Abstract
The thermodynamic behavior of hyperbranched poly(ethylenimine) with isobutyramide groups (HPEI-IBAm) during thermal-induced phase transition in water was investigated by turbidity measurement, calorimetric measurements (DSC), FT-IR, and dynamic light scattering (DLS). Both turbidity and calorimetric measurements indicated a recoverable phase transition with a small hysteresis. Detailed FT-IR investigation gave an insight into its molecular mechanism about detailed group interaction during the heating-cooling process. The second derivative and Gaussian fit were carried out to separate three components of ν(C═O): 1648, 1625, and 1600 cm(-1), which are assigned to C═O···D-N H-bonds, single and double H-bonded carbonyl groups with water molecules, respectively. Quantitative analysis of amide I groups indicates a better revival compared to PNIPAM. The isosbestic point determination and 2D correlation analysis together with dynamic light scattering were applied to draw out the mechanism. Thermosensitive HPEI-IBAm dissolves in water exhibits small particles of ca. 3 nm at room temperature at first. As temperature increases, the polymer begins to shrink and water is driven out from the polymer. Finally, the polymer results in a hydrophobic sphere, which aggregates further for a relative stable state upon heating. Above LCST, C═O···D-N hydrogen bonds form with the disassociation of C═O···D(2)O, which helps in the dehydration of CH groups. Upon cooling, the driven force of the transition is the hydration of CH groups. Compared with linear-PNIPAM, the globule-like hyperbranched polymer has a high specific area which endows the groups with a high degree of freedom and more sufficient interaction with water.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.