Maleic anhydride copolymers hydrolysis

Supemucleophilic polymers containing the 4-(pyrro-lidino)pyridine group were synthesized from the corresponding maleic anhydride copolymers and also by cyclopolymerization of N-4-pyridyl bis(methacryl-imide). The resulting polymers were examined for their kinetics of quaternization with benzyl chloride and hydrolysis of pj-nitrophenylacetate. In both instances, the polymer bound 4-(dialkylamino)pyridine was found to be a superior catalyst than the corresponding low molecular weight analog. 

As pointed out by Heller (2), polymer erosion can be controlled by the following three types of mechanisms (1) water-soluble polymers insolubilized by hydrolytically unstable cross-links (2) water-insoluble polymers solubilized by hydrolysis, ionization, or protonation of pendant groups (3) hydrophobic polymers solubilized by backbone cleavage to small water soluble molecules. These mechanisms represent extreme cases the actual erosion may occur by a combination of mechanisms. In addition to poly (lactic acid), poly (glycolic acid), and lactic/glycolic acid copolymers, other commonly used bioerodible/biodegradable polymers include polyorthoesters, polycaprolactone, polyaminoacids, polyanhydrides, and half esters of methyl vinyl ether-maleic anhydride copolymers (3). 

Structure I Is a nominal structure for the 1 2 copolymer of dlvlnyl ether and maleic anhydride, after hydrolysis In fact, the size of the ether ring Is a subject of current Investigation (4). Potentiometric titration shows that approximately 3 of the 4 carboxyl groups are Ionized at pH 7 (i)]. 

The copolymers obtained by radical copolymerization of maleic anhydride (MA) with acrylic or vinyl comonomers, and the maleic add copolymers, generally obtained by the hydrolysis of the maleic anhydride copolymers (Figure 10.1), can be called maleic copolymers. They were intensively studied from a theoretical perspective, but also for their applications [1-3]. Copolymers ofMA with electron-donating comonomers, such as styrene, vinyl acetate, N-vinyl pyrrolidone, and methyl vinyl ether, have an alternant structure [ 1 ], but when MA is copolymerized with electron-acceptor comonomers like methyl methacrylate, acrylonitrile, statistic copolymers are obtained [1,2]. MA units from the copolymers are very reactive active agents with amine or hydroxyl groups... 

Maleic anhydride has been long known for its reaction with amino groups of the proteins in basic aqueous solution, the reaction being reversible at acidic conditions [69]. Maleic anhydride copolymers could also be covalently bound with proteins in basic aqueous media, the hydrolysis of anhydride units being a competing reaction [70-75]. A water-soluble carbodiimide could also be used to activate the carboxylic acid groups [76]. 

Vinyl resins ie, copolymers of vinyl chloride and vinyl acetate which contain hydroxyl groups from the partial hydrolysis of vinyl acetate and/or carboxyl groups, eg, from copolymerized maleic anhydride, may be formulated with alkyd resins to improve their appHcation properties and adhesion. The blends are primarily used in making marine top-coat paints. 

Copolymers of vinyl chloride with vinyl acetate and maleic anhydride are made more adhesive to metals through hydrolysis of the ester and anhydride units. 

Average copolymer compositions of SAN samples were determined by elemental analysis, yielding weight percent acrylonitrile in the polymer. Compositions of S/MA and S/MA/MM were determined by sequential hydrolysis and pyridine titration to obtain maleic anhydride content and by infrared analysis for methyl methacrylate content. 

Through copolymerization there can be made materials with different properties than those of either homopolymer, and thus another dimension is added to the technology. Consider, for example, styrene. Polymerized alone, it gives a good electric insulator that is molded into parts for radios, television sets, and automobiles. Copolymerization with butadiene (30%) adds toughness with acrylonitrile (20-30%) increases resistance to impact and to hydrocarbons with maleic anhydride yields a material that, on hydrolysis, is water-soluble, and is used as a dispersant and sizing agent. The copolymer in which butadiene predominates (75% butadiene, 25% styrene) is an elastomer, and since World War II has been the principal rubber substitute manufactured in the United States. 

Scheme 6.4 Base-catalyzed hydrolysis reactions of an anhydride group in a copolymer of styrene and maleic anhydride, which renders the latter soluble in water.

This synthetic method has two steps the first step involves synthesising the polymer and the second includes modification with active groups. Some monomers generally used to form the backbone of homopolymers or copolymers include vinyl benzyl chloride, methyl methacrylate, 2-chloroethyl vinyl ether, vinyl alcohol and maleic anhydride. The polymers are then activated by anchoring antimicrobial groups, such as phosphonium salts, ammonium salts or phenol groups, via quaternisation, chloride substitution or anhydride hydrolysis. 

Special post-functionalizable copolymers have also been used to derive acid ionomers by hydrolysis, thus avoiding the difficulties of copolymerizing ionic and nonionic monomers. To this end there are many examples where carboxylic acid polymers are formed by hydrolyzing copolymers containing acrylate esters, acrylonitrile, or maleic anhydride. As described later, a sulfonic acid ionomer, Nafion, is formed by hydrolysis of tetrafluoroethylene copolymerized with a sulfonyl fluoride. 

To synthesize polynucleotide analogues closely resembling natural polymers, we have synthesized several new monomers such as dihydrofuran and dihydropyran derivatives which contained nucleic acid bases (Scheme 1). Copolymerization of the monomers either with maleic anhydride or with vinylene carbonate resulted in the alternating copolymers as shown in Scheme 2. Hydrolysis of the products gave the polymers which were optically active and soluble in water and had alternating sequences along the polymer chain. In this paper we will report synthesis of monomers, their copolymerization either with maleic anhydride or with vinylene carbonate, hydrolysis of the copolymers, and the physicochemical properties of the anhydride and hydrolyzed polymers. 

Example 5.3 Hydrolysis of a Copolymer of Styrene and Maleic Anhydride... 

The 1-1 copolymer of maleic anhydride and methylvinyl ether were commercial products and were used without fractionnation. The copolymers of maleic anhydride and decyl (or) hexadecyl vinyl ether were obtained by radical polymerization. For hydrolysis of the polymers with a long alkyl side chain, heat treatment was necessary (60 C for several days in pure water). This resulted however in a reduction of average DP and probably in an enlargement of the initial distribution. Therefore, after hydrolysis, the polymer sample was fractionated with 2 1 acetonerbenzene as solvent and methanol as precipitant. 

There has been a slight increase in activity in this area compared with that in the previous two year period. For the polymeric esters of acrylic, methacrylic acids, and related polymers the simplest reaction, apart from thermal depolymerization, is hydrolysis, and one or two papers on this subject have appeared. One of these concerns a comparison of the kinetics of hydrolysis of a number of methacrylate esters and a further two deal with the formation of copolymers containing carboxylic acid functions. Methyl trifluoroacrylate forms alternating copolymers with cE-olefins (ethylene, propylene, isobutylene) and these are readily hydrolysed in boiling aqueous methanolic sodium hydroxide to yield hydrophilic fluoropolymers. Hydrolysis is reported to be nearly quantitative with no chain scission. An alternating copolymer is also formed by radical polymerization of maleic anhydride with A-vinyl succinimide. On hydrolysis this copolymer is... 

It is interesting to note that the first styrene copolymer was a copolymer of a nonpolymerizable monomer viz, maleic anhydride and styrene (SMA) (9). This copolymer (SMA), which was called a heteropolymer by Wagner-Juaregg is resistant to the temperature of boiling water but is readily hydrolyzed by hot aqueous alkaline solutions. The product of hydrolysis viz, styrene-maleic acid copolymer retains its molecular weight (10). The viscosity of this water soluble polymer may be controlled by crosslinking with divinylbenzene (11). 

Head-to-head poly(acrylic acid) is also accessible by hydrolysis. Standing in water at ambient temperature the alternating copolymer of ethylene and maleic anhydride gives the poly acid [480]. 

---