Synthesis and thermal properties of thermosetting bis-benzocyclobutene-terminated arylene ether monomers

Loon Seng Tan, N. Venkatasubramanian, Patrick T. Mather, Marlene D. Houtz, Charles L. Benner

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

A series of new bis-benzocyclobutene-endcapped arylene ether monomers was prepared and characterized. Whereas 2,6-bis(4-benzocyclobutenyloxy)benzonitrile (BCB-EBN) could be prepared in good yield using the standard procedure (K2CO3/ NMP/toluene/Dean-Stark trap/120°C), other bis(benzocyclobutene) (BCB)-terminated monomers containing ether-benzophenone (BCB-EK), ether-phenylsulfone (BCB-ES), and ether-6F-benzoxazole (BCB-EBO) moieties were invariably contaminated by monoendcapped products under similar reaction conditions. This can be attributed to a much greater activating effect of the nitrile group on the ortho-fluorides in the aromatic nucleophilic displacement reaction than the carbonyl, sulfonyl, and benzoxazolyl groups. However, the latter monomers could be synthesized (70-80%) from 4-trimethylsiloxybenzocyclobutene and respective aromatic fluorides in the presence of CsF at 140°C. Similar curing behaviors under N2 (DSC: extrapolated onset and peak temperatures at 227-230° and 260-262°C, respectively) characterized all four monomers. BCB-EK, BCB-ES, and BCB-EBN showed melting transitions at 108, 119, and 146°C, in that order. As BCB-EBO contained more rigid benzoxazole segments, it only exhibited a glass transition (Tg) at 85°C prior to curing exotherm, after it had been previously heated to 125°C. The following Tgs were observed for the cured materials: BCB-EK (201°C), BCB-EBN (224°C), BCB-ES (264°C), and BCB-EBO (282°C). The relative thermal stability according to TGA (He) results is: BCB-ES < BCB-EBN < BCB-EK < BCB-EBO. Finally, the results from thermal analysis, infrared spectroscopic, and variable temperature microscopic studies indicated that the nitrile group plays an important role in the cure chemistry, thermal, and microstructural properties of BCB-EBN.

Original languageEnglish (US)
Pages (from-to)2637-2651
Number of pages15
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume36
Issue number14
DOIs
StatePublished - Oct 1998

Keywords

  • 4-hydroxybenzocyclobutene
  • 4-trimethylsiloxybenzocyclobutene
  • Arylene ether monomers
  • Benzocyclobutene
  • Cesium fluoride
  • Thermosets

ASJC Scopus subject areas

  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry

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