Oxidative Coupling Copolymerization of 4‐Methyltriphenylamine with Arenes

A novel synthetic method for the preparation of high‐molecular‐weight conjugated polymers is presented. It consists of the oxidation copolymerization of different arenes with triphenylamine. The structure of the copolymers was characterized by ¹H and ¹³C NMR spectra. The copolymers have good solubility in common organic solvents and are thermally stable. Photoluminescence (PL) spectra (see Figure) showed that the color of emission depends on the type of arene units in the copolymer chain. Cyclic voltammetry (CV) measurements revealed electrochemical activity of the copolymers.

PL spectra of the copolymers.     

A Facile One‐Pot Synthesis to Dextran‐Based Nanoparticles with Carboxy Functional Groups

Summary: Stabilized nanoparticles functionalized with carboxy groups were synthesized directly from dextran and acrylic acid (AA), without using any organic solvent and surfactant. The composition and morphology of these dextran‐based nanoparticles, as well as the mechanism of this one‐pot synthesis, were also investigated in this paper. This approach is anticipated to be applicable to various water‐soluble polysaccharides to fabricate nanoparticles facilely.

Facile synthesis of stabilized nanoparticles functionalized with carboxy groups from dextran and AA.     

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.     

Sulfonation of Poly(propylene) Films with Fuming Sulfuric Acid

Summary: Sulfonation is one of the most commonly used methods for the surface modification of polymers. In this study, the sulfonation of poly(propylene) (PP) films with fuming sulfuric acid has been investigated with the focus on the surface reaction. Analysis of the sulfonated PP films by X‐ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) infrared spectroscopy, and chemical modification demonstrated the formation of C?C double bonds and sulfate groups in the sulfonation process. These results and a comparison with low‐density polyethylene (LDPE) films led us to propose a new sulfonation mechanism involving hydride abstraction and the formation of β‐sultones.

The here proposed mechanism of the sulfonation of poly(propylene) involves the formation of unstable β‐sultones.     

Influence of Addition of Organoclays on Morphologies in Nylon 6/LLDPE Blends

Summary: Polymer blend nanocomposites containing linear low density polyethylene (LLDPE), nylon 6 and organoclays were prepared by melt mixing, and their morphologies and structures were examined with a field emission scanning electron microscope (FE‐SEM) and an X‐ray diffractometer (XRD). The size of phase‐separated domains decreased considerably with increasing content of organoclay. The d‐spacing of organoclay in the nanocomposites was increased from about 18.6 to over 28 Å. This effect was highly dependent on nylon 6 contents because nylon 6 is more polar and shows higher affinity to the organoclays compared to LLDPE.

     

Structural Reasons for Restricted Backbone Motion in Poly(n‐alkyl methacrylates): Degree of Polymerization,Tacticity and Side‐Chain Length

Summary: The complex dynamics of poly(n‐alkyl methacrylates) is studied by advanced ¹³C NMR spectroscopy as well as mechanical and dielectric relaxation. Extended backbone conformations are identified as the molecular units involved in structural relaxation. From the variation in the degree of polymerization and a comparison with the presence of stereoregular sequences in the sample, the length of the extended units is determined to involve about five, at most ten monomeric units. Syndiotactic and isotactic sequences behave similarly. These findings are indicative of locally structured polymer melts.

     

Functional Thin Polymer Films at High Pressure

Summary: A new thin‐film characterization setup was created based on the combination of a surface plasmon spectrometer with an electrochemical cell operated under high pressure of up to 200 MPa and at temperatures up to 120 °C. The examples given to document its performance include photoisomerization studies with poly(methyl methacrylate) (PMMA) films partly derivatized with disperse red (DR1), as well as, a preliminary account of the electropolymerization of EDOT under pressure and the assessment of the redox properties of the resulting thin PEDOT films.

Sketch of the high‐pressure electrochemistry surface plasmon cell.     

X‐Ray Diffraction Studies on the Phase‐Transformational Behavior of a Smectic Liquid‐Crystalline Elastomer Composed of Chiral Mesogens

Structural changes through successive phase transformations of a chiral smectic liquid‐crystalline elastomer are investigated by X‐ray scattering technique. In uniaxially deformed elastomers, the smectic layer seemingly tilts even in the SmA phase, in which an in‐plane chevron structure formed in the tilted smectic phase. On the basis of an analysis of the layer reflection peaks, the layer correlation length in the tilted smectic phases is shorter than that in the non‐tilted SmA phase, though smectic layers in the tilted smectic phases are better ordered than those in SmA.

Experimental arrangement for X‐ray measurements of the uniaxially deformed elastomer in the tilted smectic phase at room temperature.     

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.

     

Surfactant‐Free Emulsion Polymerization of Various Methacrylates: Towards Monodisperse Colloids for Polymer Opals

Summary: A systematic investigation of the surfactant‐free emulsion polymerization (SFEP) on three different methacrylates (MMA, tert‐butyl methacrylate and 2,2,2‐trifluoro ethyl methacrylate) is described to obtain monodisperse colloids for the preparation of artificial “polymer opals”. The experimental results are in agreement with a model, in which seed particles are formed very early during the polymerization process. The particles grow afterwards into the colloids until all monomer is consumed. This gives rise to a linear relationship between the volume of the colloids and the ratio of monomer to water in the reaction batch. The concentration of the seed particles depends thereby on the hydrophobicity of the monomers and can be varied by the addition of salt. The relationship between the composition of the reaction batch and the size of the colloids differs from monomer to monomer. It can, however, be described for all systems by the introduction of an empirical system dependent parameter p_M (master curve). It is thus possible to predict the colloidal size for new monomer (or salt) systems from a single measurement point. Colloids with a diameter of more than 500 nm can be prepared by a two stage seeded polymerization. The colloids prepared with this method are so monodispersed (well below 5%) that they can easily be crystallized into artificial polymer opals of a high optical quality.

Dried opaline films (second‐order reflection).     

Effect of Molecular Structure and Thermal Treatment on Photo‐optical Properties of Photochromic Azobenzene‐containing Polymer Films

Three novel photochromic azobenzene‐containing comb‐shaped polyacrylates are synthesized and their phase behavior and photo‐optical properties are studied. The influence of the side photochromic group structure, thermal treatment, and light irradiation on aggregation of azobenzene chromophores in thin spin‐coated films of the polymers is investigated in detail. Special attention is paid to studying the photo‐orientation processes in polymers films induced by polarized blue light (473 nm). The relationship between the photochromic group architecture, phase behavior, thermal treatment of films, and kinetics of chromophore photo‐orientation is established and discussed. It is found that the position of the N?N bond in chromophores plays an important role in the kinetics of the process, but does not affect the maximum value of dichroism.

     

Water-Based Polyurethane Filled with Multi-Walled Carbon Nanotubes Prepared by a Colloidal-Physics Method▪Author: This manuscript has been thoroughly edited. Please read the proofs carefully to ensure that no unintentional shift in meaning has been introduced.▪

MWCNT/water-based PU composites were synthesized by means of a colloidal-physics method. The effect of MWCNT addition on the electrical and thermal properties of the composites and the effect of NaCl addition on film formation of the PU latexes were investigated. The electrical conductivity of the water-based PU was improved by more than four orders of magnitude, but remained still four orders of magnitude lower than that of the MWCNTs. The percolation threshold was found to be at 0.5 wt.-% MWCNT. The thermal conductivity of the composites was improved by ≈86% at 7 wt.-% MWCNT. MWCNT/PU dispersions displayed stronger shear thinning than pure PU dispersions.

     

Aromatic Polyethers with a 4‐Chloro‐3‐trifluoromethylphenyl Group

Summary: A novel bisphenol, (4‐chloro‐3‐trifluoromethyl)phenylhydroquinone (3FC‐PH), was synthesized via a three‐step synthetic procedure. Four aromatic polyethers based on 3FC‐PH were prepared via a nucleophilic aromatic substitution polycondensation. These polymers had a high thermal stability, and the temperatures at a 5% weight loss were above 516 °C in air. The solubility of the polyethers was improved by the introduction of bulky pendant groups. The average refractive indices of the polymer films at 1 320 nm were in the range 1.5381–1.6145. The dielectric constants of the polyether films estimated from the refractive indices were 2.69–2.98. Highly fluorinated 3FC‐PAE exhibited lower light absorption in the near‐IR region.

Part of the ¹H NMR spectra of 3FC‐PAE.     

Formation Mechanism of Polyaniline Nanotubes by a Simplified Template‐Free Method

PANI nanotubes with diameters of 100–150 nm with conductivities of single nanotubes as high as 30.6 S · cm^?1 were directly oxidized with APS in the absence of hard templates and acidic dopants. The high conductivity was shown to result from protons produced during the polymerization. The pH decreases with increasing polymerization time, and the morphology changes from hollow spheres to short and long tubes. It is proposed that the micelles formed by the aniline monomer in aqueous solution serve as a soft template for forming hollow spheres at the initial stage. As the polymerization proceeds, these hollow spheres are linearly aggregated and elongated to form short and long tubes.

     

Synthesis of Chitosan Surfactants

Chitosan surfactants were prepared in a three‐step reaction starting with glycol chitosan (GC) and chitosan oligosaccharides (COS). In the case of GC, water‐insoluble products were obtained, the functionalisation of which were proven via IR spectroscopy. Starting with COS, a broad variety of products with different ratios of ionic and hydrophobic side chains were prepared and characterised by NMR and partially by IR spectroscopy. Thermogravimetric analysis showed that the thermal stability of functionalised COS did not change. The critical micelle concentration (cmc) was determined from surface tension measurements to be 0.01 mg · mL^?1 for a sample of ionic to hydrophobic units of 1:1.

     

Morphological Studies of Epoxy/Polyaniline Blends

Summary: Polyaniline‐dodecybenzenesulfonic acid (PANI‐DBSA)/epoxy resin (EP) blends were prepared by a solution‐in‐toluene process and direct mixing of PANI‐DBSA with EP. The dispersion quality of PANI‐DBSA proved to be strongly related to the final electrical properties of the cured blends. The solution processed blends showed enhanced electrical properties with small PANI‐DBSA contents (percolation threshold determined was around 2.3 wt.‐% PANI‐DBSA). The morphologies of these blends were investigated by atomic force (AFM), scanning electron (SEM) and transmission electron (TEM) microscopy. The existence of a translucent PANI‐DBSA network exists within the EP matrix. The microscopy investigations were in agreement with the results from differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA).

SEM image of the PANI‐DBSA‐rich regions (indicated by arrows) surrounded by the conductive EP/PANI‐DBSA matrix (5 wt.‐% PANI‐DBSA).     

On the Radiation‐Induced Polymerisation of 2,3‐Dihydropyran

Summary: Concentrated (5 mol‐%) solutions of 2,3‐dihydropyran in CFCl₂CF₂Cl matrix were irradiated at 77 K and several intermediates – radical cation, dimer radical cation, dihydropyryl radical and a trapped polymer radical – were observed by low‐temperature EPR spectroscopy. The irradiated solutions yielded after melting a polymeric product, which was characterised by IR spectroscopy and GPC. The polydisperse polymer is assumed to be formed by a cationic process initiated by a dimer carbocation. The polymerization proceeds via the ring double bonds, while ring‐opening reaction occurs in a small extent. The free‐radical mechanism via the dihydropyryl radical leads to low molecular weight oligomers only. The quantum chemical calculations support the interpretation of the experimental results.

     

Synthesis of Aliphatic‐Aromatic Copolyesters by a High Temperature Bulk Reaction Between Poly(ethylene terephthalate) and Cyclodi(ethylene succinate)

Summary: Cyclodi(ethylene succinate) (C2) easily reacts with poly(ethylene terephthalate) (PET) in the melt leading to the formation of high molar mass PET‐Poly(ethylene succinate) copolymers (PET‐PES). Copolyesters with a PET/C2 starting mass ratio of 90/10, 80/20, 70/30 and 50/50 were synthesized and characterized by ¹H NMR and MALDI‐TOF MS. The 50/50 copolyester was almost random, while copolyesters with higher ethylene terephthalate contents exhibited some block copolymer character. MALDI‐TOF MS/SEC off‐line coupling was used to determine copolyester absolute average molar masses. The results indicate that the conventional SEC polystyrene calibration strongly overestimates copolyester molar masses. The melting temperatures and crystallinity of the 90/10, 80/20 and 70/30 copolyesters were significantly higher than those of comparable PET‐aliphatic polyester copolymers.

     

Morphology and Phase Characteristics of High‐Density Polyethylene Probed by NMR Spin Diffusion and Second Moment Analysis

Summary: A dipolar filter pulse sequence combined with cross‐polarization‐MAS is applied to characterize the phase distribution, morphology, and spin diffusion within a high‐density polyethylene sample. A new method to obtain quantitative ¹³C NMR by combining cross‐polarization‐MAS and spin diffusion NMR is presented. The derived crystallinity is consistent with the corresponding crystallinity obtained by ¹H NMR.

Illustration of the pulse sequence(s) applied in the present work.     

Chain Growth Polycondensation as a Polymer Generating Reaction in the Synthesis of Oligo(p‐phenyleneethynylene)s with Low Polydispersity

Summary: The polycondensation of 1‐ethynyl‐2,5‐dihexyl‐4‐iodobenzene in the presence of 1‐ethynyl‐2,5‐dihexyl‐4‐(2‐phenylethynyl)benzene proceeds according to the mechanism of initiated chain growth polycondensation. It has allowed the synthesis of oligomers with a desired molecular weight and a narrow molecular weight distribution. The reasons for the side reaction leading to the formation of diyne compounds are revealed and the presumed mechanism is given. This opens prospects for the preparation of defectless poly(p‐phenyleneethynylene)s with required molecular weights and narrow molecular weight distributions.