Metathetic Selective Degradation of Polyisoprene: Low‐Molecular‐Weight Telechelic Oligomer Obtained from Both Synthetic and Natural Rubber

Summary: Degradation studies of cis‐1,4‐polyisoprene were carried out using first and second generation Grubbs catalysts to achieve end‐functionalized acetoxy oligomers in both an organic solvent and a latex phase at room temperature. Well‐defined acetoxy telechelic polyisoprene structures were obtained in a selective manner with a range of from 10 000 to 30 000, with a polydispersity index of around 2.5.

Structure produced by the metathetic depolymerization of hydroxy telechelic cis‐1,4‐polyisoprene.     

Diene/polar monomer copolymers,compatibilisers for polar/non‐polar polymer blends. A controlled block copolymerisation with a single‐site component samarocene initiator

A well‐controlled two‐step process, the polymerisation of isoprene or isoprene/hex‐1‐ene copolymerisation followed by ε‐caprolactone polymerisation, affords trans‐polyisoprene or (trans‐polyisoprene/hex‐1‐ene copolymer)–poly(ε‐caprolactone) diblocks of various lengths. The single component initiator is an allylsamarocene compound. An atomic force microscopy study shows that these copolymers are efficient compatibilisers for poly(ε‐caprolactone) and polyisoprene blends.

Poly(ε‐caprolactone) chain growth from Sm–polyisoprene chain.     

Synthesis and Characterization of Oxetane‐Functionalized Phosphorescent Ir(III)‐Complexes

In order to incorporate iridium(III) complexes covalently into an oxetane‐bearing hole‐transporting matrix, a new oxetane‐equipped acetoacetate derivative was introduced as an ancillary ligand. Model complexes with an analogical nonpolymerizable ligand were also prepared in order to perform comparative investigations. Therefore, a series of bis‐cyclometalated Ir(III) complexes, showing orange (C?N‐ligand, coumarin 6) and green (C?N‐ligand, phenylpyridine) emission were synthesized and fully characterized. The emission maxima are 569 nm for the orange and 518 nm for the green‐emitting Ir(III) complexes. Entirely solution processed devices, based on crosslinkable hole‐conductors, partially doped with the described orange and green Ir(III) emitters, respectively, were fabricated and tested.

     

Linear Terpyridine‐Ruthenium(II) Poly(ethylene glycol) Coordination Polymers

In the present contribution, we synthesized linear coordination polymers based on oligo(ethylene glycol)s as well as poly(ethylene glycol)s and terpyridine ruthenium(II) complexes. The reaction conditions, e.g., solvent, concentration, were varied to obtain well‐soluble, high molecular weight polymers. The resulting compounds were characterized by UV‐vis and NMR spectroscopy. The viscosity of the materials was also investigated with and without salt addition. Finally, the polymers were characterized with DSC and AFM. AFM revealed a lamellar morphology.

     

Fluorene‐Based Single‐Chain Copolymers for Color‐Stable White Light‐Emitting Diodes

Fluorene‐based single‐chain copolymers with a white light emitter consisting of a blue and an orange chromophore have been synthesized and their photophysical and electroluminescent properties are investigated. The experimental results suggest that only a relatively small fraction of the orange‐emitting units incorporated into the fluorene is needed to achieve efficient white light emission by controlled incomplete energy transfer. A device from a copolymer with 0.02% DDQ content showed the highest external quantum efficiency of 2.64% with a luminance efficiency of 4.06 cd · A^?1 with CIE coordinates (0.28, 0.24). The EL emissions are extremely stable over a wide range of current densities.

     

On the Interpretation of X‐Ray Diffraction Powder Patterns in Terms of the Nanostructure of Cellulose I Fibres

Summary: The average lateral dimensions of cellulose microfibrils in paper sheets can be determined from the width of X‐ray Bragg peaks at half the maximum height. The method assumes it is the finite size of the crystallite which is the main contributor to peak broadening in the directions orthogonal to the long axis of the crystallite. This assumption is examined in the context of samples from different botanical sources, of varying crystallinity and cellulose content and the various instrumental sources of broadening X‐ray powder patterns. Excellent fits to the data from paper samples can be obtained by using five Voigt functions to the powder diffraction patterns, for the 101, , 021, 002 and 040 reflections. Of these reflections, the 020 is the clearest, and the best able to determine the lateral dimension of the crystallite. Results indicate that the size of microfibrils is dependent on the botanical source of the fibres.

     

Ultra‐thin,Free‐Standing Proton‐Conducting Membrane with Organic/Inorganic Sandwich Structure

An ultra‐thin, flexible, free‐standing, proton‐conducting membrane of (PEI/PCGF)/SiO₂/(PEI/PCGF) with a sandwich structure has been prepared. Giant membranes with areas up to about 16 cm² and thicknesses of 600 nm have been obtained. The inorganic silica layer suppresses methanol permeation, while the two organic layers provide sufficient mechanical strength and flexibility. This membrane exhibits efficient proton conductivity and low methanol permeability.

     

Microwave‐Assisted Synthesis of Poly(L‐lactic acid) via Direct Melt Polycondensation Using Solid Super‐Acids

A microwave‐assisted method of synthesizing high‐molecular‐weight PLA using SSA as green catalyst was developed. Yellowish PLA with above 2.0 × 10⁴ g · mol^?1 was obtained when the reaction was run at 260 °C within 60 min under microwave irradiation with 0.4 wt.‐% SSA. This method used only 10% of the energy consumption necessary for conventional heating, and the catalyst could be used five times without losing catalytic activity. The improvement in and the decrease in the energy consumption under microwave irradiation suggested that selective heating and hot spots effects played a crucial role. The method was shown to be a time‐saving, green and a promising way to lower the cost and spread the application of PLA.

     

The Effect of PEG Crystallization on the Morphology of PEG/Peptide Block Copolymers Containing Amyloid β‐Peptide Fragments

Ordered nanostructures are observed in the melt and solid state for a series of three peptide/PEG conjugates containing fragments of amyloid β‐peptides. These are conjugated to PEG with = 3 300 g · mol^?1 and a melting temperature T_m = 45–50 °C. The morphology at room temperature is examined by AFM and POM. This shows spherulite formation for the weakly fibrillizing KLVFF‐PEG sample but fibril formation for FFKLVFF‐PEG. The fibrillization tendency of the latter is enhanced by multiple phenylalanine residues. Simultaneous SAXS and WAXS was used to investigate the morphology as a function of temperature. The secondary structure is probed by FTIR.

     

Optimization of Photorefractivity Based on Poly(N‐vinylcarbazole) Composites: An Approach from the Perspectives of Chemistry and Physics

The optimization of photorefractivity (PR) based on a poly(N‐vinylcarbazole) (PVCz) composite devise is proposed from the perspectives of chemistry and physics. The device's PR chemistry (dependence of PVCz's molecular weight) and physics (dependence of grating periodicity and laser wavelength) are studied. Increasing the molecular weight of PVCz from 23 000 to 1 270 000 g mol^?1 significantly increases diffraction efficiency, grating build‐up speed (inverse of response time), and sensitivity. Narrowing grating period from 5.1 to 1.1 μm gives faster response time and larger optical gain. Shorter wavelength of writing laser from 633 to 532 nm provides higher diffraction efficiency, faster response time, and larger optical gain.

     

Synthesis and Photovoltaic Properties of Conjugated Copolymers with Benzo[1,2‐b:4,5‐b′]dithiophene and Bis(thiophene)phthalimide Units

Two new donor/acceptor copolymers PBDTPhBT1 and PBDTPhBT2 with alternating benzodithiophene ( BDT ) and bisthiophene‐phthalimide ( PhBT ) units were synthesized by Stille coupling reaction. The copolymers showed identical optical bandgaps of 1.98 eV. The HOMO energy levels are ?5.35 and ?5.32 eV for PBDTPhBT1 and PBDTPhBT2 , respectively. The bulk heterojunction solar cell devices based on these copolymers as donors and PC₇₁BM as acceptor displayed high open‐circuit voltages of 0.90–0.93 V and achieved power conversion efficiency of 1.54% under the illumination of AM 1.5, 100 mW · cm^?2.

     

Novel Poly(butylene succinate)‐Based Ionomers with Sulfonated Succinate Units: Synthesis,Morphology, and the Unique Nucleation Effect on Crystallization

Summary: Poly(butylene succinate) (PBS) and PBS‐based ionomers (PBSi's) with 0.3 and 1.2 mol‐% of sodium sulfonated succinate unit were synthesized. The existence of ionic aggregates in the ionomer matrices was indicated by melt viscosity and glass transition data. It seems that the ionic aggregates have two opposing roles in crystallization: one is the induction of nucleation and the other is the interference with lamellar growth. Because of these two contrary effects, the crystallization behavior of the ionomers exhibited measurably different cooling rate‐dependencies than that of the parent PBS. The rate varied distinctly with ionic content.

Spherulitic morphologies of PBS and PBSi's measured with polarizing optical microscopy.     

Synthesis,Characterization, and Intramolecular End‐to‐End Ring Closure of α‐Isopropylidene‐1,1‐dihydroxymethyl‐ω‐diethylacetal Polystyrene‐block‐polyisoprene Block Copolymers

Cyclic polystyrene‐block‐polyisoprenes of controlled dimensions have been synthesized for the first time by the direct coupling of α‐isopropylidene‐1,1‐dihydroxymethyl‐ω‐diethylacetal‐heterodifunctional linear polystyrene‐block‐polyisoprene precursors previously prepared by living anionic polymerization. Cyclization is achieved under high dilution by intramolecular coupling of the polymer ends under acid catalyst conditions. Using this strategy polystyrene‐block‐polyisoprene macrocycles of controlled chain dimensions are prepared in high yield (> 90%). Pure cycles were finally recovered by flash chromatography. The synthesis and characterization of both the linear α,ω‐heterodifunctional polystyrene‐block‐polyisoprenes block copolymers precursors and of the corresponding cyclized chain architectures are reported.

200 MHz ¹H NMR spectrum (CDCl₃) of cyclized polystyrene‐block‐polyisoprene copolymer (M _n = 12 000).     

Nitroxide‐Mediated Radical Polymerization of N‐tert‐Butylacrylamide

The nitroxide‐mediated polymerization of N‐tert‐butylacrylamide (TBAM) in DMF at 120 °C using SG1/DEPN and AIBN has been investigated. Linear growth in number‐average molecular weight ( ) versus conversion and narrow molecular weight distributions (MWDs) with high livingness were obtained up to ≈8 000 g · mol^?1. For higher molecular weights, the MWDs gradually became broader with low molecular weight tailing, and deviated downwards from theoretical values. Quantitative analyses of MWDs, along with specifically designed conventional radical polymerizations at 120 °C, were consistent with chain transfer to monomer limiting the attainable . This finding can be equally applied to existing literature polymerizations of TBAM.

     

Fluorescent Nanoparticles through Self‐Assembly of Linear Ionenes and Pyrenetetrasulfonate

We investigated the association of linear cationic model polyelectrolytes with oppositely charged pyrenetetrasulfonate in aqueous solution. Water soluble ionenes were prepared via Menschutkin reaction from 1‐4‐diazabicyclo[2.2.2]octane (DABCO) and dibromoalkenes. UV? Vis results revealed that PY molecules bind to ionenes in a cooperative process due to π–π interaction. Size and structure of the particles vary in dependence of inter‐charge distance on the ionene backbone. Stable spherical dye–ionene assemblies with radii between 50 and 200 nm have been obtained with one polyelectrolyte (PD4), while this was not possible with a different polyelectrolyte (PD6) or in either case at polyelectrolyte excess. It was possible to deposit the fluorescent polyelectrolyte–dye aggregates onto mica surfaces.

     

Blue Light Emission from a Fluorene‐Carbazole‐Fluorene Trimer Incorporated as the Side Chain into a Polynorbornene

Summary: A well defined blue electroluminescent fluorene‐carbazol‐fluorene trimer 3,6‐bis‐(9,9‐dihexyl‐9H‐fluoren‐3‐yl)‐9‐alkyl‐9H‐carbazole was synthesized using a Suzuki type cross coupling reaction as the key step. A way to attach this chromophore to a norbornene was developed and the resulting electroactive monomer was polymerised using the “3^rd generation Grubbs catalyst” (N,N‐bis(mesityl) 4,5‐dihydroimidazol‐2‐ylidene)(3‐bromo‐pyridine)₂(Cl)₂Ru?CHPh), yielding an amorphous polymer with a narrow molecular weight distribution, which was used to build a light‐emitting diode exhibiting electroluminescence peaking at 410 nm.

Incorporation of the fluorene‐carbazol‐fluorene trimer as the emissive layer in an ITO/PEDOT:PSS/emitter/Ca/Al light emitting device.     

Segmented Block Copolymers with Monodisperse Aramide End‐Segments

Segmented block copolymers were synthesized using monodisperse diaramide (TΦT) as hard segments and PTMO with a molecular weight of 2 900 g · mol^?1 as soft segments. The aramide: PTMO segment ratio was increased from 1:1 to 2:1 thereby changing the structure from a high molecular weight multi‐block copolymer to a low molecular weight end‐block copolymer. The thermal and thermal‐mechanical properties were studied by DSC and DMA. Also studied were the tensile and the elastic properties as well as the melt rheological behavior as a function of frequency. The crystallinity of aramide in the end‐block copolymers was found to be higher than in the multi‐block copolymer.

     

Combination of Mechanochemical Degradation of Polymers with Controlled Free‐Radical Polymerization

The result of ultrasound on polymer solutions is the breakage of macromolecular C C‐bonds due to cavitation. The fact that termination reactions of mechanoradicals as disproportionation and combination are suppressed in the presence of radical scavengers makes the following method possible. Thus the use of nitroxides acting as chain‐terminating agents allows the creation of macroinitiators which can be used in controlled free‐radical polymerization. In this work, we investigate the mechanochemical degradation of poly(methyl methacrylate) (PMMA) in the presence of OH‐TEMPO and the application of the irradiated polymers as macroinitiators in a controlled radical polymerization. The content of OH‐TEMPO terminated chains in the degraded product is determined by a computer‐aided procedure on the basis of molecular weight distributions.

Ultrasonic degradation of PMMA, decrease of molar mass (M _n), and polydispersity (Pd) as a function of irradiation time, power output = 200 W, ϑ = 45–50 °C.     

Homo‐ and Co‐Polymers of Norbornene Containing Aryl‐ and Hetaryl‐Azo Dyes; Synthesis and Sensing Properties

A series of polynorbornene homo‐ and copolymers containing aryl‐ and/or hetaryl‐azo dyes were prepared through ring‐opening metathesis polymerization (ROMP). Thermal studies indicated that the polymers were thermally stable up to 250 °C, and possessed glass transition temperatures ranging from 93 to 133 °C. In THF solutions, the aryl‐azo dye containing homopolymers, displayed λ_max = 417 nm while the hetaryl‐azo dye containing homopolymers displayed λ_max = 495 nm. The copolymers displayed a λ_max that encompassed both the aryl‐ and hetaryl‐azo dye range. The monomers and polymers showed bathochromic shifts in solution when acidified. The polymers were cast into films that changed colour in the presence of both aqueous 1.2 M HCl or HCl_(g). The colour change reverses when exposed to aqueous 1.2 M NaOH or NH_3(g). This process was repeated several times without disintegration of the polymer film, indicating that these polymers may be useful as reusable acid sensors.

     

Two‐Dimensional Chromatography of Complex Polymers, 7 – Detailed Study of Polystyrene‐block‐Polyisoprene Diblock Copolymers Prepared by Sequential Anionic Polymerization and Coupling Chemistry

Two‐dimensional chromatographic methods were developed using LC‐CC in the first and SEC in the second dimension. These methods were applied for the investigation of PS‐b‐PI diblock copolymers synthesized by different approaches: sequential living anionic polymerization and coupling of living precursor blocks. The first dimension separates according to the individual block length of PS or PI blocks, whereas the second dimension separates with respect to the total molar masses of components. 2D‐LC analysis provides information on the purity of the reaction products, the presence of by‐products, the chemical compositions and the molar masses of all product components. The accuracy and selectivity of 2D‐LC is discussed.