Strain, Chain, Repeat: Synthesis and Optoelectronic Properties of Poly(Naphthalene Benzene Vinylene)s

Poly(phenylenevinylene)s (PPV)s are a class of fluorescent conjugated polymers used in organic light emitting diodes (OLEDs). Living chain growth polymerization of PPVs is typically achieved by ring-opening metathesis polymerization (ROMP) of highly strained cyclophanedienes. While benzene-based cyclophanedienes are routinely reported, living or controlled ROMP of naphthalene-benzene containing mixed cyclophanedienes remains a challenge. This work describes the synthesis and polymerization of an alkoxy substituted naphthalene-benzene cyclophanediene using Schrock's molybdenum olefin metathesis catalyst. We demonstrate the efficacy of this strategy in producing poly(naphthalene benzene vinylene) (PNBV)s with controlled molecular weights and narrow dispersities. The produced PNBVs are highly fluorescent polymers in solution and as thin films with distinct emission signatures arising from the benzene and naphthalene chromophores. An unoptimized PNBV thin film transistor exhibited a hole mobility of 8 × 10^-9 cm²/V·s, which increased to 1 × 10^-7 cm²/V·s upon doping with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) and (tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) (FK 209). This expansion of ROMP to include the naphthalene moiety as well as a mixed-aromatic system will usher further development of electronically diverse PPVs with advanced solid-state applications.