Network structure of polyfluorene sheets as a function of alkyl side chain length.

The formation of self-organized structures in poly(9,9-di-n-alkylfluorene)s ∼1 vol % methylcyclohexane (MCH) and deuterated MCH (MCH-d(14)) solutions was studied at room temperature using neutron and x-ray scattering (with the overall q range of 0.00058-4.29 Å(-1)) and optical spectroscopy.

Synthesis, excited state dynamics, and optical characteristics of oligophenyl-based swivel cruciforms in solution and solid state.

Oligophenyl-based swivel cruciforms are an amorphous class of materials for potential use in display applications. In this work, we describe the design, synthesis, and structural and optical properties of a group of chromophores with varying degrees of π-conjugation that produce blue emission and high photoluminescence quantum yields (PLQYs). The swivel cruciforms are branched complexes consisting of two arms, and the relative rotation of these arms is an important factor that determines the optical properties of these systems.

Decoupling 2D inter- and intrachain energy transfer in conjugated polymers.

The dimensionality of conjugated polymer systems plays an important role in energy-transfer processes, and 1D and 2D energy transfer of excitations are typically much slower than that between pi-stacked chains within a 3D polymeric solid. However, whether 2D energy transfer in conjugated polymers occurs mainly along polymer chains (intrachain), or between in-plain-adjacent polymer chains (interchain), has yet to be determined due to the difficulty of experimentally decoupling inter- and intrachain interaction in a 2D polymer system. This can be achieved by incorporating conjugated polymer chains into the planar galleries of layered matrices which sterically hinder polymer aggregation and pi-pi interchain interactions.

Control over phase behavior and solution structure of hairy-rod polyfluorene by means of side-chain length and branching.

We present guidelines on how the solution structure of pi -conjugated hairy-rod polyfluorenes is controlled by the side-chain length and branching. First, the semiquantitative mean-field theory is formulated to predict the phase behavior of the system as a function of side-chain beads (N). The phase transition at N=N{ *} separates a lyotropic phase with solvent coexistence (NN{ *}).

Stark spectroscopy of excited-state transitions in a conjugated polymer.

Stark spectroscopy, which is well established for probing transitions between the ground and excited states of many material classes, is extended to transitions between transient excited states. To this end, it is combined with femtosecond pump-probe spectroscopy on a conjugated polymer with appropriately introduced traps which harvest excitation energy and build up a sufficient excited state population. The results indicate a significant difference in the effective dipole moments between two short lived excited states.