to $10^3$. As the chain bending becomes rigid, the glass transition occurs at a higher temperature, and as a result, the density in the glass state becomes lower. The similar observation was obtained by Milkus *et al* [@Milkus:2018ha].

These behaviors of $T_g$ and $\rho$ can be understood by studying the microscopic conformation of the polymeric chains. Figure \[fig2\]a presents the probability distribution of the angle formed by three consecutive beads along the chain, $P(\theta)$, when changing the rigidity $\varepsilon_\mathrm{bend}$. Two peaks are observed at approximately $\theta \simeq 70^\circ$ and $\theta \simeq 120^\circ$ for a low rigidity ($\varepsilon_\mathrm{bend}\le 1$). A similar distribution $P(\theta)$ was also reported in Ref. [@Milkus:2018ha]. As the rigidity increases, the peak position in $P(\theta)$ shifts towards $\theta_0=109.5^\circ$. It is noted that the bending potential $U_\mathrm{bend}(\theta)$ in Eq. (\[eq:bend\]) tends to stabilize the angle $\theta$ at $\theta_0 =
109.5^\circ$. In addition, Figure \[fig2\]b presents the radius of gyration $R_g$ as a function of $\varepsilon_\mathrm{bend}$. It can be observed that $R_g$ increases from $R_g \simeq 11.5$ to $16.5$ with an increasing $\varepsilon_\mathrm{bend}$. Importantly, these variations of conformation are induced intensively when the rigidity increases from $\varepsilon_\mathrm{bend} = 1$ to $10^3$, which exactly matches the region where variations of $T_g$ 