Patent Number: 
Section: description

This application claims priority to U.S. Provisional Patent Application No. 61/096,044, filed Sep. 11, 2008, the disclosure of which is incorporated herein by reference. The present invention is related to glassy liquid crystalline compositions, and more particularly, the present invention is related to cholesteric glassy liquid crystalline compositions having hybrid chiral-nematic groups. Liquid crystals are spontaneously ordered fluids characterized by a uniaxial, lamellar, helical, or columnar arrangement in nematic, smectic, cholesteric, or discotic mesophase, respectively. By preserving these molecular arrangements in the solid state via cooling through glass transition temperature (Tg), glassy liquid crystals (GLCs) represent a unique material class potentially useful for organic optoelectronics. Whereas all liquids are expected to vitrify at a sufficiently rapid cooling rate, most organic materials, including liquid crystals, tend to crystallize upon cooling through the melting point, Tm. Crystallization of liquid crystals essentially destroys the desired molecular order that prevails in the fluid state, resulting in polycrystalline films that scatter light or impede charge transport. The first known or reported attempt to synthesize GLCs in 1971 yielded materials with a low Tg and poor morphological stability, namely, the tendency to crystallize from the glassy state. Subsequent efforts have produced GLCs that can be categorized into (i) laterally or terminally branched, one-string compounds with a Tg mostly around room temperature; (ii) twin molecules with an above-ambient Tg but generally lacking morphological stability; (iii) cyclosiloxanes functionalized with mesogenic and chiral pendants; (iv) carbosilane dendrimers exhibiting a low Tg; (v) macrocarbocycles with mesogenic segments as part of the ring structure; and (vi) pentaerythritol as the central core to yield widely varying Tg and morphological stability. In particular, cholesteric GLCs are potentially useful as large area non-absorbing polarizers, optical notch filters and reflectors, and polarizing fluorescent films. Moreover, cholesteric GLC films can serve as a one-dimensional photonic bandgap for circularly polarized lasing. Comprising separate chiral and nematic pendants, cholesteric GLCs have been synthesized either by a statistical approach, which requires intensive workup procedures to arrive at pure components, or by deterministic approaches, which require long synthesis schemes. Cholesteric GLCs with hybrid pendants having both chiral and nematic moieties chemically bonded to a volume-excluding core addresses the problems of complexity and cost associated with previous cholesteric GLC systems with separate chiral and nematic pendants. However, previous attempts at hybrid pendants have met with little or no success. For example, hybrid pendants with a chiral tail yielded exclusively smectic mesomorphism (Delavier et al., U.S. Pat. No. 5,840,097), and cyanotolan with a chiral spacer to a cyclohexane core failed to achieve mesomorphism (Shi et al., Liq. Cryst., 1994, 17, 413). Based on the foregoing, there is an ongoing unmet need for cost effective preparation of cholesteric glassy liquid crystals with elevated phase transition temperatures, stability against crystallization from the glassy state, and selective reflection across the visible to near infrared region. In one aspect, the present invention provides cholesteric GLC compositions comprising compounds with the following general structure:AL-chiral spacer moiety-L-nematic moiety)z The compounds comprise a volume-excluding core (VEC) (A) and at least one hybrid chiral-nematic pendant moiety (Ch), which is a hybrid pendant moiety with a chiral spacer moiety connected (via a chemical bond) by a linker group (L) to a nematic moiety. The Ch pendants are constructed by combining rigid nematic moieties with flexible chiral spacers intended to partially decouple nematic moieties from volume-excluding cores with a degree of chiral preference to induce the formation of cholesteric mesoporphism. The geometric dissimilarity between the core and the pendant structures is essential to the formation of glassy liquid crystals and their stability against crystallization. The GLC materials of the present invention have desirable mechanical properties for device fabrication and durability. The materials have film- and fiber-forming abilities and morphological stability (e.g., the monodomain cholesteric GLC films retain a glassy state and preserve high orientational order without crystallization). We have GLC films which have been morphologically stable for at least 3 years. In one embodiment, the GLC compositions of the present invention are formed as thin films (e.g., deposited by melt processing or spin coating). Such thin films can range in film thickness from 2 to 22 microns depending on the material types and the spectral range of interest. In another embodiment, the GLC compositions of the present invention are formed as fibers. For example, such fibers can be used in optical communication applications. In one aspect, the present invention provides a method for preparing oriented thin films of cholesteric glassy thin films. The method comprises the steps of: (a) depositing a thin film of an alignment polymer on a substrate; (b) irradiating the polymer with linearly polarized ultraviolet radiation to create a thin film such that the of the polymer molecules are oriented relative to the direction of the linear polarization of the ultraviolet radiation; (c) depositing a thin film of the composition of claim 1 on alignment surface from step b); and (d) annealing the substrate from c) at a temperature above the glass transition temperature of the composition of claim 1, which is the Tg of the compound comprising the composition. Optionally, a second substrate is provided which is prepared according to steps a) and b) above. This substrate is placed on the substrate from c) prior to annealing such that the alignment surface of the second substrate is opposed to the thin film of composition 1 on the substrate from c) and the molecular alignment of the two substrates is the same. The compositions of the present invention can be used in applications of chiral liquid crystalline materials in organic optical devices requiring compositions capable of forming both right- and left-handed helical structures. Chiral-nematic liquid crystalline compositions of the present invention, which form clear, transparent films that absorb no light in the visible region but do selectively reflect visible and near-infrared circularly-polarized light, are especially useful large-area non-absorbing (circular) polarizers, optical notch filters, reflectors (mirrors), polarizing fluorescent films and lasers (e.g. one-dimensional photonic bandgap for circularly polarized lasing). In one aspect, the present invention provides cholesteric GLC compositions comprising compounds with the following general structure:AL-chiral spacer moiety-L-nematic moiety)z The compounds comprise a volume-excluding core (VEC) (A) and at least one hybrid chiral-nematic pendant moiety (Ch), which is a hybrid pendant moiety with a chiral spacer moiety connected (via a chemical bond) by a linker group (L) to a nematic moiety. The number of potential Ch moieties is dependant on the structure of the VEC, e.g. a phenyl VEC can be substituted with 1 to 3 Ch groups. The number of Ch groups, z, is from 1 to 20, including all integers from 1 to 20. The chiral spacer moiety of the hybrid chiral-nematic group is connected to the VEC by a linker group (L). The Ch pendants are constructed by combining rigid nematic moieties with flexible chiral spacers intended to partially decouple nematic moieties from volume-excluding cores with a degree of chiral preference to induce the formation of cholesteric mesoporphism. The geometric dissimilarity between the core and the pendant structures is essential to the formation of glassy liquid crystals and their stability against crystallization. In one embodiment, all substitutions on the VEC are Ch moieties. For example, see compounds I, II, and IV in Chart 1. In another embodiment, the VEC is substituted with at least one Ch moiety and at least one moiety that is not a Ch moiety (for example, see compounds VI (substituted with a nematic moiety) and VII (substituted with an acid moiety) in Chart 1). Other examples of non-Ch moieties include alkyl moieties and alkylaryl moieties, either of which can be unsaturated or otherwise substituted with functional groups such as alcohols, halogens, nitriles, isonitriles, ether, esthers, amides, and the like. The nematic moities discussed herein are also examples of non-Ch moieties. The VEC is a single ring or multi-ring structure with one or more substitution points which can be substituted with Ch groups. Each ring of the single ring or multi-ring structure independently has 4 to 8 carbons, including all integers between 4 and 8. Examples of multi-ring structures are multiple rings which are directly connected, multiple rings with common carbons, or fused-ring structures, and the like. The number of rings in a multi-ring structure can be from 2-10, including all integers between 2 and 10. Examples of VECs include, but are not limited to, a phenyl ring, a cyclohexane ring, a (1s,4s)-bicyclo[2.2.2]oct-2-ene multi-ring structure, an adamantane (tricycle[3.3.1.13,7]) multi-ring structure, or a cubane (pentacyclo[4.2.02,5.03,8.04,7]) multi-ring structure. In various embodiments, the VEC is a monosubstituted phenyl ring, a 1,3-substituted phenyl ring, or 1,3,5-substituted phenyl ring. In one embodiment, the VECs can comprise at least one expander moiety (E). The expander moiety is comprised of a linker group (L) and an expander ring structure (ER) which is a single ring or a multi-ring structure. The expander moiety is connected to one or more Ch moieties, can increase the number of possible chiral-nematic group substitution positions on the VEC. Each ring of the single ring or multi-ring structure independently has 4 to 8 carbons, including all integers between 4 and 8. Examples of single ring expander ring structures include phenyl rings, cyclohexyl rings, or pyridine rings. An example of a multi-ring expander ring structure is a naphthalene ring. The number of E moieties is 1 to 10, including all integers from 1 to 10. An example of an expander moiety is a phenyl ring connected to the VEC by a linker group (such as an ester group). In one embodiment the compounds of the present invention have the following general structure: The number E groups, y, is from 1 to 10, including all integer in between 1 and 10. The number of Ch groups, z, is from 1 to 20. The following are examples of VECs:  Examples of compounds of the present invention include, but are not limited to, the following.  The chiral spacer moiety of the Ch moiety has at least one chiral center. For example, the chiral spacer moiety is an alkyl chain of 2 to 15, including all integers between 2 and 15, carbons and contains one or two chiral centers. The chain, optionally, includes one or more functional group(s) such as ester or amide groups. The chiral spacer should have sufficient flexibility to enable the Ch pendant groups to self-organize Examples of molecules used to form chiral spacer moieties include, but are not limited to, the following: The chiral spacer groups shown above have a functional group, e.g., a hydroxyl group or bromide, which is reacted to join the spacer, or spacer-linker, or spacer-linker-nematic group to the VEC or expander group via a linker. A linker group (L) is any functional group that can be used to connect the core and the expander ring of the expander moiety, the chiral spacer moiety with the core or expander moiety, and the chiral spacer moiety with the nematic moiety. Either terminus of the functional group can be used to connect either moiety. Examples of functional groups which can be linker groups include, but are not limited to, the following:  The nematic moiety is joined to the chiral spacer group by a linker group. Structures with a stable nematic liquid crystalline phase are suitable nematic moities. The nematic moiety is a multi-aromatic ring aromatic moiety. For example, the nematic moiety can have 2 to 15, including all integers in between 2 and 15, aromatic rings. The aromatic rings can be present as fused-ring structures (e.g., a naphthalene structure) or non-fused ring structures (e.g., a biphenyl structure) or individual rings. Individual adjacent rings (or ring structures) can be connected directly, such as by a single bond, or via an unsaturated alkyl chain comprising two carbons (e.g., a ethylene moiety) or a functional group such as an ether, esther, amide, thioether, thioesther, or the like. The moiety can be completely conjugated or partially conjugated. The moiety can include carbon-carbon multiple bonds (alkenyl or alkynl groups) which can conjugate different ring structures in the moiety. Without intending to be bound by any particular theory, it is considered that the nematic moiety provides rigidity to the molecule due to planar conjugation in the moiety. Examples of nematic moieties useful in the compounds of the present invention include, but are not limited to, the following: The nematic moieties can be substituted, as indicated by the X group in the structures above, or un-substituted, in which case X is a hydrogen. Groups suitable for substitution include, halides, nitro groups, alkyl groups, alkoxy groups, cyano and isocyano groups, and thiocyano and isothiocyano groups, and the like. Examples of X groups as substituents on the nematic moiety useful in the present invention, include but are not limited to, the following:  The compounds of the present invention can have molecular weights ranging from 500 to 5000 amu. In one embodiment, the GLC materials of the present invention have a molecular weight of less than 2000 amu. While the core and hybrid pendants are crystalline as separate entities, the chemical hybrid, with a proper flexible chiral spacer moiety connecting the two, readily vitrifies into a GLC structure on cooling. In one embodiment, the GLC compositions consist essentially of the compounds of the present invention. In another embodiment, the GLC compositions consist of the compounds of the present invention. In various other embodiments, the GLC compositions of the present invention comprise, consist essentially of, or comprise one or more of the compounds of the present invention. The compounds comprising the GLC compositions of the present invention can be synthesized using a variety of synthetic methodologies, including single-step and multi-step processes. For example, the compounds can be synthesized starting with the core and adding each successive component (e.g., linker(s), chiral spacer moiety/moieties, linker group(s), and nematic moiety/moieties). As another example, the Ch group could be independently synthesized and the pre-prepared Ch group reacted with the linker group, the combination of which is then connected with the core, or the core, which had already been reacted with linker group(s). As yet another example, individual parts of the compound can be pre-prepared and these pre-prepared parts reacted to form the compound (e.g., a core-linker-chiral spacer part and a linker-nematic moiety part can be pre-prepared and subsequently, reacted to form the desired compound). In any of these examples, the components can contain reactive groups which are not part of the final compound. Illustrations of the preparation of exemplary compounds are provided in the Examples. The compounds of the present invention can be synthesized in a cost-effective manner. The synthesis of previous compounds used to form GLCs employed synthetic schemes based on costly and time-consuming protection-deprotection and separation methodology. The protection-deprotection methodology requires multiple steps. In one example, this methodology requires six steps. In comparison, compounds of the current invention can be synthesized in a single step (assuming the Ch pendant groups have been separately prepared). In addition to the savings in materials costs and time, the efficiency of the preparation of compounds of the present invention is increased. For example, compounds of the present invention have been prepared with a 70% yield as compared to previous GLC precursors which were prepared with a yield of less than 10%. As an example of compounds of the present invention, cholesteric GLCs were successfully developed using 4′-cyanobiphenyl-4-yl benzoate nematogens and enantiomeric 2-methylpropylene spacers to a phenyl ring core. A systematic investigation of these compounds was conducted for mesomorphic behavior, morphological stability, and optical properties in relation to the extent of substitution and regioisomerism. Amenability to photo-alignment on coumarin-containing polymer films was also tested with a morphologically stable cholesteric GLC of the present invention. Key findings regarding the compounds of this system are recapitulated as follows: Glass-forming ability generally improves with an increasing substitution with hybrid chiral-nematic mesogens on the benzene ring. The para-disubstituted and the monosubstituted systems lack glass-forming ability for the compounds of this system. With respect to the substituted benzene systems, with Tg at 73° C. and Tc at 295° C., the 1,3,5-trisubstituted system is preferred. Left at room temperature for months, the cholesteric GLC films prepared with meta- and ortho-isomers in addition to 1,3,5-trisubstituted system have remained noncrystalline, evidence of superior morphological stability. Morphologically stable cholesteric GLC films based on compounds of the present invention were characterized for their selective reflection properties. Left-handed helical stacking emerged with (S)-3-bromo-2-methylpropanol as the chiral precursor. Films of the 1,3,5-trisubstituted and meta-disubstituted systems show a λR at 413 and 422 nm, respectively, whereas that of the ortho-isomer system exhibits a λR at 860 nm. Replacing one of the hybrid chiral-nematic mesogens in the 1,3,5-trisubstituted system by a nematogen loosens the helical pitch to yield a λR at 630 nm, still shorter than the ortho-isomer despite the dilution by nematogen. Computational chemistry revealed the closer packing involving chiral spacers in the meta-isomer than the ortho-isomer, thus the stronger helical twisting in the former than the latter. The ortho-isomer is amenable to photo-alignment on films of methacrylate homopolymers and a maleimide-norbornene copolymer containing pendant coumarin monomers to a varying extent. With an extent of coumarin dimerization of about 0.25 as a result of linearly polarized UV-irradiation, the films of a methacrylate polymer with a hexamethylene spacer produced a 7 μm-thick monodomain cholesteric GLC film with selective reflection properties equivalent to mechanical alignment on rubbed polyimide films. In contrast, the rigid and bulky polymer backbone and the short flexible spacer in the maleimide-norbornene copolymer produced a polydomain cholesteric GLC film with inferior selective reflection characteristics. These observations were interpreted by the rotational mobility of pendant coumarin monomers relative to the polarization axis of irradiation. The GLC materials of the present invention have desirable mechanical properties for device fabrication and durability. The materials have film- and fiber-forming abilities and morphological stability (e.g. the monodomain cholesteric GLC films retain a glassy state and preserve high orientational order without crystallization). In one embodiment, morphological stability means that films of the GLC materials do not exhibit detectable (such as by microscopy or x-ray diffraction) for a period of time when stored at ambient temperature (e.g., 65-70° C.). For example, the materials can be stable for 6 months, 1 year, or 2 years. We have GLC films which have been morphologically stable for at least 3 years. Conventional liquid crystal polymers are generally difficult to fabricate into large-area thin films due to high melt viscosity. However, because of their chemical purity, favorable rheological properties, and short and uniform mechanical relaxation time, the GLC materials can be processed into defect-free films. For example, the GLC materials can be melt processed for use in optical elements. In one embodiment, the GLC compositions of the present invention are formed as (e.g. deposited by melt processing) thin films. Such thin films can range in film thickness from 2 to 22 microns depending on the material types and the spectral range of interest. The thin films can be deposited over an area of up to, for example, one ft by one ft by vacuum filling the gap above the glass transition temperature (Tg) between glass substrates. In another embodiment, the GLC compositions of the present invention are formed as fibers. For example, such fibers can be used in optical communication applications. In one aspect, the present invention provides a method for preparing oriented thin films of cholesteric glassy thin films. The method comprises the steps of: (a) depositing a thin film of an alignment polymer on a substrate; (b) irradiating the polymer with linearly polarized ultraviolet radiation to create a thin film the surface of which is an alignment surface, such that the polymer molecules are oriented relative to the direction of the linear polarization of the ultraviolet radiation; (c) depositing a thin film of the composition of claim 1 on alignment surface from step b); and (d) annealing the substrate from c) at a temperature above the Tg of the composition of claim 1. Optionally, a second substrate coated with a thin film of a same or different alignment polymer prepared according to steps a) and b) above is provided. This substrate is placed on the substrate from c) prior to annealing such that the alignment surface of the second substrate is apposed to the thin film of composition 1 on the substrate from c) and the molecular alignment of the two substrates is the same. The annealing step results in a film of composition 1 that is oriented. By oriented is it meant that the molecular axes of the liquid crystals of the thin film are uniaxially oriented relative to a predetermined direction (i.e., the direction dictated by the linearly polarized irradiation used to prepare the alignment polymer or alignment polymers in the case where two alignment surfaces are used). The orientation can be assessed by determining the optical properties of the oriented film. For example, a film is oriented if on impinging unpolarized light on a thin film 40-50%, including all integers between 40 and 50%, of the light is reflected or transmitted and/or the degree of circular polarization of the reflected and/or transmitted light is 90 to 100%, including all integers between 90 and 100%. Based on these values the orientational order parameter can be calculated. The substrate can be any planar surface on which a thin film of the alignment polymer can be deposited. For example, glass substrates can be used. The alignment polymer is any polymer which on irradiation with linearly polarized UV radiation (typically, 300 to 320 nm) creates a surface which can orient a thin film of the composition of claim 1 when the composition is annealed. After irradiation, the alignment polymer should be such that a thin film of the composition of claim 1 can be formed on the exposed surface of the alignment polymer thin film. For example, after irradiation the alignment polymer should be insoluble in common solvents (e.g., chloroform). Examples include the coumarin-containing polymers discussed in Example 1 (e.g., methacrylate homopolymers, maleimide-norbornene copolymers containing varying numbers of pendant coumarin monomers), cinnamate-based polymers and azobenzene-based polymers. The axis selectivity of the alignment polymer determines whether the polymer molecules are oriented parallel or perpendicular to the direction of the linearly polarized light. For example, for maleimide-norbornene copolymers containing varying numbers of pendant coumarin monomers the degree of coumarin monomer dimerization can be from 0.2 to 0.5 while maintaining molecular orientation of the alignment polymer parallel to the linearly polarized ultraviolet radiation used to irradiate the polymer. The annealing step is carried out at temperatures above the Tg of the composition of claim 1 used to form the thin film on the alignment substrate. The annealing temperature should be such that thin film of the GLC composition of claim 1 is not degraded. For example, temperatures of 1 to 25 degrees Celsius, including all integers between 1 and 25 degrees Celsius, above the Tg can be used. In another example, temperatures of 10 to 15 degrees Celsius, including all integers between 10 to 15 degrees Celsius, above the Tg can be used. The annealing step is carried out until the thin-film is oriented. Typically, the annealing step is carried out for 15 to 30 minutes, depending on the composition and film thickness used. In another aspect, the present invention provides an oriented thin film comprising a GLC composition of the present invention. In one embodiment, the oriented thin-film is present on a substrate. In another embodiment, the oriented thin film is present as a one layer of a multilayer composition of one or more thin-films, and molecular axes of the composition are uniaxially ordered. For example, the multilayer composition can include a substrate, an alignment polymer thin film, and an oriented GLC thin film. As another example, the film stack can include a substrate, an alignment polymer thin film, an oriented GLC thin film, an alignment polymer thin film, and another substrate. Optical quality films prepared from GLC materials of the present invention can be used for circular polarizers, circular-polarized fluorescence films, optical notch filters and reflectors, filters for laser protection, latching electro-optical devices for optical communication, and low-threshold and efficient circularly polarized lasers. The supramolecular structure of a chiral-nematic liquid-crystal film comprised of GLC compositions of the present invention can be described a cholesteric mesophase that includes a helical stack of quasi-nematic layers in the Grandjean (or homogeneous) orientation, which is characterized by handedness and helical pitch length, p. Handedness describes the direction in which twisting of the nematic director occurs from one layer to the next, and p is defined as the distance over which the director rotates by 360°. The property of selective reflection can be described in terms of λR=p(ne+no)/2, in which ne and no are the extraordinary and ordinary refractive indices of the quasi-nematic layer, respectively. When unpolarized white light, which consists of equal amounts of left-handed (LH) and right-handed (RH) circularly polarized components, propagates through a LH film the LH circularly polarized component in the neighborhood of λR is selectively reflected, while the RH component is completely transmitted. A sufficiently thick, singlehanded cholesteric film is capable of reflecting 50% of incident unpolarized light within the selective reflection band. Outside the selective reflection band, incident light is transmitted regardless of its polarization state. It follows that a stack of RH and LH chiral-nematic films (or a single film comprising both RH and LH chiral-nematic films) tuned at the same λR will reflect 100% of incident unpolarized light within the selective reflection band without attenuating the rest of the spectrum. For example 2 to 22 micron, including all integers between 2 and 22 microns, thick films of the GLC compositions are typically sufficient to reflect/transmit light with wavelengths from visible (blue) wavelengths to near-IR wavelengths. Generally, the film thickness and refractive index of the GLC composition(s) will dictate what wavelengths of light interact with the films (e.g., GLC compositions with a high refractive index will require thinner films to reflect/transmit light relative to compositions with a lower refractive index. The compositions of the present invention can be used in applications of chiral liquid crystalline materials in organic optical devices requiring compositions capable of forming both right- and left-handed helical structures. When a film of such a composition is applied to a substrate or surface, the helical structures are capable of forming and maintaining the Grandjean texture, in which the helical axis is perpendicular to the substrate surface, to enable the selective reflection of circular-polarized light. An enantiomeric chiral pair of liquid crystalline compositions of the present invention prepared into two separate films, characterized as a right-handed and a left-handed helix, are capable of selectively reflecting right-handed and left-handed circular-polarized light, respectively. Chiral-nematic liquid crystalline compositions of the present invention, which form clear, transparent films that absorb no light in the visible region but do selectively reflect visible and near-infrared circularly-polarized light, are especially useful large-area non-absorbing (circular) polarizers, optical notch filters, reflectors (mirrors), polarizing fluorescent films and lasers (e.g. one-dimensional photonic bandgap for circularly polarized lasing). The following examples are presented to illustrate the present invention. They are not intended to limiting in any manner.  Materials and Methods Material Synthesis. All chemicals, reagents, and solvents were used as received from commercial sources without further purification except tetrahydrofuran (THF) that had been distilled over sodium and benzophenone. The 1-[(tert-butyldimethylsily)oxy]-3,5-benzenedicarboxylic acid was synthesized according to literature references. Compounds IX through XI and their intermediates were synthesized according to Reaction Scheme 3. (S)-2-(3-Hydroxy-2-methylpropoxy)-6-bromonaphthalene, 4. Acetonitrile (60 mL) was added to a mixture of 6-bromo-2-naphthol (2.7 g, 12 mmol), (S)-(+)-3-bromo-2-methylpropanol (2.0 g, 13 mmol), potassium carbonate (2.5 g, 18 mmol), and a catalytic amount of potassium iodide. After refluxing overnight, the solid residue was removed from the reaction mixture by filtration, and the filtrate was evaporated to dryness under reduced pressure. The solid residue was purified by gradient column chromatography on silica gel with hexane:methylene chloride (1:10) to pure methylene chloride to yield 4 (1.5 g, 43%). 1H NMR spectral data (400 MHz, CDCl3): δ (ppm) 1.08 (d, 3H, —CH3), 1.76 (s, 1H, HO—), 2.26 (m, 1H, —CH2CH(CH3)CH2—), 3.74 (d, 2H, HOCH2—), 4.05 (d, 2H, —CH2OAr), 7.11-7.17 (m, 2H, aromatics), 7.47 (d, 1H, aromatics), 7.58 (d, 1H, aromatics), 7.64 (d, 1H, aromatics), 7.90 (s, 1H, aromatics).(S)-2-(3-Hydroxy-2-methylpropoxy)-6-(4-cyanophenyl)naphthalene, Ch3-OH. In a mixture of 4 (1.5 g, 5.1 mmol), 4-cyanophenyl boronic acid (0.82 g, 5.6 mmol), and tetrakis(triphenylphosphine)palladium(0) (0.29 g, 0.25 mmol), toluene (20 mL) and 2M Na2CO3 solution (15 ml, 30.5 mmol) were added. The reaction mixture was stirred under argon at 90° C. overnight. Upon cooling to room temperature, ethyl acetate was added to the reaction mixture. The organic layer was separated and washed with brine before dry over anhydrous magnesium sulfate. Upon evaporating off the solvent, the solid residue was purified by gradient column chromatography on silica gel with hexane:methylene chloride (1:10) to pure methylene chloride to yield Ch3-OH (0.95 g, 59%). 1H NMR spectral data (400 MHz, CDCl3): δ (ppm) 1.10 (d, 3H, —CH3), 1.76 (t, 1H, HO—), 2.28 (m, 1H, —CH2CH(CH3)CH2—), 3.76 (d, 2H, HOCH2—), 4.10 (d, 2H, —CH2OAr), 7.21 (d, 2H, aromatics), 7.67 (d, 1H, aromatics), 7.73-7.83 (m, 6H, aromatics), 7.98 (s, 1H, aromatics).1-Hydroxy-3,5-benzenedicarboxylic acid, bis[(R)-3-[4-[(4′-cyanobiphenyl-4-yl)oxy carbonyl]phenoxy]-2-methylpropyl]ester, 5. To a solution of 1-[(tent-Butyldimethyl sily)oxy]-3,5-benzenedicarboxylic acid (0.36 g, 1.2 mmol), Ch2-OH (1.00 g, 2.6 mmol), and TPP (0.71 g, 2.7 mmol) in anhydrous tetrahydrofuran (15 mL), DEADC (0.47 g, 2.7 mmol) was added dropwise. The reaction was stirred under argon at room temperature overnight. The solvent was then removed under reduced pressure, and the solid residue was purified by gradient column chromatography on silica gel with methylene chloride:hexane 100:10 to 100:5. The tert-butyldimethylsily ether was hydrolyzed with Cs2CO3 (0.19 g, 0.59 mmol) in the mixture of N,N-dimethylformamide (15 mL) and water (1.5 mL). After stirring at room temperature for 1 h, the reaction mixture was extracted with ethyl acetate. The extracted solution was washed with brine and dry over anhydrous magnesium sulfate. Upon evaporating off the solvent, the solid residue was purified by gradient column chromatography with acetone in methylene chloride from 0 to 3% to yield 5 (0.95 g, 87%). 1H NMR spectral data (400 MHz, CDCl3): δ (ppm) 1.21 (d, 6H, —CH3), 2.53 (m, 2H, —CH2CH(CH3)CH2—), 4.06 (d, 4H, —CH2OAr), 4.43 (m, 4H, —COOCH2—), 5.50 (s, 1H, HO—), 6.99 (d, 4H, aromatics), 7.29 (d, 4H, aromatics), 7.63 (d, 4H, aromatics), 7.65-7.74 (m, 10H, aromatics), 8.14 (d, 4H, aromatics), 8.25 (s, 1H, aromatics)1-Hydroxy-3,5-benzenedicarboxylic acid, bis[(R)-3-[[[6-(4-cyanophenyl)naphthyl]-2-yl]oxy]-2-methylpropyl]ester, 6. The procedure for the synthesis of 5 was followed to prepare 6 using Ch3-OH (0.51 g, 1.6 mmol) instead of Ch2-OH in 65% yield (0.51 g). 1H NMR spectral data (400 MHz, CDCl3): δ (ppm) 1.18 (d, 6H, —CH3), 2.52 (m, 2H, —CH2CH(CH3)CH2—), 4.06 (m, 4H, —CH2OAr), 4.43 (m, 4H, —COOCH2—), 6.22 (s, 1H, HO—), 7.16 (t, 4H, aromatics), 7.63 (d, 2H, aromatics), 7.69-7.79 (m, 14H, aromatics), 7.94 (s, 2H, aromatics), 8.25 (s, 1H, aromatics).1,3,5-Benzenetricarboxylic acid, tris[(R)-3-[[[6-(4-cyanophenyl)naphthyl]-2-yl]oxy]-2-methylpropyl]ester, IX. The procedure for the synthesis of II was followed to prepare IX using Ch3-OH (0.41 g, 1.1 mmol) instead of Ch2-OH in 73% yield (0.33 g). 1H NMR spectral data (400 MHz, CDCl3): δ (ppm) 1.17 (d, 9H, —CH3), 2.52 (m, 3H, —CH2CH(CH3)CH2—), 4.05 (d, 6H, —CH2OAr), 4.45 (m, 6H, —COOCH2—), 7.15 (t, 6H, aromatics), 7.64 (d, 3H, aromatics), 7.69-7.78 (m, 18H, aromatics), 7.94 (s, 3H, aromatics), 8.85 (s, 3H, aromatics).1,3,5-Benzenetricarboxylic acid, tris[3,5-benzenedicarboxylic acid, bis[(R)-3-[4-[(4′-cyanobiphenyl-4-yl)oxycarbonyl]phenoxy]-2-methylpropyl]ester]phenyl ester, X. 1,3,5-Benzenetricarboxylic acid (0.063 g, 0.30 mmol), 5 (0.89 g, 0.97 mmol), and DPTS (0.27 g, 0.91 mmol) were dissolved in a mixture of anhydrous methylene chloride (5 mL) and anhydrous N,N-dimethylformamide (2 mL). DCC was quickly added to the reaction mixture, which was stirred under argon at room temperature overnight. Upon filtering off white solids, the filtrate was diluted with additional methylene chloride. The solution was washed with 1M hydrochloric acid and brine before being dried over magnesium sulfate. The crude product was collected by evaporation under reduced pressure and purified by gradient column chromatography on silica gel with 0 to 0.5% methanol in chloroform to yield X (0.10 g, 11%). 1H NMR spectral data (400 MHz, CDCl3): δ (ppm) 1.19 (d, 18H, —CH3), 2.53 (m, 6H, —CH2CH(CH3)CH2—), 4.04 (d, 12H, —CH2OAr), 4.47 (m, 12H, —COOCH2—), 6.98 (d, 12H, aromatics), 7.28 (d, 12H, aromatics), 7.60 (d, 12H, aromatics), 7.66 (d, 12H, aromatics), 7.70 (d, 12H, aromatics), 8.13 (d, 18H, aromatics), 8.62 (s, 3H, aromatics), 9.26 (s, 3H, aromatics).1,3,5-Benzenetricarboxylic acid, tris[3,5-benzenedicarboxylic acid, bis[(R)-3-[[[6-(4-cyanophenyl)naphthyl]-2-yl]oxy]-2-methylpropyl]ester]phenyl ester, XI. The procedure for the synthesis of X was followed to prepare XI using 6 (0.47 g, 0.60 mmol) instead of 5 in 11% yield (0.048 g). 1H NMR spectral data (400 MHz, CDCl3): δ (ppm) 1.20 (d, 18H, —CH3), 2.53 (m, 6H, —CH2CH(CH3)CH2—), 4.05 (d, 12H, —CH2OAr), 4.46 (m, 12H, —COOCH2—), 7.15 (t, 12H, aromatics), 7.61 (d, 6H, aromatics), 7.67-7.79 (m, 36H, aromatics), 7.91 (s, 6H, aromatics), 8.81 (s, 6H, aromatics), 8.64 (s, 3H, aromatics), 9.18 (s, 3H, aromatics).   FIG. 1b shows the DSC thermograms of compounds identified in Example 2. Compound IX is a morphologically stable cholesteric GLC, with Tg at 85° C. and Tc at 161° C. Because of nonlinearity caused by naphthalene in the nematic moiety, the Tc is lower for IX than II. Compounds with an extended core, X and XI, were prepared with Ch2-OH and Ch3-OH, respectively. Normally, Tg increases with an increasing number of pendant groups. While the invention has been described through illustrative examples and embodiments, routine modifications to the described examples and embodiments will be apparent to those skilled in the art and such modifications are intended to be within the scope of the present invention.