Characteristics of lamellar mesophases in strongly segregated broad dispersity ABA triblock copolymers

Adam K. Schmitt, Mahesh K. Mahanthappa

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

We report the synthesis and characterization of a series of 13 strongly segregated poly(lactide-b-1,4-butadiene-b-lactide) (LBL) triblock copolymers, in which a broad dispersity center B segment (D = Mw/Mn ∼ 1.7-1.9) is embedded between two narrow dispersity L end blocks (D ≤ 1.20). Derived from chain transfer ring-opening metathesis polymerization (ROMP-CT) of 1,5,9-cyclododecatriene in the presence of 1,4-diacetoxy-2-butene, α,ω-dihydroxytelechelic poly(1,4-butadienes) serve as ring-opening transesterification polymerization (ROTEP) macroinitiators for the parallel synthesis of LBL triblock copolymers with Mn = 12.4-28.7 kg/mol and volume fractions fB = 0.44-0.79. By determining the Flory-Huggins interaction parameter χLB = 0.192 at 155 °C from mean-field theory analyses of synchrotron X-ray scattering profiles for a narrow dispersity LB diblock copolymer, we estimate that the segregation strengths associated with the broad dispersity LBL copolymers range χLBN = 35.1-83.6. As compared to their narrow dispersity analogues reported herein, broad B segment dispersity shifts the composition-dependent lamellar phase window in LBL triblocks to higher values of fB = 0.52-0.75. Contrary to previous reports of substantial dispersity-induced, lamellar domain spacing dilation in weakly segregated AB diblock and ABA triblock copolymers, strongly segregated LBL copolymers exhibit surprisingly similar domain sizes and scaling relations (d ∞ N0.72±0.06) to their narrow dispersity analogues. This finding suggests that the magnitude of χAB determines the moment of the molar mass distribution that controls the observed lamellar domain spacing.

Original languageEnglish (US)
Pages (from-to)4346-4356
Number of pages11
JournalMacromolecules
Volume47
Issue number13
DOIs
StatePublished - Jul 8 2014

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