Diblock copolymers (BCP) consisting of poly(methyl methacrylate) (PMMA) and poly(1H,1H,2H,2H-perfluorodecyl methacrylate) (PsfMA) blocks are employed as templates for controlled dispersion and localization of multi-walled carbon nanotubes (MWCNT). Short MWCNT are modified with perfluoroalkyl groups to increase the compatibility between MWCNT and the semifluorinated (PsfMA) phase and to promote a defined arrangement of MWCNT in the BCP morphology. Thin BCP and BCP/MWCNT composite films are prepared by dip-coating using tetrahydrofuran as solvent with dispersed MWCNT. Atomic force microscopy, scanning and transmission electron microscopy reveal a strong tendency of the BCP to form micelle-like domains consisting of a PMMA shell and a semifluorinated PsfMA core, embedded in a soft phase, containing also semifluorinated blocks. MWCNT preferentially localized in the embedding phase outside the micelles. Perfluoroalkyl-modification leads to significant improvement in the dispersion of MWCNT, both in the polymer solution and the resulting nanocomposite film due to increased interaction of MWCNT with the semifluorinated side chains in the soft phase outside the micelle domains. As a result, reliable electrical conductivity is observed in contrast to films with non-modified MWCNT. Thus, well-dispersed, modified MWCNT provide a defined electrical conduction path at the micrometer level, which is interesting for applications in electronics and vapor sensing.

In this study, solvogels containing (2-((2-(ethoxycarbonyl)prop-2-en-1-yl)oxy)-ethyl) phosphonic acid (ECPA) and N,N′-diethyl-1,3-bis-(acrylamido)propane (BNEAA) as the crosslinker are synthesized by UV induced crosslinking photopolymerization in various solvents. The polymerization of the ECPA monomer is monitored by the conversion of double bonds with in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The morphology of the networks is characterized by in situ photorheology, solid state NMR spectroscopy, and scanning electron microscopy (SEM) of the dried gels. It is demonstrated that the storage modulus is not only determined by the crosslinker content in the gel, but also by the solvent used for preparation. The networks turn out to be porous structures with G′ being governed by a rigid, phase-separated polymer phase rather than by entropic elasticity. The external and internal pKa values of the poly(ECPA-co-BNEAA) gels were determined by titration with a specially designed method and compared to the calculated values. The polymer-immobilized phosphonic acid groups in the hydrogels induce buffering behavior into the system without using a dissolved buffer. The calcium accumulation in the gels is studied by means of a double diffusion cell filled with calcium ion-containing solutions. The successful accumulation of hydroxyapatite within the gels is shown by a combination of SEM, energy-dispersive X-ray spectroscopy (EDX) and wide-angle X-ray scattering (WAXS).

ABSTRACTThermotropic liquid crystalline polyesters with varied chemical structure are synthesized by melt transesterification polycondensation. They are employed as matrix for blends with lignin materials to obtain melt‐spinnable precursors for carbon fibers. The lignin samples are carefully purified by fractionation, enzymatic removal of reducing sugars, and subsequent modification of the terminal OH groups. Effective melt blending is achieved with liquid‐crystalline aromatic–aliphatic polyesters having melting ranges that match the softening temperature of the lignin fractions, which is necessary to prevent thermal decomposition of the lignin. Polyester/lignin blends are partially compatibilized, phase‐separated materials. The polyester/lignin materials are melt‐spun successfully. The fiber properties depend on the lignin purification process. X‐ray scattering reveals that orientation in lignin‐containing fibers is maintained. First experiments show that the fibers can be converted successfully to carbon fibers by thermal annealing procedures. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48257.

The phase separation and surface characteristics of poly(propyl methacrylate-b-methyl methacrylate) (PPrMA-b-PMMA) diblock copolymers were studied and compared to strongly phase-separated poly(pentyl methacrylate-b-methyl methacrylate) (PPMA-b-PMMA) block copolymers (BCPs). PPrMA-b-PMMA with varied compositions and molar masses was synthesized by living anionic polymerization. The phase separation was studied by DSC, SAXS, TEM and AFM. The experimental data were compared to the calculated phase diagram. PPrMA-b-PMMA BCPs were weakly phase-separated, and indications for the existence of a relative broad interface between the blocks were observed. Nevertheless, two ordered morphologies—hexagonally packed cylinders and lamellae—depending on the molar composition were distinguished. The phase separation in thin films was studied by AFM in comparison with PPMA-b-PMMA. The wetting behavior of the thin films was examined by contact angle measurements. The water contact angles on PPrMA-b-PMMA were clearly influenced by both blocks. XPS confirmed the presence of both blocks in the top surface layer, which was different to PPMA-b-PMMA diblock copolymers where the top layer consisted only of PPMA blocks. Thus, only the weakly phase-separated PPrMA-b-PMMA BCP system allowed the generation of phase-separated films with tunable wetting characteristics.

Diblock copolymers (BCP) with poly(methyl methacrylate) and poly(1H,1H,2H,2H‐perfluorodecyl methacrylate) (PsfMA) blocks prepared by anionic polymerization in tetrahydrofuran at −78 °C and atom transfer radical polymerization (ATRP) at 60 °C, respectively, with stepwise varied composition over a wide range in the phase diagram are compared with respect to synthesis limits, phase separation behavior in bulk, and properties of thin films. Both methods yield BCPs with low dispersity (1.1–1.2) at molar masses below 100 kg mol−1. Higher semifluorinated contents can be achieved by ATRP in 1,3‐bis(trifluoromethyl)benzene which ensured solubility of PsfMA. BCPs obtained by anionic polymerization show a more distinct phase separation, that is, more regular nanostructures. Additionally, self‐organization of the semifluorinated side chains occurs generating smectic layers which alters in turn the BCP morphology especially in thin films as compared to non‐semifluorinated BCP. All BCPs show amphiphilic behavior and form micelles in organic solvents which can be used to deposit nanoparticles. image

12 Ausgehend von der vorhandenen Expertise zur Polymersynthese, der hohen Polymergrenzflächenkompetenz sowie den bereits demonstrierten Erfolgen im Bereich der Nanostrukturbildung und Funktionskontrolle in dünnen Polymerfilmen setzt sich das ST1 das Ziel, entscheidende Beiträge im Bereich der Funktionspolymere und der nanostrukturierten (Hybrid-)Materialien für Zukunftstechnologien zu leisten. Schwerpunkt wird auf die Steuerung der Nanostruktur und Funktion in dünnen Polymerfilmen sowie die notwendige Systemintegration gelegt.

The crystallization and nucleation kinetics of poly(epsilon-caprolactones) (PCL) with molar masses between 1.4 and 6.1 kDa and negligible number of heterogeneous nuclei has been investigated by differential fast scanning calorimetry (DFSC) applying scanning rates up to 100 000 K/s. The samples were synthesized by ring-opening polymerization and chemically characterized by NMR spectroscopy, size exclusion chromatography (SEC), and multiangle laser light scattering (MALLS). For the smallest molar mass the chain length is comparable with the crystal thickness measured with small-angle X-ray scattering (SAXS), and extended chain like crystals may be formed. Because of the molar mass distribution (PDI approximate to 2), these crystals have a significant noncrystalline interface yielding nearly the same crystallinity for all molar masses. The critical cooling rate to obtain amorphous samples is below 1000 K/s and only for the lowest molar mass increased to 2000 K/s. The same trend holds for the about 1 order of magnitude higher critical heating rate to keep the samples amorphous on heating and for the analysis of isothermal nucleation and crystallization kinetics at 202 K. The samples which were shown not to contain heterogeneous nuclei active at a heating rate of >18 000 K/s were used for a study of the nucleation activity of ordered structures formed on annealing at low temperature. The analysis of the change of the thus-produced amorphous polymer samples on annealing from 202 to 272 K for times varying by a factor of more than 10(8) (0.1 ms to 8.3 h) revealed new details about the ordering processes (nucleation, poor crystal formation, crystallization, cold crystallization, and crystal perfection) and the accompanying changes in glass transition of the remaining amorphous phase (formation of rigid amorphous phases, RAF).

A series of diblock copolymers of n-pentyl methacrylab.: and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl-functionalized initiator and/or and end-capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature-dependent small-angle X-ray measurements (T-SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d-spacings L-0 as well as in the thermal expansion behavior. T-SAXS proved that the lamellar morphologies were stable over multiple heating cooling cycles without order-disorder transition (ODT) until 300 degrees C. While non-functionalized BCP formed parallel lamellae morphologies, additional OH-termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d-spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing-incidence small-angle X-ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in-situ sol-gel process. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 926-937, 2011

Diblock copolymers show phase separation on the sub-micrometer scale thus giving rise to specially ordered morphologies both in bulk and thin films. One important question is to find out relationships between bulk morphology (determined mainly by molecular parameters, i.e., the block ratio, molar mass, thermal history), and morphologies in thin films, which are strongly influenced by film parameters and film thickness related to bulk domain spacings. PPMA-b-PMMA diblock copolymers with hexagonally close-packed cylinders in the bulk and varied molar masses but identical molar composition were chosen for this study. Thin films with thicknesses below and above the bulk domain spacing were prepared and examined using different X-ray scattering methods using grazing incidence techniques. Additionally, the experimentally found phase behaviour of the diblock copolymers was compared with the calculated phase diagram.

In this paper, we would like to discuss the influence of the chemical structure of different poly(ester imide) segments as well as their molecular weight on the resulting macroscopic properties of multiblock copolymers with polysulfone. The chemical structure of the LCP segments was varied from semiaromatic [poly(ethylene terephthalate)-co-poly(ester imide)], as shown in Formula 1, to fully aromatic poly(ester imides) with two different substituents, shown in Formula 2.

New multiblock copolymers containing liquid crystalline poly(ester imide) blocks coupled with polysulfone segments have been synthesized by melt transesterification polycondensation. Connecting these segments with different molecular weights offers the opportunity to obtain both non-phase-separated and phase-separated polymers. Phase separation is detected by the occurrence of more than one glass transition as well as by transmission electron microscopy. The resulting properties depend strongly on the morphology. Non-phase-separated multiblock copolymers show synergistic effects with respect to the glass transition and the initial E modulus. The glass transition temperatures as well as the modulus of all multiblock copolymers are higher than those found of the parent homopolymers of the used blocks, which results additionally in a very high thermostability. The synthesized materials could be very interesting for both new membrane materials and barriers with controllable diffusion properties.