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Debond-on-demand polymeric adhesives for inkjet printing
No full textPolymer adhesives and polymeric inks are used widely within industrial, biomedical, and
packaging sectors; however, their presence poses issues as the inability to remove them from
surfaces can hamper the recycling and reuse of polymer materials. Therefore, the introduction
of debondable adhesives which break down into monomeric and oligomeric species provides
new markets for polymer adhesive use by offering a route for their removal from surfaces. For
example, in single use packaging the presence of polymeric adhesives during the recycling
process introduces contaminants which can decrease the quality of the recycled materials,
therefore, their removal from the surfaces is important for the development of a circular polymer
economy. Mechanical strain on adhered joints also poses a problem, as over extended periods
of time the weakening of the adhesive can result in the spontaneous detachment of the two
bonded surfaces. Therefore, adhesives which can be repeatably reused without loss of their
adhesive strength will allow for the extension of a products usable life cycle.
The objective of this research was to design new stimuli responsive adhesives capable of
debonding from a range of substrates upon exposure to external stimuli, namely specific
chemical reagents and heat. The integration of such polymers into inkjet formulations would
allow for the generation of well-resolved images which can be rapidly removed from a variety
of surfaces upon exposure to specific stimuli. The application of such polymers could ultimately
lead to the generation of a more circular polymer economy. The work towards this goal is
summarised below.
Chapter 1 provides an introduction to the fields of printing polymer-based inks, self-immolative
chemistries, and polymer recycling – three of the main topics featured in this PhD thesis.
Chapter 2 reports the design, evaluation, and implementation of a base susceptible
chain-extender for use in chain-extended polyurethane (CEPU) adhesives. Evaluation of
model small molecule analogues of the self-immolative system provided mechanistic and rate
analysis of the base (sodium hydroxide (NaOH) and tetra-butylammonium fluoride (TBAF))
triggered degradation of the commercially available 2,2’-sulfonyldiethanol chain-extender.
Detailed solution state degradation analysis of the CEPUs via 1H NMR spectroscopy and gel
permeation chromatography before and after depolymerisation indicated that rapid and
effective degradation of the polymers can be achieved upon exposure to basic conditions. The
loss of physical and mechanical properties post-solid state degradation were observed using
tensile testing, rheological analysis, and differential scanning calorimetry (DSC). Finally, the
adhesive properties of the CEPUs were evaluated on glass and aluminium substrates over five
re-adhesion cycles ̶ losses in shear strength were observed as a result of chain scission, with
the base triggered debonding of the CEPUs revealing the desired debond-on-demand nature
of the self-immolative polymer systems.
Chapter 3 reports the further exploration of the use of 2,2’-sulfonyldiethanol as a
self-immolative chain-extender within a series of CEPUs which feature variations in their polyol
backbone functionality to engineer the physical, mechanical, and adhesive properties of the
CEPUs for use in inkjet formulations. The expansion of the model small molecules
susceptibility to base indicated 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) also provided rapid
degradation. Varying of the polyol backbone functionality (i.e. from alkyl to ether or ester)
allowed for the tailoring of the viscoelastic transition of the CEPUs providing excellent adhesion
to a variety of different surfaces at lower temperatures. The base triggered debonding of the
CEPU adhesives indicated the rapid loss in adhesive strength could be achieved after
exposure to NaOH, TBAF, or DBU for only 30 minutes. Formulation of the CEPUs into
continuous inkjet (CIJ) printer inks generated well-resolved images with excellent adhesion on
a variety of substrates. Finally, a CEPU was intentionally degraded to its prepolymer form and
recycled, providing a new recycled CEPU which possessed comparable adhesive and
debonding characteristics to its pristine counterpart.
Chapter 4 reports the design and synthesis of supramolecular hydrogen bonding and π-π
stacking motifs in the form of aniline and nitroaniline derived end-caps to obtain self-healing
and re-adhesive supramolecular polyurethanes (SPUs). By exploring the effects of
ortho-methyl substituents relative to the urea and/or nitro functional groups of the end-caps,
SPUs with enhanced physical, thermal, and mechanical properties to analogous SPUs without
methyl substituents in the end caps could be achieved. Variations in the end-cap functionality
also enabled the varying of the SPUs adhesive strength and the temperature required for
adhesion; the use of supramolecular interactions of the type described also created materials
capable of full recovery of the adhesive shear strength over five cycles. Furthermore, the
self-healing of the SPUs was investigated ̶ recovery of the mechanical properties of the
pristine SPU materials was achieved upon exposure to thermal stimuli.
Finally, Chapter 5 further explores the effects of hydrogen bonding and π-π stacking
recognition motifs have on the physical properties of supramolecular comb polymers (SCPs)
through the use of aromatic meta-/para-nitro-urea isomeric recognition units and variation of
the loading of these associative supramolecular monomers. Two series of SCPs comprising
0-12.5 mol% of either novel meta-nitro or para-nitro monomers were synthesised, and their
physical and mechanical properties were investigated. Increases in supramolecular monomer
loadings were shown to enhance the phase separation and concomitant physical properties of
the resulting SCPs. Investigation of the adhesive characteristics of the SCPs on glass and
aluminium substrates showed that the loading of the recognition units can affect the adhesive
and re-adhesive properties. Finally, an investigation into the thermally triggered self-healing
capabilities of the SCPs revealed that the mechanical properties of these supramolecular
polymer networks could be recovered post-damage
From 5G to drones: for a feminist geopolitics of the electromagnetic spectrum
Get PDFThe electromagnetic spectrum (EMS) underpins and informs everyday life. Foregrounding particular portions of the EMS (radio, gamma), geographers theorise spectrum as infrastructure, territory/resource to manage, non-human and material. Extending this, we think across spectrum while bringing it into novel dialogue with feminist geopolitics. Pursuing a feminist geopolitics of the EMS, we draw on examples of spectrum-reliant technologies (5G,drones) to outline a three-part agenda. Exploring EMS and the body, we reflect on diverse bodily interactions with spectrum. In more-than-human encounters, we attend to multiple non-human relations with spectrum. In Living with EMS, we explore EMS at home and everyday spectrum practices
Spiral trajectories of asymmetric molecules
No full textSpiral patterns widely exist in both macroscopic and microscopic systems such as heart, bacteria, and active matters but have never been reported at molecular length scale. The emergence of spiral patterns has considerable impacts on the trajectories of the objects and thus usually relates to various physical, chemical, biological and physiological processes. In this Letter, we show that, down to the length scale of only several angstroms, asymmetric molecules exhibit spiral patterns in their trajectories within finite time based on under-damped Langevin equation and demonstrated by molecular dynamics simulation. The key to this observation lies in the asymmetric molecular architecture that leads to a translation-rotation coupling. The finding enriches the knowledge of spiral patterns to the molecular length scale, provides a new insight for the understanding of various processes at the molecular level, and may evokes new idea on the understanding of the vortices in turbulence
Aid Effectiveness and the Challenge of Donor Accountability to Recipients: A comparative analysis of the Global Partnership for Effective Development Co-operation and the Grand Bargain
Get PDFConcerns about the effectiveness of international aid have been a recurring theme in academia
and policy circles for decades. Two key multi-stakeholder initiatives were established in the 2010s
to promote system-wide effectiveness in development and humanitarian aid: the Global
Partnership for Effective Development Co-operation (GPEDC) and the Grand Bargain (GB),
respectively. However, progress has so far been slow, particularly in relation to the accountability
of Western donors to aid recipients, and recent research on this issue has been scarce. This study
compares and contrasts GPEDC and GB to garner lessons on what works in holding donors
accountable to recipient governments and people in humanitarian crises. Through a critical
overview of the author’s previous publications, key informant interviews and an
autoethnographic reflection on the author’s professional experience with GPEDC and GB, the
study identifies significant similarities and gaps in donor behaviour towards their recipients.
Structural power asymmetries in both initiatives show how donor accountability remains elusive.
Nevertheless, research findings also show it can be improved in two fundamental ways. The first
one is by closing the feedback loop between taxpayers, as the ultimate providers of international
aid in donor countries, and citizens in receiving countries as the ultimate recipients of aid. This
solution implies establishing independent citizen committees in both donor and recipient
countries, which would strengthen the monitoring of aid intermediaries’ practices. A second way
to ensure donor accountability to recipients is to significantly scale up the use of cash transfers in
the aid system. By shifting the power of choice from donors to recipients, international aid would
better respond to recipient needs and thus become more efficient and effective
Beyond the crisis: securitisation and mortgage risk in an evolving regulatory landscape
Get PDFThis thesis examines how financial regulation influences credit risk in the European residential mortgage-backed securities (RMBS) market, with a focus on both post-crisis reforms
and emerging environmental priorities. It brings together three empirical chapters that assess
the effectiveness of institutional safeguards and risk indicators under macroeconomic stress.
Chapters 2 and 3 analyse the impact of the 2018 European Securitisation Regulation using
loan-level data from the European DataWarehouse. Chapter 2 shows that the regulation
was associated with a significant decline in mortgage delinquency rates, suggesting that
enhanced transparency and risk retention improved loan quality. Chapter 3 focuses on the
STS framework, finding that STS-labelled deals outperformed non-STS counterparts and
were more resilient during the COVID-19 shock. Chapter 4 shifts the focus on emerging
regulatory initiatives and explores the role of environmental risk. It investigates whether
energy performance certificates (EPCs) improve the predictive accuracy and discriminatory
power of mortgage credit risk models. Using harmonised EPC data across several European
countries, the chapter finds that incorporating energy efficiency significantly enhances model
performance, particularly during periods of high energy inflation when vulnerabilities in
household finances become more pronounced. Together, the chapters highlight how evolving
regulatory frameworks, ranging from structural reforms to climate-related supervision, can
shape the dynamics of credit risk in securitised markets, especially during times of macroeconomic stress
European tree cover during the Holocene reconstructed from pollen records
Get PDFChanges in tree cover influence many aspects of the earth system. Recent regional changes in tree cover, as documented by remote-sensed observations, are insufficient in capturing the response to large climate changes or differentiating the impacts of human activities from natural drivers. Pollen records provide an opportunity to examine the causes of changes in tree cover in response to large climate changes in the past and during periods when human influence was less important than today. Here, we reconstruct changes in tree cover in Europe through the Holocene using fossil pollen records, using the modelled relationship between observed modern tree cover and modern pollen samples. At a pan-European scale, tree cover is low at the beginning of the Holocene but increases rapidly during the early Holocene and is maximal at ca. 6500 cal. BP, after which tree cover declines to present-day levels. The rapidity of the post-glacial increase in tree cover and the timing and length of maximum tree cover varies regionally, reflecting differences in climate trajectories during the early and mid-Holocene. The nature of the subsequent reduction in tree cover also varies, which may be due to differences in climate but may also reflect different degrees of human influence. The reconstructed patterns of change in tree cover are similar to those shown in previous reconstructions. Our approach is relatively simple and only requires readily available data; it could therefore be applied to reconstruct tree cover globally
Pericles and the plumber: reigniting the debate of the purpose of legal education for the age of AI
Get PDFMuch is now being said in the wake of artificial intelligence (AI) about marking and assessments. This year represents the first year in which generative AI usage is considered by the scholarly community to be widespread. The article responds to the recent policy outlined by UCL Laws to introduce a return to traditional assessments, which preserve the integrity of a law degree. We place this debate within the wider context of law schools and what legal education ought to provide for society, more generally. Universities and law schools have different public mandates and should respond in accordance with their aims, community and identity
Large-scale dependency and drug screens to characterize the therapeutic vulnerabilities of multiple myeloma with 1q.
No full textThe development of targeted therapy for patients with multiple myeloma (MM) is hampered by the low frequency of actionable genetic abnormalities. Gain or amplification of chromosome 1q (1q+) is the most frequent arm-level copy number gain in patients with MM and is associated with higher risk of progression and death despite recent therapeutic advances. Thus, developing targeted therapy for patients with MM with 1q+ stands to benefit a large portion of patients in need of more effective management. Here, we used large-scale dependency screens and drug screens to systematically characterize the therapeutic vulnerabilities of MM with 1q+ and displayed increased sensitivity to myeloid cell leukemia-1 (MCL1) and phosphatidyl inositol 3-kinase (PI3K) inhibitors. Using single-cell RNA sequencing, we compared subclones with and without 1q+ within the same patient tumors and demonstrated that 1q+ is associated with higher levels of MCL1 and the PI3K pathway. Furthermore, by isolating isogenic clones with different copy number profiles for part of the chromosome 1q arm, we observed increased sensitivity to MCL1 and PI3K inhibitors with arm-level gain. Lastly, we demonstrated synergy between MCL1 and PI3K inhibitors and dissected their mechanism of action in MM with 1q+, uncovering a cytostatic effect. In conclusion, this study highlights that MM with 1q+ may present enhanced sensitivity to MCL1 and PI3K inhibitors, enabling their use at lower doses without sacrificing efficacy, and may thus accelerate the development of targeted therapy for patients with MM and 1q+