Terahertz spectroscopy research on motion‐limited molecular chain of random polymethacrylate

Abstract

In this study, an innovative method was used to examine the impact of gamma‐ray irradiation on three specific monomers: methyl methacrylate (MMA), hexyl methacrylate (HMA), and lauryl methacrylate (LMA). The primary objective was to produce corresponding polymers—polymethyl methacrylate (PMMA), polyhexyl methacrylate (PHMA), and poly(lauryl methacrylate) (PLMA). The significance of the research was determined by conducting a thorough analysis of the thermal properties and structural characteristics of these polymers using advanced techniques, including thermogravimetric analysis and differential scanning calorimetry (TGA‐DSC), as well as Fourier transform infrared spectroscopy (FTIR). The results indicated that irradiation at a 30 kGy dose caused distinct decomposition of ester groups within the polymer matrices. Additionally, a clear trend was observed in the maximum exothermic temperature among the three polymers, with PMMA exhibiting the lowest temperature, followed by PLMA, and PHMA with the highest temperature. Surprisingly, when the radiation dose exceeded 30 kGy, PHMA's thermal stability peaked, demonstrating remarkable resistance to further changes. This highlights the crucial role of radiation dosage in adjusting polymer thermal properties. Furthermore, analysis of infrared characteristic peaks identified a critical radiation dose range between 15 and 30 kGy, where polymerization was efficiently promoted without generating extra by‐products, showcasing experimental ingenuity. Lastly, optical properties of the synthesized polymers were explored using THz time‐domain spectroscopy. Results showed intriguing changes in refractive indices following 30 kGy dose irradiation. Specifically, MMA and HMA exhibited moderate refractive index increases, while LMA displayed a significant decrease. Notably, PHMA demonstrated substantial absorption reduction beyond 15 kGy doses, with minimal further changes, highlighting the potential to customize polymer optical properties through controlled irradiation.