Abstract: A poly(imide-amide) copolymer, which is a product of a reaction between a diamine and a dianhydride, wherein the diamine comprises a diamine represented by Chemical Formula 1 and the dianhydride comprises a dianhydride represented by Chemical Formula 5: wherein, the variables in Chemical Formulae 1 and 5 are described in the specification.

Abstract: Disclosed herein is a polyamide-imide copolymer film, comprising a copolymer resin in which a unit structure derived from TFDB (2,2?-bistrifluoromethyl-4,4?-biphenyl diamine), a unit structure derived from 6FDA (4,4?-(hexa-fluoroisopropylidene)diphthalic anhydride), a unit structure derived from BPDA (3,3?,4,4?-biphenyltetracarboxylic dianhydride) and a unit structure derived from TPC (terephthaloyl chloride or 1,4-benzenedicarbonyl chloride) are copolymerized, wherein the copolymer resin has a weight average molecular weight of 10,000˜400,000.

Abstract: There is provided a gypsum dispersant and a gypsum additive that improve the fluidity of gypsum slurry even if gypsum raw materials used are different in quality and that do not induce delay of curing of gypsum slurry. A gypsum dispersant, including: (A) a polycarboxylic acid polymer; and (B) a polyamide polyamine obtained by a reaction of a polyalkylene polyamine and a dibasic acid as essential components, and/or an alkylene oxide adduct of the polyamide polyamine.

Abstract: Disclosed are a polyamic acid solution, a polyimide resin prepared by imidization of the polyamic acid solution, a flexible metal clad laminate using the polyimide resin, and a printed circuit board including the flexible metal clad laminate, wherein the polyamic acid solution includes (a) 3,3?,4,4?-biphenyltetracarboxylic acid dianhydride (BPDA), and pyromellitic dianhydride (PMDA) as aromatic tetracarboxylic acid dianhydride; (b) at least one aromatic diamine; (c) an organic solvent; and (d) an inorganic filler.

Abstract: A crosslinked aromatic polyimide having shape memory properties and methods of making the same. The crosslinked aromatic polyimide comprises at least one aromatic diamine, at least one dianhydride monomer, and a tri(oxybenzene-amine) crosslinker. The crosslinked aromatic polyimide polymers and films possess superior shape memory properties at temperatures above 225° C.

Abstract: A process for preparing polyamides by reacting starting monomers selected from dicarboxylic acids and diamines or salts of dicarboxylic acids and diamines, amino carboxylic acids, amino nitriles, lactams and mixtures thereof, in the presence or absence of water and/or of functionalizing compounds capable of attaching to carboxyl or amino groups, which process comprises performing the reaction in an ionic liquid as solvent without use of additional accelerants.

Abstract: A polyimide represented by formula (6) is provided. The polyimide is fabricated by performing a polycondensation reaction with a amine compound shown in formula (4) and a dianhydride compound shown in formula (5) as monomers. In formulas (5) and (6), Ar represents aromatic group, and n represents a positive integer.

Abstract: Disclosed embodiments concern using at least one triazine, typically an amine or polyamine triazine (referred to as amino triazines), in combination with at least one ionomer or ionomer precursor to form compositions useful for making sporting equipment, such as golf ball components. The ionomer or ionomer precursor typically includes plural acid functional groups, such as carboxyl or carboxylate groups, that react or form salts with the amino triazine. Specific examples, without limitation, of suitable amino triazines include guanamine, 6-methyl-1,3,5-triazine-2,4-diamine(acetoguanamine), 6-nonyl-1,3,5-triazine-2,4-diamine(nonylguanamine), 6-phenyl-1,3,5-triazine-2,4-diamine(benzoguanamine) and 2,4,6-triamino-triazine(melamine).

Abstract: A radiation-curable acrylate-modified aminoamide resin which is the Michael addition product of an aminoamide thermoplastic polymer derived from a polymerised unsaturated fatty acid with a polyol ester having at least three (meth)acrylate ester groups, the aminoamide thermoplastic polymer having an amine number of from 40 to 60 mgKOH/g, the ratio of the initial (meth) acrylate groups of the polyol ester to the initial amino functional groups of the aminoamide polymer being at least 4:1, is liquid at 25° C., and is useful as the resin component of various types of energy-curable coating composition, including inks, varnishes and lacquers, especially lithographic inks.

Abstract: A polyamide represented by formula (6) is provided. The polyamide is fabricated by performing a polycondensation reaction with amine compound shown in formula (4) and an acid or derivative thereof shown in formula (5) as monomers. In formulas (5) and (6), X represents aromatic groups or aliphatic groups. In formula (5), R represents OH group or halogen.

Abstract: A polyamic acid composition including a polyamic acid, the polyamic acid having an imidization ratio of from about 5.0% to about 25.0%, and being obtained by reacting a diamine compound, a tetracarboxylic dianhydride and an acid monoanhydride at an amount ratio that satisfies the following formula (1): 0.970<Y/X<0.998 and Formula (2): 0.00<Z/2(X?Y)<0.50. In Formula (1) and Formula (2), X represents a content (mol) of the diamine compound, Y represents a content (mol) of the tetracarboxylic dianhydride, and Z represents a content of the acid monoanhydride (mol).

Abstract: The present invention provides a UCST-type thermoresponsive polymer compound which responds to a temperature under physiological conditions and has biofunctionality, and various uses thereof as a thermoresponsive material. Specifically, the invention provides a thermoresponsive material containing, as an active ingredient, a polymer compound represented by Formula (I) below or an addition salt thereof, the thermoresponsive material having an upper critical solution temperature in the range of 5 to 50° C. in an aqueous solution with a salt concentration of at least 1 mM and a pH in the range of 3 to 10.5: wherein m represents an integer of 10 or more; n represents a number satisfying 0.4?n?1; R1 represents hydrogen or succinyl; and R2 represents carbamoyl.

Abstract: The invention relates to polymers (P) of amides, imides, amides-imides or their derivates. The polymer (P) comprising recurring units (I) of one or more structural formula(e): -A-B-C-D- (I), wherein, A and C, identical or different from each other and from one structural formula to another, independently represent an amido group an imido group of formula or a mixture thereof; B, identical or different from one structural formula to another, is independently selected from the set consisting of C4-C50 hydrocarbon groups, C12-C50 groups, a dibenzodiazocine-containing divalent group, and a mixture thereof; D, identical or different from one structural formula to another, independently represents a dibenzodiazocine-containing divalent group. The invention also relates to a process for the preparation of said polymers. Moreover, the invention relates to polymer compositions containing said polymer, its shaped articles or shaped parts as well as applications of those polymers.

Abstract: The invention concerns a paper comprising (a) 40 to 70 parts by weight of polypyridobisimidazole fiber, polypyridobisimidazole pulp, or mixtures thereof and (b) 30 to 60 parts by weight of friction modifiers, structural resins, wet-strength resins, processing aids, fillers, and mixtures thereof; the parts by weight being based on the total amount of a) and b) in the paper.

Abstract: The present disclosure provides polyamides and amidoamine curing agents including the reaction product of (1) a modified amine component comprising at least one multifunctional amine of structure 1: wherein R1 is selected from C1-C16 linear, cyclic, and branched alkyl, alkenyl, and alkaryl groups; R2 and R4 are hydrogen, R3 is R1 or hydrogen, X, Y, and Z are independently selected from C2-C10 alkylene, hexylene and cycloalkylene groups, n=0, 1, 2, 3, 4, 5, 6, or 7; and (2) a fatty acid component. Exemplary fatty acid components include at least one of monomer fatty acids, dimer fatty acids, trimer fatty acids, polymer fatty acids, esters of monomer, dimer, trimer, and polymer fatty acids and combinations thereof. The method for making the curing agents and articles formed therefrom are also disclosed.

Abstract: Disclosed embodiments concern using at least one triazine, typically an amine or polyamine triazine (referred to as amino triazines), in combination with at least one ionomer or ionomer precursor to form compositions useful for making sporting equipment, such as golf ball components. The ionomer or ionomer precursor typically includes plural acid functional groups, such as carboxyl or carboxylate groups, that react or form salts with the amino triazine. Specific examples, without limitation, of suitable amino triazines include guanamine, 6-methyl-1,3,5-triazine-2,4-diamine (acetoguanamine), 6-nonyl-1,3,5-triazine-2,4-diamine (nonylguanamine), 6-phenyl-1,3,5-triazine-2,4-diamine (benzoguanamine) and 2,4,6-triamino-triazine (melamine).

Abstract: A polyamide, a method for manufacturing the polyamide and compositions that include the polymer are described. A high-viscosity polyamide obtained by the polymerization of diacid and diamine monomers in the presence of multifunctional and, optionally, monofunctional compounds are also described. The polyamide can be used in particular for the production of compositions intended, for example, for being molded or blown.

Abstract: A curing agent for epoxy resin, and a coating composition using the curing agent curing agent that delivers excellent recoatability and overcoatability after a long time exposure. (A) An epoxy curing agent that is derived by adduction between amide-type reactants from polyamine compounds comprising from 25-75 mol % of a polyoxyalkylene-polyamine and carboxylic acids or a mixture thereof and glycidyl ether compound; (B) An epoxy curing agent of the mixture of (B1) amide-type reactants prepared through polyoxyalkylene-polyamine and carboxylic acids or a mixture thereof, and (B2) a reactant is derived by adduction between other aliphatic polyamines or a mixture thereof and glycidyl ether compound. Coating composition comprising the epoxy curing agent of the above described A or B.

Abstract: A metal-coated polyimide film is excellent in long-term adhesion reliability, exhibits various dimensional stabilities, and is particularly suitable for FPC, COF and TAB applications. The metal-coated polyimide film comprises a non-thermoplastic polyimide film; and a metal layer being directly formed on one surface or both surfaces of the non-thermoplastic polyimide film without using an adhesive, wherein the non-thermoplastic polyimide film contains a non-thermoplastic polyimide resin having a thermoplastic polyimide block component.

Abstract: The invention relates to a water-insoluble reaction product of an oil-soluble polar modified polymer and a polyamine.

Abstract: A liquid crystal display is provided which is capable of reducing the occurrence of defective display due to variations in the initial alignment direction of a liquid crystal alignment control film in a liquid crystal display of an IPS scheme, realizing the stable liquid crystal alignment, providing excellent mass productivity, and having high image quality with a higher contrast ratio. The liquid crystal display has a liquid crystal layer disposed between a pair of substrates, at least one of the substrates being transparent, and an alignment control film formed between the liquid crystal layer and the substrate. At least one of the alignment control films 109 comprises photoreactive polyimide and/or polyamic acid provided with an alignment control ability by irradiation of substantially linearly polarized light.

Abstract: Novel modified polyamides are prepared by polymerization of diacid and diamine monomers in the presence of certain multifunctional and, optionally, monofunctional compounds; such novel polyamides are formulated into molding compositions which can be converted into useful shaped articles.

Abstract: A polyimide represented by formula (6) is provided. The polyimide is fabricated by performing a polycondensation reaction with a amine compound shown in formula (4) and a dianhydride compound shown in formula (5) as monomers. In formulas (5) and (6), Ar represents aromatic group, and n represents a positive integer.

Abstract: A polyamide represented by formula (6) is provided. The polyamide is fabricated by performing a polycondensation reaction with amine compound shown in formula (4) and an acid or derivative thereof shown in formula (5) as monomers. In formulas (5) and (6), X represents aromatic groups or aliphatic groups. In formula (5), R represents OH group or halogen.

Abstract: A method for using citraconic anhydride and itaconic anhydride as addition cure end caps in reactions for forming polyamic acid oligomers and polyimide oligomers, is provided. Prepregs and high temperature adhesives made from the resulting oligomers, as well as, high temperature, low void volume composites made from the prepregs, are also provided.

Abstract: A compound having an amino group at a terminal thereof and at least one amino group in a repeating unit, a cross-linked material of the compound, a double cross-linked polymer thereof, an electrolyte membrane and an electrode for a fuel cell, which include the cross-linked material of the compound or the double cross-linked polymer thereof, and a fuel cell including at least one of the electrolyte membrane and the electrode.

Abstract: The object of the present invention is to provide an adhesion film for semiconductor that is capable of bonding a semiconductor chip to a lead frame tightly at an adhesion temperature lower than that of the adhesion film of a traditional polyimide resin without generation of voids and that can also be used for protection of lead frame-exposed area, a thermoplastic resin composition for semiconductor for use in the adhesive agent layer therein, and a lead frame having the adhesive film and a semiconductor device; and, to achieve the object, the present invention provides a thermoplastic resin composition for semiconductor, comprising a thermoplastic resin obtained in reaction of an amine component containing an aromatic diamine mixture (A) containing 1,3-bis(3-aminophenoxy)benzene, 3-(3?-(3?-aminophenoxy)phenyl)amino-1-(3?-(3?-aminophenoxy)phenoxy)benzene and 3,3?-bis(3?-aminophenoxy)diphenylether, and an acid component (C), an adhesion film for semiconductor using the same, a lead frame having the adhesion fi

Abstract: A single-stage melt polymerization process is demonstrated for production of a polybenzimidazole which comprises the following steps. First, a high intensity reactor having a means for controlling agitation and rate of, atmosphere, and temperature is provided. Second, the high intensity reactor is degassed and filled with nitrogen. Third, a tetraminobiphenyl (TAB), compound A and an isophthalic acid (IPA), compound B are provided. Fourth, the high intensity reactor is charged with compounds A and B. Fifth, compound A and compound B are reacted under high intensity agitation in an absence of catalyst, to temperature of between 340° C. to 430° C. to produce a polybenzimidazole having an IV of at least 0.45 and a plugging value of greater than or equal to 1.0 g/cm2.

Abstract: A non-thermoplastic polyimide film exhibits high adherability without expensive surface treatment and is made from a precursor solution having high storage stability. The non-thermoplastic polyimide film comprises a non-thermoplastic polyimide resin having a block component derived from a thermoplastic polyimide. Preferably, the block component of the thermoplastic polyimide is present in an amount of 20 to 60 mol % of the entire polyimide so that the precursor solution thereof exhibits high storage stability and that the film can exhibit high adherability, in particular, high adherability to polyimide adhesives.

Abstract: The present invention is directed to the use polycyclic diamines. These diamines, when polymerized with dianhydrides, and optionally other non-polycyclic diamines are used to form new polyamic acids. The polyamic acids can be imidized to form a new class of useful polyimide resins and polyimide films, particularly in electronics type applications.

Abstract: The invention relates to an intrinsically gel-free, randomly branched polyamide that is built up at least of units derived from AB monomers; at least one compound I, this being a dicarboxylic acid (A2); at least one compound II, this being a triamine (B3); and optionally a compound III, this being a monocarboxylic acid (A1), characterized in that the polyamide is also built up of units derived from at least one compound IV, this being a diamine (B2); and in that the relative amounts n of the said compounds satisfy the following relationships: 0 ? n A ? ? 1 n B ? ? 3 ? 4 1 ? n A ? ? 2 n B ? ? 3 ? 4 200 ? n AB n B ? ? 3 ? 2000 2 5 ? n B ? ? 2 n B ? ? 3 0.996 ? f _ n ? ? A = n A ? ? 1 + 2 ? n A ? ? 2 + n AB n A ? ? 1 + n A ? ? 2 + n B ? ? 2 + n B ? ? 3 + n AB ? 1 0.

Abstract: The present invention is directed to the use polycyclic diamines. These diamines, when polymerized with dianhydrides, and optionally other non-polycyclic diamines are used to form new polyamic acids. The polyamic acids can be imidized to form a new class of useful polyimide resins and polyimide films, particularly in electronics type applications.

Abstract: A fluorine-containing diamine represented by the formula (1), [Chemical Formula 29] is provided. Furthermore, a fluorine-containing polymer is provided by using this fluorine-containing amine as a monomer. The fluorine-containing polymer can exhibit superior characteristics such as low dielectric property and high transparency, while maintaining high fluorine content and retaining adhesive property.

Abstract: It is an object of the present invention to provide a water-borne resin composition which can form a film being excellent in flexibility and heat resistance without reducing an insulating property and can be used suitably for a cationic electrocoating composition. A water-borne resin composition, having a hydrolysable functional group and a polymerizable unsaturated carbon bond, wherein a base resin is at least one species selected from the group consisting of a polyamide-imide resin, a polyamide resin and a polyimide resin.

Abstract: A process is presented for the production of high molecular weight polybenzimidazole, in two steps. Step one: provide a first reaction vessel and charge it with at least one aromatic hydrocarbon tetraamine, and a heterocyclic ring making up the dicarboxylic component. Heat the reactants under agitation. Terminate the agitation while continuing to heat the reaction mixture to about 230° C. while allowing the reaction mass to foam. Cool the reaction mass to a friable foamed mass. Crush the friable foamed mass to obtain a ground prepolymer. Step two; provide a second reaction vessel, transferring the ground prepolymer to it. A pressure wash of the first reaction vessel and the means for agitation to obtain a second ground prepolymer. Transfer the second ground prepolymer to the second reaction vessel. Heat the ground prepolymer and second ground prepolymer under agitation to a higher temperature than the first step until the desired degree of polymerization is achieved.

Abstract: Processes for forming adducts of amines with acrylic macromonomers are provided. Also provided are processes for using ring-closing reactions of the adducts to form lactams. The adducts are useful, for example, for making adhesives, surfactants, viscosity modifiers, processing aids, and other products.

Abstract: A method for preparing poly(2,5-benzimidazole) whereby 3,4-diaminobenzoic acid is polymerized using a dehydrating reagent containing P2O5 and CX3SO3H where X is H or F. The poly(2,5-benzimidazole) has good proton conductivity and low methanol permeability, and therefore can be used as a polymer electrolyte membrane for a fuel cell.

Abstract: The present invention provides an amic acid ester oligomer with the structure of formula (1) wherein R, Rx, G, P and m are as defined in the specification. The present invention also provides a precursor composition for a polyimide resin comprising the above-mentioned oligomer of formula (1). The polyimide synthesized from the precursor composition exhibits good operations and physiochemical properties.

Abstract: An object of the present invention is to obtain a novel polymeric material capable of forming a solid polymer electrolyte excellent not only in processability, solvent resistance and durability/stability but also in ion conductivity by introducing sulfonic acid group or phosphonic acid group into a polybenzazole compound having excellent properties in view of heat resistance, solvent resistance, mechanical characteristics and the like. Means attaining the object of the present invention is a polybenzazole compound including an aromatic dicarboxylic acid bond unit having sulfonic acid group and/or phosphonic acid group and satisfying either a condition that inherent viscosity measured in concentrated sulfuric acid is in the range of 0.25 to 10 dl/g or a condition that inherent viscosity measured in a methanesulfonic acid solution is in the range of 0.1 to 50 dl/g.

Abstract: A composition comprises a condensation product of an amine-reactive fluorinated polyether and a polyamine. The compositions may be in dispersed in water.

Abstract: Crosslinkable resin compositions that are cured easily by irradiation with active energy beams and particularly cured quickly with ultraviolet ray are provided, which comprises a polymer containing a maleimido group and an ethylenically unsaturated group. The composition may be an aqueous composition. They provide cured films which are excellent in durability, free from coloring and odors, and also excellent in abrasion resistance, adhesion to substrates, surface smoothness, and chemical resistance.

Abstract: A preparation process of polyimide aerogels that composed of aromatic dianhydrides and aromatic diamines or a combined aromatic and aliphatic diamines is described. Also descried is a process to produce carbon aerogels derived from polyimide aerogel composed of a rigid aromatic diamine and an aromatic dianhydride. Finally, the processes to produce carbon aerogels or xerogel-aerogel hybrid, both of which impregnated with highly dispersed transition metal clusters, and metal carbide aerogels, deriving from the polyimide aerogels composed of a rigid aromatic diamine and an aromatic dianhydride, are described. The polyimide aerogels and the polyimide aerogel derivatives consist of interconnecting mesopores with average pore size at 10 to 30 nm and a mono-dispersed pore size distribution. The gel density could be as low as 0.008 g/cc and accessible surface area as high as 1300 m2/g.

Abstract: A process for the production of high molecular weight polybenzimidazole by one: providing a first reaction vessel; charging the reaction vessel with at least one aromatic hydrocarbon tetraamine, and a heterocylic ring making up the dicarboxylic component; heating the reactants under agitation in a substantially oxygen-free atmosphere with agitation until the agitator torque is about 1.5 times the torque before a rise in viscosity begins; terminating the agitation while continuing to heat the reaction mixture to about 230° C. while allowing the reaction mass to foam; cooling the reaction mass to a friable foamed mass; crushing the friable foamed mass to obtain a ground prepolymer; and two: providing a second reaction vessel, the second reaction vessel being a high intensity reaction vessel; transferring the ground prepolymer to the second reaction vessel; heating the ground prepolymer under agitation to over 315° C. at atmospheric pressure for a time of about 90 minutes.

Abstract: A process for a single-stage melt polymerization for the production of a high molecular weight polybenzimidazole which comprises the steps of: providing a reaction vessel having a means for agitation and a means for vacuum; charging the reaction vessel with reactants selected from: (A) a tetraaminiobiphenyl (TAB), and (B) a diphenyl isophthalate (DPIP); reacting the reactants under constant agitation and under a vacuum with an inert gas sweep; maintaining a reactant temperature which does not exceed 290° C. under constant agitation allowing pressure in the vessel to increase, with an inert gas sweep until a phase change is achieved, when the temperature reaches 250° C. pressure is increased to a slight positive pressure; and increase the reactant temperature and pressure within said reaction vessel while maintaining constant agitation and inert gas sweep, while maintaining a slight positive pressure. Preferably the vessel used in the instant invention is a high intensity reaction vessel.

Abstract: The invention relates to a modified polybenzimidazole (PBI), membranes that are fabricated from these polymers, and their use in electrochemical applications. These membranes have high ionic conductivity and are suitable for solid polymer electrolytes in electrochemical applications, especially for high temperature polymer electrolyte membrane (PEM) fuel cells.

Abstract: The present invention contemplates a process for forming polyaminoamide polymers formed by the reaction of a dibasic acid/ester with excess amounts of an amine; the intermediate polymer resulting therefrom; a process for synthesizing effective, high solids resins resulting from the reaction of intermediate polymers with an epihalohydrin; and the resultant high, solids resin. These resins may be used as wet strength resins in the papermaking industry.

Abstract: A UV-protective composition comprising a water-soluble polyaminoamide containing 1,3-diimine groups, wherein the polyaminoamide containing 1,3-diimine groups absorbs ultraviolet light radiation having a wavelength of about 200 nm to about 420 nm, and methods of treating substrates with the UV-protective polyaminoamide containing 1,3-diimine groups.

Abstract: The invention relates to hyperbranched copolyamides (HBPAs), to their production and to their use as additives, in particular as melt viscosity modifiers in thermoplastic polymer compositions. This copolyamide is obtained by a reaction between a monomer (I): A—R—Bf with A and B=polymerization functions of a 1st and 2nd type, respectively, which are capable of reacting with each other, R=hydrocarbon-based species and f=total number of B per monomer (preferably 2?f?10); and a monomer (II) A?—R?—B? or the corresponding lactams, with A?, B? and R? having the same definition as that given above for A, B and R, respectively. This HBPA has a I/II molar ratio such that 0.125?I/II?2. One of the species R or R? of (I) or (II) is aliphatic, cycloaliphatic or arylaliphatic. For example: A=NH2 and B=COOH or A=COOH and B=NH2 with F=2. A?=NH2 and B?=COOH or A?=COOH and B?=NH2. A—R—B2, e.g.: 5-aminoisophthalic acid or 3,5-diaminobenzoic acid and A?—R?—B?=?-caprolactam.

Abstract: The invention relates to a randomly branched polyamide comprising at least units derived from: 1. AB monomers, 2. at least one compound I, being a carboxylic acid (Av) having a functionality v≧2 or an amine (Bw) having a functionality w≧2, 3. at least one compound II, being a carboxylic acid (Av) having a functionality v≧3 or an amine (Bw) having a functionality w≧3, compound II being a carboxylic acid if compound I is an amine or compound II being an amine if compound I is a carboxylic acid and the amounts of all units derived from carboxylic acids and amines in the polyamide satisfying conditions as mentioned in claim 1. The composition of the randomly branched polyamide is such that it cannot form a crosslinked polyamide (and thus no gels, either), in particular during the prepolymerization, the polymerization, the post-condensation, the processing and the storage of the randomly branched polyamide, and this at a variety of ambient factors, for instance at elevated temperature and pressure.

Abstract: A polymer comprising: a polymeric backbone comprising at least one unit having the structure (I), wherein R-R4 comprise groups selected from the group consisting of H, C1-C12 alkyl, C6-C18 aryl, C7-C18 aralkyl, C6-C18 cycloalkyl or any of the group consisting of C1-C12 alkyl, C6-C18 aryl, C7-C18 aralkyl, C6-C18 cycloalkyl substituted, within the carbon chain or appended thereto, with one or more heteroatoms; R and R2 or R and R4 or R and R1 or R2 and R3 may be joined so that with the carbon atom(s) to which they are attached they together form a saturated, partially unsaturated or unsaturated ring system respectively, may have a pendent group which may incorporate a linker unit, (for example a peptide linkage) or a unit having the structure (I); A comprises a proton donating moiety selected from the group consisting of formula (1).