Impact of diblock copolymers on droplet coalescence, emulsification, and aggregation in immiscible homopolymer blends

Jeremy N. Fowler, Tonomori Saito, Renlong Gao, Eric S. Fried, Timothy Edward Long, David L. Green

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Using rheo-optical techniques, we investigated the impact of interfacial wetting of symmetric diblock copolymers (BCPs) on the coalescence and aggregation of polydimethylsiloxane (PDMS) droplets in immiscible polyethylene-propylene (PEP) homopolymers. Anionic polymerization was used to synthesize well-defined matrix homopolymers and symmetric 16 kg/mol-to-16 kg/mol PDMS-b-PEP diblock copolymers with low polydispersity (PDI ≈ 1.02) as characterized with size exclusion chromatography and nuclear magnetic resonance spectroscopy. Blends were formulated to match the viscosities between the droplets and the matrix. Moreover, molecular weights of these components were varied to ensure that the inner block of the copolymer inside the droplet was collapsed and dry, whereas the outer block of the copolymer outside of the droplet was stretched and wet. Droplet breakup and coalescence as well as interfacial tensions were measured using rheo-optical experiments with Linkam shearing stage and an optical microscope. Subsequent to droplet breakup at high shear rates, we found that the BCPs mitigated shear-induced coalescence at lower shear rates. Based on surface tension measurements, the stretching of the BCP increased in lower molecular weight matrices, causing the droplet surface to saturate at lower coverage in line with theoretical predictions. Droplet aggregation was detected with further reductions in shear rate, which was attributed to the dewetting or the expulsion of the matrix from a saturated brush. Ultimately, the regions of droplet coalescence and aggregation were scaled by balancing the forces of shear with those due to the attraction between BCP-coated droplets.

Original languageEnglish
Pages (from-to)2347-2356
Number of pages10
JournalLangmuir
Volume28
Issue number5
DOIs
Publication statusPublished - 2012 Feb 7
Externally publishedYes

Fingerprint

Emulsification
Homopolymerization
Coalescence
coalescing
Block copolymers
copolymers
Agglomeration
shear
matrices
propylene
polyethylenes
interfacial tension
Shear deformation
expulsion
magnetic resonance spectroscopy
brushes
Polyethylene
Polydimethylsiloxane
low molecular weights
chromatography

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Fowler, J. N., Saito, T., Gao, R., Fried, E. S., Long, T. E., & Green, D. L. (2012). Impact of diblock copolymers on droplet coalescence, emulsification, and aggregation in immiscible homopolymer blends. Langmuir, 28(5), 2347-2356. https://doi.org/10.1021/la2037185

Impact of diblock copolymers on droplet coalescence, emulsification, and aggregation in immiscible homopolymer blends. / Fowler, Jeremy N.; Saito, Tonomori; Gao, Renlong; Fried, Eric S.; Long, Timothy Edward; Green, David L.

In: Langmuir, Vol. 28, No. 5, 07.02.2012, p. 2347-2356.

Research output: Contribution to journalArticle

Fowler, Jeremy N. ; Saito, Tonomori ; Gao, Renlong ; Fried, Eric S. ; Long, Timothy Edward ; Green, David L. / Impact of diblock copolymers on droplet coalescence, emulsification, and aggregation in immiscible homopolymer blends. In: Langmuir. 2012 ; Vol. 28, No. 5. pp. 2347-2356.
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