Abstract: Despite a rapid growth in cationic host defence peptide (CHDP)-mimicking synthetic polymers, the importance of the secondary structure of such synthetic systems, similar to CHDPs, has not been understood well in context of bacterial membrane perturbation. Recently we have investigated a series of cationic amphiphilic alternating polyurethanes (PUs) for antibacterial activity with specific focus on the effect of the chain-folding on the antibacterial activity. Some of them contain linear flexible hydrocarbons (F-PUs), while others contain cyclic rigid hydrocarbons (R-PUs) in the segmented polymer backbone. F-PUs exhibit intra-chain H-bonding driven pleated structure, followed by hierarchical assembly, producing cationic polymersome in water. In sharp contrast, R-PUs, deprived of the chain-folding possibility due to the rigid linker, exhibit immiscibility-driven aggregation producing spherical nanoparticles. F-PUs exhibit exemplary antibacterial activity with exceptionally low minimum inhibitory concentration (MIC), while R-PUs do not show even moderate activity.1 Beyond planktonic bacteria, F-PUs also exhibit extraordinary biofilm eradication efficiency. Likewise, we have recently shown sulfated F-PUs show excellent antiviral activity while their rigid analogues fail to exhibit any antiviral effects.2 Similar foldable PUs with pendant naphthalene-diimide (NDI) moiety in hydrocarbon solvent show pleated structure with the NDI units organized at the periphery.3 In presence of pyrene (Py), NDI-Py charge transfer interaction promotes formation of elongated nanotubular structure with stable room-temperature ferroelectricity4 and highly promising piezoresponse. This presentation will focus on the chain-folding regulated self-assembly of different polyurethane derivatives in water or hydrocarbon and implications in applications such as antibacterial/ antiviral material or organic optoelectronics.

References:
1. Barman, R.; Ray, D. S.; Aswal V. K.; Ghosh, S. Polym. Chem. 2022, 13, 4384.

2. Nag, A.; Banerjee, K. J.; Barman, R.; Kar, J.; Sarkar, D. P.; Jana, S. S.; Ghosh, S. J. Am. Chem. Soc. 2023, 145, 579.

3. T. Mondal, T. Sakurai, S. Yoneda, S. Seki and S. Ghosh, Macromolecules 2015, 48, 879.

4. Mukherjee, A.; Barman, S.; Ghosh, A.; Datta, A.; Datta, A.; Ghosh, S. Angew. Chem. Int. Ed. 2022, e202203817.

Tea: 4pm