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Title: Measuring the Degree of Crystallinity in Semicrystalline Regioregular Poly(3-hexylthiophene)

Authors:
; ;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Polymer-Based Materials for Harvesting Solar Energy (PHaSE)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1370277
DOE Contract Number:
SC0001087
Resource Type:
Journal Article
Resource Relation:
Journal Name: Macromolecules; Journal Volume: 49; Journal Issue: 12; Related Information: PHaSE partners with University of Massachusetts, Amherst (lead) and Lowell; Oak Ridge National Laboratory; Pennsylvania State University; Renssalaer Polytechnic Institute; University of Pittsburgh
Country of Publication:
United States
Language:
English

Citation Formats

Shen, Xiaobo, Hu, Weiguo, and Russell, Thomas P. Measuring the Degree of Crystallinity in Semicrystalline Regioregular Poly(3-hexylthiophene). United States: N. p., 2016. Web. doi:10.1021/acs.macromol.6b00799.
Shen, Xiaobo, Hu, Weiguo, & Russell, Thomas P. Measuring the Degree of Crystallinity in Semicrystalline Regioregular Poly(3-hexylthiophene). United States. doi:10.1021/acs.macromol.6b00799.
Shen, Xiaobo, Hu, Weiguo, and Russell, Thomas P. 2016. "Measuring the Degree of Crystallinity in Semicrystalline Regioregular Poly(3-hexylthiophene)". United States. doi:10.1021/acs.macromol.6b00799.
@article{osti_1370277,
title = {Measuring the Degree of Crystallinity in Semicrystalline Regioregular Poly(3-hexylthiophene)},
author = {Shen, Xiaobo and Hu, Weiguo and Russell, Thomas P.},
abstractNote = {},
doi = {10.1021/acs.macromol.6b00799},
journal = {Macromolecules},
number = 12,
volume = 49,
place = {United States},
year = 2016,
month = 6
}
  • Here, we systematically varied the degree of fluorination along the backbone of a series of highly regioregular 3-hexylthiophene-based polymers, P3HT-50F, P3HT-33F and P3HT-25F, in which 50%, 33% and 25% of the thiophene units within the polymer chain contain fluorine atoms in the available 4-position. These materials were homopolymerized using the Kumada catalyst transfer polycondensation method from a set of mono-fluorinated bi-, ter- and quarterthiophenes, to ensure high polymer regioregularity and evenly-spaced fluorine atoms along the conjugated thiophene backbone. The monomers were obtained from a synthetic route consisting of iterative Migita-Stille couplings of fluorinated and non-fluorinated 3- hexylthiophenes. The effect ofmore » the fluorine atoms on both polymer structure and properties is presented, with supporting quantum mechanical calculations that rationalize the intrinsic conformation preferences of the three P3HT derivatives. P3HT-50F (M¯ n = 34 kg/mol, 98.5% rr), P3HT-33F (M¯ n = 46 kg/mol, 98% rr) and P3HT-25F (M¯ n = 53 kg/mol, 95% rr) displayed HOMO levels of -5.34, -5.26 and -5.24 eV, bandgaps of 1.98, 1.98 and 1.97 eV, and average field-effect transistor hole mobilities of 4.5 × 10 -3, 2.7 × 10 -2, and 1.2 × 10 -2 cm 2 V -1s -1, respectively.« less
  • Recent research on poly(alkylthiophenes) (PAT) has concentrated on the regularity and structure of the polymer chain of PAT. The 3-alkyl substituent in a thiophene ring can be incorporated into a polymer chain with two different regioregularities: head-to-tail (HT) and head-to-head (HH). Head-to-head linkages can cause defects in the polymer chain. The highest regioregularity reported to date for HT-PAT is 91% (usually 50-60% HT regioregularity). The authors report herein a new and facile synthesis which leads to the first completely head-to-tail regioregular poly(3-hexylthiophene 2,5-diyl) (HT-PHT) and an alternative synthesis which yields an unusual regiorandom PHT with almost equal distribution of differentmore » linkages in the polymer chain. Both polymers have been characterized by NMR, IR, elemental analysis, GPC (gel-permeation chromatography), and UV-vis. 11 refs., 2 figs., 1 tab.« less
  • A synthetic route was developed for the preparation of di- and trifunctional Ni complex-based initiators. Each initiator affords well-defined 2-arm (V-shaped) and 3-arm (Y-shaped) regioregular poly(3-hexylthiophene) (rr-P3HT) with controlled molecular weight and narrow polydispersities by the externally initiated Kumada catalyst-transfer polycondensation. The core spacer length and end o-tolylhalide group of the functional initiators exhibited differences in reactivity and show that the biphenyl spacers are effective for the synthesis of V-shaped and Y-shaped rr-P3HTs.
  • Inverse photoemission spectroscopy (IPES) enables the characterization of the density of states of unoccupied energy states above the Fermi level. However, due to the relatively high electron currents required to achieve useful signal to noise ratios, sample damage is a concern. Regioregular poly(3-hexylthiophene) (rr-P3HT) was used to systematically study the influence of electron radiation during IPES measurements on a prototypical conductive polymer. A series of IPES measurements exposing the samples to a range of electron fluxes was performed. An analysis of the electronic structure and the morphology showed that significant changes occurred in the investigated samples depending on the electronmore » flux. X-ray diffraction results revealed that the root cause of the spectral changes is most likely related to crystallization of the film in an edge-on orientation. This was confirmed by Raman spectroscopy where both the C-C and C=C stretch modes shifted to lower frequencies after 5 IPES scans indicating a more ordered molecular structure. The observation of these stretch modes even after exposure to higher electron flux indicates that the main chemical structure of the P3HT molecules remains mostly intact during the IPES measurements. The absence of significant changes in C 1s and S 2p photoemission core level lines also confirmed this conclusion.« less