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Continuous-Flow Laboratory SAXS for In Situ Determination of the Impact of Hydrophilic Block Length on Spherical Nano-Object Formation during Polymerization-Induced Self-Assembly.
Guild, Jonathan D; Knox, Stephen T; Burholt, Sam B; Hilton, Eleanor M; Terrill, Nicholas J; Schroeder, Sven L M; Warren, Nicholas J.
Afiliação
  • Guild JD; School of Chemical and Processing Engineering, University of Leeds, Woodhouse, Leeds LS2 9JT, U.K.
  • Knox ST; School of Chemical and Processing Engineering, University of Leeds, Woodhouse, Leeds LS2 9JT, U.K.
  • Burholt SB; Diamond House, Harwell Science and Innovation Campus, Diamond Light Source, Didcot OX11 0DE, U.K.
  • Hilton EM; School of Chemical and Processing Engineering, University of Leeds, Woodhouse, Leeds LS2 9JT, U.K.
  • Terrill NJ; Diamond House, Harwell Science and Innovation Campus, Diamond Light Source, Didcot OX11 0DE, U.K.
  • Schroeder SLM; School of Chemical and Processing Engineering, University of Leeds, Woodhouse, Leeds LS2 9JT, U.K.
  • Warren NJ; School of Chemical and Processing Engineering, University of Leeds, Woodhouse, Leeds LS2 9JT, U.K.
Macromolecules ; 56(16): 6426-6435, 2023 Aug 22.
Article em En | MEDLINE | ID: mdl-37637307
In situ small-angle X-ray scattering (SAXS) is a powerful technique for characterizing block-copolymer nano-object formation during polymerization-induced self-assembly. To work effectively in situ, it requires high intensity X-rays which enable the short acquisition times required for real-time measurements. However, routine access to synchrotron X-ray sources is expensive and highly competitive. Flow reactors provide an opportunity to obtain temporal resolution by operating at a consistent flow rate. Here, we equip a flow-reactor with an X-ray transparent flow-cell at the outlet which facilitates the use of a low-flux laboratory SAXS instrument for in situ monitoring. The formation and morphological evolution of spherical block copolymer nano-objects was characterized during reversible addition fragmentation chain transfer polymerization of diacetone acrylamide in the presence of a series of poly(dimethylacrylamide) (PDMAm) macromolecular chain transfer agents with varying degrees of polymerization. SAXS analysis indicated that during the polymerization, highly solvated, loosely defined aggregates form after approximately 100 s, followed by expulsion of solvent to form well-defined spherical particles with PDAAm cores and PDMAm stabilizer chains, which then grow as the polymerization proceeds. Analysis also indicates that the aggregation number (Nagg) increases during the reaction, likely due to collisions between swollen, growing nanoparticles. In situ SAXS conducted on PISA syntheses using different PDMAm DPs indicated a varying conformation of the chains in the particle cores, from collapsed chains for PDMAm47 to extended chains for PDMAm143. At high conversion, the final Nagg decreased as a function of increasing PDMAm DP, indicating increased steric stabilization afforded by the longer chains which is reflected by a decrease in both core diameter (from SAXS) and hydrodynamic diameter (from DLS) for a constant core DP of 400.

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Macromolecules Ano de publicação: 2023 Tipo de documento: Article País de publicação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Macromolecules Ano de publicação: 2023 Tipo de documento: Article País de publicação: Estados Unidos