Etching and morphology of poly(vinylidene fluoride)

Vaughan, A. S.

doi:10.1007/bf00595749

Cited by 82 publications

(87 citation statements)

References 37 publications

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“…These include form III poly(butene-1) solution-grown single crystals [15] and the constituent lamellae in spherulites of the c-polymorphic form of polyvinylidene fluoride (PVF2). [16,17] These scrolled crystals are similar to polymer nanotubes previously reported, [5] [18,19] In the current study, by using a carefully controlled self-seeding technique, unusual scroll/tubular lamellar morphologies have been observed. Figure 1 shows a transmission electron microscopy (TEM) image of Nylon 6,6 single crystals obtained by isothermal crystallization from solution in glycerin at 172 C for 3 h. The self-seeding temperature was 206 C. As indicated in the Experimental section, these single crystals were ultimately suspended in isopropanol and then deposited on carbon-coated TEM grids.…”

supporting

confidence: 85%

Submicrometer Scroll/Tubular Lamellar Crystals of Nylon 6,6

Cai¹,

Li²,

Li³

et al. 2004

Advanced Materials

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placed parallel atop a clean 25 mm 75 mm 1 mm microscope slide, 1.1 or 1.25 mm apart, and glued under tension (the gluing points are outside the sample area). Contacts were made to insulated electrical wires using silver epoxy or tin solder. A clean cover slide was placed atop the wires (which thus also served as sample spacers), and glued down at the 4 corners. The edges parallel to the wires were sealed with high-density wax (White Microcrystalline Wax 863, Frank B. Ross Co. Inc.): half a pellet (roughly 3 mm diameter) was placed on each edge and made to carefully fill the sample up to the closest wire by melting the wax, the sample was then filled with the colloidal suspension and the ends glued with the two-component epoxy (Bison Epoxy Rapide; resin is bisphenol-A, average chain length of 2 units; main ingredient of hardener is N-(3-dimethylaminopropyl)-1,3-propylenediamine). This ensured a controlled geometry for the subsequent slow dissolution and re-polymerization of the epoxy.

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supporting

confidence: 85%

Submicrometer Scroll/Tubular Lamellar Crystals of Nylon 6,6

Cai¹,

Li²,

Li³

et al. 2004

Advanced Materials

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“…Previous SEM [20,21], TEM [22,23], and AFM observations [24][25][26] have demonstrated that the banded polymer spherulites consist of alternative edge-on and flat-on oriented lamellar crystals. However, due to the close packing of the dense lamellae, the lamellar twisting details had not been clearly revealed before the real-time AFM observations [27].…”

Section: Real Time Atomic Force Microscopy (Afm) Observation Reveals mentioning

confidence: 98%

Organization of Twisting Lamellar Crystals in Birefringent Banded Polymer Spherulites: A Mini-Review

Zhang

et al. 2017

Crystals

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Abstract:In this mini-review, we summarize the evidences of lamellar twisting in the birefringent banded polymer spherulites demonstrated by various characterization techniques, such as polarized optical microscopy, real-time atomic force microscopy, micro-focus wide angle X-ray diffraction, etc. The real-time observation of lamellar growth under atomic force microscopy unveiled the fine details of lamellar twisting and branching in the banded spherulites of poly(R-3-hydroxybutyrate-co-17 mol % R-3-hydroxyhexanoate). Organization of the twisting lamellar crystals in the banded spherulites was revealed as well. The lamellar crystals change the orientation via twisting rather than the macro screw dislocations. In fact, macro screw dislocation provides the mechanism of synchronous twisting of neighboring lamellar crystals. The driving force of lamellar twisting is attributed to the anisotropic and unbalanced surface stresses. Besides molecular chirality, variation of the growth axis and the chemical groups on lamellar surface can change the distribution of the surface stresses, and thus may invert the handedness of lamellar twisting. Thus, based on both experimental results and physical reasoning, the relation between crystal chirality and chemical molecular structures has been suggested, via the bridge of the distribution of surface stresses. The factors affecting band spacing are briefly discussed. Some remaining questions and the perspective of the topic are highlighted.Keywords: banded polymer spherulite; ringed spherulite; lamellar twisting; organization of lamellar crystals; surface stresses; chirality When crystallized from quiescent melt or concentrated solution, polymer chains usually form spherulites consisted of multiple lamellar crystals radiating from the spherulite center. Observed under polarized optical microscope (POM), a spherulite shows the characteristic Maltese-cross extinction. Besides the Maltese cross, some spherulites demonstrate alternative bright and dark bands under POM. These spherulites are termed as banded spherulites or ringed spherulites. The band structure with different light intensities may result from different thicknesses or different birefringences but similar thickness. In the former case, the bands are due to the periodical modulation of sample thickness and there is no variation of refractive index in the spherulite. These nonbirefringent banded spherulites have been observed in some polymer single crystals formed from thin melt films [1] or solutions [2] and are reviewed by Li et al. [3] in this special issue. In the latter case, the birefringent bands can result from the wavy bending growth or twisting growth of crystals. The wavy bands have been reported in sheared liquid crystals [4,5], which do not form spherulites under the condition. In this mini-review, we focus on the birefringent banded spherulites, which consist of synchronously twisted lamellar crystals. The organization of the twisted lamellar crystals in the banded spherulites and the driving force for lamell...

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“…As a prominent feature of the phenomenon of polymer crystallization, polymer crystals form as thin lamellae with thickness in the 10 nm range and lateral dimensions in microns or larger. Even under the simplest situation of crystallization from a solution containing sufficiently long and unentangled flexible polymer molecules, single lamellar crystallites have been observed to form spontaneously into a plethora of morphologies [14][15][16][17][18][19][20][21][22][23][24][25]. The size, shape, and regularity of the crystals depend on their growth conditions such as solvent, temperature, concentration, and rate of growth.…”

mentioning

confidence: 99%

“…It is also known that {100} sectors have a lower melting temperature than the {110} sectors. In addition to sectored flat lamellae, other morphologies such as hollow tents, hollow bowls, disks, onion-like, scrolls, and twisted lamellae are also known to form [14][15][16][17][18][19][20][21][22][23][24][25]. Despite the availability of rich facts, an understanding of polymer single crystal morphology remains as one of the major challenges.…”

mentioning

confidence: 99%

“…Addressing the problem of stability of sectored polymer crystallites is therefore a formidable task. It must be noted that the lateral sizes of the lamellar crystallites are four to five orders of magnitude larger than the atomic dimensions, allowing a continuum description for these crystallites without addressing specific and non universal features of the unit cell [14][15][16][17][18][19][20][21][22][23][24][25]. In this paper we extract the essential, generic features of flat, lamellar polymer crystallites, and construct a tractable, continuum, phenomenological model for elucidating the structure and stability of sectors.…”

mentioning

confidence: 99%

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