Anthracene-labeled polystyrene blends

Experiments on temporally forcing of phase separation were performed using mixtures of poly(vinyl methyl ether) (PVME) and anthracene-labeled polystyrene (PSA). The phase diagram of this PSA/PVME blend is illustrated in Figure 1 together with the composition dependence of its glass transition... 

Anthracene labelled polystyrene chains (called PAP) with a number average molecular weight, M = 287,000, have been incorporated (at 1 % w/w concentration) in a polystyrene matrix (PS 200) with a narrow M.W. distribution (M = 191,000, M = 207,000). The samples moulded under pressure and annealed to obtain transparent bubbleless samples and to avoid any birefringence. Sample size was 8 cm long, 2 cm wide and 0.2 thicko Tg of the resultant polymer blend measured by differential scanning calorimeter at a heating rate 10 C min was 107.5 C. 

In order to study the system PS-PVME, our procedure reqjfires the addition in the blend of labelled polystyrene. The label PS, which consists of PS chains containing anthracene fluorescent groups in their middle (Fig. 1), is suitable for this purpose. As previously reported (18) it is prepared by termj nation of living PS chains by 9,10 bis (bromomethyl)anthracene. PS concentration is adjusted to be around 6 ppm of anthracenic units (i.e. less than 0.1 and 1 wt %... 

Phase separation of polystyrene/poly(vinyl methyl ether) blends was induced under spatially and temporally periodic forcing conditions by taking advantage of either photodimerization of anthracene or photoisomerization of /rt//i .9 stilbene chemically labeled on polystyrene chains. Significant mode election processes driven by these reactions were experimentally observed and analyzed for both cases. These experimental results reveal a potential method of morphology control using periodic forcing conditions. 

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