Search results for "ALK"

Infrared spectroscopic study of a phenyl benzoate side group—methacrylate main chain polymeric liquid crystal

1994

Abstract The temperature dependence of the infrared dichroism of a side chain polymeric liquid crystal was investigated for two homogeneously oriented samples, one aligned with a PVA coating and the other aligned by a magnetic field. From the apparent order parameters, it was found that the rotation of the mesogenic side group was restricted. Not only the rigid part of the side group, but also the alkyl chains were found to be partly ordered. Realignment of the side groups was observed in the case of the magnetically aligned sample at the smectic-nematic transition temperature. Unlike the other absorption bands, the C˭O bond vibration band shifted to higher wavenumbers with increasing tempe…

Synthesis and thermal behavior of Janus dendrimers, part 2

2010

Abstract The thermal properties of twelve Janus-type dendrimers up to the second generation were evaluated by termogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Compounds consist of the dendritic bisMPA based polyester moieties, and either 3,4-bis-dodecyloxybenzoic acid, 3,5-bis-dodecyloxybenzoic acid or 3,4,5-tris-dodecyloxybenzoic acid moieties, attached to opposite sides of the pentaerythritol core. The thermal stability of the compounds was evaluated by TGA, displaying onset decomposition temperatures ( T d ) at around 250 °C. DSC measurements upon heating and cooling confirmed that OH terminated Janus dendrimers featuring large polarity difference in opposite …

Formation of nanorods by self-assembly of alkyl-substituted polyphenylene dendrimers on graphite

2000

Alkyl-substituted polyphenylene dendrimers with a tetrahedral or disk-like shape form self-assembled monolayers on graphite (HOPG) which show complex supramolecular structures, such as parallel rods of 6 nm diameter or two-dimensional crystals.

On the interlayer spacing collapse of Cloisite (R) 30B organoclay

2011

Abstract When used as a nanofiller for the preparation of polymer/clay nanocomposites (PCNs), Cloisite® 30B (30B) often undergoes a d-spacing collapse, as demonstrated by a shift to wider angles of the XRD basal reflection. Such collapse has been variously attributed to organoclay contamination or, more often, to thermal degradation of the organic modifier with expulsion of the volatile products from the galleries. In this work, several PCNs loaded with 30B have been prepared by melt compounding, using different polymer matrices, and have subsequently been subjected to dissolution in appropriate solvents followed by precipitation in excess non-solvent and room temperature drying. An XRD ana…

Photoconductivity of Poly(Arylenevinylene)S and Poly(Hetarylenevinylene)S

1994

Abstract The intramolecular condensation of aromatic Schiff bases leads under strong alkaline conditions to the poly(arylenevinylene)s and poly(hetarylenevi-nylene)s A - H. Due to the extreme stereoselectivity the resulting products are rigid, (E)-configurated polymers. The broad band gap of the unsubstituted intrinsic insulators is decreased by alkoxy substituents. Investigations of the photoconductivity and the photoreactivity, as well as of the AC-conductivity of some undoped, doped and quaternized systems are performed.

2020

Heteroleptic [Cu(P^P)(N^N)][PF6] complexes, where N^N is 5,5′-dimethyl-2,2′-bipyridine (5,5′-Me2bpy), 4,5,6-trimethyl-2,2′-bipyridine (4,5,6-Me3bpy), 6-(tert-butyl)-2,2′-bipyridine (6-tBubpy) and 2-ethyl-1,10-phenanthroline (2-Etphen) and P^P is either bis(2-(diphenylphosphino)phenyl)ether (POP, PIN [oxydi(2,1-phenylene)]bis(diphenylphosphane)) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos, PIN (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane)) have been synthesized and their NMR spectroscopic, mass spectrometric, structural, electrochemical and photophysical properties were investigated. The single-crystal structures of [Cu(POP)(5,5′-Me2bpy)][PF6], [Cu(xantphos)(5,5′…

Microbiological and ageing performance of polyhydroxyalkanoate-based multilayer structures of interest in food packaging

2014

Polyhydroxyalkanoates undergo crystallization during film processing and storage. In this paper, the physico–chemical ageing properties of multilayer structures based on a commercial polyhydroxybutyrate (PHB) and a polyhydroxybutyrate-co-valerate copolymer with 3% valerate content (PHBV3), containing a nanostructured zein interlayer, were analysed. The microbiological safety of the films was also evaluated by monitoring the growth of an inoculum of Listeria monocytogenes over time. Polyethyleneglycol (PEG) was added to PHBV3 films to facilitate handling as the PHBV3 mutlilayer systems (without plasticizer) cracked during film-formation. Crystallinity, thermal, mechanical, barrier and optica…

Neutron reflectometry studies on the interfacial width between polystyrene and various poly(alkylmethacrylates)

1999

From neutron reflectometry we have obtained the interfacial width (typically 2-8 nm) between incompatible polymers above the glass transition temperatures. The investigated polymer bilayers consist of a deuterated polystyrene top layer and various poly(alkylmethacrylates) as a bottom layer. We obtained interesting effects of the length of the alkyl group on the interfacial width. Using mean-field theory we calculate Flory-Huggins-Stavermann interaction parameters X from the interfacial width a I data. These results are compared with investigations of the interfacial width between deuterated poly(methylmethacrylate) and respective polyalkyl-methacrylates.

The effect of macromolecular architecture of ethylene copolymers with multi-alkenylsilsesquioxane on morphological, rheological and dynamic mechanica…

2021

Abstract The influence of the degree and the way of incorporation of multi-alkenylsilsesquioxane into the polymer chain on morphological, rheological and dynamic mechanical parameters were determined. It was found that POSS incorporated into the polymer chain was located outside the crystalline structure of lamella in amorphous phase. The incorporation of POSS-6-2 as a pendant group resulted in significant increase of separation of macromolecules. The key factor in rheological and dynamic mechanical behavior of copolymers turned out to be the way of POSS incorporation into the polymer chain. The incorporation of POSS into the polymer chain as a pendant group resulted in decreased relaxation…

Block and graft copolymers of 2-oxazolines

1994

The cationic ring-opening polymerization of 2-oxazolines is known to be initiated by alkyl halides, Lewis acids and esters of strong acids. The polymerization proceeds by a living mechanism. Numerous block and graft copolymers have already been described. Recently it was found that chloroformates (R-O-CO-CI) are also useful initiators. The mechanism of the initiation and propagation is discussed. This type of initiators allows the synthesis of different novel two-block and three-block copolymers, star-shape polymers, and a graft copolymer with a polyvinylacetate backbone.