Adsorption of Small Cationic Nanoparticles onto Large Anionic Particles from Aqueous Solution: A Model System for Understanding Pigment Dispersion and the Problem of Effective Particle Density

The present study focuses on the use of copolymer nanoparticles as a dispersant for a model pigment (silica). Reversible addition-fragmentation chain transfer (RAFT) alcoholic dispersion polymerization was used to synthesize sterically stabilized diblock copolymer nanoparticles. The steric stabilizer block was poly(2-(dimethylamino)ethyl methacrylate) (PDMA) and the core-forming block was poly(benzyl methacrylate) (PBzMA). The mean degrees of polymerization for the PDMA and PBzMA blocks were 71 and 100, respectively. Transmission electron microscopy (TEM) studies confirmed a near-monodisperse spherical morphology, while dynamic light scattering (DLS) studies indicated an intensity-average diameter of 30 nm. Small-angle X-ray scattering (SAXS) reported a volume-average diameter of 29 ± 0.5 nm and a mean aggregation number of 154. Aqueous electrophoresis measurements confirmed that these PDMA71-PBzMA100 nanoparticles acquired cationic character when transferred from ethanol to water as a result of protonation of the weakly basic PDMA chains. Electrostatic adsorption of these nanoparticles from aqueous solution onto 470 nm silica particles led to either flocculation at submonolayer coverage or steric stabilization at or above monolayer coverage, as judged by DLS. This technique indicated that saturation coverage was achieved on addition of approximately 465 copolymer nanoparticles per silica particle, which corresponds to a fractional surface coverage of around 0.42. These adsorption data were corroborated using thermogravimetry, UV spectroscopy and X-ray photoelectron spectroscopy. TEM studies indicated that the cationic nanoparticles remained intact on the silica surface after electrostatic adsorption, while aqueous electrophoresis confirmed that surface charge reversal occurred below pH 7. The relatively thick layer of adsorbed nanoparticles led to a significant reduction in the effective particle density of the silica particles from 1.99 g cm(-3) to approximately 1.74 g cm(-3), as judged by disk centrifuge photosedimentometry (DCP). Combining the DCP and SAXS data suggests that essentially no deformation of the PBzMA cores occurs during nanoparticle adsorption onto the silica particles

Re-evaluating the Quoit Brooch Style: Economic and Cultural Transformations in the 5th Century ad, with an Updated Catalogue of Known Quoit Brooch Style Artefacts

Quoit Brooch Style material, produced from the early 5th century onwards, has previously been considered mostly from a stylistic point of view, leaving much scope for further investigation. In addition, the known corpus of material has been much expanded through newly excavated and metal-detected finds. In this article, I bring together the known extant material for the first time, and document important evidence relating to contextual dating, gender associations, manufacture (including new compositional analysis of c 75 objects), repair, and reuse. The article questions previous interpretations of Quoit Brooch Style material relating to Germanic mercenaries and/or post-Romano-British political entities. It interprets the earliest material as part of wider trends elsewhere, in Britain and in Continental northwestern Europe, for the production of material imitating late Roman symbols of power. It presents new evidence for connectivity with Continental Europe via the western Channel route in the 5th century. A detailed investigation of individual artefacts shows that many Quoit Brooch Style objects were reused, sometimes being subjected to extensive repair and modification. This provides new insights into the 5th century metal economy, for instance, acute problems in the availability of new metal objects in southeastern Britain in the middle years of the 5th century. Compositional analysis contributes further to our understanding of metal supply in the 5th century and relationships with the post-Roman West. Insights are provided into wider cultural transformations in the 5th century and the gradual loss of value that occurred for Roman-style objects

The commercial realisation of complex textile craft techniques by CAD and inkjet printing

There are many techniques in textile crafts which are virtually impossible to produce commercially, for example hand and computer generated embroidered textiles and hand knotted woven fabrics. With the growing interest in the consumer market in the UK particular for textile craft products, it is becoming increasingly important to develop reproducible techniques to enable these products to be made to a commercially acceptable level. With the capability of ink jet printing being able to print at high resolution and in almost true colour, it is possible to simulate these techniques on fabric. In doing so, accurate colour representation must be achieved; the method of colour management used will be examined. This paper will start by discussing textile CAD systems and comparing them to general graphic software. It will describe the steps required to obtain identical images of the textile craft onto a CAD system, with the correct resolution, number of colours and size

The use of embellishment techniques with ink jet printed repeated designs

This paper will discuss the use of devore printing as an additional design feature to ink jet printed fabrics. Ink jet printed fabrics are an ideal basis for bespoke fabrics to be generated in small-scale productions. To begin with this paper will discuss the production of ink jet printed fabrics in repeat using textile CAD software. The original design will include all embellishments as part of the original repeat; as an overlay. Before the application of a devore effect, the ink jet printed fabric will need to be finished conventionally, then the shrinkage which occurs can be taken into consideration and the overlay modified in repeat. To conclude the paper will discuss the extension of this process into other possible methods of embellishment such as overprinting and resist techniques, which can be used with ink jet printing onto textiles. These techniques will display alternative methods for producing high quality customised fabrics