grateful to the NSF-MRI grant (CHE-1126177) used to purchase the Bruker Advance (III) 500 NMR instrument. We are thankful to Dr. Mihaela C. Stefan, Dr. Michael C. Biewer, and Dr. Prabhath L. Gamage for their help given me to analyse the liquid crystalline images.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supporting information

NMR, and IR spectrums provided in supplemental material.