Grafting of a functionalized side-chain liquid crystal polymer on carbon fiber surfaces: Novel coupling agents for fiber/polymer matrix composites

Vassoudevane Le Bonheur, Samuel I Stupp

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Abstract

We studied covalent grafting to functionalized carbon fibers of a specially designed liquid crystalline monomer and its corresponding side-chain liquid crystalline polymer containing pendant chemical functions on their mesogenic groups. From a materials point of view these liquid crystalline compounds could act as coupling agents at fiber/polymer matrix interfaces, offering a mechanism to control composite properties not only through bonding but also through their "spontaneous" molecular orientation in interfacial regions. The grafting methodology for both monomer and polymer to fiber surfaces involved esterification through carbodiimide chemistry in solution. Carboxylic acid groups found on functionalized carbon fiber surfaces were esterified to phenolic functions in the side chains of the experimental polymer. Following grafting procedures the fibers were analyzed by scanning electron microscopy (SEM) and by contact angle measurements. SEM micrographs of fibers grafted with polymer revealed the presence of strongly attached polymeric material on the graphitic surface after rigorous extraction with polymer solvent. Contact angle measurements and polar/dispersive free energy analysis indicated also a smaller polar component of the surface free energy of fibers possibly due to the hydrophobic polymer backbone grafted on the carbon surfaces. On the basis of results, it is concluded that the esterification reaction grafted the polyphenolic liquid-crystal polymer on graphite fiber surfaces.

Original languageEnglish
Pages (from-to)1287-1292
Number of pages6
JournalChemistry of Materials
Volume5
Issue number9
Publication statusPublished - 1993

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Polymer matrix composites
Liquid crystal polymers
Coupling agents
Carbon fibers
Polymers
Fibers
Esterification
Angle measurement
Free energy
Contact angle
Monomers
Crystalline materials
Carbodiimides
Graphite fibers
Scanning electron microscopy
Molecular orientation
Liquids
Carboxylic Acids
Polymer matrix
Carboxylic acids

ASJC Scopus subject areas

  • Materials Chemistry
  • Materials Science(all)

Cite this

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abstract = "We studied covalent grafting to functionalized carbon fibers of a specially designed liquid crystalline monomer and its corresponding side-chain liquid crystalline polymer containing pendant chemical functions on their mesogenic groups. From a materials point of view these liquid crystalline compounds could act as coupling agents at fiber/polymer matrix interfaces, offering a mechanism to control composite properties not only through bonding but also through their {"}spontaneous{"} molecular orientation in interfacial regions. The grafting methodology for both monomer and polymer to fiber surfaces involved esterification through carbodiimide chemistry in solution. Carboxylic acid groups found on functionalized carbon fiber surfaces were esterified to phenolic functions in the side chains of the experimental polymer. Following grafting procedures the fibers were analyzed by scanning electron microscopy (SEM) and by contact angle measurements. SEM micrographs of fibers grafted with polymer revealed the presence of strongly attached polymeric material on the graphitic surface after rigorous extraction with polymer solvent. Contact angle measurements and polar/dispersive free energy analysis indicated also a smaller polar component of the surface free energy of fibers possibly due to the hydrophobic polymer backbone grafted on the carbon surfaces. On the basis of results, it is concluded that the esterification reaction grafted the polyphenolic liquid-crystal polymer on graphite fiber surfaces.",
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N2 - We studied covalent grafting to functionalized carbon fibers of a specially designed liquid crystalline monomer and its corresponding side-chain liquid crystalline polymer containing pendant chemical functions on their mesogenic groups. From a materials point of view these liquid crystalline compounds could act as coupling agents at fiber/polymer matrix interfaces, offering a mechanism to control composite properties not only through bonding but also through their "spontaneous" molecular orientation in interfacial regions. The grafting methodology for both monomer and polymer to fiber surfaces involved esterification through carbodiimide chemistry in solution. Carboxylic acid groups found on functionalized carbon fiber surfaces were esterified to phenolic functions in the side chains of the experimental polymer. Following grafting procedures the fibers were analyzed by scanning electron microscopy (SEM) and by contact angle measurements. SEM micrographs of fibers grafted with polymer revealed the presence of strongly attached polymeric material on the graphitic surface after rigorous extraction with polymer solvent. Contact angle measurements and polar/dispersive free energy analysis indicated also a smaller polar component of the surface free energy of fibers possibly due to the hydrophobic polymer backbone grafted on the carbon surfaces. On the basis of results, it is concluded that the esterification reaction grafted the polyphenolic liquid-crystal polymer on graphite fiber surfaces.

AB - We studied covalent grafting to functionalized carbon fibers of a specially designed liquid crystalline monomer and its corresponding side-chain liquid crystalline polymer containing pendant chemical functions on their mesogenic groups. From a materials point of view these liquid crystalline compounds could act as coupling agents at fiber/polymer matrix interfaces, offering a mechanism to control composite properties not only through bonding but also through their "spontaneous" molecular orientation in interfacial regions. The grafting methodology for both monomer and polymer to fiber surfaces involved esterification through carbodiimide chemistry in solution. Carboxylic acid groups found on functionalized carbon fiber surfaces were esterified to phenolic functions in the side chains of the experimental polymer. Following grafting procedures the fibers were analyzed by scanning electron microscopy (SEM) and by contact angle measurements. SEM micrographs of fibers grafted with polymer revealed the presence of strongly attached polymeric material on the graphitic surface after rigorous extraction with polymer solvent. Contact angle measurements and polar/dispersive free energy analysis indicated also a smaller polar component of the surface free energy of fibers possibly due to the hydrophobic polymer backbone grafted on the carbon surfaces. On the basis of results, it is concluded that the esterification reaction grafted the polyphenolic liquid-crystal polymer on graphite fiber surfaces.

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