## 3 Results
### In Situ FTIR
#### 3.1.2 Simultaneous FTIR and SANS on PEGDME in Solution
Hence, swollen single coils (\(p\) = 5/3), one-dimensional morphologies or Kuhn segments (\(p\) = 1), lamellar (\(p\) = 2), and large 3D morphologies with sharp interfaces (\(p\) = 4) can be directly identified and characterized [33]. The model curves of the semi-flexible single coil and the crystalline lamellar stacks morphologies described later are also depicted. At 30 \({}^{\circ}\)C all polymers are dissolved as semi-flexible coils in solution, as shown by the single-chain form factor features identified in the scattering profiles: the plateau towards low Q yields information about the volume fraction and molecular weight while the bending down of the intensity is characteristic of the Guinier regime, from which information about the radius of gyration of the polymer coil is obtained. The Q\({}^{-5/3}\) power law regime towards high Q is indicative of excluded volume interactions between the chain segments (with \(-5/3\)--Flory's exponent). A transition to Q\({}^{-1}\) behavior is observed at higher Q, which indicates that short stiff (linear) polymer segments with a persistence length l\({}_{\rm P}\) = \(b\)/2, with \(b\) the Kuhn segment, exist at a local length scale [34]. The small-angle scattering pattern at 30 \({}^{\circ}\)C was fitted using the unified Beaucage model [35] for multiple structural levels in hierarchical morphologies. The approach described the experimental data well and delivered the sizes involved in each structural level: the R\({}_{\rm g}\) = 37 A of the polymer coil and the persistence length l\({}_{\rm P}\) = 7.5 A. Thus, both FTIR and SANS results are in good agreement regarding the polymer conformation at 30 \({}^{\circ}\)C as semi-flexible coil in solution. Figure 5: FTIR spectral change observed during the crystallization of hPEGDME (M\({}_{\rm W}\) = 20,000 g mol\({}^{-1}\)) from solution in dTHF in decreasing temperature from 30 \({}^{\circ}\)C to 12 \({}^{\circ}\)C. The arrow indicates the evolution of the FTIR spectra collected between the initial and final states at 12 \({}^{\circ}\)C with a time step of 30 s.  
Figure 6: SANS cross sections from solution of hPEGDME (M\({}_{\rm W}\) = 20,000 g mol\({}^{-1}\)) in dTHF (\(\phi_{\rm pol}\) = 2%) measured at different temperatures, during the FTIR analysis (Figure 7). Data collected at different L\({}_{\rm D}\) and temperatures are differentiated by symbols and colors as shown in the legend. The solid lines indicate the power law behavior in different Q ranges, whereas the red curves represent the model description of the experimental data, as discussed in the text. The dotted curve represents the scattering pattern from the lamellar stacks, as resulted from the global fit of the experimental data collected in the final state at 12 \({}^{\circ}\)C (green symbols). Figure 7: _Cont._  
At 12 \({}^{\circ}\)C, due to methodical reasons, we used the typical procedure for carrying out experiments over an extended Q-range by combining different L\({}_{\text{D}}\)'s rather than the time-resolved measurements on a selected narrow Q-range. Thus, the raw data were collected for one minute at two detection distances, L\({}_{\text{D}}\) = 8 m and 20 m (always in this order), with the detector movement from one position to another taking 10 min. Two sets of measurements were performed at 12 \({}^{\circ}\)C, starting at the time when the set temperature was attained by the Peltier-based variable temperature cuvette holder, which corresponds to the acquisition start of the cyan IR spectrum in Figure 5.  
A decrease in the temperature resulted in the formation of polymer crystalline morphology that led to an increase of the scattering level towards low Q compared with the single chain scattering feature, as observed in the SANS results corresponding to the initial state at 12 \({}^{\circ}\)C (blue symbols in Figure 6).