Control of hierarchical order in crystalline composites of diblock copolymers and a molecular chromophore

Cara C. Evans, Frank S. Bates, Michael Ward

Research output: Contribution to journalArticle

Abstract

Addition of 2-chloro-4-nitroaniline (CNA) to diblock copolymers of poly(ethylene oxide) (PEO) and polystyrene (PS), poly(ethylethylene) (PEE), or poly(ethylenepropylene) (PEP) results in selective partitioning of CNA into the polar PEa domains. Calorimetry, infrared spectrosocpy, density measurements, and wide-angle X-ray diffraction support the formation of a crystalline molecular complex, comprising two ethylene oxide repeat units per one CNA. The structure of the complex is the same for PEO homopolymer and PEO-based diblocks. Wide-angle X-ray diffraction from uniaxially aligned samples of the PEO:CNA suggests a triclinic unit cell for the complex with a = 9.08 Å, b = 10.48 Å, c = 7.01 Å; and α = 90.98°, β = 88.38°, and γ = 116.72°. The data are consistent with a structural model in which the PEa chains adopt a nominally all-trans zigzag configuration, the chains organized as (100) layers separated by layers of one-dimensional stacks of CNA molecules. Polarized infrared measurements indicate that the molecular planes of the CNA molecules are nominally perpendicular to the PEO chains. The metrics associated with the zigzag PEO configuration appear to allow for optimal hydrogen bonding between the PEO oxygen atoms and the amine protons of the CNA chromophores as well as hydrogen bonding between CNA molecules in adjacent stacks. The arrangement of the CNA molecules in the crystalline PEO:CNA complex differs from the structure of bulk CNA, clearly indicating that host-guest interactions play a major role in chromophore alignment. Small-angle X-ray scattering from a series of samples reveal changes in the block copolymer microstructure as the effective volume of the PEO block is altered by the inclusion of CNA. Whereas the SAXS data for PS-PEO and PEP-PEO copolymers used here reveal hexagonally packed cylinder microstructures in which cylinders of the minority PEO block are surrounded by PS or PEP, the lamellar microstructure is observed for all three block copolymers at the composition of the 2:1 complex. Consequently, these materials can be described as rigid crystalline molecular complexes embedded in robust, ordered polymer microstructures. This control of hierarchical order over length scales, spanning several orders of magnitude, suggests a route to permanent macroscopic ordering of functional molecules, a desirable feature for applications such as optoelectronics. The conformational rigidity associated with these systems offers considerable advantages for the design of SHG materials as entropically driven disordering is inhibited compared to noncrystalline polymer-chromophore materials.

Original languageEnglish (US)
Pages (from-to)236-249
Number of pages14
JournalChemistry of Materials
Volume12
Issue number1
DOIs
StatePublished - 2000

Fingerprint

Chromophores
Polyethylene oxides
Block copolymers
Crystalline materials
Composite materials
Polystyrenes
Molecules
Microstructure
2-chloro-4-nitroaniline
Hydrogen bonds
Polymers
Infrared radiation
X ray diffraction
Ethylene Oxide
Calorimetry
Homopolymerization
X ray scattering
Rigidity
Optoelectronic devices
Amines

ASJC Scopus subject areas

  • Materials Chemistry
  • Materials Science(all)

Cite this

Control of hierarchical order in crystalline composites of diblock copolymers and a molecular chromophore. / Evans, Cara C.; Bates, Frank S.; Ward, Michael.

In: Chemistry of Materials, Vol. 12, No. 1, 2000, p. 236-249.

Research output: Contribution to journalArticle

@article{05deacd17d7c485eabcc20b080c98a34,
title = "Control of hierarchical order in crystalline composites of diblock copolymers and a molecular chromophore",
abstract = "Addition of 2-chloro-4-nitroaniline (CNA) to diblock copolymers of poly(ethylene oxide) (PEO) and polystyrene (PS), poly(ethylethylene) (PEE), or poly(ethylenepropylene) (PEP) results in selective partitioning of CNA into the polar PEa domains. Calorimetry, infrared spectrosocpy, density measurements, and wide-angle X-ray diffraction support the formation of a crystalline molecular complex, comprising two ethylene oxide repeat units per one CNA. The structure of the complex is the same for PEO homopolymer and PEO-based diblocks. Wide-angle X-ray diffraction from uniaxially aligned samples of the PEO:CNA suggests a triclinic unit cell for the complex with a = 9.08 {\AA}, b = 10.48 {\AA}, c = 7.01 {\AA}; and α = 90.98°, β = 88.38°, and γ = 116.72°. The data are consistent with a structural model in which the PEa chains adopt a nominally all-trans zigzag configuration, the chains organized as (100) layers separated by layers of one-dimensional stacks of CNA molecules. Polarized infrared measurements indicate that the molecular planes of the CNA molecules are nominally perpendicular to the PEO chains. The metrics associated with the zigzag PEO configuration appear to allow for optimal hydrogen bonding between the PEO oxygen atoms and the amine protons of the CNA chromophores as well as hydrogen bonding between CNA molecules in adjacent stacks. The arrangement of the CNA molecules in the crystalline PEO:CNA complex differs from the structure of bulk CNA, clearly indicating that host-guest interactions play a major role in chromophore alignment. Small-angle X-ray scattering from a series of samples reveal changes in the block copolymer microstructure as the effective volume of the PEO block is altered by the inclusion of CNA. Whereas the SAXS data for PS-PEO and PEP-PEO copolymers used here reveal hexagonally packed cylinder microstructures in which cylinders of the minority PEO block are surrounded by PS or PEP, the lamellar microstructure is observed for all three block copolymers at the composition of the 2:1 complex. Consequently, these materials can be described as rigid crystalline molecular complexes embedded in robust, ordered polymer microstructures. This control of hierarchical order over length scales, spanning several orders of magnitude, suggests a route to permanent macroscopic ordering of functional molecules, a desirable feature for applications such as optoelectronics. The conformational rigidity associated with these systems offers considerable advantages for the design of SHG materials as entropically driven disordering is inhibited compared to noncrystalline polymer-chromophore materials.",
author = "Evans, {Cara C.} and Bates, {Frank S.} and Michael Ward",
year = "2000",
doi = "10.1021/cm9905794",
language = "English (US)",
volume = "12",
pages = "236--249",
journal = "Chemistry of Materials",
issn = "0897-4756",
publisher = "American Chemical Society",
number = "1",

}

TY - JOUR

T1 - Control of hierarchical order in crystalline composites of diblock copolymers and a molecular chromophore

AU - Evans, Cara C.

AU - Bates, Frank S.

AU - Ward, Michael

PY - 2000

Y1 - 2000

N2 - Addition of 2-chloro-4-nitroaniline (CNA) to diblock copolymers of poly(ethylene oxide) (PEO) and polystyrene (PS), poly(ethylethylene) (PEE), or poly(ethylenepropylene) (PEP) results in selective partitioning of CNA into the polar PEa domains. Calorimetry, infrared spectrosocpy, density measurements, and wide-angle X-ray diffraction support the formation of a crystalline molecular complex, comprising two ethylene oxide repeat units per one CNA. The structure of the complex is the same for PEO homopolymer and PEO-based diblocks. Wide-angle X-ray diffraction from uniaxially aligned samples of the PEO:CNA suggests a triclinic unit cell for the complex with a = 9.08 Å, b = 10.48 Å, c = 7.01 Å; and α = 90.98°, β = 88.38°, and γ = 116.72°. The data are consistent with a structural model in which the PEa chains adopt a nominally all-trans zigzag configuration, the chains organized as (100) layers separated by layers of one-dimensional stacks of CNA molecules. Polarized infrared measurements indicate that the molecular planes of the CNA molecules are nominally perpendicular to the PEO chains. The metrics associated with the zigzag PEO configuration appear to allow for optimal hydrogen bonding between the PEO oxygen atoms and the amine protons of the CNA chromophores as well as hydrogen bonding between CNA molecules in adjacent stacks. The arrangement of the CNA molecules in the crystalline PEO:CNA complex differs from the structure of bulk CNA, clearly indicating that host-guest interactions play a major role in chromophore alignment. Small-angle X-ray scattering from a series of samples reveal changes in the block copolymer microstructure as the effective volume of the PEO block is altered by the inclusion of CNA. Whereas the SAXS data for PS-PEO and PEP-PEO copolymers used here reveal hexagonally packed cylinder microstructures in which cylinders of the minority PEO block are surrounded by PS or PEP, the lamellar microstructure is observed for all three block copolymers at the composition of the 2:1 complex. Consequently, these materials can be described as rigid crystalline molecular complexes embedded in robust, ordered polymer microstructures. This control of hierarchical order over length scales, spanning several orders of magnitude, suggests a route to permanent macroscopic ordering of functional molecules, a desirable feature for applications such as optoelectronics. The conformational rigidity associated with these systems offers considerable advantages for the design of SHG materials as entropically driven disordering is inhibited compared to noncrystalline polymer-chromophore materials.

AB - Addition of 2-chloro-4-nitroaniline (CNA) to diblock copolymers of poly(ethylene oxide) (PEO) and polystyrene (PS), poly(ethylethylene) (PEE), or poly(ethylenepropylene) (PEP) results in selective partitioning of CNA into the polar PEa domains. Calorimetry, infrared spectrosocpy, density measurements, and wide-angle X-ray diffraction support the formation of a crystalline molecular complex, comprising two ethylene oxide repeat units per one CNA. The structure of the complex is the same for PEO homopolymer and PEO-based diblocks. Wide-angle X-ray diffraction from uniaxially aligned samples of the PEO:CNA suggests a triclinic unit cell for the complex with a = 9.08 Å, b = 10.48 Å, c = 7.01 Å; and α = 90.98°, β = 88.38°, and γ = 116.72°. The data are consistent with a structural model in which the PEa chains adopt a nominally all-trans zigzag configuration, the chains organized as (100) layers separated by layers of one-dimensional stacks of CNA molecules. Polarized infrared measurements indicate that the molecular planes of the CNA molecules are nominally perpendicular to the PEO chains. The metrics associated with the zigzag PEO configuration appear to allow for optimal hydrogen bonding between the PEO oxygen atoms and the amine protons of the CNA chromophores as well as hydrogen bonding between CNA molecules in adjacent stacks. The arrangement of the CNA molecules in the crystalline PEO:CNA complex differs from the structure of bulk CNA, clearly indicating that host-guest interactions play a major role in chromophore alignment. Small-angle X-ray scattering from a series of samples reveal changes in the block copolymer microstructure as the effective volume of the PEO block is altered by the inclusion of CNA. Whereas the SAXS data for PS-PEO and PEP-PEO copolymers used here reveal hexagonally packed cylinder microstructures in which cylinders of the minority PEO block are surrounded by PS or PEP, the lamellar microstructure is observed for all three block copolymers at the composition of the 2:1 complex. Consequently, these materials can be described as rigid crystalline molecular complexes embedded in robust, ordered polymer microstructures. This control of hierarchical order over length scales, spanning several orders of magnitude, suggests a route to permanent macroscopic ordering of functional molecules, a desirable feature for applications such as optoelectronics. The conformational rigidity associated with these systems offers considerable advantages for the design of SHG materials as entropically driven disordering is inhibited compared to noncrystalline polymer-chromophore materials.

UR - http://www.scopus.com/inward/record.url?scp=0033798457&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033798457&partnerID=8YFLogxK

U2 - 10.1021/cm9905794

DO - 10.1021/cm9905794

M3 - Article

VL - 12

SP - 236

EP - 249

JO - Chemistry of Materials

JF - Chemistry of Materials

SN - 0897-4756

IS - 1

ER -