Evaluating Scales of Structures

Mohan, Saeed D.; Olley, R. H.; Vaughan, A. S.; Mitchell, Geoffrey R.

doi:10.1007/978-3-319-39322-3_2

Cited by 11 publications

(18 citation statements)

References 76 publications

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“…The |Q| value for the maximum is ~0.0325 Å −1 , corresponding to a long period of ~195 Å. This confirms observations made previously that the DBS directs the lamellar growth direction but does not otherwise change the lamellar characteristics [ 7 , 26 ]. There is also a horizontal streak on the equatorial section which was not present in the patterns recorded for the PCL and PCL/PVB samples.…”

Section: Resultssupporting

confidence: 88%

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Orthogonal Templating Control of the Crystallisation of Poly(ε-Caprolactone)

Mitchell

Olley

2018

Polymers

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Abstract:The crystal growth of poly(ε-caprolactone) can be very effectively directed through the use of small amounts of dibenzylidene sorbitol in conjunction with modest flow fields to yield extremely high levels of the preferred polymer crystal orientation. We show that by introducing small quantities of a terpolymer, based on polyvinyl butyral we can switch the symmetry axis of the final lamellar orientation from parallel to perpendicular to the melt flow direction. During shear flow of the polymer melt, the dibenzylidene sorbitol forms highly extended nanoparticles which adopt a preferred alignment with respect to the flow field and on cooling, polymer crystallisation is directed by these particles. The presence of the terpolymer, based on polyvinyl butyral, limits the aspect ratio of the dibenzylidene sorbitol (DBS) particles, such that the preferred orientation of the particles in the polymer melt changes from parallel to normal to the flow direction. The alignment of lamellar crystals perpendicular to the flow direction has important implications for applications such as scaffolds for tissue engineering and for barrier film properties.

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Section: Resultssupporting

confidence: 88%

“…The PCL sample exhibits a SAXS pattern which is typical for many semi-crystalline polymers [ 26 ]. The maximum in intensity at |Q|~0.032 Å –1 , corresponding to a long period of ~195 Å, arising from the lamellar structure.…”

Section: Resultsmentioning

confidence: 99%

Orthogonal Templating Control of the Crystallisation of Poly(ε-Caprolactone)

Mitchell

Olley

2018

Polymers

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“…SAXS is a powerful technique for evaluating the molecular organisation of materials, including polymers. These experiments have been conducted to extract information regarding the long period, which, with knowledge of the degree of crystallinity, can be used to calculate the crystalline and amorphous thickness from SAXS data [26]. The use of SAXS as a characterization technique for polymeric materials has been extended to included studies of polymer blends and nanocomposite materials [26,27].…”

Section: Introductionmentioning

confidence: 99%

“…These experiments have been conducted to extract information regarding the long period, which, with knowledge of the degree of crystallinity, can be used to calculate the crystalline and amorphous thickness from SAXS data [26]. The use of SAXS as a characterization technique for polymeric materials has been extended to included studies of polymer blends and nanocomposite materials [26,27]. Additionally, in this work we analysed the impact of processing conditions on internal morphology of the filaments and their effects on the scaffold's thermal, mechanical, and biological properties.…”

Section: Introductionmentioning

confidence: 99%

Additive Manufactured Poly(ε-caprolactone)-graphene Scaffolds: Lamellar Crystal Orientation, Mechanical Properties and Biological Performance

et al. 2022

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Understanding the mechano–biological coupling mechanisms of biomaterials for tissue engineering is of major importance to assure proper scaffold performance in situ. Therefore, it is of paramount importance to establish correlations between biomaterials, their processing conditions, and their mechanical behaviour, as well as their biological performance. With this work, it was possible to infer a correlation between the addition of graphene nanoparticles (GPN) in a concentration of 0.25, 0.5, and 0.75% (w/w) (GPN0.25, GPN0.5, and GPN0.75, respectively) in three-dimensional poly(ε-caprolactone) (PCL)-based scaffolds, the extrusion-based processing parameters, and the lamellar crystal orientation through small-angle X-ray scattering experiments of extruded samples of PCL and PCL/GPN. Results revealed a significant impact on the scaffold’s mechanical properties to a maximum of 0.5% of GPN content, with a significant improvement in the compressive modulus of 59 MPa to 93 MPa. In vitro cell culture experiments showed the scaffold’s ability to support the adhesion and proliferation of L929 fibroblasts (fold increase of 28, 22, 23, and 13 at day 13 (in relation to day 1) for PCL, GPN0.25, GPN0.5, and GPN0.75, respectively) and bone marrow mesenchymal stem/stromal cells (seven-fold increase for all sample groups at day 21 in relation to day 1). Moreover, the cells maintained high viability, regular morphology, and migration capacity in all the different experimental groups, assuring the potential of PCL/GPN scaffolds for tissue engineering (TE) applications.

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“…For each 2d SAXS pattern, an azimuthal section I(α) was obtained at constant |Q| and as a function of α, where α is the angle between the extrusion axis, which was vertical to the beamline, and the scattering vector Q. The azimuthal section I(α) was used to evaluate the level of preferred orientation of the chain-folded lamellar crystals using the methodology developed by Mitchell [19][20][21], which is shown below.…”

Section: Methodsmentioning

confidence: 99%

Changing the Paradigm-Controlling Polymer Morphology during 3D Printing Defines Properties

et al. 2022

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Direct digital manufacturing consists of a set of techniques that enable products to be fabricated directly from their digital definition, without the use of complex tooling or moulds. This manufacturing approach streamlines prototyping and small-scale production, as well as the mass customization of parts with complex designs immediately fixed before fabrication. With broad applicability, there are clearly opportunities in the field of medical devices for its use. However, many of the developments of direct digital manufacturing focus on simply specifying the shape or the form of the product, and this limited scope throws away many of the particular advantages of direct digital manufacturing. This work is focused on remedying this situation so that the digital specification of the fabricated product includes the properties as well as the form of the product. We use in situ time-resolving small-angle X-ray scattering measurements performed at the ALBA Synchrotron Light Source in Barcelona to evaluate the control that can be exerted on the morphology of a semi-crystalline polymer during extruder-based 3D printing. We use this as a methodology for printing the patterns of the morphology of the polymer to realise the patterns of properties of the polymeric material, specifically the modulus of the polymer. We give an example of products produced in this manner that contain spatial variation in their properties.

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Evaluating Scales of Structures

Cited by 11 publications

References 76 publications

Orthogonal Templating Control of the Crystallisation of Poly(ε-Caprolactone)

Orthogonal Templating Control of the Crystallisation of Poly(ε-Caprolactone)

Additive Manufactured Poly(ε-caprolactone)-graphene Scaffolds: Lamellar Crystal Orientation, Mechanical Properties and Biological Performance

Changing the Paradigm-Controlling Polymer Morphology during 3D Printing Defines Properties

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