In situ SAXS investigation of vinyl acetate polymerization-induced self-assembly
In situ small angle X-ray scattering (SAXS) was used to investigate the formation of higher-order morphologies in vinyl acetate (VAc) polymerization-induced self-assembly (PISA). Poly(ethylene glycol) (PEG) bearing a xanthate chain end was used as a hydrophilic macromolecular chain transfer agent in...
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Veröffentlicht in: | Polymer chemistry 2024-03, Vol.15 (10), p.979-990 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | In situ
small angle X-ray scattering (SAXS) was used to investigate the formation of higher-order morphologies in vinyl acetate (VAc) polymerization-induced self-assembly (PISA). Poly(ethylene glycol) (PEG) bearing a xanthate chain end was used as a hydrophilic macromolecular chain transfer agent in the macromolecular design
via
interchange of xanthates (MADIX)-mediated aqueous emulsion polymerization of VAc (see P. Galanopoulo,
et al.
,
Poly. Chem.
, 2020,
11
, 3922–3930).
In situ
SAXS monitoring confirmed that the PISA process occurs in three steps: the nucleation of PEG
45
-
b
-PVAc
200
block copolymer primary particles, a rapid morphological transition, and a final step in which the nano-objects grow slowly to their final dimensions. The transition step appears to be critical for the formation of higher-order morphologies through the aggregation of primary particles into larger clusters and their subsequent reorganization. Our results show that the transition step is extremely fast, making it highly sensitive to small perturbations. This explains why higher-order morphologies are usually obtained within a narrow window of conditions and often as a mixture. Furthermore, the morphological evolution observed in parallel static experiments appears to be more gradual than in
in situ
SAXS experiments, suggesting that in our system the sampled latexes were not thermodynamically stable and continued to evolve after sampling. Therefore, the sampling method may not provide a realistic view of the morphological transition during the reaction process in this system. |
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ISSN: | 1759-9954 1759-9962 |
DOI: | 10.1039/D3PY01381B |