Columnar mesophase behavior of Poly(Di-n-alkylsiloxane)s

Molenberg, Aart; ̈ller, Martin Mo; Sautter, E.

doi:10.1016/s0079-6700(97)00019-1

Cited by 32 publications

(42 citation statements)

References 61 publications

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“…Columnar phases appear in such flexible polymers with the mesomorphic phases originating from the parallel alignment of polymer chains. This kind of self-assembly behavior is quite similar to that of poly(di-n-alkylsiloxane)s, 117,118 poly(di-nalkoxyphosphazene)s, and other alkyl substituted polysilane, polypeptide, and cellulose polymers. 119 In this case, although the polymer chains are stretched, both the backbone and the alkyl side chains are conformationally disordered.…”

Section: Phase Identificationsupporting

confidence: 56%

Mesogen-jacketed liquid crystalline polymers

et al. 2010

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This critical review covers the recent progress in the research of mesogen-jacketed liquid crystalline polymers (MJLCPs), special side-on side-chain liquid crystalline polymers with very short spacers or without spacers. MJLCPs can self-organize into supramolecular columnar phases with the polymer chains aligned parallel to one another or smectic phases with the backbones embedded in the smectic layers. The semi-rigid rod-like MJLCP with a tunable rod shape in both length and diameter provides an excellent building block in designing novel rod-coil liquid crystalline block copolymers which can self-assemble into hierarchical supramolecular nanostructures depending on the competition between liquid crystal formation and microphase separation (229 references).

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Section: Phase Identificationsupporting

confidence: 56%

Mesogen-jacketed liquid crystalline polymers

et al. 2010

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“…All the CLPOS investigated have mesophases 29 in which the chains have an extended conformation. 30 Similar chain conformations have been observed for the mesophase of linear poly-(diethylsiloxane) (PDES) for which transmission electron microscopy 31,32 and SFM 33 show a lamellar structure. The width of the lamellae is in good agreement with estimates of the length of an extended chain.…”

Section: Discussionmentioning

confidence: 68%

“…The width of the lamellae is in good agreement with estimates of the length of an extended chain. Lamellae with two different widths are found in samples with a bimodal molecular weight distribution …”

Section: Discussionmentioning

confidence: 99%

Stepwise Collapse of Monolayers of Cyclolinear Poly(organosiloxane)s at the Air/Water Interface: A Brewster-Angle Microscopy and Scanning Force Microscopy Study

Бузин¹,

Godovsky²,

Макарова³

et al. 1999

J. Phys. Chem. B

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We report studies of the collapse of monolayers of cyclolinear poly(organosiloxane)s that consist of six-membered rings joined by oxygen bridges and that contain two phenyl groups per monomer unit. Surface pressure−area isotherms show that these films undergo a stepwise collapse. The organization within the films has been examined at different stages of the collapse process by Brewster-angle microscopy. Films transferred to mica by the Langmuir−Blodgett technique have been imaged by scanning force microscopy. Five fractions of an atactic polymer with molecular weights (M W) ranging from 8900 to 85 000 and one trans-tactic polymer (M W = 8100) have been investigated. Bilayers of the fractions with the highest M W's appear in the form of islands but the bilayers in the other samples have the form of ribbons 50−250 nm wide.

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“…In this respect, MJLCPs are similar to flexible polymer poly(dialkylsiloxanes) and poly-(di-n-alkoxyphosphazenes) exhibiting a mesomorphic state with no mesogens. [8][9][10][11] The LC phase structures of MJLCPs are identified as columnar nematic phase, 12 hexagonal columnar nematic phase, 13 and hexagonal columnar LC phase 6,7 in which each cylinder is formed by a single MJLCPs chain molecule. 13 Recently, we have observed that the LC phase of some MJLCPs does not appear immediately above glass transition, and the intensity of WAXD decreased on the cooling.…”

Section: Introductionmentioning

confidence: 99%

Unusual Phase Behavior of a Mesogen-Jacketed Liquid Crystalline Polymer Synthesized by Atom Transfer Radical Polymerization

et al. 2006

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A series of mesogen-jacketed liquid crystalline polymers, poly{2,5-bis[(4-butoxyphenyl)oxycarbonyl]-styrenes} (PBPCS), with a wide range of molecular weights (M n ) 1.24 × 10 4 -35.6 × 10 4 ) and narrow molecular weight distributions (M w /M n e 1.18) have been synthesized by atom transfer radical polymerization. The resulting polymers have been investigated by a combination of techniques including differential scanning calorimetry, polarized optical microscopy, and X-ray scattering. The samples with M n e 2.42 × 10 4 are isotropic. The samples with M n g 3.36 × 10 4 display a thermodynamically stable isotropic phase at lower temperature and a liquid crystalline (LC) phase at higher temperature. The phase behavior shows a phenomenon quite similar to the reentrant isotropic phase. These transitions are correlated with the rheological properties measured as a function of temperature. The rheological behavior of the polymer in the isotropic phase and in the LC phase has been studied as well. On the basis of these experimental observations, a generalized phase diagram is constructed for the polymers showing the influence of the molecular weight on the phase transition temperature. It is illustrated that LC phase is formed through a global change of the whole molecule from the coiled to extended chain conformation accompanied by an increase of the entropy. Higher entropy originating from the free mobilities of bulky side chains in LC phase has been proposed to be an important factor to stabilize the LC phase.

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Columnar mesophase behavior of Poly(Di-n-alkylsiloxane)s

Cited by 32 publications

References 61 publications

Mesogen-jacketed liquid crystalline polymers

Mesogen-jacketed liquid crystalline polymers

Stepwise Collapse of Monolayers of Cyclolinear Poly(organosiloxane)s at the Air/Water Interface: A Brewster-Angle Microscopy and Scanning Force Microscopy Study

Unusual Phase Behavior of a Mesogen-Jacketed Liquid Crystalline Polymer Synthesized by Atom Transfer Radical Polymerization

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