A Step Toward Recyclable Silicone Elastomers

This thesis introduces a new strategy for developing polysiloxane networks with the capacity of being recycled. The conventional methods of cross-linking polysiloxanes suffer from lack of self-repair and recyclability. Diels-Alder/retro-Diels-Alder (DA/RDA) equilibrium is a key to establish thermally reversible linkages among polysiloxane chains to enable the material’s recyclability. The equilibrium is optimized to improve the extent of reversibility of the Diels-Alder adduct through functional groups such as carboxyphenyl, ester, and carbon spacers in the structures of maleimide and furan derivatives. The DA/RDA equilibrium is studied by various nuclear magnetic resonance (NMR) spectroscopy experiments and differential scanning calorimeter analyses. The DA reaction is found to be at its highest rate at 50 ͦC while the retro-Diels-Alder reaction is predominant at 110 ͦC. Comparison of the reaction rate constant of the optimized maleimide and furan derivatives at 50 ͦC with the literature suggests that the DA reaction is among those ones described as ultra fast kinetic. Accordingly, series of polysiloxanes are functionalized with the optimized maleimide and furan derivatives to obtain recyclable polysiloxane networks. Dynamic, variable-temperature solid-state 1H NMR experiments are confirmed the rapid, reversible nature of the cross-links within the polysiloxanes. The injured networks are mended to the point that signs of defects were nearly imperceptible even by scanning electron microscopy. The binding strengths of the healed materials are quantified using stress-strain measurements. The healed networks displayed binding strengths that are equal or superior to the undamaged ones

Vibrational Spectroscopy on the Silicon Hydride Mode: Probing Ultrafast Dynamics in Small Molecules to Macromolecular Polymer Systems

University of Minnesota Ph.D. dissertation.June 2019. Major: Chemistry. Advisor: Aaron Massari. 1 computer file (PDF); xviii, 206 pages.This thesis describes Fourier transform infrared (FTIR) and two-dimensional infrared (2D-IR) spectroscopy applied to small molecule silanes (trimethoxysilane and triphenylsilane) and polydimethylsiloxane (PDMS). 2D-IR spectroscopy gives information about the dynamics that the vibrational probe is sensitive to and the heterogeneous and homogeneous contributions to the linear FTIR lineshape. The vibrational probe used for all the studies in this thesis is the silicon hydride stretch due to being present in the small molecule silanes and in PDMS. The studies presented show how the silicon hydride mode was first characterized in small molecules to understand the probe more. Then, the probe was utilized in polymer systems to study more complex motions to make the connection between the ultrafast dynamics of polymers to the macroscopic properties. The first study involved studying the solvation dynamics of two small molecule silanes in three neat solvents using FTIR and 2D-IR spectroscopies along with molecular dynamics simulations. The two different molecules exhibited different degrees of vibrational solvatochromism, and the differences was found to be a result of higher mode polarization with more electron withdrawing ligands using density functional theory calculations. The solvent dynamics were found to be dominated by their interactions with neighboring solvent molecules rather than with the solute. Next, FTIR and 2D-IR spectroscopies were used to study PDMS cross-linked films and siloxane oligomers without solvent and swollen or dissolved in various solvents. There is an absence of vibrational solvatochromism in these systems, which was shown by 2D-IR spectroscopy to be due to the heterogeneity. The silicon hydride mode in the cross-linked, solvent-free PDMS film exhibited spectral diffusion, which must be due to the polymer structural motions. However, once the solvent penetrates the network, the dynamics become a convolution of the solvent and polymer motions due to the motions being of similar timescale. In the last study discussed, FTIR and 2D-IR spectroscopies were used to study the ultrafast structural dynamics of PDMS thin films with various physical and chemical changes done to the polymer, which included elevated curing temperature, increased cross-linker agent concentration, compression, and cooling near the glass transition temperature. The FTIR spectra were found to be relatively insensitive to all of these perturbations, which 2D-IR spectroscopy revealed was caused by the overwhelming heterogeneity. There is clearly a disconnect between the microscopic and macroscopic behavior in this polymer due to having only slight differences in the heterogeneous and homogeneous dynamics

'Reunion of broken parts' (Arabic a/-jabr): A therapist's personal art practice and its relationship to an NHS outpatient art psychotherapy group: an exploration through visual arts and crafts practice

'Reunion of broken parts' explores the relationship between the therapist's personal art practice and the creative art experience of an art psychotherapy group for people with severe and complex mental health difficulties. These practices are usually kept apart. A process of artmaking is examined, including my own as therapist in and outside the studio-based group. The political implications of styles of research writing are discussed. The significance of the investigation is in using art practice as a visual heuristic methodology to explore the junction between visual arts, art psychotherapy and studio practice. Exhibition practices of curating displays of archival material and exhibition visits to examine relevant artists' work were combined with illustrated, autobiographical narratives constructed for analysis. A visually-based case study examines photographs of the group's art. Exploring my own living archive, collected over 20 years, links my art history to the present. The research shows how deep, complex and reciprocal exchanges were facilitated by the therapist's artmaking, even when unseen by the group, implying that the therapist's personal art practice is integral to clinical practice both in and outside clinical groups, and requires far greater consideration. Communication through unspoken metaphor is emphasised, especially in the containment and role modelling of the creative process by the therapist. It is suggested that the therapist's carefully considered artmaking in art psychotherapy groups can significantly enhance the clients' experiences. A non-verbal discourse appeared to take place giving visual form to the group matrix as described in group analysis, and refashioning personal histories in sustained, labour-intensive processes without necessarily being understood. An examination of craft practices is distinctive, showing they can materialise the culture and autobiography of individuals and a group, embodying complex ideas and offering visual interpretations. Genres of art are shown to offer a route for accessing issues of power and cultural meaning

Diseño y aplicaciones de catalizadores de rodio e iridio moleculares y soportados en materiales nanoestructurados de carbono.

El trabajo desarrollado en esta Memoria se ha centrado en el diseño, síntesis, caracterizacióny estudios de estabilidad de compuestos moleculares de rodio e iridio soportados en materiales nanoestructurados de carbono. La actividad catalítica de los nuevos materiales híbridos y la de los complejos moleculares relacionados de rodio e iridio se ha evaluado en la hidrosililación de alquinos y en la oxidación química y electroquímica de agua, respectivamente.Los complejos de rodio(I) y (III) soportados en un óxido de grafeno reducido térmicamente a400 ºC por enlace covalente carbono-nitrógeno entre un ligando NHC mesoiónico (4-fenil-3-metil-1,2,3-triazol-5-ilideno) y la pared del grafeno, Rh(I)/Rh(III)-NHC@TRGO, y los complejos moleculares relacionados muestran alta actividad en la hidrosililación de alquinos y una excelente regio- y estereoselectividad al isómero cinético β-(Z)-vinilsilano. Concretamente, el catalizador ciclometalado [Cp*RhI(C,C')-Triaz] (Triaz = 1,4-difenil-3-metil-1,2,3-triazol-5-ilideno) es un catalizador sobresaliente en la hidrosililación de alquinos terminales, alifáticos y aromáticos, a temperatura ambiente con completa regio- y estereoselectividad al isómero β(Z)-vinilsilano. Por otro lado, aunque el catalizador híbrido relacionado de rodio(III)-triazolilideno no es activo a temperatura ambiente, muestra la misma actividad y selectividad que el catalizador homogéneo a 60 °C. Adicionalmente, los catalizadores híbridos basados en grafeno modificado Rh-NHC@TRGO son completamente reciclables en la hidrosililación de alquinos con excelente control de la selectividad -(Z). Los estudios por DFT del mecanismo de hidrosililación para el catalizador molecular de Rh(III) evidencian la posible participación de un mecanismo bifuncional metal-ligando basado en una ciclometalación reversible.Los materiales híbridos basados en complejos Ir(I)-NHC anclados a nanotubos de carbono a través de grupos éster, Ir(I)-NHC@CNT, son catalizadores eficientes en la oxidación química y electroquímica de agua. El estudio ha revelado que tanto los catalizadores moleculares homogéneos como los heterogéneos que poseen un ligando NHC funcionalizado con un grupo sulfonato son mucho más activos que los catalizadores moleculares relacionados con ligandos NHC no hidrosolubles, tanto en la oxidación química de agua, con CAN como oxidante de sacrificio, como en la oxidación electroquímica en la que se alcanzan valores de TOF de hasta 22000 h-1 a 1.4 V para el catalizador híbrido NHC-sulfonato. Por otro lado, se ha observado que la estructura grafítica del soporte juega un papel importante en el rendimiento electrocatalítico de oxidación de agua con complejos de iridio(I)-NHC soportados por enlace carbonato a dos óxidos de grafeno de diferente estructura grafítica. Se ha comprobado que el desplazamiento del ligando cloruro en los centros metálicos de iridio por grupos oxigenados de la pared nanoestructurada del grafeno tiene un impacto negativo en la actividad electrocatalítica del catalizador híbrido resultante.<br /

Proceedings of the Resilient Materials 4 Life 2020 (RM4L2020) International Conference

The abstracts and posters appearing in this book comprise the proceedings of the RM4L2020 International Conference, held between the 20th and 22nd of September 2021. The posters presented reflect the authors’ opinions and are published as presented and without change (formatting and minor editing expected). Their inclusion in this publication does not necessarily constitute endorsement by the editors, RM4L, or Cardiff University

Bulletin 195 - 1951-1952

https://thekeep.eiu.edu/eiu_bulletin/1037/thumbnail.jp

The Schizophrenic Sign: a dialectic of semiotics and schizophrenia

This thesis posits as its central argument that placing semiotic theory in dialectic with the discourses of and about ‘schizophrenia’ will produce novel insights into both. Simultaneously, this thesis develops a semiological sign system for ‘schizophrenia’, mapping and critiquing its central narratives, organising ethics, aesthetics and thematics, whilst also offering a practical model as exemplar for a semiotic method of cultural, textual, medical, psychological and social critical analysis. In so doing, this thesis presents and develops the concept of ‘schizomimesis’, a term to describe the process by which the discourse and semiological sign system of ‘schizophrenia’ adopts formal qualities that mimetically embody the ‘disease’ symptomatology. The thesis explores this idea, placing different ‘symptoms’ in dialectic with different discourses: thought insertion, influence and the instability of signs in relation to diagnostics and aetiology; ‘psychotic’ speech and so-called thought disorder; distrubances of ipseity and magical thinking in narrative medicine and illness memoirs; hallucinations and delusions of reference in popular cinematic and televisual representations; deictic crises in the person, in the therapeutic process, and across popular culture and society. Throughout, the thesis constructs a de-psychologised and socialised, inter-subjective model of the self, inseparable from the dynamic of indivisible sign relations, and strives to understand ‘schizophrenia’ within this conceptual context. This thesis thereby offers a model of how medical humanities research can contribute evenly to the discplines from which it draws its materials and methodologies. At the same time, it hopes to offer humane and thoughtful observations on the personal, cultural, medical and social disadvantages and difficulties, and highly idiosyncratic experiences, endured by those with lived experience of ‘schizophrenia’