Crystal structure and mesophase morphology of MBPE polyethers containing odd‐number methylene spacers

Chen, Jianhua; Zhang, Anqiu; Yandrasites, Michael A.; Cheng, Stephen Z. D.; Percéc, Virgil

doi:10.1002/macp.1993.021941117

Cited by 6 publications

(5 citation statements)

References 25 publications

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“…The band width is a few micrometers. The formation of this banded texture is due to the relaxation of the oriented fluid samples and is a typical characteristic of a low-ordered N or smectic LC polymer phase [20][21][22][23] . As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Phase structures, transition behavior and surface alignment in polymers containing rigid rod-like backbones with flexible side chains, 3. The even-odd effect on phase transitions in combined liquid crystal polyesters

Ge¹,

Honigfort²,

Ho³

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: A series of "combined" liquid crystal (LC) polyesters consisting of aromatic main-chain backbones and flexible aliphatic side chains with 4-cyanobiphenyl end groups was synthesized based on the polycondensation of 2,29-bis(trifluoromethyl)-4,49-biphenyldicarbonyl chloride with 2,29-bis{x-[4-(4-cyanophenyl)phenoxy]-n-alkoxycarbonyl]}-4,49-biphenyldiol (PEFBP). In a recent study of PEFBP(n = 11) containing eleven methylene units in the side chains, four different phases were identified in addition to the isotropic melt (I). They are as follows: an orthorhombic crystalline (K O ) phase, two triclinic crystalline (K T1 and K T2 ) phases in the high temperature region, and a nematic (N) phase. In this report, we focus on the even-odd effect of the methylene units in the side chains on the phase structure and transition behavior of PEFBP(n = 8, 9, 10 and 11)s. Two even-numbered PEFBPs with either eight or ten methylene units in the side chains [PEFBP(n = 10 and 8)s] were studied. An odd-numbered PEFBP containing nine methylene units, PEFBP(n = 9), was also investigated in addition to PEFBP(n = 11) which was reported on previously 1,2) . It was found that both of the PEFBPs with even-numbered methylene units in their side chains [PEFBP(n = 10 and 8)s] exhibit only a nematic and a smectic A (S A ) phase. Their phase transition sequence during heating and cooling is T g (S A LC glass) e E S A e E N e E I Since only LC phases exist, this is a thermodynamically reversible transition sequence independent upon thermal history. For PEFBP(n = 9 and 11)s, crystalline phases with three-dimensional order are observed above the NLC glass transition temperature in addition to the N phase. In PEFBP(n = 9), the N and K O phases are similar to those seen in the case of PEFBP(n = 11). However, this polymer presents only one triclinic crystalline phase, while two triclinic crystal phases are observed in PEFBP(n = 11). The phase transition sequence in these odd-numbered PEFBPs during heating between 2.5 8C/min -10 8C/min for a sample cooled from the isotropic melt at the same rate isNevertheless, this sequence does not represent a case of thermodynamic equilibrium. The K O and K T (s) phases in PEFBP(n = 9 and 11)s and the S A phase in PEBFP(n = 8 and 10)s are characteristics of the evenodd effect observed in this series of combined LC polyesters. The number of methylene units in the side chains thus plays a critical role in the formation of phase order and transition behavior in a way quite different from the common even-odd effect seen in main-chain LC polymers. Furthermore, this effect also indicates that the 4-cyanobiphenyl groups in the side chains are incorporated with the main-chain backbones to form the liquid crystal and crystal phases.

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Section: Resultsmentioning

confidence: 99%

Phase structures, transition behavior and surface alignment in polymers containing rigid rod-like backbones with flexible side chains, 3. The even-odd effect on phase transitions in combined liquid crystal polyesters

Ge¹,

Honigfort²,

Ho³

et al. 1999

Macromol. Chem. Phys.

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“…However, after the mechanical shearing and slight relaxation banded textures can be found in TPP( n ≤13)s. This banded texture which has a spacing of about 1 μm is perpendicular to the shear direction (Figure b). The fact that banded texture appears under an external force field has been viewed as a typical orientationally ordered liquid crystalline polymer pattern in the N, S A , or S C phase. ,− Microscopic analysis has shown that, in the banded texture, the director continuously oscillates spatially about the direction imposed by the previous flow. On the other hand, Figure c shows no clear banded texture under PLM.…”

Section: Resultsmentioning

confidence: 99%

“…The fact that banded texture appears under an external force field has been viewed as a typical orientationally ordered liquid crystalline polymer pattern in the N, S A , or S C phase. 6,[19][20][21] Microscopic analysis has shown that, in the banded texture, the director continuously oscillates spatially about the direction imposed by the previous flow. On the other hand, Figure 11c shows no clear banded texture under PLM.…”

Section: Resultsmentioning

confidence: 99%

Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structures. 1. Phase Diagrams of Odd-Numbered TPP Polyethers

Yoon¹,

Zhang²,

Ho³

et al. 1996

Macromolecules

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A series of liquid crystalline polyethers has been synthesized from 1-(4-hydroxy-4‘-biphenylyl)-2-(4-hydroxyphenyl)propane and α,ω-dibromoalkanes [TPP(n)]. From the differential scanning calorimetry experiments, the TPP(n=odd)s show multiple phase transitions during cooling and heating. For each TPP(n=odd) the supercooling dependence of these transitions is found to be small. A phase diagram of the transition temperatures and the enthalpy and entropy changes of the transitions with respect to the number of methylene units (n) for TPP(n=odd)s have been obtained. Analyses have been conducted regarding the contributions of both the mesogenic groups and the methylene units to the differently ordered structures. Identification of the ordered structures in each phase has been carried out by combining wide angle X-ray powder and fiber diffraction experiments at different temperatures with polarized light and transmission electron microscopy experiments on the liquid crystal morphology and defects. It is found that for TPP(n≤13)s the highest temperature transition is from the isotropic melt to a nematic phase. However, for TPP(n≥15)s, the isotropic melt directly converts to a smectic F phase having a monoclinic unit cell (a pseudohexagonal packing tilted toward a side). The WAXD fiber patterns for this phase show that the chain orientation is parallel to the fiber direction. For TPP(n≤13)s formation of a smectic F phase with a monoclinic unit cell from the nematic phase can also be determined and the WAXD fiber pattern shows that the chain orientation is at an angle ranging between 0 and 20° with respect to the fiber direction. With an increase in the number of methylene units, this angle gradually decreases until n = 15, where this angle becomes zero. Further cooling leads to a smectic crystal G phase for all TPP(n=odd)s, and the different chain orientations with respect to the fiber direction in the WAXD fiber patterns still exist. TPP(n≤9)s remain in the smectic crystal G phase down to their glass transition temperatures, while TPP(n≥11)s form a smectic crystal H phase (a tilted herringbone, orthorhombic packing tilted toward the b-axis side, and a > b) in a low temperature range.

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“…5e). 45,46 Therefore, it is apparent that the structural transition between the spheres and cylinders oscillates within the solvent treatment time studied. Similar observations are found within the terrace of the T 2 layer as shown in Fig.…”

Section: Solvent Annealed Morphologymentioning

confidence: 92%

Phase structural formation and oscillation in polystyrene-block-polydimethylsiloxane thin films

Hsieh

Sun

et al. 2012

Soft Matter

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The solvent-induced spherical structure in a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) block copolymer was obtained and stabilized by preparing both the bulk and thin films from propylene glycol methyl ether acetate (PGMEA) solutions. The diblock copolymer possessed a total molecular weight of 42 kDa with a PS volume fraction of 72.2%, and it formed a cylindrical phase structure in the equilibrium bulk state. During thermal annealing, only changes in the sphere size and packing rearrangement were found. In contrast, a unique structure evolution route was observed during solvent treatments. Under a controlled vapour of a PS selective solvent, an oscillation of the structural transition between spheres and cylinders was observed in the thin films. The kinetics of this oscillation of structural transition was found to be closely related to the solvent vapour concentration and film thickness. This experiment revealed a unique ordering pathway towards the equilibrium structure in the thin film for this strongly segregated PS-b-PDMS diblock copolymer.

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Crystal structure and mesophase morphology of MBPE polyethers containing odd‐number methylene spacers

Cited by 6 publications

References 25 publications

Phase structures, transition behavior and surface alignment in polymers containing rigid rod-like backbones with flexible side chains, 3. The even-odd effect on phase transitions in combined liquid crystal polyesters

Phase structures, transition behavior and surface alignment in polymers containing rigid rod-like backbones with flexible side chains, 3. The even-odd effect on phase transitions in combined liquid crystal polyesters

Phase Identification in a Series of Liquid Crystalline TPP Polyethers and Copolyethers Having Highly Ordered Mesophase Structures. 1. Phase Diagrams of Odd-Numbered TPP Polyethers

Phase structural formation and oscillation in polystyrene-block-polydimethylsiloxane thin films

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