LCST phase transition kinetics of aqueous poly(N-isopropylacrylamide) solution

• Published in: Journal of the Taiwan Institute of Chemical Engineers Vol. 93; pp. 63 - 69
• Main Authors: Pham, Quoc-Thai, Yao, Zong-Han, Chang, Ya-Ting, Wang, Fu-Ming, Chern, Chorng-Shyan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2018
• Subjects: Kinetics; LCST phase transition; Nucleation and growth models; Poly(N-isopropylacrylamide); Temperature-responsive; Temperature-responsive; Kinetics; Poly(N-isopropylacrylamide); Nucleation and growth models; LCST phase transition
• ISSN: 1876-1070; 1876-1089
• DOI: 10.1016/j.jtice.2018.07.045

•LCST phase transition kinetics of PNIPAM solutions characterized by DSC and DLS.•Large activation energy (Eα) and pre-exponential factor (Aα) illustrated.•Both Eα and Aα dependent on temperature.•Cooperatively breaking multiple hydrogen bonds occurs in phase transition.•Phase transition kinetics of PNIPAM solutions obeys nucleation and growth models. LCST phase transition kinetics of aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions was studied by using non-isothermal differential scanning calorimeter (DSC) and isothermal dynamic light scattering (DLS) techniques. The DSC data obtained from 5 and 10 wt% PNIPAM solutions were used in isoconversional kinetics analysis. The resultant large activation energy (Eα) and pre-exponential factor indicated that the phase transition occurred by cooperatively breaking multiple hydrogen bonds. Eα decreased with increasing temperature approximately in a hyperbola form. Theoretical nucleation and growth models were used to adequately describe the temperature dependent Eα. Furthermore, the phase transition process obeyed Avrami–Erofeev nucleation and growth models. As to the 0.05 wt% PNIPAM solution using the isothermal DLS technique, the reaction rate constant was determined at different temperatures, and the Avrami–Arofeev nucleation and growth models adopted to predict the phase transition process. [Display omitted]