Mesogen Orientation within Smectic C* Side Chain Liquid Crystalline Diblock Copolymers

Zheng, Wenyue; Albalak, Ramon J.; Hammond, Paula T.

doi:10.1021/ma971303p

Cited by 45 publications

(58 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[5][6][7] The coil-coil diblock copolymers can self-assemble to form a variety of morphological structures such as lamellae, bicontinuous double gyroid, hexagonally packed cylinders, and body centered cubic arrays of spheres depending on these parameters. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] LC/I block copolymers can form microphase-separated morphologies with coexisting anisotropic and isotropic phases. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] LC/I block copolymers can form microphase-separated morphologies with coexisting anisotropic and isotropic phases.…”

Section: Introductionmentioning

confidence: 99%

“…[8][9][10][11][12][13] Block copolymers composed of both liquid crystalline (LC) and isotropic (I) blocks have attracted considerable recent research interest because of the ordering at two different scales and unique functions. 10,11,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Azobenzene and its derivatives have been widely used as functional groups to develop materials with various photoresponsive properties. The LC blocks of the copolymers form the ordered subphase because of anisotropic alignment of the mesogens.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Diblock copolymers composed of a liquid crystalline azo block and a poly(dimethylsiloxane) block: synthesis, morphology and photoresponsive properties

Wei

Wang

2014

RSC Adv.

View full text Add to dashboard Cite

A series of diblock copolymers, composed of a soft poly(dimethylsiloxane) (PDMS) block with a defined length and a liquid crystalline poly(6-(4-(4 0 -cyanophenylazo)phenoxy)hexyl acrylate) (POCN) block with different lengths, was synthesized by the atom transfer radical polymerization (ATRP). A homopolymer POCN was also prepared by the same method for comparison. The polymer structures, liquid crystalline phase, microphase-separated morphology, and photoisomerization were then investigated by 1 H NMR, FT-IR, GPC, UV-Vis, POM, DSC, XRD and TEM. The results showed that the well-defined diblock copolymers (PDMS n -b-POCN m ) possess four different soft/rigid ratios (n ¼ 58, m ¼ 8, 15, 24, 36) and relatively narrow molecular distributions (PDI # 1.30). POCN blocks of the copolymers form a smectic-A sub-phase, which is identical to the mesomorphic behaviour of POCN. After being annealed at 140 C in a vacuum for 24 h, the copolymers form a lamellar morphology when W PDMS is 42.3-57.8% and a morphology of PDMS spheres embedded in an azo matrix when W PDMS is 23.3-31.4%. POCN and PDMS n -b-POCN m in solution show typical photoisomerization behaviour of the azobenzene moieties. Although H-aggregation is observed to a certain extent, photochemical processes of the as-cast films of the polymers are similar to those of the solutions. On the other hand, the photoisomerization behaviour of annealed PDMS n -b-POCN m films is significantly different from that of the annealed POCN film, which is closely correlated with the phase-separated morphologies. The observations can provide deep understanding of the phase-separated structures and be used to develop new materials. † Electronic supplementary information (ESI) available: More results of the syntheses, characterization, TEM images and the cis-trans isomerization kinetics of the solution and lms of the azo polymers can be seen there. See

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diblock copolymers composed of a liquid crystalline azo block and a poly(dimethylsiloxane) block: synthesis, morphology and photoresponsive properties

Wei

Wang

2014

RSC Adv.

View full text Add to dashboard Cite

show abstract

“…[19,20] They found that LC BCPs bearing a short hexyl spacer between the mesogen and the polymer backbone exhibited perpendicular orientation of the smectic layers, whereas LC BCPs bearing a longer decyl spacer led to parallel orientation in roll-cast films. In meltdrawn fibers, on the contrary, only perpendicular orientation was observed.…”

mentioning

confidence: 99%

Directing the Smectic Layer Orientation by Shear Flow in Hierarchical Lamellar‐within‐lamellar Liquid Crystalline Diblock Copolymers

Laiho

Hiekkataipale

Ruokolainen

et al. 2009

Macro Chemistry & Physics

View full text Add to dashboard Cite

A self‐assembled lamellar‐within‐lamellar structure of a side chain liquid crystalline diblock copolymer was shear aligned to induce overall alignment and to direct the smectic layer orientation within the copolymer lamellae. The copolymer consisted of a polystyrene block and a poly(methyl methacrylate) block bearing cholesteryl mesogens with only short oxycarbonyloxyethyl spacers separating the mesogens from the backbone. Upon shearing, the copolymer lamellae exhibited uniaxial alignment whereas the smectic layers of the mesogens showed coexisting perpendicular and parallel orientations with respect to the copolymer lamellae. The fraction of the parallel oriented domains could be systematically increased by tuning the oscillation frequency and strain amplitude.magnified image

show abstract

“…The interplay of the two self-assembly processes and the consequences thereof on the structure-property relationships in these materials has been well studied by other workers in this field, 6-10 including work on mechanical shear alignment. 11,12 …”

mentioning

confidence: 99%

Alignment of Self-Assembled Hierarchical Microstructure in Liquid Crystalline Diblock Copolymers Using High Magnetic Fields

et al. 2004

View full text Add to dashboard Cite

Large area microdomain alignment in a ferroelectric liquid crystalline diblock copolymer (LCBCP) poly(styrene)-block-poly(isoprene-LC), (PS-PILC), incorporating a biphenyl 3-nitro-4-alkoxybenzoate LC mesogenic group and a non-LC block hexagonally packed cylinder microstructure, was successfully accomplished by application of a magnetic field at elevated temperatures. Small-and mediumangle X-ray scattering demonstrated that the PS cylinders in the LC matrix orient over large areas with their long axes perpendicular to the applied magnetic field. Correspondingly, the smectic layers of the LC mesophase in the matrix are also perpendicular to the field as the anchoring of the mesogens at the intermaterial dividing surface (IMDS) between the cylindrical microdomains and the matrix is planar (homogeneous) in this material. A negative diamagnetic anisotropy for the LC mesogens is inferred from the data. A lamellar sample was also studied and found to exhibit no preferred microstructural orientation when subjected to the magnetic field. This result is consistent with the orientational state degeneracy of planar anchoring of mesogens at the flat lamellar IMDS and closely parallels our prior results obtained by orientation of nonferroelectric LCBCPs using oscillatory shear. IntroductionIncreasingly, research on the structure of soft matter has focused not just on the physics of the self-assembly of interesting materials, but on methods to control and direct the formation of the structures themselves, whether by understanding and directly manipulating the physics of self-assembly in the materials 1-4 or simply by empirically searching for useful process conditions. Structure-property-processing relationships in novel and emerging classes of soft materials are, more and more, highlighted by a comprehensive understanding of structure on the micro-and nanoscales.Block copolymers, while not entirely new and unknown materials, still do represent one such class of soft mattersmany demonstrate great promise as materials for application in various macroscopic as well as microscopic technologies, 5 and their performance is often greatly affected by both their rich structure on the micron scale and at the microdomain level. Thus, methods are sought to control and produce globally wellaligned microstructure in these materials. Liquid crystalline block copolymers incorporate the mesoscale selfassembly of mesogenic units within the broader context of microphase separation and block microdomain formation. The interplay of the two self-assembly processes and the consequences thereof on the structure-property relationships in these materials has been well studied by other workers in this field, 6-10 including work on mechanical shear alignment. 11,12

show abstract

Mesogen Orientation within Smectic C* Side Chain Liquid Crystalline Diblock Copolymers

Cited by 45 publications

References 21 publications

Diblock copolymers composed of a liquid crystalline azo block and a poly(dimethylsiloxane) block: synthesis, morphology and photoresponsive properties

Diblock copolymers composed of a liquid crystalline azo block and a poly(dimethylsiloxane) block: synthesis, morphology and photoresponsive properties

Directing the Smectic Layer Orientation by Shear Flow in Hierarchical Lamellar‐within‐lamellar Liquid Crystalline Diblock Copolymers

Alignment of Self-Assembled Hierarchical Microstructure in Liquid Crystalline Diblock Copolymers Using High Magnetic Fields

Contact Info

Product

Resources

About