Cononsolvency-induced micellization kinetics of pyrene end-labeled diblock copolymer of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate studied by stopped-flow light-scattering and fluorescence

Jingyi Rao, Jingyan Zhang, Jian Xu, Shiyong Liu

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Cononsolvency-induced micellization kinetics of a pyrene end-labeled diblock copolymer of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate, Py-PNIPAM-b-POEGMA, was investigated in detail via a combination of stopped-flow light-scattering and fluorescence techniques. Upon a stopped-flow jump from pure methanol to proper methanol/water mixtures, scattered light intensity exhibited an initial increase and then stabilized out; whereas the time-dependence of monomer to excimer fluorescence intensity ratios (IE / IM) revealed an abrupt increase followed by a gradual decrease to plateau values. The dynamic traces of scattered intensity can be well fitted by double exponential functions, the obtained τ1, scat and τ2, scat can be ascribed to processes of forming quasi-equilibrium micelles and their relaxation into final equilibrium states, respectively. On the other hand, a triple exponential function was needed to fit the dynamic traces of IE / IM, leading to three characteristic relaxation times (τ1, fluo, τ2, fluo, and τ3, fluo). It was found that the time scales of τ1, scat and τ2, scat obtained from stopped-flow light scattering were in general agreement with τ2, fluo and τ3, fluo obtained from stopped-flow fluorescence. Considering that excimer fluorescence is extremely sensitive to small aggregates, the newly detected fast process (τ1, fluo ∼ 10 ms) by stopped-flow fluorescence should be ascribed to the early stage of micellization, i.e., the burst formation of small transient micelles, in which light scattering detection was still not sensitive enough. These small transient micelles fused and grew into quasi-equilibrium micelles, which then slowly relaxed into the final equilibrium state.

Original languageEnglish
Pages (from-to)196-202
Number of pages7
JournalJournal of Colloid and Interface Science
Volume328
Issue number1
DOIs
Publication statusPublished - 2008 Dec 1
Externally publishedYes

Fingerprint

Methyl Ethers
Micellization
Ethylene Glycol
Methacrylates
Pyrene
Ethylene glycol
Light scattering
Block copolymers
Micelles
Ethers
Fluorescence
Kinetics
Exponential functions
Methanol
Relaxation time
Monomers
poly-N-isopropylacrylamide
pyrene
Water

Keywords

  • Block copolymer
  • Cononsolvency
  • Fluorescence
  • Kinetics
  • Stopped-flow
  • Transient micelles

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

Cite this

@article{1b147908ad344aa6a604344fbcf1019e,
title = "Cononsolvency-induced micellization kinetics of pyrene end-labeled diblock copolymer of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate studied by stopped-flow light-scattering and fluorescence",
abstract = "Cononsolvency-induced micellization kinetics of a pyrene end-labeled diblock copolymer of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate, Py-PNIPAM-b-POEGMA, was investigated in detail via a combination of stopped-flow light-scattering and fluorescence techniques. Upon a stopped-flow jump from pure methanol to proper methanol/water mixtures, scattered light intensity exhibited an initial increase and then stabilized out; whereas the time-dependence of monomer to excimer fluorescence intensity ratios (IE / IM) revealed an abrupt increase followed by a gradual decrease to plateau values. The dynamic traces of scattered intensity can be well fitted by double exponential functions, the obtained τ1, scat and τ2, scat can be ascribed to processes of forming quasi-equilibrium micelles and their relaxation into final equilibrium states, respectively. On the other hand, a triple exponential function was needed to fit the dynamic traces of IE / IM, leading to three characteristic relaxation times (τ1, fluo, τ2, fluo, and τ3, fluo). It was found that the time scales of τ1, scat and τ2, scat obtained from stopped-flow light scattering were in general agreement with τ2, fluo and τ3, fluo obtained from stopped-flow fluorescence. Considering that excimer fluorescence is extremely sensitive to small aggregates, the newly detected fast process (τ1, fluo ∼ 10 ms) by stopped-flow fluorescence should be ascribed to the early stage of micellization, i.e., the burst formation of small transient micelles, in which light scattering detection was still not sensitive enough. These small transient micelles fused and grew into quasi-equilibrium micelles, which then slowly relaxed into the final equilibrium state.",
keywords = "Block copolymer, Cononsolvency, Fluorescence, Kinetics, Stopped-flow, Transient micelles",
author = "Jingyi Rao and Jingyan Zhang and Jian Xu and Shiyong Liu",
year = "2008",
month = "12",
day = "1",
doi = "10.1016/j.jcis.2008.09.001",
language = "English",
volume = "328",
pages = "196--202",
journal = "Journal of Colloid and Interface Science",
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T1 - Cononsolvency-induced micellization kinetics of pyrene end-labeled diblock copolymer of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate studied by stopped-flow light-scattering and fluorescence

AU - Rao, Jingyi

AU - Zhang, Jingyan

AU - Xu, Jian

AU - Liu, Shiyong

PY - 2008/12/1

Y1 - 2008/12/1

N2 - Cononsolvency-induced micellization kinetics of a pyrene end-labeled diblock copolymer of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate, Py-PNIPAM-b-POEGMA, was investigated in detail via a combination of stopped-flow light-scattering and fluorescence techniques. Upon a stopped-flow jump from pure methanol to proper methanol/water mixtures, scattered light intensity exhibited an initial increase and then stabilized out; whereas the time-dependence of monomer to excimer fluorescence intensity ratios (IE / IM) revealed an abrupt increase followed by a gradual decrease to plateau values. The dynamic traces of scattered intensity can be well fitted by double exponential functions, the obtained τ1, scat and τ2, scat can be ascribed to processes of forming quasi-equilibrium micelles and their relaxation into final equilibrium states, respectively. On the other hand, a triple exponential function was needed to fit the dynamic traces of IE / IM, leading to three characteristic relaxation times (τ1, fluo, τ2, fluo, and τ3, fluo). It was found that the time scales of τ1, scat and τ2, scat obtained from stopped-flow light scattering were in general agreement with τ2, fluo and τ3, fluo obtained from stopped-flow fluorescence. Considering that excimer fluorescence is extremely sensitive to small aggregates, the newly detected fast process (τ1, fluo ∼ 10 ms) by stopped-flow fluorescence should be ascribed to the early stage of micellization, i.e., the burst formation of small transient micelles, in which light scattering detection was still not sensitive enough. These small transient micelles fused and grew into quasi-equilibrium micelles, which then slowly relaxed into the final equilibrium state.

AB - Cononsolvency-induced micellization kinetics of a pyrene end-labeled diblock copolymer of N-isopropylacrylamide and oligo(ethylene glycol) methyl ether methacrylate, Py-PNIPAM-b-POEGMA, was investigated in detail via a combination of stopped-flow light-scattering and fluorescence techniques. Upon a stopped-flow jump from pure methanol to proper methanol/water mixtures, scattered light intensity exhibited an initial increase and then stabilized out; whereas the time-dependence of monomer to excimer fluorescence intensity ratios (IE / IM) revealed an abrupt increase followed by a gradual decrease to plateau values. The dynamic traces of scattered intensity can be well fitted by double exponential functions, the obtained τ1, scat and τ2, scat can be ascribed to processes of forming quasi-equilibrium micelles and their relaxation into final equilibrium states, respectively. On the other hand, a triple exponential function was needed to fit the dynamic traces of IE / IM, leading to three characteristic relaxation times (τ1, fluo, τ2, fluo, and τ3, fluo). It was found that the time scales of τ1, scat and τ2, scat obtained from stopped-flow light scattering were in general agreement with τ2, fluo and τ3, fluo obtained from stopped-flow fluorescence. Considering that excimer fluorescence is extremely sensitive to small aggregates, the newly detected fast process (τ1, fluo ∼ 10 ms) by stopped-flow fluorescence should be ascribed to the early stage of micellization, i.e., the burst formation of small transient micelles, in which light scattering detection was still not sensitive enough. These small transient micelles fused and grew into quasi-equilibrium micelles, which then slowly relaxed into the final equilibrium state.

KW - Block copolymer

KW - Cononsolvency

KW - Fluorescence

KW - Kinetics

KW - Stopped-flow

KW - Transient micelles

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