Biodegradable tough waterborne hyperbranched polyester/carbon dot nanocomposite: approach towards an eco-friendly material

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.

Photoluminescence, Self cleaning and Photocatalytic Behavior of Waterborne Hyperbranched Polyester/Carbon dot@TiO2 Nanocomposite

“…Hence it is evident that introducing CD can enhance the visible light photocatalytic activity of both the nanohybrid and the nanocomposites. The key role of uniformly distributed CD on the surface of TiO 2 is to absorb light in the visible region which can convert light from longer wavelength to shorter wavelength and thereby increasing the light absorption efficiency of the nanohybrid ,. Further, the optical colors of the nanocomposites in the visible region for both before and after curing, at shorter UV (254 nm) and longer UV (365 nm) wavelengths are shown in Figure B and 1C respectively.…”

“…While, upon exciting nanohybrid in the wavelengths from 700 to 800 nm corresponding emission spectra were appeared from 440 to 520 nm (Figure D ‐F) which confirmed the wavelength dependent up‐conversion property. This feature may be ascribed to the different emissive sites and distribution of different particle sizes of nanohybrid as well as to active multiphoton processes ,,. The distribution of the nanohybrid in the polyester matrix was confirmed from TEM analysis and the representative TEM image of WPN2.5 is shown in (Figure A).…”

“…This property is commonly studied for polymeric materials with TiO 2 where compatibility poses a question. In this milieu, CD with polar functional groups not only helps to stabilize TiO 2 nanoparticles but also improves compatibility with organic polymer through different interactions, as supported by FTIR spectral analysis ,. The shifting of stretching mode of Ti−O bond (681 cm −1 ) as well as ‐O−H stretching (3400 cm −1 ) and bending (1400 cm −1 ) absorption bands of TiO 2 confirmed the interaction of CD with TiO 2 .…”

“…Further, the literatures advocate that upon addition of different nanomaterials such as titanium dioxide (TiO 2 ), carbon dot (CD), ZnO, SiO 2 , etc. to various polymeric matrices resulted interesting optical attributes ,,,. Amongst them CD, a non‐toxic carbon based nanomaterial shows peculiar excitation wavelength dependent photoluminescence properties and hence interesting to study.…”

Biobased waterborne, tough hyperbranched polyester thermosets as environmentally benign polymeric materials

“…Further crosslinks between chains restrict the chain motion and thus increase T g . The presence of bulky pendant groups like benzene rings can also restrict the rotational freedom, leading to high T g , so with the increase in wt % of HBGP, the T g value increases. These values are higher than that of a citric acid–based waterborne polyester …”