“…The synthesis of monomers, polymers, and an initiator has been described in a previous publication . Thermal transition characteristics were determined using a Perkin-Elmer DSC 7 in the temperature range from 50 to 190 °C.…”
Section: Methodsmentioning
confidence: 99%
“…Recently, we have shown a facile and versatile synthetic route to acetylene monomers with mesogenic side groups . The polymerization of these monomers is possible with well-defined Schrock -type molybdenum initiators leading to polymers with a relatively narrow molecular-weight distribution. , These initiator systems also give access to the synthesis of random copolymers with nonmesogenic monomers such as 1-octyne. Furthermore, the synthesis of block copolymers is possible as well .…”
The thermal and morphological behavior of the first complete homologous series of liquidcrystalline polyacetylene derivatives has been investigated by means of X-ray diffraction, differential scanning calorimetry, thermogravimetry, and polarizing optical microscopy. The influence of the spacer length on the thermal behavior and on the structure of the mesophases is discussed. All polymers except one form smectic monolayers at room temperature. For one spacer length, the formation of bilayers is observed. Despite the connection of the mesogens to the stiff, conjugated polymer main chain, most polymers exhibit highly ordered mesophases. Copolymerization of the mesogen-containing monomers with 1-octyne leads to a decrease of the supramolecular order with an increasing amount of comonomer in the polymer and finally to the formation of a new phase.
“…The synthesis of monomers, polymers, and an initiator has been described in a previous publication . Thermal transition characteristics were determined using a Perkin-Elmer DSC 7 in the temperature range from 50 to 190 °C.…”
Section: Methodsmentioning
confidence: 99%
“…Recently, we have shown a facile and versatile synthetic route to acetylene monomers with mesogenic side groups . The polymerization of these monomers is possible with well-defined Schrock -type molybdenum initiators leading to polymers with a relatively narrow molecular-weight distribution. , These initiator systems also give access to the synthesis of random copolymers with nonmesogenic monomers such as 1-octyne. Furthermore, the synthesis of block copolymers is possible as well .…”
The thermal and morphological behavior of the first complete homologous series of liquidcrystalline polyacetylene derivatives has been investigated by means of X-ray diffraction, differential scanning calorimetry, thermogravimetry, and polarizing optical microscopy. The influence of the spacer length on the thermal behavior and on the structure of the mesophases is discussed. All polymers except one form smectic monolayers at room temperature. For one spacer length, the formation of bilayers is observed. Despite the connection of the mesogens to the stiff, conjugated polymer main chain, most polymers exhibit highly ordered mesophases. Copolymerization of the mesogen-containing monomers with 1-octyne leads to a decrease of the supramolecular order with an increasing amount of comonomer in the polymer and finally to the formation of a new phase.
“…In contrast to the ruthenium systems, polymerization of acetylenes with catalysts based upon tungsten and molybdenum has been known for years. − To get access to a detailed study on the reaction mechanism, we decided to use well-defined Schrock-type initiators of the general formula Mo(CHR‘)(NAr)(OR) 2 (formula 2). These types of carbenes have already been shown to initiate the polymerization of acetylene monomers. − Ligands and abbreviations of the respective derivatives are listed in Table . …”
The polymerization of acetylene monomers using homogeneous Schrock-type initiators of
the general formula Mo(CHR‘)(NAr)(OR)2 with different substitution patterns was investigated. The
influence of the ligands at the molybdenum center and of donor functions at the β-position with respect
to the monomer's triple bond on the polymerization was studied by means of NMR spectroscopy and size
exclusion chromatography. The results clearly indicate that kinetics and mechanism of the metathesis
reaction strongly depend on the structures of monomer and initiator. The use of partially fluorinated
alkoxy ligands instead of aliphatic alkoxides leads to a change of the regiochemistry of the insertion.
Ether functions in the monomer tend to slow the reaction, giving rise to polymers with a narrow molecular
weight distribution probably due to coordination of the oxygen atom to the metal center.
“…Recently, we could show 36,37) that the polymerization of acetylene monomers is possible with the well-defined Schrock-type molybdenum initiator Mo(CH-t-Bu)(NAr)-(O-t-Bu) 2 1 with NAr = 2,6-diisopropylaniline.…”
SUMMARY: We report the synthesis and characterization of block copolymers of mesogenic acetylene and norbornene moieties. As monomers, a norbornene derivative with cyanostilbenyl side groups and an acetylene derivative with a cholesteryl group were used. The almost quantitative polymerization is initiated with the well-defined Schrock-type molybdenum carbene Mo(CH-t-Bu)(NAr)(O-t-Bu) 2 with NAr = 2,6-diisopropylaniline, t-Bu = tert-butyl. Polydispersity indices (PDIs) in the range of 2 for the block copolymers are obtained. The thermal and morphological behaviour of the polymers is characterized by means of differential scanning calorimetry (DSC) and X-ray diffraction. Both homo-and copolymers form thermotropic mesophases, the acetylene polymer exhibiting a smectic A phase, while the polynorbornene is nematic. The block copolymer shows microphase separation retaining the homopolymers' mesophases. To our knowledge, the materials presented here are the first example of phase-separated block copolymers of two side chain liquid crystalline polymers.
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