# Structure–Property Relationships and Thermal Degradation Mechanism of Terpene Methacrylate-Styrene Copolymers

## TL;DR

This paper studies the structure and thermal behavior of copolymers made from terpene methacrylates and styrene, revealing their stability and degradation mechanisms.

## Contribution

The study provides new insights into the thermal degradation mechanisms and structure-property relationships of terpene methacrylate-styrene copolymers.

## Key findings

- Copolymers showed high solvent and chemical resistance due to their cross-linked structure.
- Thermogravimetric analysis revealed higher thermal stability in PCM/PS compared to PGM/PS copolymers.
- Degradation occurs via a radical mechanism, producing low molecular mass organic molecules and CO/CO2/H2O.

## Abstract

The ultraviolet (UV) copolymers of two monomers, one methacrylic and the other vinyl monomer (styrene, S) were prepared. As methacrylic monomers, citronellyl methacrylate (CM) or geranyl methacrylate (GM) were used. The preparation was proven to contain high solvent- and chemical-resistant copolymers due to their cross-linked structure with the conversion degree of the double bonds above 0.92 for poly(citronellyl methacrylate)/polystyrene (PCM/PS) and above 0.85 for poly(geranyl methacrylate)/polystyrene (PGM/PS) copolymers. The obtained copolymers showed only one glass transition temperature (Tg). Depending on the structure and amount of the used methacrylic monomer, the Tg values were from 0.4 °C to −15.2 °C for PCM/PS copolymers and from −23.2 °C to −50.5 °C for PGM/PS copolymers. The thermogravimetric analysis (TG/DTG) showed a higher thermal stability for PCM/PS (148–187 °C) than for PGM/PS copolymers (119–159 °C) in inert and oxidative atmospheres. The simultaneous thermogravimetric analysis coupled with Fourier Transform Infrared spectroscopy (TG/FTIR) showed that the pyrolysis and oxidative decomposition of the tested copolymers took place according to the radical mechanism. This led to receiving a mixture of low molecular mass organic molecules containing saturated and unsaturated fragments, carbonyl groups, aromatic fragments as well as to CO, CO2 and H2O. This indicated the depolymerization process (inert) and further oxidation processes of the initially formed volatiles and/or residues in oxidative conditions.