Suman Thakur

Bio-based tough hyperbranched polyurethane–graphene oxide nanocomposites as advanced shape memory materials

A fast and simple approach for the large scale fabrication of highly flexible castor oil-modified hyperbranched polyurethane (HPU)–graphene oxide (GO) nanocomposites with high toughness is reported. Three different wt% (0.5, 1 and 2) of GO are incorporated into a HPU matrix to prepare uniformly dispersed GO-based nanocomposites. The performance studies show a tremendous enhancement of the toughness (2540 to 6807 MJ m−3) as well as the increment of tensile strength (7 to 16 MPa), elongation at break (695 to 810%) and scratch hardness (5 to 6.5 kg) on the formation of the nanocomposites with 2 wt% GO. The Halpin–Tsai model suggests the 3D random distribution of GO in the HPU matrix. Thermal properties such as thermostability, melting point, enthalpy, degree of crystallinity and glass transition temperature (Tg) etc. of the nanocomposites are correlated with their shape recovery (∼99.5%) and shape fixity (∼90%) behaviour. Thus, HPU–GO nanocomposites have the potential to be used as advanced thermo-responsive shape memory materials.

Multi-stimuli responsive smart elastomeric hyperbranched polyurethane/reduced graphene oxide nanocomposites

In this report, a tough elastomeric hyperbranched polyurethane/reduced graphene oxide (HPU/RGO) nanocomposite was fabricated by an in situ polymerization technique. Reduction of graphene oxide was carried out by a green sonochemical approach using the combined effect of sonication and Fe3+ ions in presence of Colocasia esculenta leaves aqueous extract. The reduction occurred only in 3 min, while 8 min was required without sonication. Prepared RGO and nanocomposites were characterized by different spectroscopic and analytical tools. The nanocomposite demonstrated excellent thermal stability and mechanical properties, such as tensile strength (27.8 MPa), tensile modulus (36.3 MPa) and toughness (116 MJ m−3). The nanocomposite also exhibited outstanding multi-stimuli responsive shape memory behaviour under direct sunlight, microwave (360 W) and heat energy (60 °C). The performance of the nanocomposite was dependent on the loading of RGO (0.5–2.5 wt%). Thus, these nanocomposites have tremendous potential to be used as advanced non-contact triggered smart materials for different applications, including biomedical.

One step preparation of a biocompatible, antimicrobial reduced graphene oxide–silver nanohybrid as a topical antimicrobial agent

A reduced graphene oxide–silver nanohybrid (Ag–RGO) was prepared by simultaneous reduction of graphene oxide and silver ions, using the aqueous extract of the Colocasia esculenta leaf. The nanohybrid demonstrated better antimicrobial activity than the individual nanomaterials. Excellent cytocompatibility was observed for peripheral blood mononuclear cells (PBMCs) and mammalian red blood cells (RBCs). An acute dermal toxicity study on wistar rats confirmed no induction of direct or indirect toxicity to the host. Thus, this nanohybrid holds potential for applications as a non-toxic topical antimicrobial agent in dressings, bandages, ointments etc.

A tough, smart elastomeric bio-based hyperbranched polyurethane nanocomposite

Herein, we fabricate an elastomeric nanocomposite using castor oil-based hyperbranched polyurethane (HPU) and iron oxide nanoparticles decorated reduced graphene oxide (IO–RGO) nanohybrid by an in situ polymerization technique. The designed nanocomposite not only exhibits good thermal properties but also possesses excellent mechanical properties such as tensile strength (24.15 MPa), tensile modulus (28.55 MPa) and toughness (110.8 MJ m−3). In addition, the nanocomposite demonstrates rapid and repeatable self-healing abilities under exposure of 20–30 s microwave power input (180–360 W) and by direct sunlight exposure (105 lux) for 5–7.5 min. It also demonstrates excellent shape-recovery ability under microwave power (30–60 s) as well as in direct sunlight (1–2.5 min). Thus, the studied tough polymeric material has potential advanced applications.

Tuning of sunlight-induced self-cleaning and self-healing attributes of an elastomeric nanocomposite by judicious compositional variation of the TiO2–reduced graphene oxide nanohybrid

Achieving combined attributes of shape memory, self-healing and self-cleaning properties within a material is a daunting challenge to materials scientists. Here, a hyperbranched polyurethane (HPU)–TiO2/reduced graphene oxide (TiO2/RGO) nanocomposite was fabricated to address the afore-stated challenge. The fabricated nanocomposite exhibited composition and dose-dependent mechanical properties with excellent shape recovery ratio (91–95%) as well as shape recovery rate (1–3 min) under exposure to sunlight. Most importantly, the nanocomposite demonstrated both repeatable intrinsic self-healing (within 7.5–10 min) and efficient self-cleaning ability by removing model dirt, methylene blue, (within 2–3 h) under the same energy exposure. The study also showed that these novel properties of the nanocomposite can be tuned by judicious choice of the amount and composition of the nanohybrid. The presence of a high amount of RGO (0.5–1 weight%) in the nanocomposite helps in rapid and efficient healing, whereas a high amount of TiO2 nanoparticles (5–10 weight%) aids in achieving good self-cleaning properties. Therefore, the nanocomposite could be a promising futuristic material for many advanced applications.

Self-healable castor oil based tough smart hyperbranched polyurethane nanocomposite with antimicrobial attributes

Here, castor oil-based tough hyperbranched polyurethane/sulfur nanoparticles decorated reduced graphene oxide (HPU/SRGO) nanocomposites are fabricated with different weight% of nanohybrid. Tremendous enhancement of mechanical properties, such as tensile strength (from 7.2 to 24.3 MPa), tensile modulus (from 3.3 to 137.7 MPa), toughness (from 25.4 to 313.52 MJ m−3) and elongation at break (from 710% to 1456%), is observed upon incorporation of nanohybrid in HPU matrix due to strong interaction between SRGO and HPU matrix. The nanocomposite exhibited excellent repeatable self-healing (within 50–60 s at 360 W under microwave and 5–7.5 min under sunlight) and shape recovery (within 30–50 s at 360 W under microwave and 1–3 min under sunlight). The nanocomposite also demonstrated profound microbial inhibitory effect against Staphylococcus aureus, Escherichia coli and Candida albicans. Thus, the studied nanocomposite has tremendous potential for various advanced applications.