Metolose-PEG interaction as seen by positron annihilation spectroscopy.

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Methylcellulose (Metolose) is a widely used polymer with applications in various industries.
• Poly(ethylene glycol) (PEG 400) is a common plasticizer that can modify polymer properties.
• Understanding polymer-plasticizer interactions is crucial for material performance and stability.

Purpose of the Study:

• To investigate the plasticizing effects of PEG 400 on methylcellulose (Metolose) cast films.
• To characterize the structural changes and interactions between Metolose and PEG 400 at varying concentrations.
• To evaluate the impact of these interactions on the ageing behavior of the polymer films.

Main Methods:

• Conventional physicochemical methods were employed for film characterization.
• Positron annihilation spectroscopy (PALS) was utilized to probe molecular interactions and free volume.
• Controlled ageing studies were conducted at room temperature and 75% relative humidity (RH).

Main Results:

• PEG 400 integrated into the Metolose structure at concentrations below 33.3% (w/w).
• At concentrations above 50% (w/w), PEG 400 formed distinct separate phases within the Metolose films.
• Ageing studies revealed that the slow ageing process was significantly hindered in phase-separated films compared to monophase films.

Conclusions:

• The concentration of PEG 400 dictates its interaction with Metolose, leading to either structural integration or phase separation.
• Phase separation in Metolose-PEG films influences their ageing kinetics.
• PALS is a valuable tool for understanding polymer-plasticizer interactions and their effect on material stability.