A new method to make polymers with flexible main chains and photoelectric pendants for organic semiconductors

Two novel polymers (PFMA-Ma and PFMA-Mb) were synthesized through an efficient and simple method combining conventional free radical polymerization and a Diels–Alder reaction. Different molar percentage compositions of the functionalized pendants in the polymers and two different steric configurations: endo and exo in the D–A adduct structures are revealed in 1H NMR spectra. In addition, DSC curves demonstrate that the reverse Diels–Alder reactions take place at higher temperatures (between 120 °C and 150 °C). Moreover, both of the fluorescence intensities of the two polymer films (PFMA-Ma (x = 0.700) and PFMA-Mb (x = 0.609)) become weak and even almost disappear with the increase of the annealing temperature, indicating that thermal annealing induces π–π stacking and aggregation of the pendants in the polymers. Concurrently, as the molar ratios of pendant moieties in the polymers are increased, a characteristic peak of face-to-face stacking appears in the fluorescence spectra of PFMA-Ma and a slight red-shift is observed in the fluorescence spectra of PFMA-Mb. These phenomena suggest that high molar percentage of pendants is also beneficial to their π–π stacking and aggregation. This study may provide some insights into the stacking of pendants in polymers and its influencing factors, which will be useful when these polymer materials are applied in optoelectronic devices.