Interdisciplinary materials research including fundamental physics and chemistry of materials, environmental effects and related problems Semiannual progress report, Mar. 1 - Aug. 31, 1966

Interdisciplinary materials research including fundamental physics and chemistry of materials, environmental effects and related problem

Viscoelasticity and Plasticity Considerations in the Fracture of Glasslike High Polymers

Viscoelasticity and plasticity considerations in fracture of glasslike high polymer

Fabrication of nanochannels on polystyrene surfaces

Solvent-induced nanocrack formation on polystyrene surface is investigated experimentally. Solubility parameter and diffusion coefficient of alcohols are employed to elucidate the swelling and cracking processes as well as the crack size. Experimental results show that the crack size increases with the heating temperature, heating time and the concentration and volume of the alcohols. A guideline on fabricating single smaller nanocracks on polymers by solvent-induced method is provided. Nanocracks of approximately 210nm in width were created and replicated onto PDMS slabs to form nanochannels

Current issues in research on structure–property relationships in polymer nanocomposites

The understanding of the basic physical relationships between nano-scale structural variables and the macroscale properties of polymer nanocomposites remains in its infancy. The primary objective of this article is to ascertain the state of the art regarding the understanding and prediction of the macroscale properties of polymers reinforced with nanometer-sized solid inclusions over a wide temperature range. We emphasize that the addition of nanoparticles with large specific surface area to polymer matrices leads to amplification of a number of rather distinct molecular processes resulting from interactions between chains and solid surfaces. This results in a “non-classical” response of these systems to mechanical and electro-optical excitations when measured on the macroscale. For example, nanoparticles are expected to be particularly effective at modifying the intrinsic nano-scale dynamic heterogeneity of polymeric glass-formation and, correspondingly, recent simulations indicate that both the strength of particle interaction with the polymer matrix and the particle concentration can substantially influence the dynamic fragility of polymer glass-formation, a measure of the strength of the temperature dependence of the viscosity or structural relaxation time. Another basic characteristic of nanoparticles in polymer matrices is the tendency for the particles to associate into extended structures that can dominate the rheological, viscoelastic and mechanical properties of the nanocomposite so that thermodynamic factors that effect nanoparticle dispersion can be crucially important. Opportunities to exploit knowledge gained from understanding biomechanics of hierarchical biological protein materials and potential applications in materials design and nanotechnology are among future research challenges. Research on nanocomposites formed from block copolymers and nanoparticles offers huge promise in molecular electronics and photovoltaics. The surface functionalization of nanoparticles by the grafting of polymer brushes is expected to play important role in the designing of novel organic/inorganic nanocomposite materials. The formation of bulk heterojunctions at the nanometer scale leads to efficient dissociation of the charge pairs generated under sunlight. Based on the presentations and discussion, we make recommendations for future work in this area by the physics, chemistry, and engineering communities.Czech Republic. Ministry of Education, Youth, and Sports (MSM0021630501

Vulnerable and forgotten: The impact of the COVID-19 pandemic on autism special schools in England

The COVID-19 pandemic has caused, and continues to cause, unprecedented disruption in England. The impact of the pandemic on the English education system has been significant, especially for children and young people with special educational needs and disabilities (SEND). While it was encouraging that the educational rights of children and young people with SEND were highlighted during the COVID-19 pandemic, Government decision-making appeared to be centered around the needs of pupils in mainstream schools. In this article, co-authored by an academic researcher and senior leaders from the Pan London Autism Schools Network (PLASN; a collective of special schools in London and the South East of England, catering for pupils on the autistic spectrum), we reflect on the impact of the COVID-19 pandemic on special schools in England. We document and discuss a range of challenges experienced by PLASN schools, including the educational inequalities that were exposed and perpetuated by the COVID-19 pandemic, as well as the manner in which the needs and realities of special schools were overlooked by the Government. We also detail the creative and innovative solutions implemented by PLASN schools to overcome barriers that they encountered. These solutions centered on facilitating holistic approaches to support, ensuring clear and regular communication with families, providing effective support for home learning, and promoting collaborative ways of working; all of which align with good practice principles in autism education more generally, and are essential elements of practice to maintain post-pandemic. We additionally reflect on how the COVID-19 pandemic could be a catalyst for much-needed change to the SEND system: leading to better educational provision, and therefore better outcomes, for pupils with SEND

The macroscopic yield behaviour of polymers

A yield criterion, not previously compared with the actual macroscopic behaviour of polymers, is herein compared with the pressure-modified octahedral shear stress criterion earlier suggested by others. This new relation, which is a version of the von Mises criterion, accommodates differences in tensile and compressive yield strengths and accounts for any dependence of yielding on the hydrostatic component of the applied stress state.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44784/1/10853_2004_Article_BF00550671.pd