Modulating phase-separation in blends of MEHPPV-x with different conjugation lengths

We report here the phase-separation and energy transfer characteristics of segmented MEHPPV blends with two different distributions of conjugation lengths, namely MEHPPV-8 (LC, low conjugation length) and MEHPPV-100 (HC, high conjugation length). Thin films containing varying weight fractions of LC and HC were spin-cast from chloroform solutions. Photoluminescence studies of these thin films suggested that complete energy transfer from LC to HC occurred even though there was phase-separation. Selective chain-collapse of MEHPPV-100 by using a solution containing increasing volume fraction of cyclohexane for spin-coating allowed one to modulate the extent of energy transfer to some extent—typically the extent of energy transfer decreased in the presence of high volume fraction of cyclohexane.