**3. Samples**

*a*(*x*) = √

30 Optical Interferometry

and *ϕ*(*x*) = tan<sup>−</sup><sup>1</sup>

Finally, the OPLD can be obtained for the left‐hand side of Eq. (12).

\_\_\_\_\_\_\_\_\_

( \_ *J*(*x* )

(*x* ) (15)

*<sup>I</sup>*(*<sup>x</sup>* )) (16)

*I*2 (*x* ) +*J*<sup>2</sup>

**Figure 3.** (a) Interferogram obtained at 20°C for a PSA/PVME (30/70) blend; (b) 1D data obtained by averaging along the *y* direction for each 10 pixels indicated by the two arrows in (a). The peripheral of the intensity distribution in (b) is

affected by the Gaussian beam.

Polymers used in this study are the derivatives of poly(ethyl acrylate) (PEA), polystyrene (PS) and poly(vinyl methyl ether) (PVME). The mixture of PS and PVME exhibits miscibility at room temperature, providing a system for studying the effects of shrinkage on phase separa‐ tion of polymer blends. All polymers used here have molecular weight larger than 100.000 and the molecular weight distribution around 2.0. The details of chemical synthesis and sample characterization are described in previous publications [13, 14].

Samples for MZI studies were obtained by solvent casting method and were dried under vac‐ uum at least one night. All the samples PS/PVME mixtures with the dimension (20 mm × 20 mm × 10 μm) were annealed under vacuum over 2 h at temperature above the glass transition tem‐ perature (*T*<sup>g</sup> ) of the blend to erase the thermal history of the preparation process.

### **3.1. Photodimerization of anthracene as a photocuring reaction**

To photo‐cross‐link a polymer with UV irradiation, photosensitive anthracene was chemically labeled on a given polymer by copolymerizing its monomer with a photoreactive monomer by copolymerization. By doing so, photoreactive anthracene moieties were introduced into the polymer component under examination. The labeling content of anthracene can be adjusted by varying the ingredients of the coupling reactions. Upon irradiation with 365 nm UV light, anthracene undergoes photodimerization as illustrated in **Figure 5** for the case of PEA chains.
