## 4 Results and Discussion
### Intensity-Dependent Photomechanical Measurements
The time constant of the polymer made with higher CTA concentrations is marginally higher than those made with lower CTA concentrations. The Beer-Lambert law [50]  
\[I=I_{i}e^{-\alpha w} \tag{37}\]  
is used to determine the material absorbance \(\alpha\) at a wavelength of 488 nm by measuring the transmitted intensity \(I\) and the incident intensity \(I_{i}\) with a photo detector. The fiber thickness through which the light propagates, \(w\), is measured with a micrometer. Table 4 shows the absorbance for both incident polarizations. Note that the absorption length is much longer than the fiber thickness, so nonlinearities from depth effects can be ignored [72, 73], making the assumptions in our heating model appropriate. The fibers are slightly pre-stressed when first mounted to prevent buckling when they expand in response to light or temperature change. The pre-stress may result in chain alignment and thus affect the photomechanical response. If the chains and molecules were to align along the fiber axes, the vertical absorbance would be greater than the horizontal one. We find horizontal absorbance to be higher, which is inconsistent with the hypothesis that molecular alignment is induced in the fiber drawing process and/or due to prestress. Table 3 shows the photomechanical response, \(\kappa_{\
u}^{(1)}\) and \(\kappa_{\sigma}^{(2)}\), of the fiber with 2.66 \(\times\) 10\({}^{-3}\) CTA volume fraction for pre-stress values of 0.38 MPa and 0.76 MPa. The response is found to be the same within the large experimental uncertainties for both polarizations, though they are systematically higher for the higher pre-stress values. \begin{table}
\begin{tabular}{c c c} \hline
**CTA Volume Fraction** & **Polarization** & **Absorbance \(\alpha\)(m\({}^{-1}\))** \\ \hline \(1.33\times 10^{-3}\) & Vertical & 3.54 \\ \(1.33\times 10^{-3}\) & Horizontal & 5.59 \\ \(2\times 10^{-3}\) & Vertical & 6.85 \\ \(2\times 10^{-3}\) & Horizontal & 7.57 \\ \(2.66\times 10^{-3}\) & Vertical & 5.23 \\ \(2.66\times 10^{-3}\) & Horizontal & 6.15 \\ \hline \end{tabular}
\end{table} 
Table 4: Absorbance as a function of CTA volume fraction and light polarization at 488 nm. The efficiency figure of merit (FOM), which is the material's efficiency in converting light energy to mechanical work, is defined in Equation (29) [49; 50]. We determine the FOM as a function of CTA volume fraction. Table 3 summarizes the results. Within experimental uncertainties, the FOM is found to be independent of the CTA concentration. These results emphasize some of the advantages of glassy polymers as host materials. They have a large Young's modulus, so they are more rigid than other materials, such as liquid crystal elastomers, and also have a larger photomechanical stress response [49; 50]. Crystals, on the other hand have good photomechanical properties but have lower optical quality and cannot be formed into arbitrary shapes [74; 75; 76; 77; 78]. These are important qualities for providing a rigid support for the precise positioning of massive objects. Additionally, glassy polymers can be formed into thin films and fibers of high optical quality, making them promising candidates for waveguide devices and smart photomechanically morphing materials [17]. Figure 13: Time constant \(t_{1}\) (light on) as a function of intensity for different CTA volume fractions for a vertically and horizontally polarized pump. The insets show the time constants as a function of CTA volume fraction averaged over all intensities.