Gradient copolymers with broad glass transition temperature regions: Design of purely interphase compositions for damping applications

Michelle M. Mok, Jungki Kim, John M Torkelson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

95 Scopus citations


Gradient copolymers with gradients in composition along the chain lengths are synthesized by controlled radical polymerization, and their damping behaviors are compared to those of random and block copolymers. The effect of comonomer incompatibility is studied by comparing behaviors of strongly segregating styrene/4-hydroxystyrene (S/HS) and moderately segregating styrene/n-butyl acrylate (S/nBA) copolymers. The effect of composition gradient steepness is studied by designing "constant" or "increasing" gradients via the comonomer addition rate during semibatch polymerization. Dynamic mechanical analysis (DMA) is used to compare the temperature dependences of the storage modulus (E′), loss modulus (E″), and tan δ of the materials. A glass transition breadth (ΔTg) is defined by a temperature range over which E' decreases from 109 Pa to 10 8 Pa. The gradient copolymer ΔTgs are at least four times larger than the random copolymer ΔTgs. The S/nBA gradient copolymers show strong effects of gradient steepness on ATg, with ΔT g being much larger for the increasing gradient than for the constant gradient. DMA data are compared to predictions by Hashimoto et al. for tapered block copolymers in the limit where the taper extends across the entire chain. The shapes of their calculated temperature dependences of E′ and E″ correspond well to the gradient copolymers with large ΔTg values, providing strong support for symmetric gradient copolymers forming nanoscale, ordered domains with sinusoidal composition profiles.

Original languageEnglish (US)
Pages (from-to)48-58
Number of pages11
JournalJournal of Polymer Science, Part B: Polymer Physics
Issue number1
StatePublished - Jan 1 2008


  • Addition polymerization
  • Block copolymers
  • Copolymerization
  • Glass transition
  • Mechanical properties
  • Nanoheterogeneity
  • Structure-property relations

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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