**3. Methods**

### *3.1. Glass Transition Temperature*

Glass transition temperature was measured with the use of Discovery DMA 850 (TA Instruments) appliance in Oscillation Temperature Ramp. The specimen was submitted to simultaneous cyclic flexure with the amplitude of deflection equal to 0.8 μm and frequency of 1.0 Hz, and an increase in heating temperature up to 157 ◦C. The heating rate was equal to 2 ◦C/min.

The storage and loss moduli can be determined using following equations, representing the behaviour of viscoelastic material:

$$
\sigma = \sigma\_0 \sin(2\pi \text{ft}) \tag{1}
$$

$$
\varepsilon = \varepsilon\_0 \sin(2\pi \text{ft} - \delta) \tag{2}
$$

$$\tan \ \delta = \mathcal{E}'' / \mathcal{E}' \tag{3}$$

where:

ε—strain; ε0—strain's amplitude; σ—stress; σ0—stress's amplitude; f—frequency; t—time; δ—phase lag between stress and strain;

E —storage modulus;

E"—loss modulus.
