Published on Web 10/29/2005
Molecular Recognition in Structured Matrixes: Control of
Guest Localization in Block Copolymer Films
Roy Shenhar,†,§ Hao Xu, Benjamin L. Frankamp, Thomas E. Mates,
†
†
‡
Amitav Sanyal,†,¶ Oktay Uzun, and Vincent M. Rotello*
†
,†
Contribution from the Department of Chemistry, UniVersity of Massachusetts-Amherst,
Amherst, Massachusetts 01003, and Department of Materials Engineering, UniVersity of
California, Santa Barbara, California 93106-5050
Abstract: We demonstrate the use of molecular recognition to control the spatial distribution of guest
molecules within block copolymer films. Block copolymers bearing recognition units were combined with
complementary and noncomplementary molecules, and the extent of segregation of these molecules into
the different domain types within microphase-separated thin films was quantitatively analyzed using dynamic
secondary ion mass spectrometry (SIMS). Complementarity between the guest molecules and the polymer
functionalities proved to be a key factor and an efficient tool for directing the segregation preference of the
molecules to the different domain types. The effect of segregation preference on the glass transition
temperature was studied using differential scanning calorimetry (DSC), and the results corroborate the
SIMS findings. In a complementary study, guests with tunable sizes (via dendron substituents) were used
to control block copolymer morphology. Morphological characterization using transmission electron
microscopy (TEM) and X-ray diffraction reveal that selectivity differences can be directly translated into
the ability to obtain different morphologies from recognition unit-functionalized block copolymer scaffolds.
Introduction
state morphologies on the 10-100 nm scale, a property that
makes them very attractive materials for nanotechnological
applications. Additionally, block copolymers can be used as
Molecular recognition provides a powerful tool for the control
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of self-assembly processes. The combination between molecular
templates for selective incorporation and ordering of inorganic
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recognition and polymers has been receiving increased attention
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nanoparticles for optical application and for directing the
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lately, as it provides facile routes to polymer functionalization,
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segregation of additives for the creation of nano-objects,
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incorporation of performance-enhancing additives, modification
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mesoporous
and stimuli-responsive materials.
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of surface properties, and nanoparticle assembly. A different
type of self-assembly mechanism is exhibited by block copoly-
mers. Block copolymers self-organize into well-defined solid-
Integration of block copolymer self-assembly with molecular
recognition processes provides access to hierarchical materials
with a wide range of potential applications. In recent studies, a
variety of electrostatic and single-point hydrogen-bonding motifs
have been used to control guest localization in block co-
†
‡
§
University of Massachusetts.
University of California.
Current address: Institute of Chemistry, The Hebrew University of
Jerusalem, Jerusalem, Israel 91904.
¶
Current address: Department of Chemistry, Faculty of Arts and
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