Creating true molecular composites containing a liquid crystalline polymer by optimizing intermolecular hydrogen bonding

Blending a liquid crystalline polymer (LCP) with an amorphous polymer to create a molecular composite offers a method to use the desirable properties of a LCP at a more modest cost. However, very few such blends are miscible. This study seeks to correlate the extent of intermolecular hydrogen bonding between the two polymers in a blend with the phase behavior of the blend. Using Fourier Transform Infrared technique to quantify the amount of intermolecular hydrogen bonding between the two polymers and Differential Scanning Calorimetry and optical microscopy to determine the blend phase behavior, this study provides results which demonstrate that the broadest miscibility window in the blends studied corresponds to the system that optimizes the extent of intermolecular hydrogen bonding. The first part of this study demonstrates that it is possible to create a true molecular composite by inducing miscibility in a blend containing a LCP and an amorphous polymer by slightly modifying the structure of the amorphous polymer to promote hydrogen bonding between the two polymers. The system that maximizes the extent of intermolecular hydrogen bonding is one where the hydrogen bonding moieties on one of the polymers are spaced out along the chain. The results show that by optimizing the extent of hydrogen bonding between the two blend components, the broadest miscibility window in the phase diagram can be found. To sum up, these results provide guidelines by which miscibility may be induced in polymer blends by such minor structural modification of the polymers

Intermolecular hydrogen bonding of the two independent molecules of N-3,5-dinitrobenzoyl-L-leucine

The title compound, C₁₃H₁₅N₃O₇, crystallizes as two independent molecules which differ in their conformation. Intermolecular hydrogen bonding between the amide and carboxylic acid groups as N-H...O=C interactions results in the formation of one-dimensional chains with N...O distances of 2.967 (6) and 3.019 (6) Å. Neighbouring chains are linked by C=O...H-O interactions to form a two-dimensional network, with O...O distances of 2.675 (6) and 2.778 (6) Å

Enhancement of the properties of polymer blends by hydrogen bonding and transesterification

The importance of polymer rigidity on the extent of intermolecular hydrogen bonding in the blends of copolymers of 4-vinylphenol and styrene (PS-co-PVPh) and polyethers has been studied utilizing FT-IR spectroscopy. A series of polyethers containing mesogens with different rigidity including a liquid crystalline poly ether (LCP) are synthesized using phase transfer polyesterification and blended with PS-co-PVPh. The extent of intermolecular hydrogen bonding between the hydroxyl group ofPS-co-PVPh and the ethereal oxygen is correlated to the rigidity of polyethers. The results of this study indicate that extent of intermolecular hydrogen bonding in blends increases as the flexibility of polyethers increases, causing a shift in the frequency of the hydrogen bonded hydroxyl band towards lower frequency. The rigidity of the polyethers inhibits the formation of intermolecular hydrogen bonds, however this effect is not dramatic. It must be recognized that the LCP utilized in this study can not be considered as a rod-like LCP, as it contains flexible aliphatic spacers. Therefore, the result shows that the rigidity of LCP does not dramatically affect the formation of intermolecular hydrogen bonds is only applicable to non-rodlike LCP. The data also show that a lower concentration of the polyether in the blends induces better mixing and higher extent of intermolecular hydrogen bonding due to better dispersion of polyether in PS-co-PVPh. This suggests that a one-phase system may exist in the region of the phase diagram of the blends that are rich in PS-co-PVPh. The result also shows that the extent of intermolecular hydrogen bonding between PSco-PVPh and polyethers decreases at the higher temperatures. The concept of functional group accessibility of hydroxyl groups for intermolecular hydrogen bonding is also examined in these blends. The amount of intermolecular hydrogen bonds increases with an increase in spacing between the hydroxyl groups. The transesterification Reaction between poly(carbonate) (PC) and thermoplastic liquid crystalline poly (hydroxy benzoate)-poly(ethylene terephthalate) (PHB-PET) and its consequences on the blend morphology and mechanical properties of the blend has also been investigated. The transesterification reaction between PC and PHB-PET upon annealing at 260 °C is characterized and quantified by 13C NMR spectroscopy, showing peaks at 120.9 ppm, 148.3 ppm, and 165.9 ppm corresponding to bisphenol-A terephthalate and bisphenol-A oxybenzoate diads, respectively. These peaks are the result of the initial formation of block copolymer and eventual formation of random copolymer at the interface as the mole fraction of corresponding diads increases. Polarized optical microscopy and tensile measurements reveal that there is a direct correlation between the loss of liquid crystallinity character and mechanical properties of the blend to the extent of transesterification reaction. The results of this study indicate a trade-off between the loss of liquid crystallinity of the blend and its strength resulting from transesterification upon annealing

2,2'-(Ethane-1,2-diyl)bis(4-chlorophenol)

The X-ray structure of the title compound, obtained as a byproduct in a natural product synthesis, has been determined and shows an unusual pattern featuring chains of molecules with both intra- and intermolecular hydrogen bonding of the OH groups.Publisher PDFPeer reviewe

Variable coordination of amine functionalised N-heterocyclic carbene ligands to Ru, Rh and Rr: C-H and N-H activation and catalytic transfer hydrogenation

Chelating amine and amido complexes of late transition metals are highly valuable bifunctional catalysts in organic synthesis, but complexes of bidentate amine–NHC and amido–NHC ligands are scarce. Hence, we report the reactions of a secondary-amine functionalised imidazolium salt 2a and a primary-amine functionalised imidazolium salt 2b with [( p -cymene)RuCl 2 ] 2 and [Cp*MCl 2 ] 2 (M = Rh, Ir). Treating 2a with [Cp*MCl 2 ] 2 and NaOAc gave the cyclometallated compounds Cp*M(C,C)I (M = Rh, 3 ;M = Ir, 4 ), resulting from aromatic C–H activation. In contrast, treating 2b with [( p -cymene)RuCl 2 ] 2 ,Ag 2 O and KI gave the amine–NHC complex [( p -cymene)Ru(C,NH 2 )I]I ( 5 ). The reaction of 2b with [Cp*MCl 2 ] 2 (M = Rh, Ir), NaO t Bu and KI gave the amine–NHC complex [Cp*Rh(NH 2 )I]I ( 6 ) or the amido–NHC complex Cp*Ir(C,NH)I ( 7 ); both protonation states of the Ir complex could be accessed: treating 7 with trifluoroacetic acid gave the amine–NHC complex [Cp*Ir(C,NH 2 )I][CF 3 CO 2 ]( 8 ). These are the first primary amine– or amido–NHC complexes of Rh and Ir. Solid-state structures of the complexes 3–8 have been determined by single crystal X-ray diffraction. Complexes 5 , 6 and 7 are pre-catalysts for the catalytic transfer hydrogenation of acetophenone to 1-phenylethanol, with ruthenium complex 5 demonstrating especially high reactivity

Seven 3-methylidene-1H-indol-2(3H)-ones related to the multiple-receptor tyrosine kinase inhibitor sunitinib

The solid-state structures of a series of seven substituted 3-methylidene-1H-indol-2(3H)-one derivatives have been determined by single-crystal X-ray diffraction and are compared in detail. Six of the structures {(3Z)-3-(1H-pyrrol-2- ylmethylidene)-1H-indol-2(3H)-one, C13H10N2O, (2a); (3Z)-3-( 2-thienylmethylidene)-1H-indol-2(3H)-one, C13H9NOS, (2b); (3E)-3-(2-furylmethylidene)-1H-indol-2(3H)-one monohydrate, C13H9NO2 center dot H2O, (3a); 3-(1-methylethylidene)-1H-indol- 2(3H)-one, C11H11NO, (4a); 3-cyclohexylidene-1H-indol- 2(3H)-one, C14H15NO, (4c); and spiro[1,3-dioxane-2,3'-indolin]- 2'-one, C11H11NO3, (5)} display, as expected, intermolecular hydrogen bonding (N-H center dot center dot center dot O=C) between the 1H-indol-2(3H)-one units. However, methyl 3-(1-methylethylidene)- 2-oxo-2,3-dihydro-1H-indole-1-carboxylate, C13H13NO3, (4b), a carbamate analogue of (4a) lacking an N-H bond, displays no intermolecular hydrogen bonding. The structure of (4a) contains three molecules in the asymmetric unit, while (4b) and (4c) both contain two independent molecules

Sporopollenin, a natural copolymer, is robust under high hydrostatic pressure

Lycopodium sporopollenin, a natural copolymer, shows exceptional stability under high hydrostatic pressures (10 GPa) as determined by in situ high pressure synchrotron source FTIR spectroscopy. This stability is evaluated in terms of the component compounds of the sporopollenin: p-coumaric acid, phloretic acid, ferulic acid, and palmitic and sebacic acids, which represent the additional n-acid and ndiacid components. This high stability is attributed to interactions between these components, rather than the exceptional stability of any one molecular component. We propose a biomimetic solution for the creation of polymer materials that can withstand high pressures for a multitude of uses in aeronautics, vascular autografts, ballistics and light-weight protective materials

Study of aggregation of the 2', 7'-dichlorofluorescein dye caused by the intermolecular hydrogen bond

The project's main objective is to study the aggregation of the 2',7'-dichlorofluorescein dye molecule through intermolecular hydrogen bonding in various solvents. With two chromophores perpendicular to each other, 2',7'-dichlorofluorescein likely demonstrate J-aggregate and H-aggregate simultaneously. The present project is expected to provide some insights in the knowledge-based molecular design to improve device performance for optoelectronic applications