Remarkable glass transition breadths up to 120 K exhibited by block-gradient copolymers and by gradient copolymers plasticized by oligomer

Lingqiao Li, Stephen R. Marrou, John M. Torkelson*

*Corresponding author for this work

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

The glass transition temperature (Tg) breadth of gradient copolymers can be dramatically increased by covalent attachment of homopolymer (or random copolymer heavy in one comonomer) leading to block-gradient copolymers or by blending with oligomer. Styrene/n-butyl acrylate (S/nBA) and styrene/4-vinyl pyridine (S/4VP) gradient and block-gradient copolymers were synthesized by one-pot, semi-batch nitroxide-mediated polymerization. The glass transition responses were characterized using derivative heat flow curves from differential scanning calorimetry. For moderately segregating S/nBA gradient copolymer, covalently attaching a homopolymer or quasi-homopolymer block leads to nanophase separation with extreme local compositions closer to those of neat S or neat nBA repeat units. The achievement of such extreme local compositions results in significant Tg breadth increases (from 87 K for gradient copolymer up to 120 K in the block-gradient copolymer) and the onset or endpoint of the block-gradient copolymer Tg breadth being close or equal to the Tg of high molecular weight (MW) polystyrene (PS) or poly(n-butyl acrylate). Equally notable, with 20 wt% PS oligomer blended as selective plasticizer, the Tg breadth of a strongly segregating S/4VP gradient copolymer nearly triples relative to that of neat gradient copolymer (109 K vs. 38 K) and exhibits an onset ∼80 K below the onset of neat gradient copolymer and the Tg of high MW PS. Besides its scientific significance in tuning local compositions accessible in nanophase-separated gradient copolymers, this study provides powerful tools for the design of gradient copolymer systems for potential applications as damping materials that are effective over extraordinarily broad temperature ranges.

Original languageEnglish (US)
Pages (from-to)145-153
Number of pages9
JournalPolymer
Volume151
DOIs
StatePublished - Aug 29 2018

Keywords

  • Glass transition breadth
  • Gradient copolymer
  • Nanophase separation
  • Selective plasticization

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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