ANHYDRIDE GROUP

Anhydride Groups. Anhydride groups present on commercially available ethylene-maleic anhydride copolymers are readily reactive with the nucleophile-containing amino acid residues of proteins.11 These groups react directly with lysine residues, for example, to form amide bonds (4.16)  

Van Houwelingen discussed the determination of anhydride groups in a resin derived from octadecene-1 and maleic anhydride. 

The common method for anhydride groups involving reaction with an excess of aniline and subsequent backtitration of the excess is unsuitable, as the reactivity of the anhydride group is low. Even after hydrolysis with aqueous pyridine (containing 40% v/v of water) in a Parr bomb at 150 C for 4 hours, anhydride groups are still seen in the infrared spectra. 

A suitable method for determining the anhydride group is titration with aqueous potassium hydroxide in pyridine after previous esterification of the carboxyl group with diazomethane. This esterification is carried out in diethyl ether methanol (9+1). After methylation, which takes about 10 m for 0.5g of sample, the solv ts are removed by evaporation and a portion of the derivatised polymer is dissolved in pyridine and titrated. In Ae infrared spectra of the resin before and after methylation it can be seen that the absorption band of the acid group at 1710 cm (5.84u) disappears and a carbonyl band of the ester at 1740 cm (5.74u) is formed. The acid content of the sample is found from the difference in titres of an unmethylated and a methylated product. 

---

Polymerization. Maleic anhydride which contains a double bond and an anhydride group is used in both addition and condensation... 

Derivatives. The dual functionaUty of trimellitic anhydride makes it possible to react either the anhydride group, the acid group, or both. Derivatives of trimellitic anhydride include ester, acid esters, acid chloride, amides, and amide—imides (136). Trimellitate esters are the most important derivatives, and physical properties of more significant esters are Hsted in Table 34. 

Monomer Reactivity. The poly(amic acid) groups are formed by nucleophilic substitution by an amino group at a carbonyl carbon of an anhydride group. Therefore, the electrophilicity of the dianhydride is expected to be one of the most important parameters used to determine the reaction rate. There is a close relationship between the reaction rates and the electron affinities, of dianhydrides (12). These were independendy deterrnined by polarography. Stmctures and electron affinities of various dianhydrides are shown in Table 1. 

If more than one acid anhydride group per mole of tetraalkyl titanate is used, a polytitanyl acylate is formed ... 

PMVEMA, supphed as a white, fluffy powder, is soluble in ketones, esters, pyridine, lactams, and aldehydes, and insoluble in aUphatic, aromatic, or halogenated hydrocarbons, as well as in ethyl ether and nitroparaffins. When the copolymer dissolves in water or alcohols, the anhydride group is cleaved, forming the polymers in free acid form or the half-esters of the corresponding alcohol, respectively. Table 7 illustrates the commercially available alternating copolymers and derivatives. 

Epoxy Resins. Epoxy resins (qv) are used to cross-link other resins with amine, hydroxyl, and carboxyHc acid (or anhydride) groups. The epoxy group, properly called an oxkane, is a cycHc three-membered ether group. By far the most widely used epoxy resins in coatings are bisphenol A (BPA) (4,4 -(l-methylethyHdene)bisphenol) [80-05-7] epoxy resins. 

The products of these reactions with maleic anhydride, termed maleated oils, react with polyols to give moderate mol wt derivatives that dry faster than the unmodified oils. For example, maleated, esterified soybean oil is a drying oil with a drying rate comparable to that of a bodied linseed oil with a similar viscosity. Maleated linseed oil can be converted to a water-dilutable form by hydrolysis with aqueous ammonium hydroxide to convert the anhydride groups to ammonium salts of the diacid. Such products have not found significant commercial use, but similar reactions with alkyds and epoxy esters are used on a large scale to make water-dilutable derivatives. 

Until recently, maleic anhydride has been used mostly for the functionalization of polyolefins due to the high reactivity of the anhydride group toward sucessive... 

Blends based on polyolefins have been compatibilized by reactive extrusion where functionalized polyolefins are used to form copolymers that bridge the phases. Maleic anhydride modified polyolefins and acrylic acid modified polyolefins are the commonly used modified polymers used as the compatibilizer in polyolefin-polyamide systems. The chemical reaction involved in the formation of block copolymers by the reaction of the amine end group on nylon and anhydride groups or carboxylic groups on modified polyolefins is shown in Scheme 1. 

Scheme 1 The proposed acid/amine and anhydride/ amine reaction between carboxylic groups/anhydride groups on modified polyolefins and amine end groups on Nylon-6.

The polarity of the matrix helps to improve the adhesion between melamine fiber and rubber because of the polar-polar interaction between the fiber and the matrix [118]. The presence of fiber in the absence of bonding system showed only marginal improvement in tensile strength (from 1.5 to 1.6 MPa) in the case of EPDM rubber-melamine hber composites. However, maleated EPDM rubber-melamine hber composites showed more than 50% improvement in tensile strength in the absence of the bonding system [118]. This is because of the presence of maleic anhydride groups, which imparts polarity to the mbber. 

The initial formulation of Epon 828 and NMA must be such that oxirane equivalents equal the concentration of anhydride groups. A balanced stoichiometric ratio enables the polymerization to develop macromolecules at high extents of reaction (10). Therefore... 

Further examination of the infrared spectra reveals a decrease in the C-H vibrations at 3029 and 2946 cm-1, appearing to occur at different rates. A new broad signal that appears at 1879 cm-1 may be due to CO adsorbed on metallic palladium. The position of this stretch is also suggestive of a carbonyl or anhydride group perhaps contained in a macromolecular residue, as discussed below. 

Figure 10.1 DTPA reacts with amine-containing molecules via ring opening of its anhydride groups to create amide bond linkages. The potential also exists for both anhydride groups to react and cause crosslinking of modified molecules, which is undesirable.

I".a designed to make more extended heterobridged [n]polynorbomanes, the bis-aZ n n. was prepare from the dioxasesquinorbomadiene anhydride 116 <97T3975>. The re ate is-epoxi e was secured, in the N-methoxyethyl succinimide series, from the bis-cyc o utene t at was derived from 119 (Scheme 20) using the standard protocols described earlier. It is noteworthy that only the aziridine protocol tolerates the anhydride group. 

In the present paper, we report on the compatibilization of clay with polyolefins, specifically low and high density poly-ethylenes (LDPE, HDPE), through the radical-induced polymerization of maleic anhydride (MAH) in the presence of the polymer and clay, so that the MAH is grafted on the PE and the anhydride groups concurrently react with the filler surface (l, 2). 

A molecule of water is then lost, giving rise to the heterocyclic anhydride grouping and thus, MA... 

The most reactive of the three is maleic because of the combination of the anhydride group and the highly reactive double bond. 

---