Abstract: The invention herein relates to a soluble polyimide resin and the process of preparation of the same, wherein aromatic tetracarboxylic dianhydride and aromatic diamine having an alicyclic group with various structures of substituted alkyl groups are used to yield a novel form of a polyimide resin, which has superior heat-resistance, solubility and transparency.More specifically, the invention herein relates to a novel polyimide resin having excellent heat-resistance and solubility, which is prepared by means of reacting aromatic diamine monomers having a novel chemical structure with various types of aromatic tetracarboxilic acid dianhydrides, in stead of aromatic diamine used for the preparation of the conventional polyimide resin. As a result, the polymers so obtained had the glass transition temperature of 250.degree. C..about.400.degree. C. and showed a increase in solubility in proportion to the increase in volume of the alkyl group.

Abstract: A polyamideimide for optical communications, having a minimum light absorption loss in a near infrared light wavelength range, high thermal stability and excellent film processibility, and a method for preparing the same are provided. The polyamideimide has a higher refractive index than the conventional fluorinated polyamideimide. Thus, when using such polyamideimide as a material for a core of an optical fiber, the selection range on the material for cladding becomes wide. Also the coating property and adhesiveness to a substrate are improved, thereby providing a good film processibility and heat resistance.

Abstract: A photosensitive polyimide, which comprises a copolymer of (A) three diamine compounds mixture consisting of a diaminopolysiloxane, a hydroxyl group-containing diamine or carboxyl group-containing diamine and 1,4-bis[2-(3-aminobenzoyl)ethenyl]benzene with (B) an aromatic tetrocarboxylic acid dianhydride or a dicarboxylic anhydride having a 2,5-dioxotetrahydrofuryl group as one acid anhydride group, is soluble in all-purpose low boiling organic solvents, typically methyl ethyl ketone and provides a negative type photosensitive polyimide, which is developable with an aqueous alkaline solution.

Abstract: Novel molten-salt type polyelectrolytes are disclosed which contain as an essential ingredient a molten salt polymer obtained by reacting an imidazolium derivative, such as a 1,3-dialkylimidazolium halide, 1,2,3-trialkylimidazolium halide, 1-vinyl-3-alkylimidazolium halide, or 1-vinyl-2,3-alkylimidazolium halide, with an acid monomer, a poly(vinylsulfonamide), trifluoromethanesulfonimide, or the like. The electrolytes show high ionic conductivity at room temperature and have excellent stability to temperature fluctuations and excellent mechanical properties.

Abstract: Light-colored phenolic-modified rosin esters, suitable for use as, for example, tackifiers in adhesive compositions, are prepared by reacting together rosin, a phenolic compound, formaldehyde or a reactive equivalent thereof, and a non-phenolic hydroxyl-containing organic compound in the presence of at least one lightening agent selected from phenol sulfide compounds, phosphorous acid, esters of phosphorous acid, and hypophosphite salts. The formaldehyde or reactive equivalent is present in an amount ranging from about 1.1 to about 3.5 equivalents of --CHO moieties per 1 equivalent of Ar--OH moiety of the phenolic compound, in order to obtain rosin esters having desirably low color, and adequately low molecular weight to effectively function as tackifiers.

Abstract: Disclosed is a process which comprises reacting a polymer of the general formula ##STR1## or ##STR2## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR3## B is one of several specified groups, such as or mixtures thereof, and n is an integer representing the number of repeating monomer units, with a halomethylethyl ether, a hydrohalic acid, and acetic acid in the presence of a halogen-containing Lewis acid catalyst, thereby forming a halomethylated polymer.

Abstract: The invention herein relates to a soluble polyimide resin for a liquid crystal alignment layer and the process of preparation of the same, wherein aliphatic tetracarboxylic dianhydride and aromatic diamine having the amide group are used to yield a novel form of a polyimide resin having superior heat-resistance, solubility, transparency, and liquid crystal alignment capacity.More specifically, the invention herein relates to a novel polyimide resin having excellent heat-resistance, solubility, liquid crystal alignment property, and high pretilt angle, which is prepared by means of jointly using the aromatic diamine, used for the preparation of the conventional polyimide resin, and the aromatic diamine having a long alkyl chain with a substituted amide group, and reacting the same with various types of carboxylic dianhydride.

Abstract: Disclosed is a composition which comprises a polymer containing at least some monomer repeat units with water-solubility- or water-dispersability-imparting substituents and at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula ##STR1## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR2## B is one of several specified groups, such as ##STR3## or mixtures thereof, and n is an integer representing the number of repeating monomer units. In one embodiment, a single functional group imparts both photosensitivity and water solubility or dispersability to the polymer. In another embodiment, a first functional group imparts photosensitivity to the polymer and a second functional group imparts water solubility or dispersability to the polymer.

Abstract: The invention relates to a crosslinkable polymer for use in optics and non-linear optics, which comprises at least one chromophore, characterized in that it has, on at least two of its ends, at least one reactive end group of a different chemical type from the group predominantly used in polymerization and the preparation of a polymer skeleton. Said reactive end group comprises at least one CC, CN, CS, SS or NS double bond and/or triple bond, and/or an epoxy group and/or a thiol group or a derivative of said groups, and the polymerization groups are selected from at least one of the following groups: urethane, ester, amide, imide, ether, carbon-carbon, sulfide, silane and siloxane, urethane and ester groups being particularly preferred. Application in optical and opto-electronic materials and devices.

Abstract: Provided is a polymer electrolyte which is cheap and easily synthesized, and has a high water resistance and high output performance.

Abstract: The present invention provides a series of easily processable poly(ether-imide)s that are organic-soluble and can afford colorless films, their organic solutions and their manufacturing process. The poly(ether-imide) is prepared from a dianhydride and a diamine, wherein the dianhydride is a bis(ether anhydride) having tert-butyl group, i.e. 1,4-bis(3,4-dicarboxyphenoxy)-2-tert-butylbenzene dianhydride. The present invention is also directed to synthesis of this special dianhydride.

Abstract: A novel polyimide having a repeating structure unit expressed by the following general formula (1), a method for manufacturing the same, a gas separation membrane using the novel polyimide and the method for manufacturing the same. The gas separation membrane using this polyimide is excellent in gas permeable performance and separation selectivity for gas, for example, carbon dioxide, methane, etc.General Formula (1) ##STR1## where R denotes a quadrivalent organic group.

Abstract: The morphology of multidimensional, thermally stable oligomers is combined with the inclusion of charge carrier linkages within the polymer arms to produce thermally stable advanced composites from cured oligomers that are conductive or semiconductive if suitably doped.

Abstract: A novel polyalkyl ether/polyaryl ether sulfone or ketone copolymer and a specific polyether ester copolymer are useful for producing a medical material to be used to contact the blood; and methods for producing the medical material comprising said polyalkyl ether/polyaryl ether sulfone or ketone copolymer or a specific polyether ester copolymer.

Abstract: Disclosed are a polymer alloy comprising a polyester resin having a specified acid value, an epoxidized diene-based block copolymer, and an unvulcanized rubber, a composition in which an unvulcanized rubber is mixed with the polymer alloy, and parts for tires in which the composition is employed.

Abstract: This invention relates to a poly (imide amic ester) random copolymer, a precursor thereof, and a process for preparing the same. Specifically this invention relates to a novel precursor of polyimide, poly(imide amic ester) which is chemically stable and has excellent workability in either liquid or solid state, a polyimide obtained therefrom and a process for preparing the same.

Abstract: An improved polybenzimidazole wherein the total concentration of metals other than alkali metal and alkaline earth metals is 10 ppm or less. The resulting polybenzimidazole is industrially useable in parts or components of apparatus for the manufacture of semiconductors and display devices.

Abstract: The present invention relates to amine compositions and the preparation of polyimides. The polyimides can be used for inducing alignment of a liquid crystal medium with polarized light and liquid crystal display elements.

Abstract: Micropowders having spherical particles possessing an essentially smooth surface structure contain, as essential components, polyarylene ether sulfones or polyarylene ether ketones and are obtainable by prilling melts thereof or spray-drying solutions thereof.

Abstract: Copolyetherimides are prepared by the reaction of an alkali metal salt of a dihydroxyaromatic compound with a bis(substituted phthalimide) and a third compound which may be a substituted aromatic ketone or sulfone or a macrocyclic polycarbonate or polyarylate oligomer. The reaction takes place the in presence of a solvent and a phase transfer catalyst having high thermal stability, such as a hexaalkylguanidinium halide. Random or block copolymers may be obtained, depending on the reaction conditions.

Abstract: Improved process for producing a polybenzimidazole compound in solution by dissolving a fully dried polybenzimidazole of the following general formula (1) or (2) in N,N-dimethylacetamide of a sufficiently reduced water content at an elevated temperature of 260.degree. C. or higher in an inert gas atmosphere and a solution of the polybenzimidazole compound produced by the process. The solution remains useful for an extended time without using metal salts or any other stabilizers: ##STR1## where R.sup.1, R.sup.2 and R.sup.5 are tetra-, di- and trivalent aromatic groups, respectively; R.sup.3, R.sup.4 and R.sup.6 are each independently a hydrogen atom, an alkyl group or an aryl group; n is an integer of 2 or more.

Abstract: A new class of polyarylene co-polymers include repeating units comprising one or more arylene units having the general formula (--Ar--/--Y--).sub.n, where Y is a divalent group chosen from nil, --Z--, --Z--Ph--, and --Ph--Z--Ph--, where Z is a divalent group chosen from the group consisting of --O--, --S--, --NR--, --O(CO)--, --O(CO.sub.2)--,--(CO)NH(CO)--, --NR(CO)--, phthalimide, pyromellitimide, --CO--, --SO--, --SO.sub.2 --, --P(O)R--, --CH.sub.2 --, --CF.sub.2 --, and --CRR'--; Ph is phenylene (ortho, meta or para); and n is greater than 4. The co-polymers are useful as molding resins, and composite matrix resins, and where Ar is heteroarylene as ion exchange resins.

Abstract: A method for synthesizing 1,4-bis(4-aminophenoxy)naphthalene and a series of polyamides, polyimides and copoly(amide-imide)s derived from the said compound is disclosed. These polymers possess excellent thermal stability and mechanical strength.

Abstract: The invention relates to polysulphone/polyether block copolycondensates having the recurring structural unit as in formula (I)--(--O--E--O--Ar.sup.1 --SO.sub.2 --Ar.sup.2 --)--W-- (I)whereinE is a divalent diphenolate radical andW is a polyether, polythioether or polyacetal possessing at least two hydroxyl groups and having an average molecular weight (M.sub.n) of from 400 to 30,000 andwherein the proportion of the radical W in the total polymer amounts to 5 to 99 wt. %,the preparation and use thereof for the production of moulded shapes, for example, membranes or catheter tubes.

Abstract: A process for inducing pre-tilt in alignment of a liquid crystal medium comprising exposing at least one optical alignment layer, comprising anisotropically absorbing molecules and hydrophobic moieties, to polarized light; the polarized light having a wavelength within the absorption band of said anisotropically absorbing molecules; wherein the exposed anisotropically absorbing molecules induce alignment of the liquid crystal medium at an angle + and -.theta. with respect to the direction of the polarization of the incident light beam and along the surface of the optical alignment layer, and induce a pre-tilt at an angle .PHI. with respect to the surface of the optical alignment layer and applying a liquid crystal medium to said optical alignment layer, is described. The invention also is directed to liquid crystal display elements made by the process of the invention and to novel polyimide compositions that are useful as optical alignment layers in the invention.

Abstract: A photosensitive resin composition comprising, as its main ingredient, a poly(amic acid) resin constituted of a diamino compound represented by formula: ##STR1## and optionally used other diamino compound and a tetracarboxylic acid dianhydride as its constituent monomers and/or a poly(amic acid) ester resin obtained by esterifying said poly(amic acid) resin and/or a polyimide resin obtained by a dehydrating or alcohol-eliminating ring-closure reaction of said poly(amic acid) resin or poly(amic acid) ester resin has an excellent developability and a high film strength and can form a relief patter of low thermal expansion.

Abstract: Aromatic polyether polymers, illustrated by polyethersulfones, polyetherketones and polyetherimides, are prepared by a phase transfer catalyzed reaction between a salt of at least one dihydroxyaromatic compound and at least one substituted aromatic compound such as bis(4-chlorophenyl) sulfone, bis(4-chlorophenyl) ketone or 1,3-bis?N-(4-chlorophthalimido)!benzene, in a monoalkoxybenzene such as anisole as diluent and in the presence of a phase transfer catalyst, preferably a hexaalkylguanidinium salt.

Abstract: Polyetherimide polymers prepared from monomers containing indane moieties are disclosed. The high molecular weight indane polyetherimides are transparent, ductile, and exhibit high glass transition temperatures (>200.degree. C.). In addition, the polyetherimides are thermally stable at high temperatures and exhibit good optical properties making them useful in high temperature processing applications, in the fabrication of optoelectronics devices, and in optical applications.

Abstract: The morphology of multidimensional oligomers is combined with the inclusion of charge carrier linkages within the oligomer arms to produce oligomers that are useful for preparing conductive or semiconductive composites, if suitably doped. The Schiff base linkages are prepared by the condensation of aldehydes and amines. The oligomers can be blended, and either the oligomers or their blends can be prepregged.

Abstract: The physical properties of high performance composites can be tailored by using blends to make the composites. The resulting composites are relatively easy to make and have long-term, high performance capabilities even in harsh service conditions. The blends of the present invention include at least one oligomer having an aromatic, aliphatic, or mixed aromatic and aliphatic backbone from one chemical family and an unsaturated hydrocarbon end cap and at least one polymer from a different chemical family. Upon curing, the oligomer in the blend addition polymerize to form composites possessing advanced properties with respect to those exhibited by the pure oligomer or the pure polymer. Coreactive oligomer blends can be used instead of a pure oligomer to form composites that include addition polymers, block copolymers, and the compatible polymer, thereby further achieving a tailoring of properties in the cured composite. The blends can be prepregged and cured to form composites.

Abstract: The present invention relates to a new polyesterimide of the type containing ester repeat functional groups E=--CO--O--, imide repeat functional groups I: ##STR1## and at least one chromophore, characterized in that it contains a quantity of recurrent amide functional groups capable of ring closure to imides which is smaller than or equal to 5 mol % relative to the sum of the imide functional groups and of the amide functional groups capable of ring closure to imides, which are present, and in that the polymerization functional groups consist essentially of E functional groups.This polyesterimide is preferably free from amide functional groups capable of ring closure to imides.One of the processes for obtaining this polyesterimide constitutes another subject-matter of the invention.Such a polymer is advantageously capable of behaving like a material that is transparent and/or active in nonlinear optics.

Abstract: A sulfonated dicarboxylic acid and a diaromatic carbonate are reacted by a solution process to form a sulfonated aromatic diester such as diphenyl sodium 5-sulfoisophthalate. The sulfonated aromatic diester is reacted with an aromatic polymer precursor mixture such as bisphenol A and diphenyl carbonate, polymer or combination thereof, at a temperature above the melting point of the polymer or a member of the aromatic polymer precursor to form a randomly positioned sulfonated aromatic moiety in a polymer chain of a thermoplastic non-crosslinked aromatic polymer such as a linear polycarbonate.

Abstract: The present invention relates generally to a new adhesive comprising a vinyl containing siloxane-containing polyimide for use in TSM capping of electronic package assemblies with adhesive capability of providing a seal band width of less than 4mm and even less than 2mm, solubility in non-toxic and environmentally safe solvents and durable adhesive properties and to a method for making the polyimides, a method for using the polyimides to make electronic packages and electronic packages made using the adhesive. The preferred vinyl-containing siloxane containing polyimide is a block type polymer containing blocks of a dianhydride-aromatic diamine oligomeric reaction product joined by non-vinyl/vinyl containing siloxane diamine forming links.

Abstract: In a process for the preparation of poly-o-hydroxyamides and poly-o-mercaptoamides, a bis-o-aminophenol or a bis-o-aminothiophenol is reacted at a temperature of .ltoreq.0.degree. C. with a mixed dianhydride of a dicarboxylic acid and a sulfonic acid with the following structure:E--SO.sub.2 --O--CO--R*--CO--O--SO.sub.2 --Ewhere E is an (optionally substituted) methyl, phenyl, or naphthyl group and R* is the parent body of the dicarboxylic acid.

Abstract: Disclosed is a process which comprises reacting a polymer of the general formula ##STR1## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR2## B is one of several specified groups, such as ##STR3## or mixtures thereof, and n is an integer representing the number of repeating monomer units, with an acetyl halide and dimethoxymethane in the presence of a halogen-containing Lewis acid catalyst and methanol, thereby forming a haloalkylated polymer. In a specific embodiment, the haloalkylated polymer is then reacted further to replace at least some of the haloalkyl groups with photosensitivity-imparting groups. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymer.

Abstract: Disclosed are cosmetic melanins of different colors produced by procedures involving oxidative polymerization of monomeric precursors of melanin and/or co-monomers that enhance substantivity or adherence of the melanins to the skin and hair. Also disclosed are methods for preparing cosmetic melanins and methods for using these compositions topically to produce a natural-appearing tan and to prevent damage to skin caused by UV exposure.

Abstract: An aromatic polyimide having a recurring unit of the formula (I): ##STR1## wherein Ar is a divalent aromatic group having one or two benzene rings which has a sulfonate group of --SO.sub.3 H, --SO.sub.3 M, and --SO.sub.3 N(L).sub.4 on the ring, wherein M is an alkali metal and L is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, is favorably employed in the form of a semipermeable film for gas separation.

Abstract: High performance polyester sulfone oligomers are prepared for aerospace applications by condensing mono- or difunctional crosslinkable end caps (i.e. unsaturated hydrocarbons having one or two crosslinking sites) with dicarboxylic acid halides and dialcohols (i.e. diols). Multidimensional oligomers have an aromatic hub from which the polyester chains radiate. Blends of the linear and multidimensional oligomers can be made using compatible, non-crosslinking polymers. Prepregs and composites are formed from the oligomers or blends.

Abstract: A process for inducing pre-tilt in alignment of a liquid crystal medium comprising exposing at least one optical alignment layer, comprising anisotropically absorbing molecules and hydrophobic moieties, to polarized light; the polarized light having a wavelength within the absorption band of said anisotropically absorbing molecules; wherein the exposed anisotropically absorbing molecules induce alignment of the liquid crystal medium at an angle + and -.theta. with respect to the direction of the polarization of the incident light beam and along the surface of the optical alignment layer, and induce a pre-tilt at an angle .PHI. with respect to the surface of the optical alignment layer and applying a liquid crystal medium to said optical alignment layer, is described. The invention also is directed to liquid crystal display elements made by the process of the invention and to novel polyimide compositions that are useful as optical alignment layers in the invention.

Abstract: A novel polyimide is soluble in organic solvents and excels in heat resistance. The polyimide comprises 95-40 mol % of the repeating unit represented by the formulas (1) and 60-5 mol % of the repeating unit represented by the formula (2) and has a number average molecular weight of 4,000-200,000: ##STR1## wherein X is --SO.sub.2 -- and/or --C(.dbd.O)--OCH.sub.2 CH.sub.2 O--C(.dbd.O)--, Ar is a divalent group containing aromatic rings, and R is an alkylene group having 1-10 carbon atoms or a group: --CH.sub.2 OC.sub.6 H.sub.4 --, and n is an integer of 1-20.

Abstract: Poly(ester-imides) containing t-butylhydroquinone and trimellitic anhydride as part of the repeat units, as well as other monomers, are useful as molding resins. The polymers have a high glass transition temperature and are particularly useful in applications requiring good wear resistance.

Abstract: High performance polyester sulfone oligomers are prepared for aerospace applications by condensing mono- or difunctional crosslinkable end caps (i.e. unsaturated hydrocarbons having one or two crosslinking sites) with dicarboxylic acid halides and dialcobols (i.e. diols). Multidimensional oligomers have an aromatic hub from which the polyester chains radiate. Blends of the linear and multidimensional oligomers can be made using compatible, non-crosslinking polymers. Prepregs and composites are formed from the oligomers or blends.

Abstract: Novel polyimides which are soluble in various organic solvents and excellent in thermal resistance, processability are disclosed. The polyimides comprise repeating units represented by the following formula (1) and/or (2) and having a number average molecular weight of 4,000-200,000. ##STR1## wherein Ar is a divalent group represented by the following formula (2) or (3): ##STR2## wherein Y is --O--, --CO--, --S--, --SO.sub.2 -- or --C(CH.sub.3).sub.2 --, ##STR3## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are each a C.sub.1-4 alkyl group or a C.sub.1-4 alkoxy group, Ra is a divalent group having 2-6 benzene rings, X.sup.1 represents NH, NR (wherein R is a C.sub.1-4 alkyl group or a C.sub.1-4 alkoxy group) or S, Rb is C.sub.2-20 alkylene group, ether group or dimethylsiloxane group, and X.sub.2 represents NH, NR (wherein R is a C.sub.1-4 alkyl group or a C.sub.

Abstract: An aromatic polyethersulphone incorporating sub-unit (1) where A is an electron withdrawing group, the designation "o,p" represents that the bond is at the ortho or para position to the A group, and X is selected from: OH; --O M where M is an organic or inorganic cation (other than hydrogen) and n is at least 1; --NR1R2 where R1 and R2 are the same or different and are selected from hydrogen and alkyl, aryl, aminoalkylene or ammonoalkylene groups; and --OR3 where R3 is an alkyl or aryl group; either as the only sub-units of the polymer or in combination with comonomer units.

Abstract: The present method provides a method for preparing the PI varnish which has the steps of: 1) preparing a mixed solution of 60-100% by weight aprotic solvent, and 0-40% by weight aromatic solvent; 2) adding into the mixed solution in a mole ratio of 1:9 two aromatic diamines; and 3) further adding in the mixed solution in a mole ratio of 1:5 two aromatic dianhydrides. Such PI has a suitable thermal expansion coefficient and characteristics different form those of the PI currently in use.

Abstract: A sulfonated dicarboxylic acid and a diaromatic carbonate are reacted by a solution process to form a sulfonated aromatic diester such as dipbenyl sodium 5-sulfoisophthalate. The sulfonated aromatic diester is reacted with an aromatic polymer precursor mixture such as bisphenol A and diphenyl carbonate, polymer or combination thereof, at a temperature above the melting point of the polymer or a member of the aromatic polymer precursor to form a randomly positioned sulfonated aromatic moiety in a polymer chain of a thermoplastic non-crosslinked aromatic polymer such as a linear polycarbonate.

Abstract: This invention relates to polymers having non-linear optical properties which polymers include fluorene moieties having at least one electron accepting group and at least one electon donating group substituted to different phenyl rings of the fluorene moiety.

Abstract: The invention provides novel thermoplastic polyimide featuring solid adhesive property under low temperature, low hygroscopic coefficient, and solid resistivity to radioactive rays. The invention also provides novel polyamide acid which is substantially precursor of the thermoplastic polyimide, and also provides novel thermally fusible laminated film for covering conductive wires, featuring solid adhesive property under low temperature, solid resistivity to radioactive rays, and distinct suitability for covering superconductive wires in particular.The novel thermoplastic polyimide is represented by general formula (1) corresponding to the chemical structure shown below; ##STR1## wherein, Ar.sub.1, Ar.sub.2, Ar.sub.4, and Ar.sub.6, respectively designate divalent organic radical, whereas Ar.sub.3 and Ar.sub.

Abstract: A photosensitive resin composition comprising, as its main ingredient, a poly(amic acid) resin constituted of a diamino compound represented by formula: ##STR1## and optionally used other diamino compound and a tetracarboxylic acid dianhydride as its constituent monomers and/or a poly(amic acid) ester resin obtained by esterifying said poly(amic acid) resin and/or a polyimide resin obtained by a dehydrating or alcohol-eliminating ring-closure reaction of said poly(amic acid) resin or poly(amic acid) ester resin has an excellent developability and a high film strength and can form a relief patter of low thermal expansion.

Abstract: A diaminobenzene derivative of the formula (I): ##STR1## wherein each of P and Q which may be the same or different from each other, is a single bond, or a bivalent organic group selected from the group consisting of --O--, --COO-- and --CONH--, R.sub.1 is a C.sub.2-22 straight chain alkylene group, and R.sub.2 is a cyclic group selected from the group consisting of an aromatic ring, an aliphatic ring, a heterocyclic ring and substituted forms of such rings.