Interplay of localized pyrene chromophores and π-conjugation in novel poly(2,7-pyrene) ladder polymers.

We present a detailed spectroscopic study, along with the synthesis, of conjugated, ladder-type 2,7-linked poly(pyrene)s. We observe a delocalization of the first singlet excited state along the polymer backbone, i.e., across the 2,7 linkage in the pyrene moiety, in contrast to earlier studies on conjugated 2,7-linked poly(pyrene)s without ladder structure. The electronic signature of the pyrene unit is, however, manifested in an increased lifetime and reduced oscillator strength as well as a modified vibronic progression in absorption of the singlet state compared to a ladder-type poly(para-phenylene) (MeLPPP). Furthermore, the reduced oscillator strength and increased lifetime slow down Förster-type energy transfer in films, where this transfer occurs to sites with increasing inter-chain coupling of H-type nature.

Incorporating an Alternating Donor-Acceptor Structure into a Ladder Polymer Backbone.

Incorporation of the donor-acceptor structure of an alternating conjugated copolymer into a rigid ladder polymer backbone is reported. The resulting ladder polymers show optical features typical of rigid ladder polymers, but present an increased Stokes shift if compared to their non-polar counterparts. This behavior reflects the occurrence of charge transfer processes during excitation and leads to a positive solvatochromism.