From sequence-defined macromolecules to macromolecular pin codes

Dynamic sequence-defined oligomers carrying a chemically written pin code are obtained through a strategy combining multicomponent reactions with the thermoreversible addition of 1,2,4-triazoline-3,5-diones (TADs) to indole substrates. The precision oligomers are specifically designed to be encrypted upon heating as a result of the random reshuffling of the TAD-indole covalent bonds within the backbone, thereby resulting in the scrambling of the encoded information. The encrypted pin code can eventually be decrypted following a second heating step that enables the macromolecular pin code to be deciphered using 1D electrospray ionization-mass spectrometry (ESI-MS). The herein introduced concept of encryption/decryption represents a key advancement compared with current strategies that typically use uncontrolled degradation to erase and tandem mass spectrometry (MS/MS) to analyze, decipher, and read-out chemically encrypted information. Additionally, the synthesized macromolecules are coated onto a high-value polymer material, which demonstrates their potential application as coded product tags for anti-counterfeiting purposes

Applications of discrete synthetic macromolecules in life and materials science : recent and future trends

In the last decade, the field of sequence-defined polymers and related ultraprecise, monodisperse synthetic macromolecules has grown exponentially. In the early stage, mainly articles or reviews dedicated to the development of synthetic routes toward their preparation have been published. Nowadays, those synthetic methodologies, combined with the elucidation of the structure-property relationships, allow envisioning many promising applications. Consequently, in the past 3 years, application-oriented papers based on discrete synthetic macromolecules emerged. Hence, material science applications such as macromolecular data storage and encryption, self-assembly of discrete structures and foldamers have been the object of many fascinating studies. Moreover, in the area of life sciences, such structures have also been the focus of numerous research studies. Here, it is aimed to highlight these recent applications and to give the reader a critical overview of the future trends in this area of research

Stereocontrolled, multi-functional sequence-defined oligomers through automated synthesis

In contrast to biomacromolecules, synthetic polymers generally lack a defined monomer sequence, therefore one of the challenges of polymer chemists these days is gaining more control over the primary structure of synthetic polymers and oligomers. In this work, stereocontrolled sequence-defined oligomers were synthesised using a thiolactone-based platform. Step-wise elongation of the oligomer occursviaring-opening of the thiolactone, resulting in the formation of stereocenters along the backbone. These initial studies indicate remarkable differences in the strength of non-covalent interactions in isotactic and atactic oligomers. Different side-chain moieties were introduced using alkyl halide building blocks and the synthetic protocol was succesfully optimised and automated. Furthermore, the possible post-synthesis modification of the oligomers was demonstrated using 'click' chemistry

Non-linear PEG-based thermoresponsive polymer systems

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Reading comprehension performance, self-efficacy perceptions, and causal attributions within a Collaborative Strategic Reading (CSR) approach and an attributional feedback intervention

The present study sought to examine the effect of instruction based on collaborative strategic reading (CSR) both with and without attributional feedback on Algerian university students’ reading comprehension performance, self-efficacy perceptions, and causal attributions for success and failure. A total number of 104 second year English as a foreign language students (EFL) were invited to take part in the study and were divided into three groups. One group referred to as the CSR Plus group received the CSR instruction as well as the teacher’s attributional feedback on their reading comprehension performance and strategy use. The CSR group received only training on the use of the CSR strategies, whereas, the Control group was not exposed to any training program. Qualitative and quantitative research designs were adopted within the present quasiexperimental study. A pre-post-test design and an intervention was implemented over 10 weeks to provide answers for the research questions addressed. The research data in this thesis were drawn from six main sources: an English language placement test, a reading comprehension test, an English reading questionnaire, a semi-structured interview, learning logs, and an evaluation questionnaire about student’ perceptions of the intervention. Findings of the study revealed that the CSR and the attributional feedback interventions were effective in improving students’ reading comprehension proficiency and sense of self-efficacy. In other words, the Intervention groups significantly outperformed the Control group in both reading comprehension and self-efficacy scores. However, at post-test the CSR and the CSR Plus did not differ significantly in their reading comprehension level, but in the self-efficacy perceptions they did, in that the CSR Plus had significantly higher levels. With regards to the impact of the intervention on students’ causal attributions for success and failure, analysis revealed that the only significant differences observed were at post-test between the Control and the CSR group on internal attributions for success, with higher levels for the Control group. Additionally, the Control group alone showed a change in attributions over time, becoming less likely to attribute success to external causes. Moreover, looking particularly at strategy use attribution, the overall analysis indicated that the CSR Plus group alone significantly increased their strategy attributions for both success and failure at post-test. That is, the attributional feedback intervention was successful in making the CSR Plus students link their success and failure to the internal, controllable, and changeable strategy use factor. Regarding the impact of the intervention by proficiency levels on students’ reading comprehension performance, results showed that for the low proficiency learners, the Intervention groups significantly outperformed the Control group, however the CSR and the CSR Plus did not differ significantly. No such difference was found between the high proficiency learners in the three groups. Moreover, for self-efficacy level, students’ scores did not differ significantly by their proficiency level. In terms of students’ perceptions of the CSR and the attributional feedback intervention, the overall results revealed positive perceptions. In other words, students believed that the intervention was effective and helped them to improve their reading comprehension performance, self-efficacy perceptions, and attributions for success and failure. Accordingly, the outcomes from this research seek to provide EFL teachers in general and Algerian EFL teachers in particular with pedagogical implications for the teaching of reading comprehension to their students to help them achieve well and feel more self-efficacious in dealing with reading comprehension , and in English language learning more generally

Polymérisation anionique de l oxyde d éthylène amorcée par des cyclodextrines modifiées: Application à l étude des canaux artificiels

L'objectif de ce travail est la synthèse et l étude de canaux artificiels à partir de cyclodextrines. Celles-ci sont modifiées par des greffons hydrophobes sur la face secondaire ou par des groupements 3-hydroxypropyl sur les deux faces. Les composés ainsi obtenus servent de macro-amorceurs de la polymérisation anionique de l oxyde d éthylène et permettent la synthèse de polymères en étoile amphiphiles. L étude de l insertion de ces macromolécules amphiphiles dans des membranes bi-lipidiques modèles à permis de mettre en évidence l importance de la taille de la partie hydrophobe et du contrôle de la balance amphiphile de ces composés. Ce travail a permis en outre, de mettre en évidence une synergie d hémolyse entre la sphingomyélinase, une b-toxine produite par une souche de Staphylococcus aureus et certains dérivés de CD, en particulier ceux possédant des chaînes heptyle sur la face secondaire et POE sur la face primaire.In this work, the synthesis and the study of cyclodextrin-based artificial channels is described. Cyclodextrins are modified by hydrophobic alkyl chains in their secondary face or by 3-hydroxypropyl groups at both faces. Star-shaped poly(ethylene oxide) are then obtained from the anionic polymerization of ethylene oxide initiated by the new cyclodextrin derivatives. The study of the insertion of those macromolecules in bilayer lipid membranes has highlighted the importance of both the hydrophobic moiety s size and the control of the amphiphilic balance. This work has underlined the hemolytic effect of some cyclodextrin derivatives when combined to the Staphylococcus aureus b-toxin (sphingomyelinase).EVRY-BU (912282101) / SudocSudocFranceF

Sequence control in polymer synthesis

The control over comonomer sequences is barely studied in macromolecular science nowadays. This is an astonishing situation, taking into account that sequence-defined polymers such as nucleic acids and proteins are key components of the living world. In fact, fascinating biological machines such as enzymes, transport proteins, cytochromes or sensory receptors would certainly not exist if evolution had not favored chemical pathways for controlling chirality and sequences. Thus, it seems obvious that synthetic polymers with controlled monomer sequences have an enormous role to play in the materials science of the next centuries. The goal of this tutorial review is to shed light on this highly important but embryonic field of research. Both biological and synthetic mechanisms for controlling sequences in polymerization processes are critically discussed herein. This state-of-the-art overview may serve as a source of inspiration for the development of new generations of synthetic macromolecules

Synthesis of half-channels by the anionic polymerization of ethylene oxide initiated by modified cyclodextrin

Amphiphilic star-shaped oligomers are produced by anionic polymerization of ethylene oxide (EO) using per-2,3-di-O-heptyl-beta- (or gamma)cyclodextrins as initiators a versatile way of synthesizing artificial channels bearing one polyEO branch per glucose unit. The behavior of the amphiphilic molecules in lipid membranes is studied by electrical measurements, which confirms the formation of transient, well-defined dimeric ionic channels (see figure)