The Impact of Polydispersity and Molecular Weight on the Order-Disorder Transition in Poly(3-hexylthiophene).
Conjugated poly(3-hexylthiophene) (P3HT) chains are known to exist at least in two distinct conformations: a coiled phase and a better ordered aggregated phase. Employing steady state absorption and fluorescence spectroscopy, we measure the course of aggregation of P3HT in tetrahydrofuran (THF) solution within a temperature range of 300 K to 170 K. We show that aggregation is a temperature controlled process, driven by a thermodynamic order-disorder transition. The transition temperature increases with the molecular weight of the chains and can be rationalized in the theory of Sanchez. This implies a smearing out of the phase transition in samples with increasing polydispersity and erodes the signature of a first order phase transition. The detection of a hysteresis when undergoing cooling/heating cycles further substantiates this reasoning.
†Experimental Physics II, ‡Bayreuth Institute of Macromolecular Science, and §Applied Functional Polymers, Macromolecular Chemistry 1, University of Bayreuth, 95540 Bayreuth, Germany.
Fabian
F
Panzer
†Experimental Physics II, ‡Bayreuth Institute of Macromolecular Science, and §Applied Functional Polymers, Macromolecular Chemistry 1, University of Bayreuth, 95540 Bayreuth, Germany.
Heinz
H
Bässler
†Experimental Physics II, ‡Bayreuth Institute of Macromolecular Science, and §Applied Functional Polymers, Macromolecular Chemistry 1, University of Bayreuth, 95540 Bayreuth, Germany.
Ruth
R
Lohwasser
†Experimental Physics II, ‡Bayreuth Institute of Macromolecular Science, and §Applied Functional Polymers, Macromolecular Chemistry 1, University of Bayreuth, 95540 Bayreuth, Germany.
Mukundan
M
Thelakkat
†Experimental Physics II, ‡Bayreuth Institute of Macromolecular Science, and §Applied Functional Polymers, Macromolecular Chemistry 1, University of Bayreuth, 95540 Bayreuth, Germany.
Anna
A
Köhler
absorption; aggregation; fluorescence; phase-transition; temperature-dependent