Rheo-PIV Investigation of Fracture and Self-Healing in a Triblock Copolymer Gel

Physically associating polymer gels have shown the ability to heal after failure, making them promising candidates for various medical applications or consumer products. However, the processes by which these materials self-heal is not well-understood. This study seeks to explain the self-healing behavior of the triblock copolymer poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate), or PMMA-PnBA-PMMA, by probing the material’s post-fracture behavior with rheometry and particle image velocimetry (PIV). The self-healing behavior was studied by deforming each gel in shear until failure multiple times with “recovery” periods in-between. PIV was used to verify the occurrence of each fracture in both time and space. Stress relaxation experiments were also performed on the gels to give greater context to the results of the investigation into fracture recovery. Using these data, it was possible to determine the activation energy required for the network chain dissociation and re-association that transpires during the deformation and self-healing of the gel. Stress relaxation experiments yielded an activation energy of 359 kJ/mole for chain dissociation, while fracture-recovery experiments produced an activation energy of 439 kJ/mole for chain re-association. Building upon these insights could lead to a better understanding of the microscopic mechanisms that govern the behavior of intrinsic self-healing materials so that they can be used to their full potential

Identifying human waste contribution of phosphorus loads to domestic wastewater

This paper describes an approach to identify the phosphorus contribution of faeces and urine in domestic wastewater as part of a model verification exercise for a collaborative project between UK Water Industry Research (UKWIR), Scotland & Northern Ireland Forum for Environmental Research (SNIFFER) and UK Technical Advisory Group (UKTAG). The approach develops a methodology used in recent investigations by University of Abertay Dundee, by combining behaviour questionnaire with in sewer sampling and flow monitoring. The approach aimed to reduce the uncertainties associated with the apportionment of Total Phosphorus (TP) and Soluble Reactive Phosphorus (SRP) from domestic sources as identified during the literature review as part of the collaborative project. A domestic sub-catchment was identified which could be isolated, sampled and analysed to identify domestic contribution of SRP and TP load in domestic foul water. This data analysed with the results of product usage questionnaires, was used to verify a generic model developed to determine the significance of laundry and dishwasher phosphorus contributions to domestic wastewater. Conclusions were drawn regarding the effectiveness of this approach in identifying and quantifying the sources of phosphorus to wastewater treatment works

Прогностические факторы повторного образования полипов желудка после проведения эндоскопической полипэктомии

полипыЖЕЛУДКА БОЛЕЗНИХИРУРГИЧЕСКИЕ ОПЕРАЦИИ МАЛОИНВАЗИВНЫЕЭНДОСКОПИЯ ГАСТРОИНТЕСТИНАЛЬНАЯжелудокРЕЦИДИВполипэктоми

Toward Bioinspired Polymer Adhesives: Activation Assisted Via HOBt For Grafting of Dopamine Onto Poly(Acrylic Acid)

The design of bioinspired polymers has long been an area of intense study, however, applications to the design of concrete admixtures for improved materials performance have been relatively unexplored. In this work, we functionalized poly(acrylic acid) (PAA), a simple analogue to polycarboxylate ether admixtures in concrete, with dopamine to form a catechol-bearing polymer (PAA-g-DA). Synthetic routes using hydroxybenzotriazole (HOBt) as an activating agent were examined for their ability in grafting dopamine to the PAA backbone. Previous literature using the traditional coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) to graft dopamine to PAA were found to be inconsistent and the sensitivity of EDC coupling reactions necessitated a search for an alternative. Additionally, HOBt allowed for greater control over per cent functionalization of the backbone, is a simple, robust reaction, and showed potential for scalability. This finding also represents a novel synthetic pathway for amide bond formation between dopamine and PAA. Finally, we performed preliminary adhesion studies of our polymer on rose granite specimens and demonstrated a 56% improvement in the mean adhesion strength over unfunctionalized PAA. These results demonstrate an early study on the potential of PAA-g-DA to be used for improving the bonds within concrete