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<p>Polyvinyl butyral (PVB) and six nominal good solvents are used as a model system to delve into the correlation between solution and thin-film properties in the rarely explored good-solvent regime. To facilitate fulfilling the above goal, solvent evaporation rate is properly controlled to be nearly the same (1&#xa0;day) for all solution-cast PVB films, so that the sole impact of solvent quality may be clearly discerned. Dynamic light scattering (DLS) analysis reveals that, contrary to the usual expectation, all six solvent media produce two coexisting aggregate and cluster species of PVB with varying sizes and fractions under the same dilute condition. Small-angle light scattering (SALS) reveals anisotropic, coexisting isotropic/anisotropic, or isotropic shape of the cluster species in the individual PVB solutions. Corresponding thin films cast from semidilute solutions are uniform, transparent and mutually indistinguishable, while the mechanical properties from both dynamic rheology and universal tensile machine analyses differ substantially. Combined SALS and scanning electron microscopy (SEM) analyses confirm an intimate correlation between the solvent-induced mesoscale structures and the thin-film morphologies that dictate the mechanical properties above. In particular, both characterization schemes reveal three different types of structural features that may be traced back to the slow-mode cluster species formed in the pristine solutions. Overall, the present findings suggest that polymer aggregate/cluster may still prevail well into the good-solvent regime and continue to have a notable impact on all quenched-state applications.</p>

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Correlating polymer solution and thin-film properties in the good-solvent regime

  • 期刊论文

  • 发表日期：

    2026年6月20日

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  • Cheng-Hao Yang,
  • Yu Wei,
  • Chi-Chung Hua

摘要

Polyvinyl butyral (PVB) and six nominal good solvents are used as a model system to delve into the correlation between solution and thin-film properties in the rarely explored good-solvent regime. To facilitate fulfilling the above goal, solvent evaporation rate is properly controlled to be nearly the same (1 day) for all solution-cast PVB films, so that the sole impact of solvent quality may be clearly discerned. Dynamic light scattering (DLS) analysis reveals that, contrary to the usual expectation, all six solvent media produce two coexisting aggregate and cluster species of PVB with varying sizes and fractions under the same dilute condition. Small-angle light scattering (SALS) reveals anisotropic, coexisting isotropic/anisotropic, or isotropic shape of the cluster species in the individual PVB solutions. Corresponding thin films cast from semidilute solutions are uniform, transparent and mutually indistinguishable, while the mechanical properties from both dynamic rheology and universal tensile machine analyses differ substantially. Combined SALS and scanning electron microscopy (SEM) analyses confirm an intimate correlation between the solvent-induced mesoscale structures and the thin-film morphologies that dictate the mechanical properties above. In particular, both characterization schemes reveal three different types of structural features that may be traced back to the slow-mode cluster species formed in the pristine solutions. Overall, the present findings suggest that polymer aggregate/cluster may still prevail well into the good-solvent regime and continue to have a notable impact on all quenched-state applications.