Only recently, post‐polymerization modification reactions of unactivated polyacrylates have been emerging as an attractive alternative to utilizing reactive monomers, enabling the synthetic upcycling ...of these widely applied polymers. Within this contribution, the triazabicyclodecene‐catalyzed transesterification of polyacrylates is reported, including the reaction kinetics and the broad scope for macromolecular design of functional copolyacrylates. More specifically, the transesterification is performed under equilibrium conditions with a set of primary alcohols whereby the reaction kinetics and the obtained conversion as a function of stoichiometric excess of alcohol are evaluated. The results show that the obtained conversion is dependent on the polarity of the solvent and of the alcohol. Through this approach, the transesterification degree can be accurately controlled by stoichiometry, enabling the precise modulation of the macromolecular structure. Finally, the utility of this approach is demonstrated to incorporate functional side chains that are incompatible with radical polymerization, to facilitate Diels–Alder and thiol‐ene reactions, enabling access to a broad range of functional materials from simple polyacrylate homopolymer precursors.
Transesterification of polyacrylates under equilibrium conditions enables accurate modification of this industrially relevant polymer class. This article shows the wide range of modification degrees attainable (up to 90%) and the introduction of several polymerization incompatible groups by an organocatalyzed approach. This method enables straightforward synthesis of new functional materials from a wide range of commercial precursors.
Cherenkov Radiation (CR), this blue glow seen in nuclear reactors, is an optical light originating from energetic β-emitter radionuclides. CR emitter
Y triggers a cascade of energy transfers in the ...presence of a mixed population of fluorophores (which each other match their respective absorption and emission maxima): Cherenkov Radiation Energy Transfer (CRET) first, followed by multiple Förster Resonance Energy transfers (FRET): CRET ratios were calculated to give a rough estimate of the transfer efficiency. While CR is blue-weighted (300-500 nm), such cascades of Energy Transfers allowed to get a) fluorescence emission up to 710 nm, which is beyond the main CR window and within the near-infrared (NIR) window where biological tissues are most transparent, b) to amplify this emission and boost the radiance on that window: EMT6-tumor bearing mice injected with both a radionuclide and a mixture of fluorophores having a good spectral overlap, were shown to have nearly a two-fold radiance boost (measured on a NIR window centered on the emission wavelength of the last fluorophore in the Energy Transfer cascade) compared to a tumor injected with the radionuclide only. Some CR embarked light source could be converted into a near-infrared radiation, where biological tissues are most transparent.
An additive‐free nickel‐catalyzed α‐allylation of aldehydes with allyl alcohol is reported. The reaction is promoted by 1 mol % of in situ formed nickel complex in methanol, and water is the sole ...by‐product of the reaction. The experimental conditions allow the conversion of various α‐branched aldehydes and α,β‐unsaturated aldehydes as nucleophiles. The same catalyst and reaction conditions enabled a tandem aldol condensation of aldehyde/α‐allylation reaction.
Nickel‐based catalysts efficiently promote the α‐allylation of α‐branched aldehydes and α,β‐unsaturated aldehydes with allylic alcohols under additive‐free conditions. The reaction proceeds with high yield and water is formed as the only byproduct. The nickel catalysts proved to be suitable for the promotion of a tandem aldolisation/allylation reaction of simple linear aldehydes with allylic alcohols.
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•Direct method for introducing amine side chains into polyacrlyamides.•Direct amidation of polymethylacrylate as tool for making functional polyacrylamides.•Reported method has ...potential for polymer upcycling.
Post-polymerization modification of poorly reactive polyacrylates using efficient catalytic transesterification and amidation reactions has recently emerged as a valuable tool to access diversely functionalized poly(meth)acrylates and poly(meth)acrylamides. The method is particularly useful to introduce functional groups incompatible with the polymerization mechanism, such as non-protected reactive amino groups. In this work, we explored the TBD-catalyzed amidation of polymethylacrylate (PMA) with various difunctional amines to obtain polyacrylamide homo- and copolymers with a pendant reactive amine group. As anticipated, functional polymers could not be attained from amidation with ethylenediamine, because of competing cross-linking side reactions, but could be prepared from the mono-Boc-protected ethylenediamine instead, requiring, however, additional unwanted protection and deprotection steps. More interestingly, we found that the direct amidation of PMA with unprotected N-ethylethylenediamine is an efficient method for preparing secondary amine functionalized polymers, without the occurrence of crosslinking side-reaction even at lower catalyst loading. The crucial role of the ethyl group to prevent side reactions was clearly demonstrated as the use of N-methyl ethylenediamine led to crosslinking. The utility of the developed platform for the rapid preparation of a series of hydrophilic copolymers and hydrogel materials is also demonstrated. The hydrogels were prepared by reacting the secondary amine side chains with methacrylic anhydride, followed by photocuring in the presence and absence of dithiols.
Non‐activated esters are prominently featured functional groups in polymer science, as ester functional monomers display great structural diversity and excellent compatibility with a wide range of ...polymerization mechanisms. Yet, their direct use as a reactive handle in post‐polymerization modification has been typically avoided due to their low reactivity, which impairs the quantitative conversion typically desired in post‐polymerization modification reactions. While activated ester approaches are a well‐established alternative, the modification of non‐activated esters remains a synthetic and economically valuable opportunity. In this review, we discuss past and recent efforts in the utilization of non‐activated ester groups as a reactive handle to facilitate transesterification and aminolysis/amidation reactions, and the potential of the developed methodologies in the context of macromolecular engineering.
Modification of non‐activated esters represents interesting opportunities in polymer science. While early attempts indicated severe synthetic challenges in this area, recently several researchers have made significant progress, thus enabling structural diversification and synthetic upcycling of various polymers. This review summarizes this progress, and highlights unique structural features that can be exploited in a macromolecular context.
Subphthalocyanine (SubPc) could be reversibly protonated at the azomethine bridge. This phenomenon was examined by addressing the p
K
a
of the acid (TFA, MSA, TMSA) and the SubPc electron-withdrawing ...properties of the peripheral isoindolic substituents (F
12
vs.
H
12
and NO
2
), which tunes the basic character of the azomethine moiety. The protonation of up to three azomethines was suggested and monitored spectrophotometrically with the appearance of new absorption bands at 610, 630 nm and 660 nm, together with marked colour changes from purple to blue to green. Evidence of such a protonation was also shown by significant changes in the
1
H-NMR spectrum and new bands in the infrared spectrum.
Protonation of subphthalocyanine azomethine bridges is reversible and was evidenced by UV/Vis,
1
H-NMR and IR.
We report the synthesis and characterization of a novel photo-switch based on biomimetic cyclocurcumin analogous and interacting with the lipid bilayer, which can be used in the framework of ...oxygen-independent light-induced therapy. More specifically, by using molecular dynamics simulations and free energy techniques, we show that the inclusion of hydrophobic substituents is needed to allow insertion in the lipid membrane. After having confirmed experimentally that the substituents do not preclude the efficient photoisomerization, we show through UV–vis and dynamic light scattering measurements together with compression isotherms that the chromophore is internalized in both lipid vesicles and monomolecular film, respectively, inducing their fluidification. The irradiation of the chromophore-loaded lipid aggregates modifies their properties due to the different organization of the two diastereoisomers, E and Z. In particular, a competition between a fast structural reorganization and a slower expulsion of the chromophore after isomerization can be observed in the kinetic profiles recorded during E to Z photoisomerization. This report paves the way for future investigations in the optimization of biomimetic photoswitches potentially useful in modern light-induced therapeutic strategies.
Photothermal therapy (PTT) is a method of growing attention, owing to its controllable process, high efficiency and minimal side effect. Indocyanine Green (ICG) is as Food and Drug Administration ...(FDA) approved agent that stands on the frontline of further developments of PTT toward clinics. However, the applicability of ICG-mediated PTT is limited by the rapid in vivo clearance and photo-degradation of ICG. To improve those parameters, nanosized ICG-loaded nanoparticles (ICG-J/CX) were fabricated in this study by co-assembly of anionic ICG J-aggregates (ICG-J) with cationic tetraguanidinium calix4arene (CX). This very simple approach produces ICG-J/CX with a well-defined nanometer range size and a close to neutral charge. The nanoparticles demonstrate high photothermal conversion efficiency (PCE) and dramatically improved photostability, as compared with ICG. The in vitro cellular uptake and cytotoxicity studies further demonstrated that the ICG-J/CX nanoparticles enhance uptake and photothermal efficiency in comparison with ICG or non-formulated ICG-J, overall demonstrating that ICG-J/CX mediated photothermal therapy have significant potential for attaining cancer treatment.
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•Caveolin-dependent incorporation of ICG-J calixarenes nanoparticles.•Improved photostability of ICG when in J-aggregates and included in nanoparticles.•Enhanced photothermal effect when ICG is J-aggregated and in nanoparticle form.
Four novel biobased monomers (
i.e.
two diesters and two hydroxyesters) bearing a tertiary amine in their backbone have been synthesized from the sustainable methyl levulinate and ...amino-alcohols/amino-esters derived from natural amino acids. Their homopolymerization/copolymerization with diols leads to six poly(amine-
co
-ester)s with various microstructures. These families of biodegradable polyesters have been reported to be efficient carriers for gene delivery. The polymers are carefully characterized by nuclear magnetic resonance spectroscopy (
1
H and
13
C NMR) and size exclusion chromatography (SEC), and exhibit molecular weights (
M
n
) up to 36 kg mol
−1
and dispersities (
Đ
) between 1.5 and 2.1. They also present good solubility in aqueous acidic media due to amine protonation. Such properties are promising for applications in the biomedical field or in personal care products.
The catalytic conversion of esters to amides represents new opportunities in the synthetic diversification and upcycling of polymers, as esters are commonly featured in various polymer structures. ...Yet, direct amidation is typically hampered by poor reaction kinetics and the effects of polymer structure on the reactivity remain poorly understood. We report the accelerated amidation for amines with additional hydrogen bond donating or accepting groups. These amines facilitate the expeditious (co)amidation of polymers with pendant ester groups, displaying at least a 400‐fold higher reactivity relative to polyesters with esters in the main chain. Furthermore, a positive correlation between the reactivity and degree of polymerization for poly(methyl acrylate) suggests a hydrogen‐bond mediated intramolecular activation of the esters, which was confirmed by FT‐IR spectroscopy and basic molecular mechanics modeling. The reported method paves the way to synthesize diverse (co)polymers with amide side chains from readily available polymeric precursors.
The post‐polymerization amidation of non‐activated esters is an interesting opportunity in the structural diversification and synthetic upcycling of various polymers. While amidation typically proceeds slowly, polymers with ester side‐chains benefit from intramolecular activation when reacted with amines featuring a second hydrogen‐bonding functional group. The observed acceleration is dependent on the macromolecular structure.
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