Abstract
The dynamics of polymer solutions are heterogeneous. The different molecule sizes and structures cause different mobilities of polymers and solvents. Recently, regarding the heterogeneity of water, two dielectric relaxation processes of water were argued in several supercooled polymer–water mixtures. To investigate whether this is unique to water, we performed broadband dielectric spectroscopy measurements of poly(vinylpyrrolidone)–water (PVP–water), PVP–propylene glycol, PVP–ethylene glycol, and PVP–propanol mixtures with 65 wt% PVP in a temperature range of 123–298 K. For the PVP–water mixture, α-relaxation of PVP and two distinct relaxation processes appeared simultaneously: one was the primary relaxation process of water (fast water process) and the other was the relatively small relaxation process (slow process), at a frequency between that of the α-process of PVP and the fast water process. The strength ratio of the large fast water and small slow processes remained nearly constant in all the temperatures measured. For the PVP–alcohol mixtures, in addition to the α-process of PVP, two or three relaxation processes of alcohol appeared. The primary relaxation process of alcohol above 240 K changed to the small fast secondary process. The small slow processes, which can be recognized below 240 K (the glass transition temperature of the α-process of PVP, Tg,PVP) appears at intermediate frequency between that of the PVP α-process and the primary process of alcohol. The small slow process changed to the primary larger process. The properties of the multiple relaxation processes of solvents below Tg,PVP in PVP–alcohol mixtures are completely different from those in PVP–water mixture.
Highlights
Water is the most abundant liquid on Earth and exhibits numerous peculiar properties
The results clearly show that Tg of the αPVP-process obtained by BDS falls into the range of the high-T side Tg obtained by differential scanning calorimetry (DSC), whereas for the PVP– propylene glycol (PG) and –ethylene glycol (EG) mixtures, Tg of the slowest solvent process falls into the range of the low-T side Tg
This paper reports the dielectric relaxation processes observed in PVP mixtures with water and three types of alcohol
Summary
Water is the most abundant liquid on Earth and exhibits numerous peculiar properties. Dielectric Relaxation in Polymer Solutions confinements, respectively The physics of such systems involves the water and the interaction between water and the guest molecules or the surface of the porous material. The glass-forming materials whose apparent activation energy increases with decreasing temperature are called the fragile glasses [41] For this reason, the non-A-A crossover of water dynamics has been called the fragile– strong transition of water. In order to discuss the non-A-A crossover of water dynamics in a polymer matrix, in addition to the previous works, we performed broadband dielectric spectroscopy measurements of poly(vinylpyrrolidone)–water (PVP–water), PVP–propylene glycol (PG), PVP–EG, and PVP−1-propanol (PrOH) mixtures with 65 wt% of PVP in a wide frequency over a temperature range of 123–318 K. To determine Tg, differential scanning calorimetry (DSC) measurements were carried out over a temperature range from 108 to 298 K, at a rate of 20 K/min using a DSC 7 (PerkinElmer)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: 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.
