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.

     

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.     

Polymer‐in‐ionic‐liquid electrolytes

In order to achieve high conductivity in a polymer electrolyte, polymer‐in‐ionic‐liquid electrolytes have been explored. It is found in this study that poly[vinylpyrrolidone‐co‐(vinyl acetate)] (P(VP‐c‐VA)) in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethyl sulfonyl) amide (EtMeIm⁺Tf₂N⁻) and poly(N,N‐dimethyl acrylamide) (PDMAA) in trimethyl butyl ammonium bis(trifluoromethane sulfonyl) amide (N₁₁₁₄⁺Tf₂N⁻) produce ion‐conducting liquids and gels. The P(VP‐c‐VA)/ EtMeIm⁺Tf₂N⁻ mixture has a conductivity around 10⁻³ S · cm⁻¹ at 22 °C, for copolymer concentrations up to 30 wt.‐%. Thermal analysis shows that the T_g of the P(VP‐c‐VA)/ EtMeIm⁺Tf₂N⁻ system is well described by the Fox equation as a function of polymer content. Poly(methyl methacrylate) (PMMA)/ EtMeIm⁺Tf₂N⁻ gel electrolytes were prepared by in‐situ polymerisation of the monomer in the ionic liquid. In the presence of 0.5–2.0 wt.‐% of a crosslinking agent, these PMMA‐based electrolytes displayed elastomeric properties and high conductivity (ca. 10⁻³ S · cm⁻¹) at room temperature.

Conductivity versus temperature in crosslinked PMMA/ EtMeIm⁺Tf₂N⁻ gel electrolytes with different concentrations of crosslinking agent.     

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.

     

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.

     

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.

     

Stimuli‐Responsive Polymers Based on N‐Isopropylacrylamide and N‐Methacryloyl‐L‐Leucine

Linear and cross‐linked polymers capable of responding to both temperature and pH changes were synthesized by radical copolymerization of N‐isopropylacrylamide (NIPAAm) and N‐methacryloyl‐L ‐leucine (MALEU) in different NIPAAm/MALEU molar ratios. The solution behavior of linear polymers was investigated in 0.1 M NaCl and in citrate buffers pH 4.0, 4.5, 5.0 and 6.0. A sharp increase in the cloud point temperature (T_CP) was observed to occur around pH 4–5. Hydrogels were synthesized employing N,N ′‐methylenebisacrylamide as cross‐linking agent. The influence of composition and degree of cross‐linking on water absorption was investigated in 0.1 M NaCl and in citrate buffers pH 4.0 and 5.0. A reversible phase transition within a wide range of temperatures, depending on the composition and the pH, in accordance with the behavior of linear polymers, was observed.     

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.

     

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.

     

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.     

Hydrogen‐Bonding‐Directed Template Synthesis of Novel Stereo‐Regular Organo‐Bridged Ladder‐Like Polymethylsiloxane

A novel stereo‐regular organo‐bridged ladder‐like polymethylsiloxane ( LPMS ) was synthesized by a stepwise coupling polymerization on the basis of an amido H‐bonding‐assisted self‐assembling template. The monomer N,N′‐bis{4‐[3‐(diethoxymethylsilyl)propoxy]‐phenyl}terephthalamide ( M ), prepared by hydrosilylation reaction at high temperature, was hydrolyzed in a dilute solution at a low temperature to form a ladder‐like supramolecular intermediate through amido H‐bonding interactions, which was further condensed to form the polymer LPMS . A combination of techniques including ¹H NMR, ²⁹Si NMR, and FT‐IR spectroscopies X‐ray diffraction (XRD), and differential scanning calorimetry (DSC) were used to characterize the titled polymer LPMS , and the results indicate that the polymer possesses an ordered ladder‐like structure.

²⁹Si NMR spectrum of the polymer LPMS .     

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.

     

Gas‐phase polymerization of 1,3‐butadiene with supported half‐sandwich‐titanium‐complexes

Using half‐sandwich‐titanium‐complexes polybutadiene (BR) can be produced with a particular microstructure of about 81% cis, 18% 1,2, and 1% trans units. A stirred bed reactor and a fluidized bed reactor were constructed for gas‐phase polymerization of 1,3‐butadiene by cyclopentadienyltrichlorotitanium (CpTiCl₃) on MAO (methylaluminoxane) impregnated silica (MAO/SiO₂). The major determinant of polymerization activity and molecular weight is the Al_MAO/Ti‐ratio on the carrier. Polymerization activity increases to 14 500 kg BR/(mol Ti*h) with a molecular weight of 1.9×10⁶ g/mol and the catalyst becomes noticeably more stable. Activity further increases when the CpTiCl₃ catalyst is prealkylated with small quantities of TIBA (triisobutylaluminium). Systematic methodological experimentation of the heterogenization suggests that a Ti(III)‐species is responsible for polymerization. The gas‐phase polymerization of 1,3‐butadiene reveals a rate of polymerization which is considerably greater than the equivalent rate in the homogeneous system. The polymers all have similar characteristics, pointing to the same active species. The microstructure of the polybutadiene produced was investigated by spectroscopic measurements and by hydration; a preference to block structures of 1,2‐units could not be established.     

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.

     

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.     

Encapsulating Hydrophilic Solution by PU‐PMF Double‐Component Capsule Based on Water‐In‐Oil‐In‐Oil Emulsion Template

This study demonstrates an effective method to encapsulate a hydrophilic payload through the use of polyurethane‐poly(melamine‐formaldehyde) (PU‐PMF) dual‐component capsules based upon the water‐in‐oil‐in‐oil (W/O/O) emulsion template. This emulsion has a middle oil layer that hosts the PU (outer shell) forming reaction while the internal PMF skeleton, fabricated concurrently by polymer precipitation in the aqueous dispersive phase, provides additional mechanical support. The resultant capsules exhibit dense and spherical shape, low permeability, and diameter of ≈50 µm. Remarkably, interfacial tension is the driving factor in the formation of the W/O/O template. This microencapsulation system and the methods used for its fabrication have a great technical potential for use in industrial applications.