# Boson peak, elasticity, and glass transition temperature in polymer glasses: Effects of the rigidity of chain bending

## TL;DR

This study uses molecular dynamics simulations to explore how chain bending rigidity influences the vibrational and elastic properties of polymer glasses, revealing correlations among the boson peak, elasticity, and glass transition temperature.

## Contribution

It demonstrates the impact of chain bending rigidity on the vibrational spectrum, elastic moduli, and glass transition temperature in polymer glasses, highlighting the role of non-affine elasticity.

## Key findings

- Boson peak frequency scales as the square root of shear modulus.
- Increasing rigidity raises the glass transition temperature and affects elastic moduli.
- A positive correlation exists among the boson peak, shear elasticity, and glass transition temperature.

## Abstract

The excess low-frequency vibrational spectrum, called boson peak, and non-affine elastic response are the most important particularities of glasses. Herein, the vibrational and mechanical properties of polymeric glasses are examined by using coarse-grained molecular dynamics simulations, with particular attention to the effects of the bending rigidity of the polymer chains. As the rigidity increases, the system undergoes a glass transition at a higher temperature (under a constant pressure), which decreases the density of the glass phase. The elastic moduli, which are controlled by the decrease of the density and the increase of the rigidity, show a non-monotonic dependence on the rigidity of the polymer chain that arises from the non-affine component. Moreover, a clear boson peak is observed in the vibrational density of states, which depends on the macroscopic shear modulus $G$. In particular, the boson peak frequency is scaled as $\omega_\mathrm{BP} \propto \sqrt{G}$. These results provide a positive correlation between the boson peak, shear elasticity, and the glass transition temperature.