I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[9490, 10237]
Abstract: Binary mixtures of anionic and non-ionic macromolecular chain transfer agents (macro-CTAs) are utilized in order to rationally design diblock copolymer nanoparticles with tunable morphologies and anionic character via pseudo-living radical polymerization. More specifically, poly(methacrylic acid) (PMAA) and poly(glycerol monomethacrylate) (PGMA) macro-CTAs are pre-mixed prior to reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). This strategy facilitates the formation of PHPMA-based diblock copolymer spheres, worm-like micelles and vesicles via polymerization-induced self-assembly (PISA). The presence of the anionic PMAA stabilizer block has a dramatic impact on the resulting copolymer morphology, particularly if the degree of polymerization (DP) of the PMAA stabilizer chains is longer than that of the PGMA. Two phase diagrams have been constructed to investigate the effect of the relative proportion and molar mass of the two macro-CTAs. Such a systematic approach is essential for the reproducible synthesis of pure worm-like micelles, which occupy relatively narrow phase space. The rheological behavior of a series of soft, free-standing worm gels is investigated. Finally, such gels are examined as model matrices for the growth of biomimetic calcite crystals and the role of the anionic PMAA stabilizer chains in directing crystal growth is evaluated.
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Aug 2019
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[8065]
Abstract: Uniform, periodic and ordered iron oxide nanopatterns can be generated by selective metal ion inclusion into microphase separated polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin films. After solvent mediated metal ion inclusion into the PEO block, an ultraviolet-Ozone (UVO) treatment was used to remove the polymer and oxidize the metallic ions to their oxides. This paper provides an in-depth study of the UVO processing steps as a function of exposure time. Surface wettability, topography, morphology, compositional and interfacial changes were analysed by contact angle measurement, microscopic and spectroscopic techniques through the UVO treatment. It was found that the UVO treatment initially cross-links the polymer network followed by oxidation and removal of the polymer simultaneously. It was also found that if short UVO exposure times are used, a post calcination treatment can be used to generate similar patterns. The iron oxide nanopatterns created due to strong coordination bond between metallic ions and free electron pairs of O atoms in the PEO and these interactions are responsible for the final pattern mimicking the original self-assembled BCP morphology. The film thicknesses, surface roughness, the size/shape of the iron oxides and patterns, the amount of residual polymers were also investigated regarding the UVO exposure time.
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Apr 2019
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[16500]
Abstract: The mechanical behaviour, crystalline and macromorphology structure development during uniaxially deformation and annealing of poly-L- lactic acid (PLLA), with varying strain rate and draw temperatures, (Td) above Tg, have been investigated using Small- and wide-angle X-ray scattering (SAXS/WAXS), microscopy, thermal and mechanical techniques. The mechanical behaviour of PLLA, was strongly dependent on Td where embrittlement and eventual failure were observed as Td was increased, during uniaxial drawing of the amorphous polymer. This was mirrored in the bulk surface morphology where crazing, microvoiding and cavitation occurred with increasing Td. SAXS/WAXS data showed that strain-induced crystallization occurs on drawing, but crystallite orientation decreased with increasing Td, due to chain relaxation at temperatures ≥30 oC above Tg. However, no long-range oriented lamellar macromorphology was observed post-draw directly and only developed in the samples that were step annealed at temperatures above Td. Also, the disordered α’ crystal form was observed post-draw at Td between 60 – 80 oC, whereas Td ≥ 90 oC, resulted in the ordered α crystal form directly. However, on annealing at temperatures of ≥110 oC, the α’- α crystal transition ensued and in all samples, an oriented lamellar macromorphology developed. Therefore, Td and post-draw annealing, have a significant influence on the mechanical properties, crystallinity and crystalline phase transformation in PLLA, which in-turn, affects the polymers medical and industrial applications.
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Feb 2018
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B21-High Throughput SAXS
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Diamond Proposal Number(s):
[12411]
Abstract: We report on the self-assembly behavior of poly(2-methyl-2-oxazoline)–block–poly(2-octyl-2-oxazoline) comprising different terminal perfluoroalkyl fragments in aqueous solutions. As reported previously [Eur. Polym. J., 2017, 88, 645-655] such polyphiles can form a plethora of nanostructures depending of the composition and on the way of preparation. Here we report, for the first time, detailed information on the internal structure of the nanoparticles resulting from the self-assembly of these copolymers. Small-angle neutron and x-ray scattering (SANS/SAXS) experiments unambiguously prove the existence of polymersomes, wormlike micelles and their aggregates in aqueous solution. It is shown that increasing content of fluorine in the poly(2-oxazoline) copolymers results in a morphological transition from bilayered or multi-layered vesicles to wormlike micelles for solutions prepared by direct dissolution.
In contrast, nanoparticles prepared by dialysis of a polymer solution in a non-selective organic solvent against water are characterized by SAXS method. The internal structure of the nanoparticles could be assessed by fitting of the scattering data, revealing complex core-double shell architecture of spherical symmetry. Additionally, long range ordering is identified for all studied nanoparticles due to the crystallization of the poly(2-octyl-2-oxazoline) segments inside the nanoparticles.
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Jan 2018
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B21-High Throughput SAXS
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Manuel
Hartweg
,
Charlotte J. C.
Edwards-gayle
,
Elham
Radvar
,
Dominic W. P.
Collis
,
Mehedi
Reza
,
Michael
Kaupp
,
Jan
Steinkönig
,
Janne
Ruokolainen
,
Robert
Rambo
,
Christopher
Barner-kowollik
,
Ian W.
Hamley
,
Helena S.
Azevedo
,
C. Remzi
Becer
Diamond Proposal Number(s):
[15778]
Abstract: Monodisperse sequenced peptides and peptoids present unique nano-structures based on their self-assembled secondary and tertiary structures. However, the generation of peptide and peptoid hybrid oligomers in a sequence-defined manner via Ugi multicomponent reaction has not yet been studied. Herein, we report a synthetic strategy that enables both the modification of peptides as well as the generation of sequence-defined peptide-peptoid hybrid structures. Our synthetic methodology rests on the fusion of solid phase peptide synthesis with Ugi multicomponent reactions. We evidence that a diversity of chemical functionalities can be inserted into peptides or used in the design of peptide-peptoid hybrids exploiting a wide functional array including amines, carboxylic acids, hydrocarbons, carbohydrates as well as polymers, introducing a sequence-defined synthetic platform technology for precision peptoid hybrids.
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Dec 2017
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Abstract: In this work, fire inhibition performance of four flame retardant formulations of brominated flame retardant (BFR: GreenArmor®), antimony(III) oxide (Sb2O3) and high impact polystyrene (HIPS) is reported. The standard Underwriters Laboratory (UL 94) vertical burn test was applied for assessing the flame retardancy of a variety of polymer blends. A formulation having 13.3 wt% GreenArmor®, 4 wt% Sb2O3 and 82.7 wt% HIPS, named sample D, successfully passed the flame test and was rated V-0. The other formulations with deficient composition exhibited low flame retardancy, as expected. The X-ray grating interferometry method is introduced for probing the 3D internal structures across the burnt UL 94 flame retarded polymer blend formulations to present the detailed mechanisms of flame retardancy. The X-ray images revealed several features for the formulation (sample D) that passed the UL 94 test: heat-induced dissolution of BFR and Sb2O3 residual particles, formation of gas bubbles inside the burnt polymer test bar, deflation of gas bubbles in a char layer through a microcrack, and thick char layer development, defined by the Br and Sb concentration profile to a depth of 100–220 μm. Also, the X-ray images show clear differences between formulations that pass and fail the UL 94 test. X-ray grating interferometry imaging is proposed as a novel technique for assessment of new generation flame retardants.
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Apr 2017
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[10168]
Abstract: We present a novel family of biocompatible hydrogels containing Nafion and poly(ethylene oxide) based block copolymers. In aqueous environment, thermodynamically stable ionomer-copolymer complexes are formed, as evident by light scattering and quartz crystal microbalance experiments. Moreover, incorporation of Nafion dramatically modifies the phase behaviour and the rheological properties of copolymer hydrogels. The hybrid systems not only undergo sharp and thermally reversible sol-gel transitions below the body temperature, thus retaining their injectable nature, but they also generate mechanically robust hydrogels. Moreover, ibuprofen was continuously released over a period of 26 days for the Nafion/Pluronic hydrogel, compared to only 3 days for the Nafion-free system. The hybrid gels are promising candidates for 3D-bioprinting and controlled drug release applications.
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Apr 2017
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I22-Small angle scattering & Diffraction
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Abstract: Combined small- and wide-angle X-ray scattering (SAXS/WAXS), mechanical and thermal techniques have been used to follow the morphology evolution in a series of poly(ethylene terephthalate) (PET) multiwall carbon nanotube (MWCNT) composite films during quasi solid-state uniaxial deformation at low strain rates. Uniaxially deformed PET-MWCNT films displayed improved mechanical properties compared with unfilled PET films. SAXS/WAXS data revealed a well oriented lamellar structure for unfilled PET films. In contrast, the PET-MWCNT composites revealed a nanohybrid shish-kebab (NHSK) morphology, with reduced orientation and crystallinity. Mechanistically, this morphology development is attributed to the MWCNTs acting as shish for the epitaxial growth of PET crystallites. Furthermore, nucleation and crystal growth occurs in the PET matrix, but MWCNTs ultimately inhibit crystallite development and hinder a final lamellar structure developing. The results show unequivocally the role MWCNTs play as nanofillers, in the morphology development, thermal and mechanical properties in composite polymer films.
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Mar 2016
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[6634]
Abstract: Simultaneous SAXS-WAXD measurements are carried out to gain information about the microstructure and the molecular orientation developed by polymeric chains during the electrospinning process. Three semicrystalline polymers were studied, namely polyacrylonitrile, Nylon 6,6, and poly(ethylene oxide), as non-woven mats with either randomly arranged or aligned electrospun fibers. Mat thermal and morphological properties are investigated, together with their structural details in order to derive their hierarchical structure from the macro to the nano-scale. SAXS patterns have an elliptical shape with the main axis along the equator direction. No reflections are noticeable along the meridional direction, suggesting that the investigated electrospun fibers have a fibrillar structure with no trace of lamellar morphology. Combining the values of the unit cell and of the crystal size it can be concluded that in the fibers the ordered domains are organized into a bundle of fibrils due to the lateral aggregation of roughly 10 unit cells and the regular ordering of about either 50 (Nylon 6,6 and polyacrylonitrile) or 25 (poly(ethylene oxide)) cells in the chain direction.
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Apr 2015
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I22-Small angle scattering & Diffraction
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Abstract: A method for the study of structure–property relationships of polyethylene (PE)-based films of potential use in food packaging has been set up. The approach has been demonstrated in the case of films obtained by blow-molding using model mixtures of two different polyethylenes, namely a metallocene-made grade of linear low density polyethylene (mLLDPE) and a low density polyethylene (LDPE). We show that physical properties important for numerous applications of these films, such as water vapor and oxygen permeability, toughness and stress strength, are related to the molecular structure and structural and morphological parameters of the blends, in particular, thickness of amorphous layers in lamellar stacks, lamellar thickness, lamellar twisting, and degree and type of branching.
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Jan 2015
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