Polymeric materials with inherent stimulus response represent an ever-growing area of research. In particular, block copolymers demonstrate exciting properties owing to their enhanced mechanical strength and microphase separation. Incorporating functionality into block copolymers proves useful in enhancing their utility. Presently, synthesis and subsequent post-polymerization modification achieved this for a range of block copolymers. In particular, neutralization of acid-containing polymers readily imparted ionic functionality and yielded microphase-separated block copolymer domains, enhancing polymer thermomechanical properties and ion transport. An ABA triblock copolymer composed of mechanically reinforcing polystyrene outer blocks and ionic central poly(1-methylimidazolium acrylate) block acted as a host for ionic liquid that caused an evolution in bulk morphology, resulting in enhanced ionic conductivity. The resulting membrane also exhibited a strong electromechanical actuation response under applied potential. Adding ionic liquid doped with a corresponding lithium salt enabled evaluation of sulfonated block copolymers as components of ternary polymer electrolytes, relevant for battery applications. Modification of a sulfonic acid-containing pentablock copolymer presented photocurable functional groups to the ionic domains which enabled their UV irradiation-induced curing. This novel route of modifying ion-containing block copolymers resulted in enhanced thermomechanical properties and enabled healing of physical defects in the film, unprecedented for ion-containing block copolymers. Covalent networks represent a relevant area of research for a wide variety of applications such as coatings, adhesives, and scaffolds. Careful design of degradable crosslinkers enables stimulus response in these networks by eliminating covalent crosslinks and affording a soluble product. Extension of poly(ethylene glycol) methacrylate-based network formation into three dimensions using microstereolithography resulted in novel acid-degradable 3D-printed parts. An additional study investigated mixtures of acrylamide-modified poly(vinyl alcohol) and poly(ethylene glycol) diacrylate as water-soluble resins for the direct formation of hydrogels from solution. Photorheology and photocalorimetry investigated the thermal and mechanical changes inherent in the curing process and evaluated the mixtures as a platform for microstereolithography. / Ph. D.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24905号 / 工博第5185号 / 新制||工||1990(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 大内 誠, 教授 田中 一生, 教授 大北 英生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Every year, millions of people contract antibiotic-resistant bacterial infections, and tens of thousands die from infection-related complications in the United States alone. Bacterial infections are one of the leading causes of death worldwide, especially in healthcare institutes such as hospitals and nursing homes where people are more susceptible to infection and complications. Bacteria can cause infections in any part of the body and often interact with sugar molecules on the surface of cells; once bacteria are attached, the cells stop functioning properly. When a bacterial infection is suspected, samples from the patient's blood or urine are taken to confirm the diagnosis. If the bacterial infection is sever enough, patients are treated with broad-spectrum antibiotics before the type of bacteria is known, and once it has been identified they are given antibiotics that target the specific bacterial strain. The high death rate associated with bacterial infections is largely due to the emergence of antibiotic-resistant bacterial strains. Although antibiotic resistance is present in some naturally occurring bacterial strains, misuse and over-prescription of antibiotics have accelerated the process. To combat the ever-growing threat of antibiotic-resistant bacteria, antibacterial polymers have been developed. Antibacterial polymers prevent bacterial infections by either killing the bacteria themselves or by preventing them from interacting with the body altogether This dissertation primarily focuses on using sugar-containing polymers to prevent bacterial growth. These materials may potentially be used as a replacement for or supplement to traditional antibiotics. / Doctor of Philosophy / All living cells possess a coating of glycomaterials on, or as critical components of their cell walls. Bacteria, including invasive bacterial pathogens, are no exception and have cell walls comprised of peptidoglycans. Glycomaterials on cell surfaces play a role in critical biological processes such as molecular recognition, cellular interaction, infection, and inflammation. Traditional antibiotic remediations are becoming less effective in treating bacterial infections due to the emergence of antibiotic-resistant strains. The formation of biofilms, an extracellular coating composed of polysaccharides, contributes to the antibiotic resistance of bacteria. The development of novel antibiotics is extremely costly and often unsuccessful, with billions in investment often producing zero new drugs. As a result, antibacterial polymers have been investigated as they are comparatively less expensive and offer unique characteristics to combat bacterial infections. Polymers with inherently antibacterial properties, or those that can be conjugated with antibacterial compounds, offer a replacement for traditional antibiotic remediation. To investigate the role of glycomaterials in antibacterial activity, a series of sugar-containing norbornene homopolymers were prepared and evaluated for their antibacterial activity. Protected glycomonomers consisting of galactose, glucose, N-acetyl glucose, and mannose were prepared in a two- or three-step synthesis by first appending an acrylate to the anomeric carbon through Koenigs-Knorr-type chemistry. After generation of the -anomer, the norbornene carboxylate was prepared by the Diels-Alder reaction of the acrylate with cyclopentadiene. Homopolymers with molecular weights ranging from 25–250 KDa were synthesized using ring-opening metathesis polymerization (ROMP) catalyzed by Grubbs 3rd generation catalyst, and subsequently deprotected to reveal the sugar-norbornene. While the galactose polymers showed no bacterial inhibition, those composed of glucose, N-acetyl glucose, or mannose prevented the growth of Escherichia coli (E. coli) and were effective at concentrations as low as 1.25 mg mL-1. Some strains of pathogenic bacteria, such as Clostridioides difficile (formerly known as Clostridium difficile), interfere with the normal cell functions by indirect means, producing toxins that adversely interact with the surrounding tissue. To sequester the toxins produced by C. difficile before they cause damage to the gastrointestinal (GI) tract, polymers containing the -gal epitope, a naturally occurring trisaccharide, were also prepared. The -gal epitope possessing a propyl azide handle at the anomeric carbon was prepared in a 15-step reaction, followed by reaction with an alkyne-functionalized polymer resin using copper-catalyzed azide-alkyne Huisgen cycloaddition. After global deprotection and thorough washing to remove residual copper from the glycomaterial, cell viability studies showed >80% cell survival. While these materials showed good cell viability, the rigorous synthesis of -Gal and the affinity of the polymer scaffolding for copper was a deterrent to further toxin-binding studies. Non-biological surfaces are also often susceptible to bacterial colonization and fouling. Although such materials may be modified to impart antimicrobial properties, their modification may also be a detriment to other key physical properties. To investigate the tradeoffs between material properties and functionalization, we synthesized a series of poly(arylene ether)s from monomers that possessed a modifiable handle and differed only in the pattern of leaving group on the aromatic ring. These polymers were further modified using post-polymerization thiol-ene reactions to evaluate the effect of the side-chains on the material's properties. The regioisomer incorporated into the polymer was found to influence its thermal properties irrespective of the installed functional group, suggesting that new functionality can be incorporated into these polymers without adversely impacting their physical properties.

No description available.

Ce travail décrit d'abord l’élaboration de nanogels hydrophiles stimulables, sensibles à un changement de pH et à un environnement où les propriétés d’oxydo-réduction peuvent varier. Ils ont été synthétisés en milieu dilué, d’une part, et en émulsion inverse, d’autre part; dans les deux cas à partir d’un copolymère statistique composé d’unités 2-éthyl-2-oxazoline et éthylène imine. Ces nanogels n’ont pas montré d’interactions spécifiques avec des protéines telles que la BSA et se sont avérés non-toxiques in vitro. Une plateforme à base d’un copolymère POx statistique porteur de fonctions aldéhydes a par ailleurs permis d’accéder à une librairie de POx, incluant des structures greffées et réticulées. Enfin, l’autoassemblage en solution d’un copolymère à blocs de type poly(2-methyl-oxazoline)-bpoly(2-isopropyl-2-oxazoline) (PMeOx-b-PiPrOx), a été étudié en détail. Des micelles ont été observées à des temps courts au-dessus du point trouble du PiPrOx. Pour des temps plus longs, la formation de fibres et de micelles réticulées physiquement ont été mise en évidence, comportement expliqué par la cristallisation des chainesde PiPrOx stabilisées par les blocs PMeOx hydrophiles. / This PhD work is based on the design of poly(2-oxazoline) (POx)hydrogels and nanogels, by chemical or physical cross-linking, aimed to be used for biomedical applications. Nanogels were first prepared in dilute media and in inverse emulsion based on a statistical copolymer made of 2-ethyl-2-oxazoline and ethyleneimine units. These stimuli-responsive nanogels were swelling in acidic media and were cleaved in reductive environment. They proved to be non-cytotoxic and act as protein repellent. Second, a reactive platform based on a statistical POx polymerbearing aldehyde functionalities was engineered, enabling the synthesis of graft and cross-linked POx. Last, a block copolymer made of 2-methyl- and 2-isopropyl-2-oxazoline units, proved to self-assemble into micelles when heated above its LCST,for a short period of time (< 1h30). When annealed for a longer time (> 1h30),crystallization-driven self-assembly led to the formation of different morphologies(fiber rods and cross-linked micelles).

New complex silicon-containing molecules were made by B(C6F5)3-catalyzed hydrosilation, dehydrocoupling, and dealkylative coupling reactions starting from Si-H reagents. The scope of reactions starting from disilane was expanded to include the formation of silicon-sulfur1, silicon-oxygen and silicon-alkyl side-chains. Reaction inhibition was found with some heteroatom substrates, such as phenols and imines, that strongly bound to B(C6F5)3, and was consistent with the proposed mechanism (Chapter 2). B(C6F5)3 was found to be selective for Si-H activation in reactions of disilane and no competing Si-Si bond cleavage side-reactions were observed. This result will guide future studies and application of B(C6F5)3-catalyzed reactions with polysilanes. A different type of selectivity, the competing B(C6F5)3-catalyzed over-reduction, is evaluated and discussed in Chapter 3. This over-reduction reaction was classified into two distinct cases: alkyl groups for which over-reduction reaction was dependent on the steric bulk of the alkyl group and benzylic groups for which over-reduction was dependent on having an alpha-aryl group. These reactions are consistent with the proposed Piers-Oestreich mechanism (see Chapter 3) and suggest the rate-determining step for over-reduction is the nucleophilic attack of the alkoxysilane (R -O-SiR3) to the R3Si•••H•••B(C6F5)3 complex. Benzylic side-chains were over-reduced regardless of the steric bulk of the aryl groups. Literature precedents suggest that benzyl over-reductions must undergo an alternative mechanism to the Piers-Oestreich mechanism. A number of mechanisms have been proposed in the literature and in Chapter 3, suggesting conventional heteroatom substrate borane or silane-borane complexation. Furthermore, over-reduction of benzylic sulfur containing side-chains was found and this reaction was exploited in the B(C6F5)3-catalyzed synthesis of unique silicon-sulfur silicon-containing products. These over-reduction reactions highlighted the role of the silane for over-reduction and the challenges associated with the post-polymerization modification of poly(phenylsilane). The advances in B(C6F5)3-catalyzed synthesis of small silane molecules suggested reaction conditions and gave spectroscopic benchmarks that were applied to the post polymerization modification of poly(phenylsilane) (Chapter 4). New X-modified poly(phenylsilane) derivatives with thiolato (sulfur), alkoxy/aryloxy (oxygen), amido (nitrogen) and alkyl(carbon) side-chains were prepared with 10-40% incorporation of the ‘X’ group into poly(phenylsilane). These new polysilanes were characterized by the following methods: 1H/13C/29Si NMR, IR, MALS-GPC, EA, and UV-vis absorption spectroscopy. Together, these characterization methods showed that the polysilane had not undergone Si-Si cleavage and thus demonstrated the utility of B(C6F5)3 for the selective activation of Si-H bonds. Thermal decomposition of X-modified poly(phenylsilane) derivatives and parent poly(phenylsilane) showed interesting redistribution pathways (Chapter 5). The thermal decomposition products of poly(phenylsilane) were identified: volatile monosilanes, a structurally complex not-yet-identified phenylsilicon-containing material generated at 500 °C, and a mixture of silicon carbide (SiC) and elemental carbon generated at 800 °C. The B(C6F5)3-catalyzed post-polymerization method (Chapter 4) was evaluated based on the substitution percentage for X-functionalized poly(phenylsilane) derivatives. Reactions of highly electron-donating substrates gave a low amount of X incorporation (10%, e.g. aryloxy side-chains derived from phenol). Aryloxy groups were alternatively introduced via demethanative coupling, which gave a polymer with a greater substitution percentage (25%). The overall impact of the H-to-X substitution reactions was gauged by UV-vis absorption spectra and desirable UV absorption properties would require the modified poly(phenylsilane) to have a high degree of substitution. / Graduate / 2017-09-02

L’objectif de ce travail de thèse a été de développer l’ingénierie des polymères liquides ioniques(PILs) de type imidazolium ainsi qu’une nouvelle famille de copolymères à blocs apparentés.Des PILs type imidazolium ont été utilisés en tant que polymères réactifs pour la catalyse organique etla modification chimique par post-polymérisation. Divers composés (homopolymères, copolymèresstatistiques de type styrénique, polymères réticulés) stables à l'air, portant divers contre-anions (bromures,hydrogénocarbonates, carboxylates), ont été spécialement conçus via des stratégies de synthèserelativement simples. La génération de carbènes N-hétérocycliques supportés sur polymères (poly(NHC)s)a permis de comparer les performances catalytiques de tous ces précurseurs à travers des réactions deréférence de la catalyse organique. Spécifiquement, les copolymères statistiques type styrénique peuventégalement être fonctionnalisés de manière stoechiométrique par post-polymérisation avec différentssubstrats électrophiles (e.g. CS2, isothiocyanate, métaux de transition).Une nouvelle famille de copolymère à blocs contenant un bloc poly(acétate de vinyle) et un bloc detype poly(bromure de N-vinyl-3-alkylimidazolium), a été synthétisé par CMRP. La capacité de cescomposés à s'auto-assembler en diverses mésostructures en masse comme en solution a ensuite étédémontrée. Des mesures de conductivité ionique ont montré l’influence de la préparation des échantillonset des conditions de mesures sur les valeurs obtenues. Le comportement en solution par la réactivité ioniquedu bloc PIL et la modification chimique du bloc hydrophobe poly(acétate de vinyle) en hydrophilepoly(alcool vinylique) ont permis la formation de différentes nanostructures micellaires.Mots clés : Polymères liquides ioniques, Copolymères à blocs, Imidazolium, catalyse organique,Modification post-polymérisation, Auto-assemblage, Conductivité ionique, nanoparticules d’or. / The aim of this PhD work is to expand the scope of engineered imidazolium-based poly(ionicliquid)s (PILs) and their related PIL-block copolymers (PIL BCPs).The use of the imidazolium-based PILs as true reactive polymers for organocatalysis and post-chemicalmodification is first described. Miscellaneous air-stable PIL derivatives featuring various counter-anions(e.g. bromides, hydrogen carbonates, carboxylates), including homopolymers, statistical copolymers ofstyrenic-type and crosslinked copolymer networks have been specifically designed by relatively simplesynthetic strategies. The generation of related polymer-supported N-heterocyclic carbenes, poly(NHC)s,enables comparing the catalytic performances in selected organocatalyzed reactions. Specific polystyrenebasedcoPILs can be also stoichiometrically derivatized by post-chemical modification using variouselectrophilic substrates (e.g. CS2, isothiocyanate, transition metals).A novel family of imidazolium-based PIL BCPs, namely poly(vinyl acetate)-b-poly(N-vinyl-3-alkylimidazolium bromide)s synthesized by CMRP, is then described. The ability of these compounds toself-assemble into various types of mesostructures in bulk or in solution has been demonstrated. Ionicconductivity measurements evidenced the influence of sample preparation and measurement conditions.The behavior in solution evidenced via the ionic responsiveness of the PIL block but also by post-chemicalmodification of the hydrophobic poly(vinyl acetate) block into hydrophilic poly(vinyl alcohol) theformation of various micelle-like nanostructures.Keywords: Poly(ionic liquid)s, Block copolymers, Imidazolium, Organocatalysis, Post-polymerizationmodification, Self-assembly, Ionic conductivity, Gold nanoparticles / El objetivo de esta tesis fue el desarrollo de polímeros de ingeniería iónicoslíquidos (pils) y tipo imidazolio una nueva familia de copolímeros de bloques relacionados.Lager tipo imidazolio fueron utilizados como reactivos para la catálisis orgánica ymodificación química de polímeros después de la polimerización. Varios compuestos(homopolímeros, copolímeros aleatorios de tipo estireno, polímeros reticulados) estable en elaire, contra de la realización diversos aniones (bromuros, bicarbonatos, carboxilatos), hansido especialmente diseñadas utilizando estrategias de síntesis relativamente simple. Se utilizóla generación de carbenos N-heterocíclicos soportado sobre polímeros (poli (NHC) s) paracomparar el rendimiento catalítico de estos precursores de referencia a través de reacciones decatálisis orgánica. Específicamente, los copolímeros de tipo estireno también se puedenfuncionalizar sustratos por polimerización posterior estequiométricamente con diferenteselectrófilos (por ejemplo, metales CS2, isotiocianato, de transición).Una nueva familia de copolímero de bloque que contiene un poli (acetato de vinilo) y unbloque de poli (bromuro de N-vinil-3-alquilimidazolio) se sintetizó en CMRP. La capacidadde estos compuestos a auto-ensamblan en varias mesoestructuras como entonces se demostrósolución en masa. Mediciones de conductividad iónica han demostrado la influencia de lascondiciones de preparación y medición de la muestra en los valores obtenidos. Elcomportamiento en solución por el bloque PIL reactividad de iones, y la modificaciónquímica del bloque hidrófobo de poli (acetato de vinilo) hidrófilo poli (alcohol vinílico)permitió la formación de nanoestructuras diferentes micelares.Palabras clave: polímeros líquidos iónicos, copolímeros de bloque, imidazolio, catálisisorgánica, Cambiar post-polimerización, auto-ensamblaje, conductividad iónica, lasnanopartículas de oro.

A material to function as a molecular electronic device should have a strong coupling with electrodes through appropriate and well-defined anchoring groups and have to support an effective traveling of charges via a conjugated molecular backbone. Oligo(3-hexylthiophene)s are π-conjugated molecules having large applicability in several areas of organic electronics owing interesting semiconducting properties and they also hold great promises in the field of single-molecule electronics. Polymerization methods, in principle, allow construction of long conjugated systems in a single synthetic step, however, most of them lack precision. This work uses externally initiated chain-growth Kumada Catalyst - Transfer Polycondensation (KCTP) for the synthesis of semiconductive oligo(3-hexylthiophene) wires with controllable molecular weights, low polydispersities, high regioregularities as well as with well-defined starting and end groups. In such a way, the synthetic efforts were compromised to obtain relatively easy a series of very complex molecular wires with a reasonable structural precision. To modulate the electronic function of oligomer backbones, specific charge-transfer moieties (DMA-TCBD and Fc-TCBD) were inserted as side chains or end groups. In-situ termination of KCTP with ZnCl-functionalized electron rich alkynes followed by Diederich-type click reaction resulted in the synthesis of asymmetrical oligo(3-hexylthiophene)s having thiolate-functionalized starting groups and donor-functionalized end-groups with a high degree of end-group functionalizations. Side chains of double-thiolate functionalized oligo(3-hexylthiophene)s, on the other hand, were further modified with the insertion of charge-transfer groups by post-polymerization functionalization. While the facile synthesis and modification of oligo(3-hexylthiophene)s enable the control over the molecular backbone, the specific starting and end anchoring groups allow the control over the electrode oligomer interface. To assure the formation of alligator clips between oligomer backbone and Au electrode, the optimizations including proper end-group conversion into mild counterparts followed by in-situ deprotection into thiolates and the binding abilities on gold were investigated. Finally, the conductance of bis-end functionalized oligo(3-hexylthiophene)s was preliminarily studied through oligomer backbone by Mechanically Controllable Break Junctions (MCBJs) setup and through oligomer-attached DNA origami-templated gold nanowires by individual electrical contacts. The developed KCTP-based synthetic route, at the end, presents new opportunities for the facile synthesis, the ease of modification and the feasibility of asymmetrical and side chain functionalized oligo(3-hexylthiophene) wires for needs of molecular electronics.

A material to function as a molecular electronic device should have a strong coupling with electrodes through appropriate and well-defined anchoring groups and have to support an effective traveling of charges via a conjugated molecular backbone. Oligo(3-hexylthiophene)s are π-conjugated molecules having large applicability in several areas of organic electronics owing interesting semiconducting properties and they also hold great promises in the field of single-molecule electronics. Polymerization methods, in principle, allow construction of long conjugated systems in a single synthetic step, however, most of them lack precision. This work uses externally initiated chain-growth Kumada Catalyst - Transfer Polycondensation (KCTP) for the synthesis of semiconductive oligo(3-hexylthiophene) wires with controllable molecular weights, low polydispersities, high regioregularities as well as with well-defined starting and end groups. In such a way, the synthetic efforts were compromised to obtain relatively easy a series of very complex molecular wires with a reasonable structural precision. To modulate the electronic function of oligomer backbones, specific charge-transfer moieties (DMA-TCBD and Fc-TCBD) were inserted as side chains or end groups. In-situ termination of KCTP with ZnCl-functionalized electron rich alkynes followed by Diederich-type click reaction resulted in the synthesis of asymmetrical oligo(3-hexylthiophene)s having thiolate-functionalized starting groups and donor-functionalized end-groups with a high degree of end-group functionalizations. Side chains of double-thiolate functionalized oligo(3-hexylthiophene)s, on the other hand, were further modified with the insertion of charge-transfer groups by post-polymerization functionalization. While the facile synthesis and modification of oligo(3-hexylthiophene)s enable the control over the molecular backbone, the specific starting and end anchoring groups allow the control over the electrode oligomer interface. To assure the formation of alligator clips between oligomer backbone and Au electrode, the optimizations including proper end-group conversion into mild counterparts followed by in-situ deprotection into thiolates and the binding abilities on gold were investigated. Finally, the conductance of bis-end functionalized oligo(3-hexylthiophene)s was preliminarily studied through oligomer backbone by Mechanically Controllable Break Junctions (MCBJs) setup and through oligomer-attached DNA origami-templated gold nanowires by individual electrical contacts. The developed KCTP-based synthetic route, at the end, presents new opportunities for the facile synthesis, the ease of modification and the feasibility of asymmetrical and side chain functionalized oligo(3-hexylthiophene) wires for needs of molecular electronics.

Récemment, la chimie des phosphoramidites s’est montrée efficace et polyvalente en tant que plateforme pour accéder à des poly(phosphodiester)s à séquence définies abiotiques. Grâce à cette stratégie, les monomères peuvent être placés dans la chaîne à des positions choisies, ouvrant la voie à de nombreuses possibilités pour la préparation de macromolécules fonctionnelles. Ici, la méthode phosphoramidite a été explorée pour la synthèse de polymères dits numériques, qui contiennent des séquences de monomères encodées binairement. Des polymères dont les longueurs de chaînes et les séquences numériques sont contrôlées ont été préparés en utilisant une stratégie phosphoramidite classique impliquant des groupements protecteurs diméthoxytrityles, ou bien un procédé photocontrôlé faisant intervenir des groupements nitrophénylpropyloxycarbonyles clivables à la lumière. En outre, plusieurs stratégies pour modifier l’information contenue dans les chaînes latérales ont été étudiées dans cette thèse. Une modification binaire post-polymérisation à travers deux cycloadditions alcyne-azoture catalysées par le cuivre(I) consécutives a été examinée pour optimiser les chaînes latérales des poly(phosphodiester)s à séquences définies. De plus, la libération photocontrôlée de différents motifs éthers ortho-nitrobenzyliques latéraux a été étudiée. Ces fonctions ont permis la conception d’oligo(phosphodiester)s numériques dont les séquences d’information peuvent être effacées ou révélées grâce à la lumière. / Phosphoramidite chemistry has recently been evidenced to be an efficient and versatile platform to access sequence-defined abiotic poly(phosphodiester)s. Using this strategy, monomers can be placed at defined positions positions in a chain, thus opening up wide possibilities for the preparation of functional macromolecules.Here, the phosphoramidite platform was explored to synthesize so-called digital polymers, which contain monomer-coded binary sequences. Polymers with controlled chain lengths and digital sequences were prepared using either a standard phosphoramidite strategy involving dimethoxytrityl protective groups or a photo-controlled process involving light-cleavable nitrophenylpropyloxycarbonyl protective groups. Additionally, several strategies to modify the side chain information were investigated in this thesis. A binary post-polymerization modification by means of sequential copper(I)-catalyzed alkyne-azide cycloadditions was investigated for tuning the side chain functionality of sequence-defined poly(phosphodiester)s. Moreover, the photo-controlled release of several ortho-nitrobenzylic ether side chain motifs was studied. These moieties allowed the design of digital oligo(phosphodiester)s whose sequence information can be erased or revealed with light as a trigger.