Breadth of glass transition temperature in styrene/ acrylic acid block, random, and gradient copolymers: Unusual sequence distribution effects

Christopher L.H. Wong, Jungki Kim, John M. Torkelson*

*Corresponding author for this work

Research output: Contribution to journalArticle

50 Scopus citations

Abstract

Block, random, and gradient copolymers of styrene (S) and acrylic acid (AA) are synthesized by conventional or controlled radical polymerization, and their glass transition temperature (Tg) behaviors are compared. The location and breadth of the TgS are determined using derivatives of differential scanning calorimetry heating curves. Each S/AA random copolymer exhibits one narrow Tg, consistent with a single phase of limited compositional nanoheterogeneity. Block copolymers exhibit two narrow T gs originating from nanophase separation into ordered domains with nearly pure S or nearly pure AA repeat units. Each gradient copolymer exhibits a Tg response with a ∼50-56 °C breadth that extends beyond the upper Tg of the block copolymers. For copolymers of similar composition, the maximum value in the gradient copolymer Tg response is consistent with that of a random copolymer, which has an enhanced T g relative to poly( acrylic acid) due to more effective hydrogen bonding when AA units are separated along the chain backbone by S units. These results indicate that gradient copolymers with ordered nanostructures can be rationally designed, which exhibit broad glass transitions that extend to higher temperature than the Tgs observed with block copolymers.

Original languageEnglish (US)
Pages (from-to)2842-2849
Number of pages8
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume45
Issue number20
DOIs
StatePublished - Oct 15 2007

Keywords

  • Addition polymerization
  • Block copolymers
  • Calorimetry
  • Copolymerization
  • Diblock copolymers
  • Glass transition
  • Hydrophilic
  • Microstructure
  • Polymers
  • Radical polymerization
  • Thermal properties

ASJC Scopus subject areas

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

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