Precise inter-lamellar/inter-fibrillar localization and consequent fabrication of porous membranes with crystallization-modulated pore-size

Ye, Cuicui; Zhao, Jun; Ye, Lijun; Jiang, Zhiyong; You, Jichun; Li, Yongjin

doi:10.1016/j.polymer.2018.02.004

Cited by 25 publications

(14 citation statements)

References 23 publications

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“…In our previous work, crystalline/amorphous bi-continuous structures in their miscible blends fabricated based on crystallization template have been validated by selective solvent extraction [ 36 , 37 , 38 , 39 ]. In this work, this strategy was employed to identify the location of PMMA in the PVDF crystal framework.…”

Section: Resultsmentioning

confidence: 99%

Effect of PMMA Molecular Weight on Its Localization during Crystallization of PVDF in Their Blends

Lin

Wang

et al. 2021

Polymers

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In miscible crystalline/amorphous polymer blends, the exclusion behaviors of the latter with various molecular weights during the crystallization of the former were investigated by the combination of SAXS and DSC by taking a PVDF/PMMA blend as an example. The ratio between internal crystallinity from SAXS and overall crystallinity of the entire blend from DSC was employed to characterize the exclusion of PMMA. Our results indicate that the molecular weight of the amorphous component produces a remarkable influence on the diffusion coefficient (D) and the crystal growth rate (G) of the crystalline component. There are both inter-lamellar and inter-fibrillar structures when PVDF blended with lower-molecular-weight PMMA. With increasing molecular weight of PMMA, the decrease in crystal growth rate (G) dominates the enhanced exclusion behaviors of PMMA, resulting in bigger pores after extraction. Our results are significant not only for the basic understanding of crystallization in polymer blends, but also for the fabrication and structure control of porous structures based on crystallization templates.

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Section: Resultsmentioning

confidence: 99%

Effect of PMMA Molecular Weight on Its Localization during Crystallization of PVDF in Their Blends

Lin

Wang

et al. 2021

Polymers

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“…PVDF and TAIC exhibit excellent miscibility, which was confirmed by the DSC and SEM results (Figure 1) [27,28,29]. After hot-pressing, PVDF crystallizes, expelling TAIC into the interlamellar regions (Figure 9A) [38]. Upon irradiation for the first time, only a part of TAIC participates in the radical reaction because of the low irradiation dose (10 kGy), producing not 3D networks but some local crosslinked points (Figure 9B) [39,40].…”

Section: Resultsmentioning

confidence: 83%

Multiple-Step Melting/Irradiation: A Strategy to Fabricate Thermoplastic Polymers with Improved Mechanical Performance

et al. 2019

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To fabricate thermoplastic polymers exhibiting improved ductility without the loss of strength, a novel multiple-step melting/irradiation (MUSMI) strategy was developed by taking poly(vinylidene fluoride)/triallyl isocyanate (PVDF/TAIC) as an example, in which alternate melting and irradiation were adopted and repeated for several times. The initial irradiation with a low dose produced some local crosslinked points (not 3-dimensional network). When the specimen was reheated above the melting temperature, they redistributed in the PVDF matrix, which is an efficient way to avoid the high crosslinking density at certain positions and the disappearance of thermoplastic properties. During the subsequent cooling process, the crosslinked domains in the thermoplastic polymer matrix is expected to play double roles in turning crystal structures for enhancing the ductility without reducing strength. On one hand, they can act as heterogeneous nucleation agents, resulting in higher nucleation density and smaller spherulites; on the other hand, the existence of crosslinked structures restricts the lamellar thickening, accounting for the thinner crystal lamellae. Both smaller spherulites and thinner lamellae contribute to better ductility. At the same time, these local crosslinked points enhance the connectivity of crystal structures (including lamellae and spherulites), which is beneficial to the improvement of strength. Based on the influence of local crosslinked points on the ductility and strength, thermoplastic PVDF with much higher elongation at break and comparable yielding stress (relative to the reference specimen upon strong irradiation only once) was prepared via MUSMI successfully.

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“…This is the well-known "Tm depression effect" reported by Nishi and Wang [28]. This effect has always been observed in miscible polymer blends and has thus been regarded as a method to assess the miscibility of adopted blends [13][14][15]27]. Obviously, this phenomenon can be attributed to the depression of crystallization of PLLA due to the existence of TAIC and subsequent melting behaviors during heating.…”

Section: Resultsmentioning

confidence: 88%

“…Similar volume fractions of account for the interlamellar structures of these blends. When PVDF acts as the minority phase, it locates between PBSU crystal stacks, which is the reason for interfibrillar structures [13]. In the studies of Lin, the effect of poly(methyl methacrylate) (PMMA) molecular weight on its localization during the crystallization of PVDF in their miscible blend were investigated in detail by the combination of small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC).…”

Section: Introductionmentioning

confidence: 99%

Inclusion/Exclusion Behaviors of Small Molecules during Crystallization of Polymers in Miscible PLLA/TAIC Blend

et al. 2022

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In this work, PLLA/TAIC has been taken as a model system to investigate the inclusion and exclusion of small molecules during the crystallization of polymers in their miscible blend. Our results indicate that it is the growth rate and diameter of PLLA spherulites that dominate the localization of TAIC. On the one hand, crystallization temperature plays an important role. Crystallization at higher temperature corresponds to higher growth rates and a greater diameter of PLLA spherulites. The former improves the ability of PLLA crystals to trap TAIC while the latter leads to a lower volume fraction of space among neighboring PLLA spherulites. The combination of the two contributes to the enhanced inclusion behaviors. On the other hand, when compared to melt crystallization, cold crystallization results in much smaller spherulites (from higher nucleation density) and sufficient space among spherulites, which accounts for the enrichment of TAIC in interspherulitic regions and for its enhanced exclusion. In the adopted polymer–small molecule blend, TAIC can enrich in interspherulitic regions even in its miscible blend with PLLA, which can be attributed to its stronger diffusion ability.

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Precise inter-lamellar/inter-fibrillar localization and consequent fabrication of porous membranes with crystallization-modulated pore-size

Cited by 25 publications

References 23 publications

Effect of PMMA Molecular Weight on Its Localization during Crystallization of PVDF in Their Blends

Effect of PMMA Molecular Weight on Its Localization during Crystallization of PVDF in Their Blends

Multiple-Step Melting/Irradiation: A Strategy to Fabricate Thermoplastic Polymers with Improved Mechanical Performance

Inclusion/Exclusion Behaviors of Small Molecules during Crystallization of Polymers in Miscible PLLA/TAIC Blend

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