Dendronized electrochromic polymer based on poly(3,4-ethylenedioxythiophene)

In order to improve electrochromic contrast, 3,4-ethylenedioxythiophene (EDOT) substituted with the first generation dendritic wedge based on gallic acid (M2) was synthesized by connecting 3,4,5-tribenzyloxy benzyl chloride to hydroxymethyl EDOT (M1). Electropolymerization of M1 and M2 resulted in the formation of an electroactive and well adhered film on the electrode surface. In the case of PEDOT substituted with the dendritic wedge (P2), it was observed that the resistance of the film increases with thickness. Spectroelectrochemical studies indicated that the polymers switch from a highly opaque dark-blue reduced state to highly transmissive oxidized state with a contrast of 67% in P2 and 46% in P1. In situ conductivity studies showed a sharp transition from a dedoped insulating state to doped conducting state at around −0.4 V with maximum in situ conductance of 0.06 S for P1 and 0.04 S for P2.© Elsevie

Large PAMAM Dendron Induces Formation of Unusual <i>P</i>4₃32 Mesophase in Monoolein/Water Systems

Compact macromolecular dendrons have previously been shown to induce the formation of discontinuous inverse micellar assemblies with <i>Fd</i>3<i>m</i> symmetry in monoolein/water systems. Here, we demonstrate that a large PAMAM dendron (G5: fifth generation) induces the formation of a very unusual mesophase with <i>P</i>4₃32 symmetry. This mesophase had previously been observed in monoolein/water systems only on addition of cytochrome <i>c</i>. The <i>P</i>4₃32 mesophase can be considered an intermediate phase between the bicontinuous <i>Ia</i>3<i>d</i> and discontinuous micellar mesophases. We present a detailed investigation of the phase behavior of monoolein/water as a function of G5 concentration and temperature. Addition of 1% G5 in 85/15 monoolein/water system induces a transition from the L_α to <i>Ia</i>3<i>d</i> phase. Further increase in G5 concentration to above 2% induces the formation of the <i>P</i>4₃32 phase. In contrast to this, incorporation of lower generation PAMAM dendrons (G2–G4) in monoolein/water yields a qualitatively different phase diagram with the formation of the reverse micellar <i>Fd</i>3<i>m</i> phase. PAMAM dendrons of all generations, G2–G5, bear terminal amine groups that interact with the monoolein headgroup. The compact molecular architecture of the dendrons and these attractive interactions induce bending of the monoolein bilayer structure. For smaller dendrons, G2–G4, this results in the formation of the <i>Fd</i>3<i>m</i> phase. However, the large size of the G5 dendron precludes this and a rare intermediate phase between the <i>Ia</i>3<i>d</i> and discontinuous micellar phase, and the <i>P</i>4₃32 mesophase forms instead

Visible light and pH-responsive star copolymer and doxorubicin-polymer conjugate micelles for combination drug delivery and bioimaging

Amphiphilic 3-arm star copolymer containing visible light-cleavable BODIPY group and pH-responsive imine bonds at the junction of hydrophilic poly(ethylene glycol) (PEG) and two poly(ε-caprolactone) (PCL) arms was synthesized by the combination of ring-opening polymerization (ROP) and click chemistry. The formation and stimuli-responsive disruption of micelles were analyzed using dynamic light scattering and transmission electron microscopy. Dual stimuli-responsive release of anticancer drugs Doxorubicin (Dox) and Camptothecin (CPT) from the micelles was studied. Micellar assemblies containing Dox conjugated to PEG-BODIPY through imine bonds were prepared and controlled release of Dox in response to visible light and pH was shown. CPT and Dox-loaded star copolymer micelles as well as CPT loaded Dox-conjugated micelles were used in cellular uptake studies on MDA-MB 231 cells, and the synergistic effect of the two stimuli on the release of the two drugs was demonstrated inside the cells. Micellar assemblies also showed excellent bioimaging properties in the cellular uptake studies.</p

Nonedible Thevetia peruviana Oil for the Synthesis of Biobased Thermosets and Vitrimers with Tunable Mechanical Properties

Current attempts to replace fossil-derived materials with vegetable oils for polymer production mainly rely on edible oils. This approach raises sustainability concerns due to potential food security risks. This report introduces the first in-depth examination of Thevetia peruviana oil (TPO) epoxidation, an easily accessible nonedible vegetable oil, utilizing diverse acidic ion-exchange resins as catalysts. It is followed by the development of vitrimers based on epoxidized oil (ETPO) with various dicarboxylic acid hardeners. Amberlite IRC120H emerged as the most effective catalyst for the epoxidation of the oil, allowing for repeated catalyst reusability for up to five cycles. An impressive relative oxirane conversion of 98.9% was achieved after optimization. DSC analysis revealed that among the diacids, 2,2′-dithiodibenzoic acid (DTBZ) has the lowest activation energy with ETPO. Additionally, the ETPO–DTBZ-based thermosets displayed exceptional solvent resistance and thermal stability, indicative of a high degree of cross-linked networks within the system. Mechanical analyses revealed that all aliphatic hardeners resulted in soft materials, while DTBZ resulted in thermosets with tensile stress and modulus of 15 and 843 MPa, respectively. Consequently, DTBZ–ETPO thermosets were successfully recycled, repaired, and reshaped with minimal changes in the mechanical properties. The shape memory of the thermosets was also established

Multiple Topologies from Glycopolypeptide–Dendron Conjugate Self-Assembly: Nanorods, Micelles, and Organogels

Glycopolypeptides (GPs) were synthesized by ring-opening polymerization of glycosylated <i>N</i>-carboxyanhydride monomer and attached to hydrophobic dendrons at one chain end by “click” reaction to obtain amphiphilic anisotropic macromolecules. We show that by varying polypeptide chain length and dendron generation, an organogel was obtained in dimethylsulfoxide, while nanorods and micellar aggregates were observed in aqueous solutions. Assemblies in water were characterized by electron microscopy and dye encapsulation. Secondary structure of the GP chain was shown to affect the morphology, whereas the chain length of the poly­(ethylene glycol) linker between the GP and dendron did not alter rod-like assemblies. Bioactive surface chemistry of these assemblies displaying carbohydrate groups was demonstrated by interaction of mannose-functionalized nanorods with ConA

Tunable Nanocarrier Morphologies from Glycopolypeptide-Based Amphiphilic Biocompatible Star Copolymers and Their Carbohydrate Specific Intracellular Delivery

Nanocarriers with carbohydrates on the surface represent a very interesting class of drug-delivery vehicles because carbohydrates are involved in biomolecular recognition events in vivo. We have synthesized biocompatible miktoarm star copolymers comprising glycopolypeptide and poly­(ε-caprolactone) chains using ring-opening polymerization and “click chemistry”. The amphiphilic copolymers were self-assembled in water into morphologies such as nanorods, polymersomes, and micelles with carbohydrates displayed on the surface. We demonstrate that the formation of nanostructure could be tuned by chain length of the blocks and was not affected by the type of sugar residue. These nanostructures were characterized in detail using a variety of techniques such as TEM, AFM, cryogenic electron microscopy, spectrally resolved fluorescence imaging, and dye encapsulation techniques. We show that it is possible to sequester both hydrophobic as well as hydrophilic dyes within the nanostructures. Finally, we show that these noncytotoxic mannosylated rods and polymersomes were selectively and efficiently taken up by MDA-MB-231 breast cancer cells, demonstrating their potential as nanocarriers for drug delivery

Function and Structure of MalA/MalA′, Iterative Halogenases for Late-Stage C–H Functionalization of Indole Alkaloids

Malbrancheamide is a dichlorinated fungal indole alkaloid isolated from both <i>Malbranchea aurantiaca</i> and <i>Malbranchea graminicola</i> that belongs to a family of natural products containing a characteristic bicyclo[2.2.2]­diazaoctane core. The introduction of chlorine atoms on the indole ring of malbrancheamide differentiates it from other members of this family and contributes significantly to its biological activity. In this study, we characterized the two flavin-dependent halogenases involved in the late-stage halogenation of malbrancheamide in two different fungal strains. MalA and MalA′ catalyze the iterative dichlorination and monobromination of the free substrate premalbrancheamide as the final steps in the malbrancheamide biosynthetic pathway. Two unnatural bromo-chloro-malbrancheamide analogues were generated through MalA-mediated chemoenzymatic synthesis. Structural analysis and computational studies of MalA′ in complex with three substrates revealed that the enzyme represents a new class of zinc-binding flavin-dependent halogenases and provides new insights into a potentially unique reaction mechanism