Hierarchical Morphology of Polymer Blend Films Induced by Convection-Driven Solvent Evaporation

Fang, Qiang; Feng, Yutong; Yang, Xiaoniu

doi:10.1021/acs.langmuir.8b00600

Cited by 9 publications

(6 citation statements)

References 39 publications

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“…When the PVA content is high, the morphology consists of uniformly distributed spherical domains of pectin in a matrix of PVA as shown in Figure 2(b) for the PVA/pectin 80/20. At intermediate blend ratios (PVA/pectin 50/50 and 60/40), the blends form hierarchical domains and disordered structures, which are characteristics of spinodal decomposition during phase separation 30,31 …”

Section: Resultsmentioning

confidence: 99%

Morphology control and ionic crosslinking of pectin domains to enhance the toughness of solvent cast PVA/pectin blends

John

Deshpande

Varughese

2020

J of Applied Polymer Sci

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Blending water soluble synthetic polymers, such as polyvinyl alcohol (PVA), with natural polymers, such as pectin, has many advantages. However, due to the brittle nature of pectin, the mechanical properties become inferior in the blends. In this work, two strategies to enhance the toughness and tensile strength of solvent cast PVA/pectin blends are presented. This study shows that the tensile strength and toughness of PVA/pectin 80/20 blends can be enhanced by decreasing the solvent evaporation rate. The phase separation proceeds through 'nucleation and growth' and spinodal decomposition, respectively, at lower and higher rates of solvent evaporation. The equilibrium phase morphology has spherical domains of pectin dispersed in the PVA matrix. The size of the pectin domains and the separation between them are controlled by the solvent evaporation rate. At higher rates of solvent evaporation, pectin domains are larger and farther apart from each other and vice versa. Ionically crosslinking the pectin domains with calcium, further enhances the tensile strength and toughness of the blends compared to that of pure PVA. When the pectin domains are small, the failure happens at larger strains through 'cavitation' and 'shear yielding' and when pectin domains are large, the failure happens at smaller strains and the failure mechanism shifts to 'multiple crazing'.

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Section: Resultsmentioning

confidence: 99%

Morphology control and ionic crosslinking of pectin domains to enhance the toughness of solvent cast PVA/pectin blends

John

Deshpande

Varughese

2020

J of Applied Polymer Sci

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“…Furthermore, it has been demonstrated that temperature gradient or compositional gradient results in spatial variations in surface tension, which produce a morphology of Bénard cells at the microscale. − The microscaled cells are generated through either Rayleigh–Bénard convection or Bénard–Marangoni convection. The former convection is due to the temperature gradient, whereas the latter is due to the compositional gradient.…”

Section: Introductionmentioning

confidence: 99%

Hierarchical Surface Instability in Polymer Films

Junisu,

Sun

2023

Langmuir

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This study demonstrates hierarchical instabilities in thin films. The hierarchical instabilities display three morphological characteristics: (1) windmill-like patterns at the macroscale, (2) Beńard cells and striations at the microscale, and (3) holes at the mesoscale. Such hierarchical instabilities occurred when spin coating was performed on high-volatile solutions under a high relative humidity (RH) but were suppressed when spin coating was performed on low-volatile solutions regardless of the RH. The high-volatile solutions comprise poly(4-vinylpyridine) (P4VP) in methanol or ethanol. The low-volatility solutions comprise P4VP in propanol or butanol. P4VP molecular weights, P4VP concentrations, spin rates, and film thicknesses are not vital factors in forming hierarchical instability in spin-coated P4VP films. Instead, the formation of hierarchical instabilities depends on the RH and solvent types. Namely, the hierarchical instabilities are driven by Beńard−Marangoni convection, water vapor condensation, and disturbance of spin-up and spin-off stages during spin coating of highly volatile solutions under high RH. Mechanisms of hierarchical instabilities are interpreted in detail.

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“…For example, “striations” appeared due to Marangoni flow induced by the surface tension gradient as a result of concentration or temperature gradient . Hierarchical morphology of polymer blend films was generated due to the coupling of phase separation and convection-driven solvent evaporation . The surficial solid “crust” layer was likely formed when underneath was still fluid .…”

Section: Introductionmentioning

confidence: 99%

“…Nascent holes, that is, ring structures or pinholes, appear after the spin-coating process, particularly severe when the substrate was poor wetting. Therefore, variation in even a single factor, such as preparation atmosphere, solvent, spin speed, immersion time (the amount of time the solution stays on the substrate), and so forth, may finally result in a dramatic change in the structure of the film. ,,, Our previous work demonstrated the morphological changes in nascent holes induced by film thickness, in atmosphere during spin-coating, and in interfacial properties. Moreover, the study on the nascent holes provided us a unique tool to reveal formation of nanofilms at various conditions.…”

Section: Introductionmentioning

confidence: 99%

“…26 Hierarchical morphology of polymer blend films was generated due to the coupling of phase separation and convection-driven solvent evaporation. 27 The surficial solid "crust" layer was likely formed when underneath was still fluid. 28 Nascent holes, that is, ring structures or pinholes, appear after the spin-coating process, particularly severe when the substrate was poor wetting.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Nascent Holes on Spin-Coated Polymer Nanofilms: Effect of Processing and Solvents

Fan

Wang

Fei

et al. 2022

ACS Appl. Polym. Mater.

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The hole structure has great impact on the performance of polymeric film materials. In the current work, we focused on the formation mechanism and control of nascent holes that frequently appeared when preparing polymer films on poor wetting substrates. Number density and dewetting area of nascent holes on nanofilms of two model polymers, polystyrene and polymethyl methacrylate prepared from various solvents and spincoating conditions, were systematically studied. Sufficiently large spin speed and prolonged immersion time demonstrated both inducing more and larger holes as a result of high capillary stress and chain adsorption at the surface, respectively. Moreover, solvents played the most critical roles on the formation of nascent holes. Faster evaporative, intermediate Hassen parameter between the polymer and the solvent, and smaller surface tension of solvents promote the formation of more intact films. This work provided deeper understandings on the formation mechanism of polymer nanofilms and an effective approach for controlling nascent holes, which were both of particular importance in the fabrication of functional organic thin-film materials.

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Hierarchical Morphology of Polymer Blend Films Induced by Convection-Driven Solvent Evaporation

Cited by 9 publications

References 39 publications

Morphology control and ionic crosslinking of pectin domains to enhance the toughness of solvent cast PVA/pectin blends

Morphology control and ionic crosslinking of pectin domains to enhance the toughness of solvent cast PVA/pectin blends

Hierarchical Surface Instability in Polymer Films

Nascent Holes on Spin-Coated Polymer Nanofilms: Effect of Processing and Solvents

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