A waterborne polymer is a greener alternative than a solvent borne one because of its nontoxicity and nonflammability nature as well as it does not need any organic solvent. Thus, three biodegradable waterborne hyperbranched aliphatic polyesters were synthesized from citric acid, poly(ethylene glycol), glycerol and 2,2-bis(hydroxyl methyl) propionic acid, by a polycondensation reaction without using any additional catalyst or neutralizing agent. The structures of these polyesters were elucidated from spectroscopic analyses. Degrees of branching of the polymers were evaluated from 13 C NMR spectra and found to vary from 0.59 to 0.70. Thermoset of these polyesters was obtained by curing of a formulation composed of waterborne hyperbranched polyester (57.1%), hyperbranched epoxy (28.87%) and poly(amidoamine) (14.28%) using water as a solvent with a little amount of THF as a cosolvent. The performance characteristics such as tensile strength (4.0−7.8 MPa), elongation at break (175−245%), toughness (655−1742 MPa), impact resistance (>1 m), gloss (89− 96), scratch resistance (3−4 kg) and chemical resistance (good) of the thermosets were evaluated. The results clearly revealed the profound influence of citric acid content on performance of such polyester thermosets. These polyester thermosets were found to be highly biodegradable by Pseudomonas aeruginosa and Bacillus subtilis bacterial strains and also exhibited hemocompatibilty. Therefore, the citric acid based sustainable tough hyperbranched polyester thermosets with acceptable performance were obtained through a facile and environmentally benign route.

No abstract

In this study, environmentally friendly waterborne hyperbranched polyester/carbon dot (CD) nanocomposites were fabricated by in situ polymerization through a facile and greener route in absence of catalyst, solvent and neutralizing agent. Three nanocomposites were prepared at different loadings of CD (0.1, 0.5 and 1 wt %). CD was prepared from citric acid and glycerol in presence of cost free cow urine through a one step greener method. The structural attributes of the nanocomposites were evaluated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared and UV-visible spectroscopic studies. The thermosets were obtained by curing the polyester nanocomposite with glycerol based hyperbranched epoxy and fatty acid based poly(amido amine) hardener. The nanocomposites exhibited excellent wavelength dependent down-and up-conversion fluorescence properties. The significant improvements in mechanical properties like tensile strength (7.8 -47 MPa), Young's modulus (243 -745 MPa), toughness (17.82 -51.1 MJm -3 ) and scratch hardness (4 -10 kg) were observed for the thermosetting nanocomposites. Thermogravimetrc analysis supports high thermostability (234 -265 °C) while differential scanning calorimetry authenticated glass transition temperature in the range of 49-56 °C. The rheological study demonstrated shear thining behaviour. The nanocomposite films exhibited good transparency in the visible range. Further, thermosetting nanocomposites were found to be highly biodegradable by Bacillus subtilis and Pseudomonas aeruginosa bacterial strains. The nanocomposite also possesses efficient self-cleaning ability as observed by photodegradation of formaldehyde (within 7 h) and methylene blue (80 min) under exposure of normal sunlight. Thus, this nanocomposite could be used as a promising eco-friendly material for advanced applications.

Herein, we wish to report fabrication of multifaceted environmentally friendly benign renewable resource-based waterborne hyperbranched polyester nanocomposites using three different doses of carbon dot@TiO 2 nanohybrid through a facile in situ polymerization technique in the absence of solvent or additional catalyst. Carbon dot@TiO 2 nanohybrid was prepared through a greener one-pot hydrothermal process from bio-based raw materials. The nanocomposites were characterized by different instrumental techniques. The thermosets of these nanocomposites are obtained by curing them with glycerol-based hyperbranched epoxy and fatty acid-based poly(amido amine). Enhancements of 6.67 folds tensile strength, 3.8 folds toughness, 1.7 folds Young’s modulus, >2.5 units gloss, and 46 °C thermal stability were observed for the thermosets by the formation of nanocomposites. The nanocomposites also showed antifogging and anti-icing properties. More interestingly, they can also be used for efficient separation of crude oil and water from their mixture. Thus, these environmentally benign polymeric materials could find applications in different fields.

Functional materials with innovative optical features have attracted cumulative attention owing to their indispensable and inimitable roles in the advanced human‐civilization. Thus, in the present work, an excellent excitation wavelength dependent down‐ and up‐conversion photo‐luminescent carbon dot@TiO2 containing waterborne hyperbranched polyester nanocomposite was reported for the first time. Further, the thermosets of the nanocomposite were transparent and emitted different colors on exposure of different wavelengths of UV light. Most interestingly, the nanocomposite showed anti‐reflecting as well as self‐cleaning properties. The self‐cleaning behavior was achieved through photocatalytic degradation of different organic contaminants namely pesticide, phenol, bis‐phenol A and mixed dyes under normal sunlight. Further, the thermosetting nanocomposite can be used as an efficient photocatalyst for reduction of common nitro‐aromatic compound under normal sunlight. The nanocomposites also exhibited strong antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae and Pseudomonas aeruginosa bacterial strains. Thus, the studied nanocomposite has remarkable prospect in different advanced applications.