Side-chain Liquid Crystalline Diblock Research Articles

Design, synthesis, and phase behaviors of a novel triphenylene-based side chain liquid crystalline diblock copolymer

Influence of the weight fraction of PMT6S on the phase behaviors of diblock copolymers.

Synthesis of azobenzene‐containing side chain liquid crystalline diblock copolymers using RAFT polymerization and photo‐responsive behavior

ABSTRACTWell‐defined azobenzene‐containing side chain liquid crystalline diblock copolymers composed of poly[6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl methacrylate] (PAzoMA) and poly(glycidyl methacrylate) (PGMA) were synthesized by a two‐step reversible addition–fragmentation chain transfer polymerization (RAFT). The thermal liquid‐crystalline phase behavior of the PGMA‐b‐PAzoMA diblock copolymers in bulk were measured by differential scanning calorimetry (DSC) and polarized light microscopy (POM). The synthesized diblock copolymers exhibited a smectic and nematic liquid crystalline phase over a relatively wide temperature range. With increasing the weight fraction of the PAzoMA block, the phase transition temperatures, and corresponding enthalpy changes increased. Atomic force microscope (AFM) measurements confirmed the formation of the microphase separation in PGMA‐b‐PAzoMA diblock copolymer thin films and the microphase separation became more obvious after cross‐linking the PGMA block. The photochemical transition behavior of the PGMA‐b‐PAzoMA diblock copolymers in solution and in thin films were investigated by UV–vis spectrometry. It was found that the trans–cis isomerization of diblock copolymers was slower than that of the corresponding PAzoMA homopolymer and the photoisomerization rates decreased with increasing either the length of PAzoMA block or PGMA block. The photo‐induced isomerization in solid films was quite different with that in CHCl3 solution due to the aggregation of the azobenzene chromophore. The cross‐linking structures severely suppressed the photoisomerization of azobenzene chromophore. These results may provide guidelines for the design of effective photo‐responsive anisotropic materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2165–2175, 2013

Normally Oriented Cylindrical Nanostructures in Amphiphilic PEO–LC Diblock Copolymers Films

The amphiphilic diblock copolymers consist of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) having azobenzenes as mesogen units in the side chain afford highly ordered phase-segregated nanostructures, in which PEO cylindrical domains are hexagonally arranged and normally oriented in PMA matrix in the thin films. The liquid crystalline ordering in the strongly segregated block copolymers plays one of the most important roles to attain such an excellent arrangement of the nanostructure, potentially leading to practical use. In order to elucidate the role of the mesogen units in the side chain of the PMA segment, a new series of amphiphilic liquid crystalline diblock copolymers were synthesized to tune molecular interaction between mesogen units in liquid crystalline segments by using azobenzene, benzylideneaniline, and stilbene as mesogen cores. All the side-chain liquid crystalline diblock copolymers exhibited smectic phase and gave hexagonally arranged cylindrical nanostructures in the bulk pell...

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

AbstractA 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

Understanding and controlling the morphology of styrene–isoprene side-group liquid crystalline diblock copolymers

In side-chain liquid crystalline diblock copolymers, driving forces for ordering of the material may be provided by the chemical incompatibility between the blocks and by the liquid crystalline nature of one of the blocks. We study the microstructure and its development from initially isotropic solutions in side-group liquid crystalline copolymers based on styrene–isoprene diblocks. Hierarchical structure from the 5Å to the 500Å length scale is observed, the product of coherent block copolymer microphase separation and liquid crystalline mesophase formation. The presence of cylindrical microdomains of either the poly(isoprene-LC) or poly(styrene) block markedly increased the thermal stability of the LC. Confinement of the LC to cylindrical microdomains strongly inhibited defect formation within the mesophase after suitable orientation and thermal treatment, readily manifested by the significantly improved optical clarity of these samples versus LC matrix or LC lamellar samples. We consider the relative stabilities of parallel–transverse, perpendicular–parallel, parallel–parallel and transverse–perpendicular arrangements of the microdomain and mesophase structures in interpreting the development of structure in these materials under oscillatory shear.

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

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTMesogen Orientation within Smectic C* Side Chain Liquid Crystalline Diblock CopolymersWen-Yue Zheng, Ramon J. Albalak, and Paula T. HammondView Author Information Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 Cite this: Macromolecules 1998, 31, 8, 2686–2689Publication Date (Web):March 26, 1998Publication History Received29 August 1997Revised26 January 1998Published online26 March 1998Published inissue 1 April 1998https://doi.org/10.1021/ma971303pCopyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views321Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (59 KB) Get e-AlertsSUBJECTS:Chromatography,Copolymers,Layers,Liquid crystals,Polymers Get e-Alerts

Phase Behavior of New Side Chain Smectic C* Liquid Crystalline Block Copolymers

The liquid crystalline and microphase behavior of new chiral side chain liquid crystalline diblock copolymers is described. The materials, which contain a smectic C* mesogen, are block copolymers of polystyrene and methacrylates containing (s)-2-methyl-1-butyl-4‘-(((4-hydroxyphenyl)carbonyl)oxy)-1,1‘-biphenyl-4-carboxylate mesogens. The influences of the liquid crystalline (LC) mesophase on block copolymer ordering and of the block copolymer morphology on LC properties as a function of molecular weight and block copolymer composition are discussed. Microphase segregated structures were observed for blcok copolymers ranging from 24 to 63% w/w LC block. The lamellar domains of the block copolymers stabilize the layered smectic mesophase, particularly the smectic C* phase. The length of the polystyrene block, as well as the LC block, affected LC phase transition temperatures, probably due to phase mixing and the nature of the block copolymer interface. When the molecular weight is low, and the liquid crystal block content is high, the order−disorder transition temperature, at which block copolymer phase segregation is observed, and the LC clearing point occur at the same temperature; this correlation between LC order and the ODT has not been reported before for LC side chain block copolymers. The block copolymer morphology in these cases is arranged to accommodate the focal conic superstructure seen in optical micrographs of this LC block copolymer.