Aviation and space applications can benefit significantly from lightweight organic electronics, now spanning from displays to logics, because of the vital importance of minimising payload (size and mass). It is thus crucial to assess the damage caused to such materials by cosmic rays and neutrons, which pose a variety of hazards through atomic displacements following neutron-nucleus collisions. Here we report the first study of the neutron radiation tolerance of two poly(thiophene)s-based organic semiconductors: poly(3-hexylthiophene-2,5-diyl), P3HT, and the liquid-crystalline poly(2,5-bis (3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene), PBTTT. We combine spectroscopic investigations with characterisation of intrinsic charge mobility to show that PBTTT exhibits significantly higher tolerance than P3HT. We explain this in terms of a superior chemical, structural and conformational stability of PBTTT, which can be ascribed to its higher crystallinity, in turn induced by a combination of molecular design features. Our approach can be used to develop design strategies for better neutron radiation-tolerant materials, thus paving the way for organic semiconductors to enter avionics and space applications.

Background #KindnessByPost (KbP) is a participatory public health initiative in which people anonymously send and receive cards containing messages of goodwill with others also taking part in the programme. Quantitative evaluations of KbP consistently find evidence of improvements to peoples mental wellbeing and feelings of loneliness after participation and three months later. Our aim in the present study is to develop a programme theory of KbP, which describes for whom the KbP intervention improves mental wellbeing, other reported impacts, in which contexts it has these effects, and the mechanisms by which it works Methods We use a realist interviewing methodology to develop the programme theory. We conducted a focus group with the KbP executive team, and 20 one-to-one interviews with KbP participants. During analysis, a co-production working group iteratively developed a Theory of Change model comprising context-mechanism-outcome statements [CMOs] to map out the mechanisms present in KbP. Results We developed 145 CMO statements, which we condensed and categorized into 32 overarching CMOs across nine thematic topics: access to scheme; pathways to involvement; resources; culture; giving post; receiving post; content of received post; community; long term impact. These CMOs set out pathways through which KbP benefited participants, including from doing something kind for someone else, of receiving post and appreciating the effort that went into it, and from the creative process of creating post and writing the messages inside them. Effects were sustained in part through people keeping the cards and through the social media communities that emerged around KbP. Discussion Both giving and receiving post and the sense of community benefited participants and improved their mood and feelings of connectedness with others. Connection with a stranger, rather than friends and family, was also an important feature of the initiative for participants. Our wide range of CMO pathways by which KbP produced positive outcomes may mean that the intervention is applicable or adaptable across many communities and settings. Taken together with evidence from the quantitative evaluations, KbP is potentially an effective, low-cost, and highly scalable public health intervention for reducing loneliness and improving wellbeing.