Journal of Materials Research

Reviews

Length-dependent self-assembly of oligothiophene derivatives in thin films

Brian S. Rolczynskia1, Jodi M. Szarkoa2, Byeongdu Leea3, Joseph Strzalkaa3, Jianchang Guoa4, Yongye Lianga5, Luping Yua6 c1 and Lin X. Chena7 c2

a1 Department of Chemistry, Northwestern University, Evanston, Illinois 60208; Chemical Sciences and Engineering Division and Argonne National Laboratory, Argonne, Illinois 60439; and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208

a2 Department of Chemistry, Northwestern University, Evanston, Illinois 60208; and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208

a3 X-ray Sciences Division, Argonne National Laboratory, Argonne, Illinois 60439

a4 Chemical Sciences and Engineering Division and Argonne National Laboratory, Argonne, Illinois 60439; and Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637

a5 Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637

a6 Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208; and Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637

a7 Department of Chemistry, Northwestern University, Evanston, Illinois 60208; Chemical Sciences and Engineering Division and Argonne National Laboratory, Argonne, Illinois 60439; and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208

Abstract

Thin-film aggregation characteristics of a series of oligothiophenes with a central thieno[3,4-b]thiophene ester unit and 4 (M5), 8 (M9), and 16 (M17) regioregular hexylthiophene units were investigated. These oligomers exhibited length-dependent self-assembly characteristics upon spin coating. M9 formed long fibers, while M5 and M17 formed random domains. Grazing incidence x-ray diffraction was performed to understand the reason for this length dependence. The M5 had a dominant ester–ester interaction that disrupted long-range order. The M9 morphology was due to a balance of orthogonal backbone and ester effects, which imposed long-range order on the M9 aggregates. Meanwhile, the M17 ester chain had a smaller relative contribution to packing and functioned as a molecular defect, disrupting long-range order. As a result, though the local self-assembly between monomers was very similar for the molecules, backbone length dependent changes in intermolecular forces dominated long-range structure. The analysis of self-assembly characteristics in these materials provides guidance in the design of organic conjugated materials for use in semiconductor devices.

(Received May 06 2010)

(Accepted August 04 2010)

(Online publication January 19 2011)

Key Words:

  • X-ray Diffraction (XRD);
  • Self-Assembly;
  • Polymer

Correspondence:

c1 Address all correspondence to these authors. e-mail: lchen@anl.gov

c2 e-mail: lupingyu@uchicago.edu

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