Unusual phase behavior of some poly(dialkoxyphosphazenes)

Папков, В. С.; Il’ina, M. N.; Zhukov, V. P.; Tsvankin, D.Ya.; Tur, D. R.

doi:10.1021/ma00033a030

Cited by 37 publications

(33 citation statements)

References 3 publications

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“…144-150°C (<0,1 mm) ' ). I3C NMR (63 MHz): 6 = l19,51 (C4 '),26,[15][16][17][18][19][20][21][22][23][24][25][26]13,25,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]72 (C2,C3),20,31,19,54 (CT,C3'),15,55 (Cl,Cl'),13,68 (C4). a) Distillation of the apolar fraction yielded 12,7 g (60,9%) hexabutylcyclotrisiloxane (purity 99,7% GLC); b.p.…”

Section: Pentabutyl(3-cyanopropyl)cyclotrisiloxane (1) 12)mentioning

confidence: 99%

Columnar mesophase behaviour of poly(dibutylsiloxane) and related copolymers containing polar substituents

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Schlössels

Turetskii

et al. 1995

Macro Chemistry & Physics

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SUMMARYThe columnar mesophase formation of poly(dibutylsi1oxane) (PDBS) was studied with respect to the influence of molecular weight. Additionally, the synthesis of random copolymers containing dibutylsiloxane and butyl(3-cyanopropyl)siloxane units was performed in order to examine the influence of side group polarity on the columnar mesophase behaviour without disturbing the overall molecular geometry. Introduction of 6% 3-cyanopropyl groups appeared to hinder crystallization while copolymers containing 17% 3-cyanopropyl groups did not show crystallization at all. All copolymers formed a columnar mesophase which seemed to gain stability from the presence of the polar substituents.

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Section: Pentabutyl(3-cyanopropyl)cyclotrisiloxane (1) 12)mentioning

confidence: 99%

Columnar mesophase behaviour of poly(dibutylsiloxane) and related copolymers containing polar substituents

Out

Schlössels

Turetskii

et al. 1995

Macro Chemistry & Physics

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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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“…[1,11] Moreover, investigations of the temperature dependence of the intrinsic viscosity [g] were carried out to clear up the role of long-range interactions in PPhPh macromolecules. It was shown experimentally [3,6] that, using such an analysis, additional information could be obtained about the influence of short-and long-range interactions on the macromolecular conformation. For real polymer solutions, according to the Flory equation,…”

Section: Resultsmentioning

confidence: 99%

“…The FB method is used for the determination of the value Dn of solution flow birefringence, which is directly related to the optical anisotropy of the macromolecule, being characterized by the difference (a 1 -a 2 ) between the macromolecular polarizabilities along the backbone (a 1 ) and perpendicular to it (a 2 ). The details of the FB investigation in PPhPh solutions have been described earlier, [4,6,8] and the results obtained are summarized in Table 1 and 2. The macroscopic value characterizing FB is the optical shear coefficient which is equal to…”

Section: Optical Properties Derived From Flow Birefringence Datamentioning

confidence: 99%

“…[4,5] The phase transitions in PPhPh and the side-chain length influence on mesophase formation were also studied, and different models of backbone and side-chain packing were examined. [6] Experimental Part All PPhPh molecules were synthesized by the condensation of linear poly(dichlorophosphazene) with the corresponding sodium fluoroalcoholate. [4] Fractionation of PPhPh was performed by distribution between two liquid phases in the systems.…”

Section: Introductionmentioning

confidence: 99%

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Equilibrium Rigidity of Polyorganophosphazene Molecules

Shtennikova¹,

Kolbina

Bushin

et al. 2001

Macromol. Chem. Phys.

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The optical anisotropy and orientation angles of polyorganophosphazene (PPhPh) molecules with different lengths and side‐chain structures have been investigated by flow birefringence and viscosimetry methods. Quantum‐chemical calculations of the optical anisotropy per monomer unit within the polymer fragments with different conformations were carried out. It was shown that both short‐range and long‐range interactions (i. e. the structure of the polymer backbone and steric interactions between side chains) influenced the conformation of the PPhPh molecules and should be taken into account for the determination of the thermodynamic rigidity value A. The experimental value of A, (50 ± 5)·10–8 cm, obtained by different methods, adequately corresponds to the structure and observed physical parameters of the PPhPh molecules. Molecules of this class of polymers are not rigid chains in a common way (A > 150·10–8 cm), but alternating double bonds of their backbones bring about some increase in the equilibrium rigidity. It can be assumed that, for this class of polymers, the mesogeneity on a molecular level is defined by the strong interactions of fluorine‐containing side chains rather than by the rigidity of their backbones.

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Unusual phase behavior of some poly(dialkoxyphosphazenes)

Cited by 37 publications

References 3 publications

Columnar mesophase behaviour of poly(dibutylsiloxane) and related copolymers containing polar substituents

Columnar mesophase behaviour of poly(dibutylsiloxane) and related copolymers containing polar substituents

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

Equilibrium Rigidity of Polyorganophosphazene Molecules

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