Spiropyran (SP) is an effective mechanophore because it is easy to be covalently incorporated into polymers and capable of changing color upon mechanical loading. SP motif is a model mechanophore in fundamental studies of mechanochemistry. Therefore, it is of great significance to gain a deep and comprehensive knowledge of SP mechanochemistry for the exploration of mechanochemistry in general. In the beginning of this thesis, a review of SP mechanophore was presented from an engineering perspective. A workflow for SP mechanochemistry, applications in various polymeric systems, impacting factors and characterization techniques as well as conclusions were thoroughly presented. The review aimed to offer deep insight into polymer mechanochemistry and provide approaches to study other mechanophores using the example of SP mechanochemistry in polymers. So far there have been three types of SP mechanophores (SP1, SP2 and SP3) reported in the literature. SP1 and SP2 are sensitive to both UV light and mechanical force, whereas SP3 is sensitive to mechanical force but not to UV, which is an excellent candidate for outdoor applications. Due to the unique feature of SP3, this project is mainly focused on applying SP3 mechanophore into functional and structural polymeric materials. • We designed and synthesized divinyl SP3 mechanophore cross-linker, which can be employed in chain growth polymerization, accounting for more than 80% of total polymer products. As a demonstration, SP3 was incorporated as a cross-linker in the free radical polymerization of methyl acrylate (MA). The mechanoactivation and UV activation of SP3-cross-linked PMA were investigated in details. • SP3 mechanophore cross-linker was covalently incorporated into two widely used polyolefins through facile cross-linking. It represents the first example of smart polyolefins that feel the force by color changing, opening the possibilities of applying SP mechanophore into widely used polyolefin materials, accounting for more than half of the total polymer materials. • We prepared force sensitive acrylic latex coating via covalent incorporation of SP3 mechanophore cross-linker. It is the first example of mechanochromic acrylic latexes, and it provides insight into the design of force-sensitive and self-reporting polymer coatings. • We reported the CO2-breathing induced reversible activation of SP3 mechanophore within microgels. This work provides an effective approach to study the forces inside swollen microgels. It also demonstrates the biomimetic processes with shape deformation and concomitant color/fluorescence change. / Thesis / Doctor of Philosophy (PhD) / Smart polymer has been a research focus for recent decades. One of the most critical responses is to monitor mechanical failures of structural materials, such as stress fraction, fatigue and hysteresis within the polymer by giving off early warnings to prevent the catastrophic failure from occurring. The most prevalent approaches to design a mechanoresponsive polymer is to incorporate a “mechanophore”, containing mechanically labile bonds that are subjective to change under exogenous forces. Spiropyrans (SP) are great candidates for stress/strain sensing in terms of mechanochromism. When mechanical force is applied onto Cspiro-O bond, SP undergoes reversible 6-π ring opening reaction to yield merocyanine (MC). The ring-closed form SP is colorless or yellow and nonfluorescent, whereas the ring-open form MC is purple or blue or red and fluorescent. In this project we first designed and synthesized divinyl spiropyran cross-linker, fitting for chain growth polymerization, which accounts for more than 80% of polymer products. Then the divinyl spiropyran cross-linker was covalently incorporated into polymethylacrylate, polyolefins, acrylic latex coating and CO2-breathing microgels, aiming to broaden the potential applications of mechanophore into various polymers. We also summarized the recent development and studies of spiropyran mechanophore into a comprehensive review from an engineering prospective to provide insights into polymer mechanochemistry and study approaches for other mechanophores.

Organic conjugated polymers (CPs) are emerging materials for advanced electronic applications such as organic photovoltaics (OPVs), field-effect transistors (OFETs), light-emitting diodes (OLEDs), flexible and wearable electronics, and biomedicals. High-spin donor-acceptor CPs have been investigated for their potential applications in magnetic and spintronic devices. Inter-chain charge transfer among these high-spin polymers mainly depends on the nature of the local structure of the thin film and pi-stacking between the polymer chains. However, the microscopic structural details of high-spin polymeric materials are rarely studied, especially in the liquid phase, and remain largely unexplored. This study examined the effects of oligomer chain length, side chain, and processing temperature on the organization of the high-spin cyclopentadithiophene-benzobisthiadiazole donor-acceptor conjugated polymer in chloroform solvent. We have found that the oligomers exhibit ordered aggregation based on chain length, with an average pi-stacking distance of 3.38±0.03 (angstrom), aligning well with the experiment. During the solution processing of CPs, smart polymers are widely used for controlling the device performance. Polymethyl-methacrylate (PMMA) is a smart polymer exhibiting solvation behavior in aqueous alcohol mixtures that is different from individual solvents. However, a thorough understanding of the microscopic details underlying PMMA cosolvency remains elusive, which is essential for tailoring smart polymers for advanced applications. Using molecular dynamics simulation, this study elucidates the PMMA's cosolvency behavior in a binary mixture of aqueous tert-butanol and successfully captures the re-collapsing behavior observed experimentally. We have observed that the excess hydrogen bonding between PMMA and water mimics the re-collapsing pattern, suggesting a key role in PMMA's cosolvency. Efforts to discover new organic molecules are hindered by the vast chemical space. Machine learning (ML) approaches offer a promising solution to accelerate the development of new materials. However, predicting properties accurately with ML models typically involves high computational costs and complexity. This study employs a first-generation ML model, ridge regression, to predict the electronic properties — electronic gap, HOMO, LUMO, and singlet-triplet gap of pi-conjugated organic molecules. This research provides molecular-level insights to control device performance by managing aggregation in thin films and reduces the effort required to screen for desirable organic CPs. These findings will facilitate the development of new organic molecules tailored for advanced electronic devices.

Les micelles apparaissent comme prometteuses dans le domaine de la vectorisation de médicaments. Afin d’améliorer leur biocompatibilité nous nous intéressons ici à des synthèses originales de copolymères amphiphiles comportant un bloc hydrophobe lipidique biosourcé. Un polymère intelligent constitue le bloc hydrophile. L’huile de lin subit une modification chimique afin d’introduire un site amorceur de polymérisation. Le bloc hydrophile est alors ajouté par polymérisation contrôlée. Deux copolymères sont obtenus, le lipide-b-poly(acide acrylique), pH-sensible et le lipide-b-poly(2-isopropyl-oxazoline), thermo-sensible. Une caractérisation physico-chimique complète révèle des concentrations micellaires critiques basses et des micelles de 10 nm. Un système mixte est préparé par mélange des deux copolymères. L’étude de ce système prouve une sensibilité aux deux stimuli. Afin d’améliorer la stabilité des micelles, nous proposons la photo-réticulation des insaturations de la chaîne lipidique. / Small micellar systems seem to be really promising candidates for drug delivery applications. In order to improve the bio-assimilation of our system, the original synthesis of amphiphilic copolymers from linseed oil is carried out. First, linseed oil is chemically modified in order to introduce a polymerization initiating site. Then, the lipoinitiator is engaged in the controlled polymerization of the hydrophilic block. Two amphiphilic copolymers are obtained through this strategy: a pH-sensitive lipid-b-poly(acrylic acid), and a thermo-sensitive lipid-b-poly(2-isopropyl-oxazoline). Both present a low critical micellar concentration and form small micelles (~10 nm). By mixing both copolymers, mixed micelles responding to both stimuli were obtained. In order to improve the system’s stability, the photo-cross-linking of the lipidic double bonds in the micelle’s core is finally realized.