Search

Smart materials encompass a class of materials capable of reorienting themselves in response to external stimuli (heat, light, and chemical), and generate smart properties such as self‐healing (SH) and shape‐memory (SM), etc. Recently, castor oil has emerged as a bio‐renewable feedstock facilitating the synthesis of smart polymers such as polyurethanes and epoxidized castor oil (CO)‐based polymers. Furthermore, fillers and nanomaterials have been added to prepare responsive materials (SH and SM) and drug delivery systems. This review delves into the recent developments in CO‐based smart materials since 2015 under thermal, photo, and chemical stimuli and their applications in coating, adhesive, soft robotics, and drug delivery. Additionally, the challenges and future scopes for the development of castor oil‐based advanced smart materials have been discussed. [ABSTRACT FROM AUTHOR]

Smart materials that respond to external stimuli are useful for applications ranging from artificial skin to sensing to cosmetics. Inspired by natural phenomena (self‐healing, shape memory, and shrinking), this work develops a novel smart bio‐composite using sustainable polyurethane (PU) and sugarcane bagasse (SB) waste without using a solvent. PU is synthesized using polycaprolactone (PCL) diol, castor oil (CO) as a polyol, and isophorone diisocyanate (IPDI) as diisocyanate. Composites are prepared using PU and SB in the presence and absence of poly(acrylic acid) (PAA) and are denoted as PBA and PB, respectively. TGA and DSC analysis indicate the broad (−68.4 °C to 192 °C) thermal stability of these materials. PBA and PB composites exhibited relatively fast (20–30 min) self‐healing and high shape fixity ratio (Rf) (70–83%), and shape recovery ratio (Rr) (82–100%) at 60 °C in the air. Furthermore, PBA shows hot water‐responsive rapid 100% shape recovery and also exhibits thermoresponsive shrinkage properties like human skin. PBA lifts a material 13.3±2 % of its original length by utilizing its thermoresponsive shrinking property. These inexpensive materials with self‐healing, shape recovery, high thermal stability, and thermo‐responsive properties are attractive and may be useful in artificial skin, sensor, and coating applications. [ABSTRACT FROM AUTHOR]

Hexamethylene diisocyanate (HMDI) reacts with 4-bromo-1H-pyrazole as a blocking agent to form blocked adducts of isocyanates. The adducts were characterized by FTIR, NMR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). In the FTIR spectra, disappearance of a peak at 2250–2270 cm−1 is the indication of blocking of diisocyanate molecule with 4-bromo-1H-pyrazole blocking agent. The DSC thermogram shows that at 185 °C, the blocked adduct de-blocks and HMDI and blocking agent 4-bromo-1H-pyrazole has been regenerated. At 185 °C, regenerated HMDI reacts with polyols of different molecular weights to form polyurethane. The polyurethanes were characterized by FTIR, NMR, DSC, TGA and contact angle measurements. These are useful for hydrophilic coating. [ABSTRACT FROM AUTHOR]

Featured Application: Ionogels containing bio-ionic liquids help in the area of biomolecule encapsulation. Bio-ionic liquids can retain the stability of biomolecules at room temperature within the pores of ionogels. Ionogels have interesting applications in biosensors, electrochemical devices, super capacitors, batteries, gas sensors, CO2 capture, and so forth. We developed a facile and greener approach for the preparation of silica-aerogel-based ionogels using choline dihydrogen phosphate ionic liquid by the sol–gel approach. A series of silica-based aerogels as ionogels were prepared by varying the ionic liquid concentrations: 0.1, 0.5, 1, 3, 5, and 10 wt %. The as-prepared ionogels were characterized using several analytical techniques, namely, attenuated total reflectance (ATR)/FT-IR, TGA, XRD, and particle size analyses. The role of ionic liquid in the viscoelastic properties of the sol–gel transition was monitored using time-dependent rheological measurements. The addition of ionic liquid to the sol–gel system favored the formation of a more interconnected silica network structure. The formation of a silica network structure during sol–gel hydrolysis and condensation was confirmed from 29Si solid-state CP/MAS NMR spectra. The effect of the ionic liquid on the morphological properties was investigated using SEM and TEM studies. The cell viabilities of the prepared gel samples were clearly evident from the cytotoxicity assay studies using Swiss and HaCaT cells. The main advantages of using biocompatible ionic liquids for the preparation of these aerogels as ionogels are that they may be used for encapsulating biological molecules and retain their conformational stability for a longer duration. [ABSTRACT FROM AUTHOR]

Melt polymer nanocomposites were prepared using polyvinyl alcohol (PVA) with the different weight percentage of calcined clays (CCs) in a twin-screw extruder at 210°C and 70 r min−1 for 8 min. Bentonite was surface functionalized with benzidine using dilute hydrochloric acid at 60°C and calcined at 600°C for 6 h. The CCs were incorporated into the PVA matrix to study their morphology and rheological properties. The melt viscosities of the composites were measured by the cone-plate rheometer, the rheogram show non-Newtonian and thixotropic flow behavior. Scanning electron microscope confirmed the degree of exfoliated nanocomposites. The polymer and functionalized nanoclay interactions were reflected in the enhancement of thermal stability and mechanical properties. The melting endotherm temperature (T m) and glass transition temperature (T g) of the nanocomposites tend to increase with increase in weight percentage of the calcined nanoclays. Thermal properties show that addition of calcined nanoclays would improve the thermal decomposition temperatures from 295°C to 307°C when CC content was 2 wt% in covalent or ionic bonding system. [ABSTRACT FROM AUTHOR]