Well‐Defined High‐Molecular‐Weight Polyacrylonitrile Formation via Visible‐Light‐Induced Metal‐Free Radical Polymerization

Polyacrylonitrile (PAN) with high molecular weight and low dispersity is successfully synthesized by visible‐light‐induced metal‐free radical polymerization at room temperature. This polymerization technique uses organic dye Eosin Y as photocatalyst and benzenediazonium tetrafluoroborates as initiator. Gel permeation chromatography‐multiangle laser light scattering shows the absolute molar weight of the PAN more than 1.50 × 10⁵ g mol⁻¹ with a polydispersity index < 1.3 while MALDI‐TOF MS and ¹⁹F NMR spectroscopy indicate the F‐chain‐end process. The first‐order kinetic behavior, molecular weight distributions shifting, and “ON/OFF” experiment results suggest this reaction may follow the atom‐transfer‐like radical polymerization mechanism. In addition, this new approach allows for the efficient synthesis of well‐defined random copolymers.

     

Polyelectrolyte‐in‐Ionic‐Liquid Electrolytes

Novel polymer electrolyte materials based on a polyelectrolyte‐in‐ionic‐liquid principle are described. A combination of a lithium 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPSLi) and N,N′‐dimethylacrylamide (DMMA) are miscible with the ionic liquid, 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIDCA). EMIDCA has remarkably high conductivity (≥ 2 · 10^?2 S · cm^?1) at room temperature and acts as a good solvating medium for the polyelectrolyte. At compositions of AMPSLi less than or equal to 75 mol‐% in the copolymer (P(AMPSLi‐co‐DMAA)), the polyelectrolytes in EMIDCA are homogeneous, flexible elastomeric gel materials at 10 ? 15 wt.‐% of total polyelectrolyte. Conductivities higher than 8 · 10^?3 S · cm^?1 at 30 °C have been achieved. The effects of the monomer composition, polyelectrolyte concentration, temperature and lithium concentration on the ionic conductivity have been studied using thermal and conductivity analysis, and pulsed field gradient nuclear magnetic resonance techniques.

Comparison of the measured and calculated lithium conductivity at 30 °C.     

Ring‐Opening Homo‐ and Copolymerization of Cis/Trans‐3‐oxa‐4‐oxobicyclo‐ and Cis/Trans‐4‐oxa‐3‐oxobicyclo[5.4.0]undecane

Ring‐opening polymerization of the bicyclic lactone mixture 2 , cis/trans‐3‐oxa‐4‐oxo‐ and cis/trans‐4‐oxa‐3‐oxobicyclo[5.4.0]undecane with Sn(Oct)₂ as a catalyst was investigated for the first time (Scheme 1 ). The lactones were obtained by Baeyer–Villiger oxidation of cis/trans‐2‐decalone 1 (Scheme 2 ). Additionally, copolymerization of 2 with ε‐caprolactone in different ratios was performed. GPC measurements and ¹H NMR spectroscopy proved that 2 was quantitatively incorporated into the polymer, leading to polycaprolactone with cyclohexane moieties in its backbone. values were up to 25 000 with ≤ 2.4. DSC measurements revealed a linear dependence of the melting points and the glass transition temperatures of the polymers on the feed of the bicyclic lactone 2 . Additionally, the time dependence of the cis/trans ratio of the residual monomers was followed during the course of polymerization reaction by gas chromatography. The crystallinity of the resulting copolymers was investigated via polarization microscopy. Finally, it was shown that the mixture of 2 with ε‐caprolactone could be selectively polymerized with lipase. Only ε‐caprolactone was converted, while 2 remained unreacted in the residue.

     

Copolymerization of N‐(prop‐1‐yne‐3‐yl)‐4‐(piperidine‐1‐yl)‐1,8‐naphthalimide with Arylacetylenes into Fluorescent Polyacetylene‐Type Conjugated Polymers

N‐(prop‐1‐yne‐3‐yl)‐4‐(piperidine‐1‐yl)‐1,8‐naphthalimide (PNPr), i.e., the monomer with a terminal ethynyl group and 1,8‐naphthalimide fluorophore, has been successfully copolymerized with a series of monoethynylarenes into well‐soluble high‐molecular‐weight (M_w up to 210 000) linear polyacetylene‐type copolymers containing from 14 to 51 mol% units derived from PNPr. The copolymerization of PNPr with bifunctional 4,4′‐diethynylbiphenyl provides polyacetylene‐type micro/mesoporous fluorescent network containing 8 mol% PNPr units and exhibiting the Brunauer–Emmett–Teller surface of ≈1000 m² g^?1. The copolymerizations (catalyzed with acetylacetonato(norborna‐2,5‐diene)rhodium complex, [Rh(nbd)acac]) proceed smoothly despite the fact that the homopolymerization of PNPr fails. The fluorescence of PNPr (emission at ≈ 510 nm) has been retained after the incorporation of PNPr into the copolymers. The fluorescence of the copolymers can be induced by a direct excitation of PNPr units or via an energy transfer mechanism. In the latter case, the comonomeric units with aromatic hydrocarbon fluorophores (e.g., of the biphenyl‐type) emitting at 380–400 nm (after irradiation with 300 nm UV radiation) serve as energy donors for fluorescent PNPr acceptors. The difference between the wavelengths of the primary absorbed radiation and the finally emitted radiation is 210 nm.

     

Self‐Assembly of ATRP‐Synthesized PCH‐b‐PtBA‐b‐PCH Triblock Copolymers Observed by Time‐Resolved SAXS

The phase behavior of PCH‐b‐PtBA‐b‐PCH triblock copolymers has been studied. Measurements in the wide‐angle region probed the existence of microphase segregation through variation of block mobility and thermal expansion coefficients. SAXS experiments pointed out that most copolymers present ordered nanostructures, mostly hexagonally packed cylinders, the morphology being confirmed by AFM. An unusual disorder‐to‐order transition is observed in one copolymer synthesized from a macroinitiator with intermediate length and the highest outer‐block molecular weight, whereas none of the copolymers shows an order‐to‐disorder transition upon heating over the temperature range analyzed.

     

Poly(N‐isopropylacrylamide‐co‐N‐isopropylmethacrylamide) Thermo‐Responsive Microgels as Self‐Regulated Drug Delivery System

Poly(N‐isopropylacrylamide‐co‐N‐isopropylmethacrylamide) (poly(NIPAAm‐co‐NIPMAAm)) is synthesized as an attractive thermo‐responsive copolymer by an original procedure. Due to the similar structure of the two co‐monomers, the poly(NIPAAm‐co‐NIPMAAm) copolymer displays a very sharp phase transition, under physiological conditions (phosphate buffer solution at pH = 7.4). The copolymer, showing the 51/49 co‐monomer NIPAAm/NIPMAAm molar ratio, displays a lower critical solution temperature (LCST) close to that of the human body temperature (36.8 °C). The poly(NIPAAm‐co‐NIPMAAm) microgels obtained at the 51:49 co‐monomer ratio displays a volume phase transition temperature (VPTT) slightly smaller than LCST. The deswelling rate of the microgels is very high (k = 0.019 s^?1), the shrinkage occurring almost instantaneously, whereas the swelling rate is slightly lower (k = 0.0077 s^?1). The microgels are loaded with the model drug dexamethasone and the drug release is investigated at different temperatures, below and above the VPTT. Under thermal cycling operation between 32 and 38 °C, the pulsatile release of dexamethasone is observed.

     

T‐cell‐derived,but not B‐cell‐derived,IL‐10 suppresses antigen‐specific T‐cell responses in Litomosoides sigmodontis‐infected mice

IL‐10, a cytokine with pleiotropic functions is produced by many different cells. Although IL‐10 may be crucial for initiating protective Th2 responses to helminth infection, it may also function as a suppressive cytokine preventing immune pathology or even contributing to helminth‐induced immune evasion. Here, we show that B cells and T cells produce IL‐10 during murine Litomosoides sigmodontis infection. IL‐10‐deficient mice produced increased amounts of L. sigmodontis‐specific IFN‐γ and IL‐13 suggesting a suppressive role for IL‐10 in the initiation of the T‐cell response to infection. Using cell type‐specific IL‐10‐deficient mice, we dissected different functions of T‐cell‐ and B‐cell‐derived IL‐10. Litomosoides sigmodontis‐specific IFN‐γ, IL‐5, and IL‐13 production increased in the absence of T‐cell‐derived IL‐10 at early and late time points of infection. In contrast, B‐cell‐specific IL‐10 deficiency did not lead to significant changes in L. sigmodontis‐specific cytokine production compared to WT mice. Our results suggest that the initiation of Ag‐specific cellular responses during L. sigmodontis infection is suppressed by T‐cell‐derived IL‐10 and not by B‐cell‐derived IL‐10.     

PEG‐Based Microgels Formed by Visible‐Light‐Mediated Thiol‐Ene Photo‐Click Reactions

Step‐growth PEG‐based microgels are produced via three liquid–liquid two‐phase suspension polymerization systems: i) hexane with surfactants Span80/Tween80; ii) mineral oil with surfactant Pluronic F‐68; and iii) surfactant‐free dextran‐rich aqueous solution. Following short vortexing to create monomer droplets, microgels are polymerized by a visible‐light‐initiated thiol‐ene photo‐click reaction using eosin‐Y as the only photoinitiator. The use of hexane as the organic phase and Span‐80/Tween‐80 as the surfactants leads to PEG microgels with entrapped solvent droplets that dissolve rapidly with time. Microgels polymerized in mineral oil with surfactant Pluronic F‐68 contain no entrapped droplets and are more uniform with smaller sizes. Visible‐light‐cured step‐growth thiol‐ene microgels can also be photo­polymerized in a surfactant‐free aqueous two‐phase system. The sizes of the microgels formed in aqueous phase are one order of magnitude smaller than those formed in organic solvent. Dual‐layer microgels are also prepared using two‐step thiol‐ene reactions.

     

Stereocomplex‐ and Homo‐Crystallization and Phase‐Transition Behavior of Relatively High‐Molecular‐Weight Linear One‐ and Two‐Armed and Star‐Shaped Four‐Armed Poly(l‐lactide)/Poly(d‐lactide) Blends

Relatively high‐molecular‐weight linear one‐ and two‐armed and star‐shaped four‐armed poly(l ‐lactide) and poly(d ‐lactide) are synthesized and the multiplicate effects of arm‐number (branching architecture, coinitiator moiety), crystallization temperature (T _c), and number‐average molecular weight (M _n) on stereocomplex (SC)‐ and homo‐crystallization and phase‐transition behavior are investigated. For nonisothermal and isothermal crystallization, in addition to SC crystallites, homo‐crystallites are formed in the blends with higher M _n values, irrespective of arm number. For isothermal crystallization, the transition T _c ranges below which in addition to SC crystallites, homo‐crystallites are formed depended on M _n per one arm‐determining melting temperature or thickness of homo‐crystallites. The transition M _n ranges above which in addition to SC crystallites, homo‐crystallites are formed are not affected by arm number. The high molecular weight disturbs the change of crystalline growth mechanism of one‐ and two‐armed blends, whereas the branching architecture inhibits the change of crystalline growth mechanism of four‐armed blends.     

Synthesis and Characterization of Poly[((maleic anhydride)‐alt‐styrene)‐co‐(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)]

Summary: Novel polyfunctional sulfone‐ and anhydride‐containing reactive terpolymers with different compositions have been synthesized by complex‐radical polymerization of the ternary MA‐St‐APMS acceptor‐donor‐acceptor monomer system. This method allows preparing terpolymers with a sufficiently high content of APMS which essentially increased polyelectrolyte, swelling, IEC and thermal stability of terpolymer films. The terpolymer structure‐composition‐properties (polyelectrolyte, thermal, swelling and cation exchange behavior) relationships were studied by FTIR and ¹H{¹³C} NMR (DEPT‐135) spectroscopy, viscometry, DSC‐TGA methods, and by means of swelling and exchange capacity. The observed H‐bonding between sulfonic acid, amide and anhydride fragments played an important role in the formation of the physically crosslinked and self‐assembled architectures with controllable hydrophilic‐hydrophobic balance. These reactive terpolymers can be used as synthons for exchange membrane preparation and fuel cell applications.

Physically crosslinked and self‐assembled macrocomplex.     

Solution‐Processable Donor‐Acceptor‐Donor Oligomers with Cross‐Linkable Functionality

Electron‐acceptor units, combined with bithiophene substituted with flexible chains end‐functionalized with cross‐linkable moieties, provide soluble donor‐acceptor‐donor (DAD) π‐conjugated oligomer‐type molecules with cross‐linking ability and broad absorption in the visible spectrum. A study on the cross‐linking conditions of the new oligomers to yield insoluble polymer networks is presented, including conditions for obtaining polymer films over poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate‐covered substrates. The combination of the DAD molecular design and cross‐linking functionality opens prospects for applications in solution‐processed small‐molecule solar cells with morphologically‐stable organic layers.

     

Effect of Fullerene on Photocurrent Performance of 6‐O‐Porphyrin‐2,3‐di‐O‐stearoylcellulose Langmuir‐Blodgett Films

Thin films consisting of 6‐O‐porphyrin‐2,3‐di‐O‐stearoylcellulose (H₂PCS) and fullerene (C₆₀) were fabricated for anodic photocurrent generation systems by the Langmuir‐Blodgett (LB) technique. The π‐complexation between the porphyrin moiety and C₆₀ in the LB films was investigated by means of the surface pressure (π)‐area (A) isotherms, UV‐vis, and fluorescence spectroscopy. The photocurrent density generated from the H₂PCS–C₆₀ LB monolayer films exhibited an increase with increasing the C₆₀ proportion and reached a maximum at a mixing ratio of 1:2, yielding a quantum yield of 12.5% and an IPCE (incident photon‐to‐current efficiency) of 0.50% at a bias potential of +100 mV vs. SCE. Furthermore, the LB five‐layer films could give rise to the IPCE value of 1.5% at +100 mV without significant decline of the quantum yields, which was due to the function of C₆₀ as an electron carrier to improve the interlayer electron transfer through each layer. These results have demonstrated a promising method for preparing the donor–acceptor systems using cellulose as a scaffold in the LB films.

     

Curcumin alleviates immune‐complex‐mediated glomerulonephritis in factor‐H‐deficient mice

Complement factor H (Cfh) is a key regulator of the complement cascade and protects C57BL/6 mice from immune complex-mediated complement-dependent glomerulonephritis. In chronic serum sickness (CSS) there are increased deposits of immune complexes in the glomeruli with inflammation and a scarring phenotype. As cucurmin is an effective anti-inflammatory agent and reduces complement activation, we hypothesized that it should alleviate renal disease in this setting. To determine the effectiveness of curcumin, an apoferritin-induced CSS model in Cfh-deficient (Cfh^−/−) mice was used. Curcumin treatment (30 mg/kg) given every day in parallel with apoferritin reduced glomerulonephritis and enhanced kidney function (blood urea nitrogen, 45·4 ± 7·5 versus 35·6 ± 5·1; albuminuria, 50·1 ± 7·1 versus 15·7 ± 7·1; glomerulonephritis, 2·62 + 0·25 versus 2 + 0·3, P < 0·05). In line with reduced IgG deposits in mice with CSS given curcumin, C9 deposits were reduced indicating reduced complement activation. Mice treated with curcumin had a significant reduction in the number of splenic CD19⁺ B cells and the ratio of CD19 : CD3 cells (P < 0·05) with no change in the T-cell population. Myeloperoxidase assay showed reduced macrophages in the kidney. However, a significant reduction in the M2 subset of splenic macrophages by apoferritin was prevented by curcumin, suggesting a protective function. Curcumin treatment reduced mRNA expression of inflammatory proteins monocyte chemoattractant protein-1 and transforming growth factor-β and matrix proteins, fibronectin, laminin and collagen. Our results clearly illustrate that curcumin reduces glomerulosclerosis, improves kidney function and could serve as a therapeutic agent during serum sickness.     

Amphiphilic PEG‐b‐PMCL‐b‐PDMAEMA Triblock Copolymers: From Synthesis to Physico‐Chemistry of Self‐Assembled Structures

A synthetic route toward a new family of amphiphilic mPEG‐b‐PMCL‐b‐PDMAEMA triblock copolymers is reported. Chemical structures and compositions are confirmed by ¹H NMR and SEC. Polydispersity indices are typically <1.4, indicating good control of the reactions. The physicochemical parameters associated with mPEG‐b‐PMCL‐b‐PDMAEMA self‐assembled structures are investigated. Nanoparticles are prepared via a co‐solvent method, and parameters such as nanoparticle $\overline {M} _{{\rm w}} $ , N_agg, A₂, and R_h are calculated based on static and dynamic light scattering data. Critical aggregation concentrations for the polymers are determined by measuring surface tensions of polymer solutions. TEM is employed to visualize the morphology of the assemblies.

     

Extremely Color‐Stable Blue Light‐Emitting Polymers Based on Alternating 2,7‐Fluorene‐co‐3,9‐carbazole Copolymer

Novel alternating 2,7‐fluorene‐co‐3,9‐carbazole copolymer(3,9‐PFCz) was synthesized by Suzuki polycondensation between 3‐bromo‐9‐(2‐iodo‐9,9‐dioctyl‐9H‐fluoren‐7‐yl)‐9H‐carbazole and 2,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9‐dioctylfluorene. Cyclic voltammetry studies showed a higher HOMO level (?5.23 eV) than the polyfluorene homopolymer(PFO). The glass transition temperature of the copolymer (110 °C) was much higher than that of the PFO (67 °C). After the copolymer had been annealed at 200 °C for 2 h, the PL spectra showed almost no change and no aggregation‐ or oxidation‐related undesirable long‐wavelength emission has been observed. The light‐emitting diode in configuration of ITO/PEDOT/EML/CsF/Al showed a maximum external quantum efficiency of 1.54% with a luminance of 435 cd · m^?2 and the maximum brightness of 2 630 cd · m^?2 with CIE coordinate (0.17, 0.14) was achieved at 8.4 V. The device prepared in configuration of ITO/PEDOT/PVK/polymer/Ba/Al exhibits an efficient, stable blue emission; it has a turn‐on voltage of 6 V and maximum external quantum efficiency of 1.1%. The EL emission remains stable at high current density and after thermal treatment at 150 °C for 30 min. Extremely color‐stable blue emission from alternating poly[(2,7‐fluorene)‐co‐(3,9‐carbazole)] copolymer makes it a promising candidate for flat‐panel display applications.

     

Bioapplications of Polythiophene‐g‐Polyphenylalanine‐Covered Surfaces

The fabrication of electro and bioactive surfaces by electrochemical deposition of the thiophene‐functionalized polyphenylalanine macromonomer (T‐g‐PPhe) is reported. The resulting conducting graft copolymer, polythiophene‐graft‐polyphenylalanine (PT‐g‐PPhe) formed on the indium tin oxide (ITO) glass surface, is characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and fluorescence microscopy. Then, possible uses of PT‐g‐PPhe as matrices in the sensor design for both electrochemical biosensing and cell adhesion studies are investigated. In the first part, PT‐g‐PPhe that is deposited on ITO is further functionalized with the arginylglycylaspartic acid peptide via 1‐Ethyl‐3‐(3 dimethylaminopropyl) carbodiimide for the selective cell adhesion. Immunofluorescence staining is performed to detect the difference between adherences of “integrin αvβ3” receptor positive (U87‐MG) and negative (HaCaT) cell lines on to the biofunctional surface. In the second part, an electrochemical glucose sensor is constructed by immobilizing glucose oxidase on the surface of PT‐g‐PPhe, which is deposited on a glassy carbon electrode.

     

Synthesis and Properties of pH‐ and Temperature‐Sensitive Poly[(N‐isopropylacrylamide)‐co‐(2‐methylenebutane‐1,4‐dioic acid)] Hydrogels

Summary: Hydrogels of NIPA and MBDA were synthesized by free‐radical crosslinking copolymerization with different monomer ratios and with two concentrations of the crosslinking agent. The aim of this work was to study the swelling behavior of these gels that are both temperature and pH sensitive. PNIPA hydrogels are typical examples of thermo‐shrinking hydrogels with a LCST, T_C, around 31–34 °C. MBDA is a weakly ionizable monomer which imparts a pH sensitiveness to the copolymer hydrogels. The pH influence on the swelling behavior of the studied hydrogels was analyzed using deionized water and aqueous HCl and NaOH as swelling media. According to the results found in deionized water, the swelling processes of P(NIPA‐MBDA) hydrogels follow second‐order kinetics at 22 and 37 °C. The equilibrium water content, W_∞, and the rate constant, K, increased at greater concentrations of MBDA and decreased as the crosslinking agent concentration increased. As the MBDA content in the hydrogel increased, the collapsing of the hydrogels at higher temperatures than the LCST became of less importance. The degree of swelling of pure PNIPA hydrogels was not influenced by the pH of the swelling medium. However, this influence increased as the MBDA content increased. This was due to the fact that at low pH most of the MBDA units are in the protonated (neutral) form and at high pH in the ionized one.

Swelling isotherms of hydrogels with different copolymer compositions and with 1.5 wt.‐% of BIS at 22 °C in deionized water.     

Preparation and Characterization of Novel Low‐Temperature/pH Dual‐Responsive Poly(N‐isopropylacrylamide‐co‐1H‐benzimidazolyl‐ethyl acrylate) Copolymers

Stimuli‐responsive polymers in response to both low temperature and pH are of great potential for designing drug carriers to obtain a better therapeutic effect during cryotherapy of tumors. In this work, novel low‐temperature and pH dual‐responsive poly(N‐isopropylacrylamide‐co‐1H‐benzimidazolyl‐ethyl acrylate) (PNBM) linear copolymers are developed, which can undergo stretching/shrinking conformational transition at low temperature and mildly acidic conditions. The dual‐responsive properties of PNBM copolymers can be affected and regulated by the host–guest inclusion action between benzimidazole and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) molecules. The critical response temperature of the copolymers can be flexibly adjusted when the benzimidazole groups in copolymer chains are captured by HP‐β‐CD. And the PNBM copolymers present a pH‐responsive stretching‐to‐shrinking‐to‐stretching conformational transition in a narrow pH range in HP‐β‐CD solution. The results provide valuable guidance for designing and applying PNBM‐based smart materials in biomedical applications.