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Many sophisticated chiral materials are found in living organisms, giving specific functions and required complexity. Owing to the remarkable optical properties of chiral materials, they have drawn significant attention for the development of synthetic materials to give optical activities for appealing applications. In contrast to a top-down approach, the bottom-up approach from self-assembled systems with chiral host-achiral guest and achiral guest-chiral host for induced circular dichroism and induced circularly polarized luminescence has greatly emerged because of its cost-effective advantage with easy fabrication for mesoscale assembly. Self-assembled hierarchical textures with chiral sense indeed give significant amplification of the dissymmetry factors of absorption and luminescence (g

Herein, we suggest a unique approach to control the handedness of twisted lamellae in banded spherulites of a stereoregular polymer, isotactic poly(2-vinylpyridine) (iP2VP). When (R)- or (S)-hexahydromandelic acid (HMA), which can associate with iP2VP, was introduced as a chiral dopant, mirror-image CD spectra in the complex systems showed induced circular dichroism (ICD) of the iP2VP by chiral HMA. Banded spherulites resulting from lamellar twisting due to the imbalanced stresses at the opposite folding surfaces could be formed by crystallization of the iP2VP/HMA complexes, which had a crystalline structure similar to that of neat iP2VP. A preferential sense of the twisted crystalline lamellae was found in the iP2VP/HMA complex, thus suggesting homochiral evolution from conformational to hierarchical chirality.

Banded spherulites are formed by crystallization of a chiral polymer that is end-capped with chromophore. Induced circular dichroism (ICD) of the chromophore can be found in the crystallized chiral polymers, giving exclusive optical response of the ICD. The ICD signals are presumed to be driven by the lamellar twisting in the crystalline spherulites, and the exclusive optical activity is attributed to the chirality transfer from molecular level to macroscopic level. To verify the suggested mechanism, the sense of the lamellar twisting in the crystalline spherulite is determined using PLM for the comparison with the ICD signals of the chromophore in the electron circular dichroism spectrum. The conformational chirality of the chiral polymer is determined by the vibrational circular dichroism spectrum. On the basis of the chiroptical results, evolution of homochirality from helical polymer chains (conformational chirality) to lamellar twisting in the banded spherulite (hierachical chirality) is suggested.

Herein, two asymmetric chiral bent-core molecules, 3-((4-{(4- (heptyloxy)benzoyl)oxy}benzoyl)oxy)- phenyl-4-((4-{((1R)-1-methylheptyl)- oxy}benzoyl)oxy) benzoate (BC7R) and 3-((4-{(4-(heptyloxy)benzoyl)oxy}- benzoyl)oxy)-phenyl-4-((4-{((1S)-1- methylheptyl)oxy}benzoyl)oxy) ben- zoate (BC7S), were synthesized to demonstrate control of the helicity of their self-assembled hierarchical super- structures. Mirror-imaged CD spectra showed a split-type Cotton effect after the formation of self-assembled aggre- gates of BC7R and BC7S, thereby sug- gesting the formation of intermolecular exciton couplets with opposite optical activities. Both twisted and helical rib- bons with preferential helicity that cor- responded to the twisting character of the intermolecular exciton couplet were found in the aggregates. The for- mation of helical ribbons was attribut- ed to the merging of twisted ribbons through an increase in width to im- prove morphological stability. As a result, control of the helicity of hier- archical superstructures from the self- assembly of bent-core molecules could be achieved by taking advantage of the transfer of chiral information from the molecular level onto the hierarchical scale.

H.-Y. Hsueh , Prof. R.-M. Ho Department of Chemical EngineeringNational Tsing Hua UniversityHsinchu 30013, Taiwan E-mail: rmho@mx.nthu.edu.tw .-C. Y Huang , Prof. C.-H. Lai Department of Materials Science and EngineeringNational Tsing Hua UniversityHsinchu 30013, Taiwan Makida , . T Prof. H. Hasegawa Department of Polymer ChemistryGraduate School of EngineeringKyoto UniversityNishikyo-ku, Kyoto, 615-8510, Japan

Magnesium (Mg) and zinc (Zn) complexes incorporating tridentate anilido-aldimine ligand, (E)-2, 6-diisopropyl-N-(2-((2-(piperidin-1-yl)ethylimino)methyl)phenyl)aniline (AAPip-H, 1), were synthesized and structurally characterized. The reaction of AAPip-H (1) with MgnBu2 or ZnEt2 in equivalent proportions afforded the monomeric complex [(AAPip)MgnBu] (2) or [(AAPip)ZnEt] (3), respectively. The coordination modes of these complexes differ in the solid state: Mg complex 2 shows a four-coordinated and distorted tetrahedral geometry, whereas Zn complex 3 adopts a trigonal planar geometry with a three-coordinated Zn center. Complexes 2 and 3 are efficient catalysts for the ring-opening polymerization of β-butyrolactone (β-BL) in the presence of 9-anthracenemethanol (9-AnOH). The polymerization of β-BL with the Zn catalyst system is demonstrated in a living fashion with a narrow polydispersity index, PDI = 1.01–1.10. The number-averaged molecular weight (Mn) of the produced poly(3-hydroxybutyrate) (PHB) is quite close to the expected Mn over diverse molar ratios of monomer to 9-AnOH. A greater ratio of monomer to alcohol catalyzed by Zn complex 3 served to form PHB with a large molecular weight (Mn > 60000). An effective method to prepare PHB-b-PCL and PEG-b-PHB by the ring-opening copolymerization of β-BL catalyzed by zinc complex 3 is reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

Inspired by research on organometallics, the incorporation of transition metals into organic derivatives through covalent attachment has become a mature field. Because of improvements in synthesis, the ferrocene-based moiety is now a well-known organometallic moiety. Tunable ferrocene residues provide an attractive method to expand the range of properties. By taking advantage of self-assembly, various self-assembled organometallic morphologies including spheres, cylinders, vesicles, and lamellae with nanoscale iron-rich microdomains can be used in applications such as switches, transistors, and sensors for integration into microelectronic technology. Also, ordered nanostructures transform into semiconducting materials after oxidation and yield iron-rich magnetic ceramics after pyrolysis treatment. Helical morphologies can be obtained from the self-assembly of chiral supramolecules such as chiral liquid crystals, folded oligomers, chiral counterions, chiral dendrimers, dendron rod–coils, chiral homopolymers, chiral block copolymers, and chiral discotic molecules. In our previous studies, the self-assembly of a series of chiral Schiff based rod–coil amphiphiles was systematically examined. The self-assembled helical superstructures could be induced by chiral sugar, and a morphological transformation from helical to platelet-like morphology was driven by simply increasing the hydrophobic chain length at the chain end of the chiral rod–coil amphiphiles. The helical morphology results from the steric-hindrance effect of the chiral sugar packing in the self-assembly. Herein we aim to create iron-rich spiral superstructures by taking advantage of the self-assembly of chiral Schiff based rod–coil molecules that are end-capped with ferrocene (namely, chiral rod–coil organometallics). Figure 1

Exploring the ordering mechanism and dynamics of self-assembled block copolymer (BCP) thin films under confined conditions are highly essential in the application of BCP lithography. In this study, it is aimed to examine the self-assembling mechanism and kinetics of silicon-containing 3-arm star-block copolymer composed of polystyrene (PS) and poly(dimethylsiloxane) blocks as nanostructured thin films with perpendicular cylinders and controlled lateral ordering by directed self-assembly using topographically patterned substrates. The ordering process of the star-block copolymer within fabricated topographic patterns with PS-functionalized sidewall can be carried out through the type of secondary (i.e., heterogeneous) nucleation for microphase separation initiated from the edge and/or corner of the topographic patterns, and directed to grow as well-ordered hexagonally packed perpendicular cylinders. The growth rate for the confined microphase separation is highly dependent upon the dimension and also the geometric texture of the preformed pattern. Fast self-assembly for ordering of BCP thin film can be achieved by lowering the confinement dimension and also increasing the concern number of the preformed pattern, providing a new strategy for the design of BCP lithography from the integration of top-down and bottom-up approaches.

In this study, a novel perovskite quantum dot (QD) spray-synthesis method is developed by combining traditional perovskite QD synthesis with the technique of spray pyrolysis. By utilizing this new technique, the synthesis of cubic-shaped perovskite QDs with a homogeneous size of 14 nm is demonstrated, which shows an unprecedented stable absolute photoluminescence quantum yield ≈100% in the solution and even in the solid-state neat film. The highly emissive thin films are integrated with light emission devices (LEDs) and organic light emission displays (OLEDs). The color conversion type QD-LED (ccQD-LED) hybrid devices exhibit an extremely saturated green emission, excellent external quantum efficiency of 28.1%, power efficiency of 121 lm W-1 , and extraordinary forward-direction luminescence of 8 500 000 cd m-2 . The conceptual ccQD-OLED hybrid display also successfully demonstrates high-definition still images and moving pictures with a 119% National Television System Committee 1931 color gamut and 123% Digital Cinema Initiatives-P3 color gamut. These very-stable, ultra-bright perovskite QDs have the properties necessary for a variety of useful applications in optoelectronics.

A diblock copolymer system constituting both achiral and chiral blocks, polystyrene-block-poly( L -lactide) (PS-PLLA), was designed for the examination of chiral effects on the self-assembly of block copolymers (BCPs). A unique phase with three-dimensional hexagonally packed PLLA helices in PS matrix, a helical phase (H * ), can be obtained from the self-assembly of PS-rich PS-PLLA with volume fraction of PLLA f v PLLA =0.34, whereas no such phase was found in racemic polystyrene-block-poly( D . L -lactide) (PS-PLA) BCPs. Moreover, various interesting crystalline PS-PLLA nanostructures can be obtained by controlling the crystallization temperature of PLLA (T c , PLLA ), leading to the formation of crystalline helices (PLLA crystallization directed by helical confined microdomain) and crystalline cylinders (phase transformation of helical nanostructure dictated by crystallization) when T C , PLLA < T g ,PS (the glass transition temperature of PS) and Tc,PLLA ≥ T g,PS , respectively. As a result, a spring-like behavior of the helical nanostructure can be driven by crystallization so as to dictate the transformation (i.e., stretching) of helices and to result in crystalline cylinders. For PS-PLLA with PLLA-rich fraction (F v PLLA = 0.65), another unique phase, a hexagonally packed core-shell cylinder phase with helical sense (CS * ), in which the PS microdomains appear as shells and PLLA microdomains appear as matrix and cores, can be found in the self-assembly of PLLA-rich PS-PLLA BCPs. The formation of those novel phases: helix and core-shell cylinder is attributed to the chiral effect on the self-assembly of BCPs, so we named this PS-PLLA BCP as chiral BCP (BCP * ). For potential applications of those materials, the spring-like behavior with thermal reversibility might provide a method for the design of switchable nanodevices, such as nanoscale actuators. In addition, the PLLA blocks can be hydrolyzed. After hydrolysis, helical nanoporous PS bulk and PS tubular texture can be obtained and used as templates for the formation of nano-composites.

The crystallization of helical nanostructure resulting from the self-assembly of a chiral diblock copolymer, poly(styrene)-b-poly(L-lactide) (PS-PLLA), is studied. Various crystalline PS-PLLA nanostructures are obtained by controlling the crystallization temperature of PLLA (T{sub c,PLLA}), at which crystalline helices and crystalline cylinders occur while T{sub c,PLLA} < T{sub g,PS} (the glass transition temperature of PS) and T{sub c,PLLA} T{sub g,PS}, respectively. As evidenced by selected-area electron diffraction and two-dimensional X-ray diffraction results, the PLLA crystallites under confinement reveal a unique anisotropic character regardless of the crystallization temperature. On the basis of observed uniaxial scattering results the PLLA crystallites grown within the microdomains are identified as crystals with preferential growth directions either along the [100] or along the [110]-axes of the PLLA crystalline unit cell, at which the molecular chains and the growth direction are normal and parallel to the central axes of helices, respectively. The formation of this exclusive crystalline growth is attributed to the spatial confinement effect for crystallization. While T{sub c,PLLA} < T{sub g,PS}, owing to the directed crystallization by helical confinement, the preferential crystalline growth leads to the crystallization following a helical track with growth direction parallel to the central axes of helices through a twisting mechanism. Consequently, windingmore » crystals with specific crystallographic orientation within the helical microdomains can be found. By contrast, while T{sub c,PLLA} {ge} T{sub g,PS}, the preferential growth may modulate the curvature of microdomains by shifting the molecular chains to access the fast path for crystalline growth due to the increase in chain mobility. As a result, a spring-like behavior of the helical nanostructure can be driven by crystallization so as to dictate the transformation of helices, resulting in crystalline cylinders that might be applicable to the design of switchable large-strain actuators.« less

The self-assembly of 1,3-phenylene bis[4-(4-n-heptyloxybenzoyloxy)-benzoates] (BC7) is studied to examine the formation of helicalmorphologiesfromachiralbanana-shapedliquidcrystalmoleculesatdifferentself-assemblinglevels.Varioushierarchical superstructures including flat-elongated lamellar crystal, left- and right-handed helical ribbons, and tubular texture are observed while the BC7 molecules self-assemble in THF/H2O solution. By contrast, only plate-like morphology is observed in the selfassembly of achiral linear shaped 1,4-phenylene bis[4-(4-n-heptyloxybenzoyloxy)-benzoates] (LC7) molecules, indicating that the chirality of the self-assembled texture is strongly dependent upon the molecular geometry of the achiral molecules. The formation of the helical superstructures, namely hierarchical chirality, is attributed to the conformational chirality from the achiralbanana-shaped liquid crystalline molecules, as evidenced by significant optical activity in time-resolved circular dichroism experiments. Selective area electron diffraction is performed to examine the structural packing of the hierarchical superstructures. Asobserved, themoleculardispositionofthelamellarcrystal isidentical tothat ofthehelical superstructure. Also, the diffraction patterns of the helical superstructures appeared arc-like patterns consisting of a series of reflections, suggesting that the helical morphology resulted from the curving of the lamellar crystals through a twisting and bending mechanism. Consequently, the model of molecular disposition in the self-assembled helical superstructures from the achiral banana-shaped molecules is proposed. The morphological evolution in this study may provide further understanding with respect to the chiral information transfer mechanism from specific molecular geometry to hierarchical chirality in the achiral banana-shaped molecules.

The preparation of polyolefin-based stereoregular diblock copolymers by postpolymerization of ethenyl-capped syndiotactic polypropylene-based propylene/norbornene copolymer (sPP-based P-N copolymer) led to the successful generation of a structurally uniform stereoregular diblock copolymer for self-assembly studies. The ethenyl-capped prepolymer was prepared by conducting propylene/norbornene copolymerization in the presence of Me2C(Cp)(Flu)ZrCl2/MAO. Ozonolysis of ethenyl-capped sPP-based P-N copolymer provided the formyl group end-capped, end-functionalized prepolymer with a quantitative functional group conversion ratio. Subsequently, connecting the formyl end-group of the stereoregular prepolymer by coupling with living anionic polystyrene resulted in the high yield production of stereoregular diblock copolymer (sPP-based P-N-block-polystyrene), which is difficult to prepare by other methods. The resulting stereoregular diblock copolymer possesses precise chemical architecture to self-organize into consistent nanostructures as evidenced by transmission electron microscopy and small angle X-ray scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4843–4856, 2008

Various crystalline textures have been identified in a crystallizable block copolymer system, polystyrene-block-[syndiotactic poly(propylene)] (PS-sPP), having a glass-transition temperature of PS (T g,PS ) located in the midst of the sPP crystallization window. A confined morphology for the crystallization of sPP was observed while the crystallization temperature of sPP (T c,sPP ) was less than T g,PS . A further increase in T c,sPP could lead to a breakout in nanostructure. This study revealed the T g effect on crystallization-induced morphological changes of block copolymers from confinement to breakout.

A series of low-ether-content polyether-polyester block copolymers with amide linkages were synthesized. Their crystallization kinetics and mechanisms were investigated. The crystallization kinetics were analyzed via Avrami treatment; an average value of 1.8 for the Avrami index was thus obtained. Athermal nucleation was evidenced by observations of a linear boundary between impinged spherulites under polarized light microscopy and transmission electron microscopy. The development of spherulitic morphology with a hedgehog texture was attributed to the mechanism of lamellar branching. On the basis of the morphological observations and Avrami analysis, a crystallization mechanism through a heterogeneous nucleation process with homogeneous lamellar branching was proposed. No regime transition was found for polyether-polyesters in the examined temperature ranges, and the crystallization was identified as regime I kinetics on the basis of a Lauritzen Z test. The copolymerization of poly(ether amide)s with polyesters led to a significant suppression of the crystallization rate of polyester crystals. The suppression was explained as the result of a dilution effect in nucleation combined with an increasing nucleation barrier.

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 2,2'-bis(trifluoromethyl)-4,4'-biphenyldicarbonyl chloride with 2.2'-bis(ω-[4-(4-cyanophenyl)phenoxy]-n-alkoxycarbonyl )-4,4'-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 (SA) phase. Their phase transition sequence during heating and cooling is T g (S A LC glass) ↔ S A ↔ N ↔ 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°C/min - 10°C/min for a sample cooled from the isotropic melt at the same rate is T g (NLC glass)K 0 → N→ K T (s) → N → I Nevertheless, 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 even-odd 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.

A model asphalt has been separated into two parts, asphaltene and maltene, through solvent extraction by n-heptane. The interactions of asphaltene and maltene with the triblock copolymer poly( styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) were investigated by transmission electron microscopy (TEM ), small-angle X-ray scattering (SAXS), dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC). Asphaltene was found to be essentially immiscible with both blocks of SEBS, while maltene was miscible with SEBS. An unusual sequence of morphological transformations of SEBS microstructure with respect to the addition of maltene was observed. The morphology transformed from hexagonal cylinder, to perforated layers, to lamellae and then back to the original hexagonal cylinder. The observed transformation reflects a limited solubility for both S and EB domains: at lower concentration maltene is a preferential additive for S domains, while increasing concentration the swelling of EB-rich microdomains by maltene becomes significant. The basic understanding of the interactions of the components of asphalt with SEBS gives a simple path to characterize and predict the microstructure of triblock copolymers in asphalt oligomers.

Poly(aryl ether ketone ketone)s (PEKKs) are prepared via a Friedel-Crafts acylation reaction with diphenyl ether and terephthalic acid (T) and/or isophthalic acid (I). The crystal structure, polymorphism and morphology of three PEKK homopolymers have been investigated using transmission electron microscopy (TEM), electron diffraction (ED) and wide angle X-ray diffraction (WAXD) experiments. The PEKKs studied consist of either all para-phenylene linkages [PEKK(T)], one meta-phenylene linkage [PEKK(I)] or alternating T and I isomers [PEKK(T/I)]. PEKK(T) and PEKK(T/I) show crystalline polymorphism depending upon the crystallization conditions and methods. In PEKK(T) two forms (I and II) can be observed, and their unit cell dimensions and symmetry groups are determined via ED experiments. A possible epitaxial relationship between these two forms is proposed when they coexist. PEKK(I) possesses only one crystal unit cell which belongs to the same category as the form I structure in PEKK(T). The c-axis dimension of the unit cell has been determined as three phenylenes having a zig-zag conformation, with the meta-phenylene lying on the backbone plane. PEKK(T/I) shows a complicated polymorphism. In addition to forms I and II, as in the case of PEKK(T), a possible form III is also observed.

Blends of polypropylene (PP) and ethylene-propylene rubber (EPR) and blends of polystyrene (PS) and styrene-butadiene rubber (SBR) were prepared in a laboratory-scale internal mixer at various blend compositions and rotor rates. Blend morphology was studied by means of electron microscopy. For each blend pair under the given processing conditions, the phase inversion process occurred progressively with respect to the variation in blend composition; it is within this composition range of phase inversion that dual-phase continuity was observed. In addition, characteristic torque values of blends were found to deviate negatively from a linear additivity rule; the composition range of maximum deviation from linear additivity corresponded approximately to the composition range where dual-phase continuity was observed. Sperling’s predictive scheme was found to yield acceptable (although not completely satisfactory) estimates for compositions of dual-phase continuity in the present systems. It was also observed that partial cross-linking of SBR during the mechanical blending process, as suggested by the appearance of a cure peak in the torque curve and supported by infrared spectroscopic evidence, resulted in morphological features drastically different from those of the uncured blends.