Units In Main Chain Research Articles

Design of pH/Redox Co-Triggered Degradable Diselenide-Containing Polyprodrug via a Facile One-Pot Two-Step Approach for Tumor-Specific Chemotherapy.

The diselenide bond has attracted intense interest for drug delivery systems (DDSs) for tumor chemotherapy, owing to it possessing higher redox sensitivity than the disulfide one. Various redox-responsive diselenide-containing carriers have been developed for chemotherapeutics delivery. However, the premature drug leakage from these DDSs was significant enough to cause toxic side effects on normal cells. Here, a pH/redox co-triggered degradable polyprodrug was designed as a drug self-delivery system (DSDS) by incorporating drug molecules as structural units in the polymer main chains, using a facile one-pot two-step approach. The proposed PDOX could only degrade and release drugs by breaking both the neighboring acid-labile acylhydrazone and the redox-cleavable diselenide conjugations in the drug's structural units, triggered by the higher acidity and glutathione (GSH) or reactive oxygen species (ROS) levels in the tumor cells. Therefore, a slow solubility-controlled drug release was achieved for tumor-specific chemotherapy, indicating promising potential as a safe and efficient long-acting DSDS for future tumor treatment.

Synthesis of photodegradable polyesters from bio-based 3,4-dimethoxycinnamic acid and investigation of their degradation behaviors

To address the issue of petroleum resource depletion, it is desirable to develop recyclable materials from bio-based compounds. In addition, low-energy recycling methods such as light irradiation and hydrolysis should be considered. In this paper, bio-based materials, cinnamic acid (CA) derivatives, are introduced as repeating units in polyester main-chain, because CA derivatives undergo reversible [2 + 2] cycloaddition reactions to form dimers under light exposure. Photopolymerization of the monomer with CA moieties at both ends failed, probably because it was difficult to bring the two CA moieties closer together intermolecularly. Polycondensation between the CA dimer with two carboxylic acid moieties and diol compounds successfully provided the polyesters containing CA dimers as repeating units. Furthermore, orthogonal degradation methods, such as light exposure and hydrolysis, of the obtained polyester were investigated.

Cross-coupling and dehalogenation reactions of novel π-conjugated polymers bearing high-soluble coumarin unit in the main chain and their acid-base responsive fluorescence

A highly soluble coumarin monomer, 3,7-dibromo-4-octyloxycoumarin, was developed as the novel building block for π−conjugated polymers. Sonogashira coupling reaction, dehalogenation reaction, and Suzuki-Miyaura coupling reaction were carried out by using this new monomer as the main chain unit of π−conjugated polymer for polymerization. Introduction of a long alkoxy chain into coumarin monomer unit significantly improved the solubility of thus obtained polymers. The absorption and emission spectra of polymers showed red-shift compared to those of monomer, indicating the expansion of the π−conjugated system in the polymer main chain. Especially the polymers synthesized via Sonogashira coupling formed excimer in film state. The polymers showed acid-base responsibility with the addition of KOHaq and HClaq.

Design and Synthesis of Amphiphilic Graft Polyphosphazene Micelles for Docetaxel Delivery.

The structural versatility of polydichlorophosphazene derived from the inestimable possibilities to functionalize the two halogens, attached to each phosphazene main chain unit, attracted increasing attention in the last decade. This uncountable chemical derivatization is doubled by the amphiphilic roleplay demonstrated by polyphosphazenes containing twofold side-chained hydrophilic and hydrophobic moieties. Thus, it is able to encapsulate specific bioactive molecules for various targeted nanomedicine applications. A new amphiphilic graft, polyphosphazenes (PPP/PEG-NH/Hys/MAB), was synthesized via the thermal ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a subsequent two-step substitution reaction of chlorine atoms with hydrophilic methoxypolyethylene glycol amine/histamine dihydrochloride adduct (PEG-NH2)/(Hys) and hydrophobic methyl-p-aminobenzoate (MAB), respectively. Fourier transform infrared spectroscopy (FTIR) and 1H and 31P-nuclear magnetic resonance spectroscopy (NMR) have been used to validate the expected architectural assembly of the copolymer. Docetaxel loaded micelles based on synthesized PPP/PEG-NH/Hys/MAB were designed by dialysis method. The micelles size was evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The drug release profiles from the PPP/PEG-NH/Hys/MAB micelles were established. In vitro cytotoxicity tests of PPP/PEG-NH/Hys/MAB micelles loaded with Docetaxel revealed that designed polymeric micelles exhibited an increased cytotoxic effect on MCF-7 cells.

Effects of Mesogenic Cycloaliphatic Units on the Microstructure and Properties of Thermotropic Liquid Crystalline Polyesters

AbstractWe report the synthesis and structure‐property relationship of new thermotropic liquid crystalline polyesters (TLCPs) with different mesogenic cycloaliphatic unit content in the mainchain. For this purpose, a series of TLCPs composed of three different repeating units based on 4‐hydroxybenzoic acid (HBA, 75.0 mol%), 2‐hydroxy‐6‐naphthoic acid (HNA, 25.0–15.0 mol%), and terephthalic acid/1,4‐cyclohexanedimethanol (TPA/CHDM, 0.0–10.0 mol%) were synthesized via two‐step bulk polymerization. The structure, thermal and mechanical properties of the TLCPs were investigated by considering the effects of size and content of TPA/CHDM‐derived repeating units, in comparison to HNA‐based repeating units. Infrared spectroscopic data showed that TPA/CHDM‐derived repeating units were successfully incorporated into HBA/HNA‐based TLCPs. The polarized optical and electron microscopic images revealed the existence of thermotropic liquid crystalline features and associated fibrillar structures for all TLCPs. The melting temperatures of the TLCPs decreased with increasing the TPA/CHDM‐based repeating units, whereas the glass transition temperature increased, which is due to the trade‐off effect of the segmental mobility restriction in the amorphous phase and the destruction of the thermotropic liquid crystalline phase by the introduction of TPA/CHDM‐derived repeating units in the TLCP mainchain. In addition, the maximum elastic storage modulus was attained for the TLCP with 2.5 mol% TPA/CHDM‐derived repeating units.

Synthesis of Polymer Having Thioxanthene Unit in Main Chain and Application to Photorefractive Composites

Synthesis of Polymer Having Thioxanthene Unit in Main Chain and Application to Photorefractive Composites

Novel Metallo-Supramolecular Polymers with 1-Thioxophosphole Main-Chain Units and Remarkable Photoinduced Changes in Their Resonance Raman Spectra.

New low-bandgap unimers, with the central thiophene-(1-thioxophosphole)-thiophene (TPT) ring sequence and 2,2':6',2″-terpyridin-4'-yl (tpy) end groups connected to the central unit via conjugated linkers of different size, are prepared and assembled with Zn(II) and Fe(II) ions to metallo-supramolecular polymers (MSPs) that are studied regarding their properties. The most interesting feature of Zn-MSPs is the luminescence extended deep into the NIR region. Fe-MSPs not only show the metal-to-ligand charge transfer (MLCT) manifested by the MLCT band (an expected feature) but also an as-yet-undescribed remarkable phenomenon: specific damping of the bands of the TPT sequence in the resonance Raman spectra taken from solid Fe-MSPs using the excitation to the MLCT band (532 nm). The damping is highly reversible at the low laser power of 0.1 mW but gradually becomes irreversible as the power reaches ca. 5 mW. The revealed phenomenon is not shown by the same Fe-MSPs in solutions, nor by Fe-MSPs containing no phosphole units. A hypothesis is proposed that explains this phenomenon and its dependence on the irradiation intensity as a result of the interplay of three factors: (i) enhancement of the MLCT process by excitation radiation, (ii) the electron-acceptor character of the 1-thioxophosphole ring, and (iii) morphological changes of the lattice and their dependence on the population of new structures in the lattice.

Poly(terphenyl piperidinium) containing hydrophilic crown ether units in main chains as anion exchange membranes for alkaline fuel cells and water electrolysers

Poly(arylene piperidinium) polymers are recognized as promising anion exchange membrane (AEM) materials for alkaline fuel cell and water electrolysis, due to the aryl-ether free polyaromatic backbones and stable piperidinium cations. Herein, hydrophilic crown ether units have been introduced into poly(terphenyl piperidinium) (PDTP) by readily superacid-catalyzed polycondensation of dibenzo-18-crown-6 (DE), p-terphenyl and N-methyl-4-piperidine followed via quaternization. The obtained PDTP membranes showed much higher hydroxide conductivity than the control poly(terphenyl piperidinium) (PTP) sample without DE units, due to their high water uptake. The highest hydroxide conductivity of 110 mS/cm was reached at 80 °C for PDTP-10 (where 10 denoted the molar content of crown ether units) membrane with an ion exchange capacity (IEC) of 2.57 meq./g. The introduction of DE units alleviated the chemical degradation of PDTP membrane in 1 M NaOH at 80 °C as compared to the PTP membranes. Furthermore, membrane electrode assemblies based on PDTP-10 membrane shown a peak power density of 621 mW/cm2 at 60 °C in AEM fuel cells and a current density of 2000 mA/cm2 at 2.1 V for water electrolysers circulated with 1 M NaOH at 80 °C. The in-situ stability tests in fuel cells and water electrolysers also manifested that the chemical structure of PDTP-10 membrane remained intact during short-term durability tests under galvanostatic mode. The above results manifested that AEMs containing hydrophilic crown ether units in the polymer mainchain showed potential in the application for AEM based electrochemical devices.

Vanadium-Catalyzed Terpolymerization of α,ω-Dienes with Ethylene and Cyclic Olefins: Ready Access to Polar-Functionalized Polyolefins

α,ω-Dienes are an important class of monomers due to their utility in the synthesis of cyclopolyolefins and reactive polyolefin intermediates. In this contribution, the terpolymerization of two α,ω-dienes (i.e., 1,5-hexadiene and 1,7-octadiene) with ethylene and various cyclic olefins [i.e., norbornene (NB), 5-ethylidene-2-norbornene (ENB), and dicyclopentadiene (DCPD)] catalyzed by a chelated imido vanadium complex has been examined. The ENB and DCPD diene termonomers provide additional sites for post-polymerization functionalization. Vanadium-catalyzed terpolymerization of the investigated α,ω-dienes yields polyolefins with a high molecular weight (Mw up to 200 × 103 g mol–1), unimodal and narrow molecular weight distribution, subambient glass transition temperatures (−30 < Tg °C < −3), and a proper content of C═C bonds. Comprehensive NMR investigation of the obtained polymers revealed that subtle changes in the α,ω-diene size have important effects on the numerous combinations of insertion paths (ring closure vs ring opening), from which different repeating units with a C═C bond in the side or main polymer chain and cyclic units are installed. Finally, the poly(ethylene-ter-1,5-hexadiene-ter-NB) was subjected to thiol-ene addition using thioglycolic acid, methyl thioglycolate, and N-acetyl-l-cysteine to access polar-functionalized polyolefins with a degree of functionalization and properties dependent on the thiol substitution.

Antioxidant activity and rheological properties of the polysaccharides isolated fromRibes stenocarpummaxim with different extraction methods

The purpose of the present study is to illustrate the effects of extraction methods on the antioxidant activity and rheological properties of polysaccharides isolated from Ribes stenocarpum Maxim (RPs). RPs were extracted by ultrasonic-assisted extraction (RPs-1), alkaline extraction (RPs-2), acid extraction (RPs-3), microwave-assisted extraction (RPs-4), and three-phase separation (RPs-5). The results showed that RPs-1, RPs-2, RPs-3, RPs-4, and RPs-5 are acidic heteropolysaccharides with glucose, arabinose, and galacturonic acid as the main chain units and absence of triple-helix structure. Of them, RPs-3 possess the highest uronic acid content, best thermal stability, and strongest DPPH, ABTS, and hydroxyl radical scavenging abilities. Rheological properties showed that the above-mentioned polysaccharides are non-Newtonian fluids and own the similar shear thinning properties. RPs-3 represent the highest apparent viscosity and better stability in the over-acid or over-alkali environment. The above results indicated that the acid extraction could serve as the most favorable extraction method for RPs. Novelty impact statement A novel polysaccharide was isolated from Ribes stenocarpum Maxim by acid extraction, showing a stronger antioxidant activity and excellent rheological properties, which has a good application prospect in food processing.

Synthesis and properties of novel poly(ether ketone ketone)s containing 1,4‐naphthylene units by electrophilic solution copolycondensation

AbstractSemicrystalline poly(aryl ether ketone)s (PAEKs) represent an industrially important class of high‐performance engineering thermoplastics with excellent physicochemical and mechanical properties, and the synthesis of PAEKs with enhanced glass transition temperatures (Tg) and moderate melting temperatures (Tm) is highly desirable. In the work reported, novel poly(ether ketone ketone)s (PEKKs) containing 1,4‐naphthylene units in main chains were synthesized by Friedel–Crafts solution copolycondensation of terephthaloyl chloride with a mixture of diphenyl ether and 1,4‐di(4‐phenoxybenzoyl)naphthalene (1,4‐DPOBN). The polymerization proceeded smoothly in 1,2‐dichloroethane in the presence of anhydrous AlCl3andN‐methylpyrrolidone under mild conditions and afforded polymers having inherent viscosities of 0.66–0.98 dL g−1. The polymers with 5–30 mol% 1,4‐DPOBN are semicrystalline and have obviously enhancedTgover commercial poly(ether ether ketone)s and PEKKs due to the incorporation of rigid and bulky 1,4‐naphthylene moieties into the main chain. The polymers with 20–30 mol% 1,4‐DPOBN not only have highTgof 175–177 °C, but also relatively lowTmof 331–336 °C, having high potential for melt processing. The polymers with 20–30 mol% 1,4‐DPOBN also exhibit excellent thermal stability and good mechanical and solvent‐resistance properties. © 2021 Society of Chemical Industry

Hybrid Sequences that Express both Aromatic Amide and α-Peptidic Folding Features.

Foldamers combining aliphatic and aromatic main‐chain units often produce atypical structures that cannot easily be accessed from purely aromatic or aliphatic sequences. We report solid‐state evidence that sequences comprising α‐amino acids and quinoline‐based monomers adopt conformations that combine the folding propensities of both components. Foldamers 2 and 3 having an XQQ repeat motif (X=α‐amino acid, Q=quinoline) were synthesized. Crystals of 2 (X=Phe, Q with an anionic side chain) obtained from water revealed an aromatic helix where amide groups belonging to the α‐amino acids created a hydrogen‐bond array typical of peptidic helices. Crystals of 3 (X=Ser, Q with a lipophilic side chain) obtained from organic solvents revealed a helix‐turn‐helix structure in which α‐amino acid side chains interfere with main‐chain hydrogen bonding. High sequence‐dependency of the conformation is typical of peptides but is shown here to include aromatic folding features.

Efficient, stable and high color rendering index white polymer light-emitting diodes by restraining the electron trapping

Abstract Superior solid-state light source should possess not only a high device efficiency but also high color rendering index (CRI) and excellent color stability. Here, we obtained efficient, stable and high CRI white polymer light-emitting diodes (WPLEDs) through applying the well-chosen trichromatic polymers and restraining the electron trapping. The trichromatic polymers all possess the similar mainchain units, their EL spectra shows an equidistant distribution. Detailed studies revealed that the part of green and red emission in the WPLED derive from the electron trapping which led to the current-dependent spectra. Applied proper electron transporting layer can enhance the direct electron injection which resulted in the electron trapping being restrained and improving the color stability. The optimized WPLED got a LEmax of 10.17 cd A−1 and CRI of 92, the CIE coordinates (0.346, 0.345) almost keep the same with the operating current density increasing from 10.53 mA cm−2 to 263.16 mA cm−2.

High Conductivity, Lithium Ion Conducting Polymer Electrolyte Based on Hydrocarbon Backbone with Pendent Carbonate

Solid polymer electrolytes (sPE) offer a pathway for safer, less flammable lithium batteries. However, developing a polymer that provides high Li+ mobility as well electrochemical stability remains a challenge, because ion conductive functional units in the polymer main-chain (e.g., polycarbonate and polyether) usually suffer from poor electrochemical stability at high and low potentials. Herein, an sPE with pendent carbonate on a hydrocarbon backbone has been designed and synthesized to overcome conductivity and electrochemical stability problems. This pendant polycarbonate is different from conventional polycarbonate electrolytes because the carbonate moiety is in the sidechain, which mitigates polycarbonate backbone stability problems while still providing high ionic conductivity when used with a plasticizer. Conductivity as high as 1.1 mS cm−1 at 22 °C was obtained. Stable lithium metal plating and stripping using the sPE was observed for 1,200 h and electrochemical stability up to 4.6 V vs Li+/Li has been demonstrated. The low interfacial resistance (<160 ohm∙cm2 at 22 °C) and reasonable ionic conductivity have enabled acceptable cycling performance in a Li-LiFePO4 battery at 0.98 mA cm−2 for 2,300 cycles.

High thermal conductivity and excellent flexibility of crystalline polyesters with flexible segments in main chains

Thermal conductivity (TC) of polymers can be enhanced by incorporating rigid conjugated structures, which will result in sacrifice of other characteristics such as flexibility. To deal with such problem, a series of polyesters (PEmC) with long methylene units in main chains were synthesized by polycondensation and transesterification. A sharp increment of 219.7% in TC was observed and the maximum TC reached to 0.227 Wm−1 K−1, which is twice that of traditional thermoplastic. It is intriguing that thermal diffusivity for above samples changed few while specific heat capacity of PEmC increased from 0.620 J g−1 K−1 to 1.470 J g−1 K−1 on elongating the length of flexible methylene segments in main chains. Thus TC in this system was mainly enhanced by enhancing specific heat capacity. Due to flexible segments in main chains, Young modulus of PEmC (around 0.2 GPa) is one order of magnitude lower than that of conventional thermoplastic. Moreover, PEmC exhibited good performance both in maintaining flexibility below glass-transition temperature and preserving modulus above glass-transition temperature, which might be remarkable in potential application for flexible electronics.

A new SiC precursor with high ceramic yield: Synthesis and characterization of CHxMeSiH2‐containing poly(methylsilane‐carbosilane)

ABSTRACTA new poly(methylsilane‐carbosilane) (PMSCS) for silicon carbide precursor was prepared using Wurtz‐type copolymerization of methyldichlorosilane (MeHSiCl2), chloromethyldichloromethylsilane (ClCH2MeSiCl2), and (dichloromethyl)methylsilane (Cl2CHMeSiH2), with (chloromethyl)methylsilane (ClCH2MeSiH2) or trimethylchlorosilane (Me3SiCl) as terminated reagent. The ceramic yield of PMSCS was markedly increased by introduction of Cl2CHMeSiH2 comonomer and capped with ClCH2MeSiH2. The H2MeSiCH2‐capped PMSCS with CHMeSiH2 structure unit in main chain produced SiC ceramic with 1.21 of C/Si atomic ratio in a ceramic yield of 78 wt % upon pyrolyzed at 1000 °C. The excellent pyrolytic properties, combining with its economical preparation, good storage stability in air, and favorable processabilty, make the CHxMeSiH2‐containing PMSCS a new cost‐effective SiC ceramic precursor. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47618.

Realizing efficient bipolar deep-blue light-emitting poly(2,7-carbazole) derivatives by suppressing intramolecular charge transfer

Two series of twisted bipolar poly(2,7-carbazole) derivatives, namely PCz-37RSOs and PCz-28SOs, were synthesized by introducing electron-deficient 2,8-dioctyl- dibenzothiophene-S,S-dioxide-3,7-diyl (37RSO) and dibenzothiophene- S,S –dioxide −2,8-diyl (28SO) unit into poly(9-heptadecanyl-2,7-carbazole) (PCz) backbone, respectively. The incorporation of electron-withdrawing 37RSO and 28SO into PCz backbone decreased effective conjugation length, and further restrained charge transfer effect existed in dipolar system, simultaneously, the balanced charge carrier injection/transportation were realized due to the eletrophilicity of SO unit. Consequently, the resulting polymers showed hypsochromic shift and narrowed emission spectra regarding to PCz-37SOs that contains linear SO unit in main chain, and exhibited balanced hole/electron fluxes with respect to PCz in the range of 0–10 V. The single-layer devices based on resulting bipolar polymers exhibited excellent electroluminescent spectra stability in the current densities from 100 to 400 mA cm−2, and displayed deep blue electroluminescence spectra with the Commission Internationale de L’ Eclairage (CIE) of (0.16, 0.07) for PCz-37RSO5 and (0.16, 0.09) for PCz-28SO5. The superior device performance was achieved with the maximum luminous efficiency (LEmax) of 2.69 cd A−1 for PCz-28SO20, which obviously outperformed that of 0.24 cd A−1 for PCz. These results indicated that twisted molecular structure design is a promising strategy for efficient deep blue light-emitting polymers.

Degradable Crystalline Polyperoxides from Fatty Acid Containing Styrenic Monomers

Vinyl polyperoxides, alternating copolymers of vinyl monomers and molecular oxygen, are highly viscous amorphous materials because of the flexible peroxy (−O–O−) bonds in the main chain. In this study, crystalline polyperoxides have been synthesized by oxidative radical polymerization of styrenic monomers having fatty acid moieties attached to the phenyl ring using molecular oxygen at 100 psi pressure. Determination of active oxygen contents in polyperoxides, 13C NMR spectroscopy, and electron impact mass spectroscopy (EI-MS) confirmed alternating placement of −O–O– bonds after every styrenic monomer unit in the copolymer main chain. Thermal stability was studied by thermogravimetric analysis (TGA). Exothermic degradation of these polyperoxides was observed by differential scanning calorimetry (DSC), and degradation products have been identified from EI-MS study. DSC and powder X-ray diffraction (PXRD) studies revealed crystallinity in the polyperoxides with fatty acids having 12 carbon atoms or longer. T...

Cyclic arylopeptoid oligomers: synthesis and conformational propensities of peptide-mimetic aromatic macrocycles.

Macrocyclic peptide-mimetic molecules are attracting renewed attention and have found widespread application in research fields ranging from biochemical science to materials science. Herein, we describe the synthesis and structural elucidation of cyclo[n]-p-arylopeptoids (classified into cyclic aromatic ε-amino acids) bearing various side chains, namely, C[n]pAP(Rn) (where n inside brackets denotes the number of main chain units and R inside parentheses represents side chains). We investigate the influence of n and R on the macrocyclization efficiency of linear p-arylopeptoid oligomers (n = 3, 4, 5) under high-dilution conditions with or without slow addition. The structures of the cyclo[4]-p-arylopeptoids (C[4]pAP(Rn)) and their conformational dynamics are disclosed on the basis of single-crystal X-ray analyses, viable-temperature (VT) 1H NMR studies, and density functional theory (DFT) calculations. We found two representative conformations (open and closed) of cyclo[4]-p-arylopeptoids (C[4]pAP(Rn)) in the solid state and whose preference in the solution state was most likely dependent on solvent polarity. We believe that this simple but dynamic macrocyclic peptide-mimetic molecular scaffold would be attractive for developing new functional molecular tools based on rational molecular design as well as molecular library screening strategies.

Switching Light Transmittance by Responsive Organometallic Poly(ionic liquid)s: Control by Cross Talk of Thermal and Redox Stimuli

AbstractA novel organometallic poly(ionic liquid) with both redox‐ and thermoresponsive properties is synthesized from a poly(ferrocenylsilane) (PFS) via a one‐step Strecker sulfite alkylation reaction by using tetraalkylphosphonium sulfite as an effective and versatile nucleophile. This dual‐responsive polymer is composed of a PFS backbone and quaternary phosphonium sulfonate side groups and exhibits a concentration‐dependent lower critical solution temperature (LCST)‐type phase transition in aqueous solution. Furthermore, the LCST‐type phase behavior of the polymer can be switched between the “off” state and “on” state by chemical or electrochemical oxidation and reduction on the ferrocene units in the polymer main chain. As a consequence, a classical LCST‐type phase transition, as well as an “isothermal” redox‐triggered phase transition can be induced by using thermal and electrochemical triggers without changing the composition of the system. On the basis of this dual responsiveness, a “smart window” device is fabricated. The optical characteristics of this device are completely unaltered after 100 thermal and/or redox cycles.