Emergence of Heptazine-Based Graphitic Carbon Nitride within Hydrogel Nanocomposites for Scarless Healing of Burn Wounds

• Published in: ACS applied polymer materials 2020-12, Vol.2 (12), p.5743-5755
• Main Authors: Singh, Aarti, Kochhar, Dakshi, Jeevanandham, Sampathkumar, Kar, Chirantan, Bhattacharya, Rohan, Shakeel, Adeeba, Mukherjee, Monalisa
• Format: Article
• Language: English
• ISSN: 2637-6105; 2637-6105
• DOI: 10.1021/acsapm.0c01020

Graphitic carbon nitride (gCN) has only recently experienced a renaissance in a myriad of domains despite existing as a long-established material described in the chemical literature. Notwithstanding the upturn, their conventional synthesis at extremely high temperatures yielding limiting compositions stands in the way of achieving a paradigm shift in gCN fabrication. With the ultimate goal of surpassing these hurdles, we utilize N-doped carbon nanosheets (N-CNS) as a filler in free-radical-mediated aqueous copolymerization. By dispersing N-CNS in a polymer matrix, high-performance mechanically robust composites could be developed and tailored to individual applications. As-synthesized hydrogel nanocomposite systems are used to decode the balance for emulating evolutionary accomplishments of nature’s nanocomposites like the “abalone’s nacre”. At a lower concentration (0.05%), N-CNS disperse homogeneously and interact intimately with the polymer matrix forming an “interphase” zone around individual nanofillers dramatically affecting the mobility of polymer chains to yield sheet architectures. On increasing the filler concentration (0.3%), the intercalation phenomenon gets perturbed due to an intrinsically oriented aggregation of nanofiller giving rise to a surge in entropy that leads to conspicuous buckling and tubular aggregates. At the interfacial regime, the poly­(acrylic acid) domains come in closer proximity to the hydrophobic cages of N-CNS, and a nanoconfinement effect exerts high pressure manifesting acid-catalyzed condensation of melamine units to form, for the first time, quasi-two-dimensional heptazine-gCN (h-gCN) within hydrogel nanocomposites. Polymer properties are enhanced by the addition of N-CNS through complex interfacial interactions and the unique distributions of internanofiller distances. Endowed with mechanical properties that closely mimic natural skin and combined with the repurposed drug “losartan”, these hydrogel nanocomposites offer scarless healing of second-degree burns.