Biomass-derived carbon helices induced phase transition in poly(N-ispropylacrylamide): A sustainable tailoring of coil-globule transition in thermoresponsive polymer.

Functional carbon helices (FCHs) containing various oxygenated functionalities derived directly from lignocellulosic biomass is proved to be a potential eco friendly candidate for biomolecules. No study reports the effect of biomass derived platform molecules on the thermoresponsive behavior of polymers, which have been proved potential candidates in carrying various drug delivery applications, gels, and tissue engineering in this vast area of research. Poly(N-isopropylacrylamide) (PNIPAM) is a thermoresponsive polymer that has been found to be a prevailing tool in carrying various aforesaid applications. This study reports a powerful impact on the thermoresponsive behavior of PNIPAM by a non-hazardous alternative form of a herbecious plant Parthenium hysterophorus. Fluorescence spectroscopy was deployed to study the microenvironment provided by carbon helices around the polymer structure. The results obtained are directly correlating with the increased polarity with higher concentration of FCHs and further confirmed a decrease in fluorescence intensity. Moreover, for better understanding of interactions between PNIPAM and FCHs, Fourier transform infrared spectroscopy (FTIR) was employed. The analysis of hydrodynamic diameter (d) was carried out by dynamic light scattering (DLS) and the aggregate size of PNIPAM was found to increase in higher concentration of FCHs. A decrease from 34.7 °C to 29.0 °C in the lower critical solution temperature (LCST) of PNIPAM in FCHs was further confirmed by differential scanning calorimetry (DSC). Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) were also taken into account to understand the morphological changes of PNIPAM in presence of biomass derived carbon helices. The micrographs of PNIPAM-biomass are representing a perturbed morphology of PNIPAM during interaction with FCHs. In this study, high degree of oxygenated functionalities on the carbon helices has a meaningful impact on the conformational phase behavior of PNIPAM. The tendril like functional carbon helices (TLFCHs) are uniquely causing a decrease in the lower critical solution temperature (LCST) of PNIPAM. Our combined study indicates that biomass derived carbon helices significantly decrease the LCST of PNIPAM by 5 °C. Ultimately, the polymer achieves compact globule conformational and complete aggregated state.