Polyimines

The polymerization products of ethylene imine are known as polyimines. The ring-opening polymerization of ethylene imine can be initiated by acids HA or alkylating agents RX e.g., 

The charged species then initiates polymerization. Through transfer reactions, the resulting polymer contains primary and tertiary, as well as secondary, amine groups, so that the structure is highly branched  

The commercial polymers have molecular weights of up to 100,000 g/mol and ratios of primary-.secondary tertiary amino groups of 1 2 1. They are used as adhesives (e.g., bonding polyester cord to rubber), paper additives, etc. Quaternized poly(ethylene imines) form water-soluble polycations and are used as flocculants in the processing of tap water. 

Unbranched poly(ethylene imines) can be produced by the isomerization polymerization of unsubstituted 2-oxazolines  

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The condensation of the monomers with the elimination of water and the formation of a polyimine [XII] occurs at temperatures around 250°C. 

The literature of polyimines is extensive [164-173]. A number of researchers have tried to synthesize high molecular weight polymers but failed due to poor solubility in organic solvents. Polyimines are of great interest because of their high thermal stability [174-176], ability to form metal chelates [174-177], and their semiconducting properties [178-181]. Due to insolubility and infusibility, which impeded characterization of the molecular structure, the application of these polymers is very limited and of little commercial importance. 

The first polyimine was reported by Adams and coworkers [182] from terephthalaldehyde and benzidine and dianisidine. Between 1950 and 1959 Marval and coworkers [174-176] reported a number of polyimines. Suematsu and coworkers [170] reported the first successful synthesis of high molecular weight fully aromatic polyimines by solution polycondensation method using w-cresol as reaction medium. 

Wojtkonski [185] has also reported on three series of melt spinnable thermotropic aromatic-aliphatic polyimines. The polyimines were prepared by reaction of 1,2-bis(4-formylphenoxy) ethane, terephthalaldehyde, or 4,4 -biphenyldicarboxaldehyde, respectively, with l,n-bis(4-amino-3-methylphenoxy) alkanes where n = 1-10, 12, 14, and 16 in dry DMAC containing 5% dry lithium chloride. The polymers decomposed at 400°C, and as the length of the flexible aliphatic segments increased, melting points decreased. Polymers with an odd... 

Yang and Jenekhe [186,187] reported a successful solubilization of aromatic polyimines in organic solvents via their soluble coordination complexes, which facilitated their solution characterization by NMR and processing films and coatings by spin coating and other techniques. This has created opportunities for various studies of the aromatic polyimines. 

Recently, polyimines include the synthesis of long alkoxy (Cg-Cig) side chain derivatives [188,189], which are presumably soluble to some extent in organic solvents and derivatives containing fluorene cardo unit [190]. Trifluoromethyl groups [191] in the polymer backbone provide solubility in organic solvents. Studies of the electrical conductivity of doped conjugated aromatic polyimines and alkoxy derivatives have been reported [188], and the values are in the range of 10 to 10 S/ cm. 

The presence of ether linkages in the polymer molecule imparts chain flexibility, lowers glass transition temperature, and enhances solubility while maintaining the desired high temperature characteristics [192]. Recently, polyether imines were prepared by the reaction of different diamines with 4,4 -[l,4-phenylene bis(oxy)] bisbenzaldehyde [184]. The polymers synthesized by the solution method were yellow to white in color and had inherent viscosities up to 0.59 dl/g in concentrated H2SO4. Some of these polyimines can be considered as... 

Macrocyclic polyamines may be viewed as an extended form of linear polyamines 13-161 with one less degree of saturation. Polyamines with lower degrees of saturation, have important biological functions. Compounds such as macrocyclic polyimines 171 and porphyrines 18), function as 02 carriers and activators, promote photosynthesis, form the basic structure of vitamine B12, etc., and for these reasons have been subjects of intense investigation. 

Polyamines are usually open chain compounds with primary, secondary, or tertiary amino groups. Instead of polyamines, polyimines are used without a sharp difference. Actually, imines are compounds with the =N— group or cycles such as ethyleneimine. Examples of oligoamines and polyamines are ethylenediamine, propanediamine, and 1,4-butanediamine and the respective products of condensation such as diethyleneamine, dipropylenetriamine, and triethylenetetramine. The compounds are colorless to yellowish liquids or solids with alkaline reaction. 

Besides the polyether-based polymer electrolytes, the nitrogen analogues (polyimines) were also extensively studied. Various other oxygen-containing... 

Polyimines of low-valent Co are now well represented, particularly with macrocyclic or mixed-donor ligands. The monovalent Co complex (5) of the 14-membered macrocyclic hexamethyl diimine (hmd), may be generated electrochemically from its divalent precursor. Furthermore,... 

A number of alkylperoxy Co111 complexes including mainly polyimine ligands have been prepared, exemplified by (223).979 Hydroxylation of saturated hydrocarbons, preferentially at the more nucleophilic C—H bonds, yields alcohols, ketones, and t-butylperoxo products, whereas olefins form epoxides if they carry no allylic H atoms. 

In contrast, the related diamines 45 and 46 [cf. (3,5-/-Pr2C6H2-4-NH2)2CH2 above] give, on treatment with 2,6-diacetylpyridine, oligomeric polyimines that can be readily complexed with iron dichloride to afford 47 and 48, respectively (Fig. 14). Notably, on activation with MAO, 47 and 48 are active catalysts for ethylene polymerisation and indeed perform more efficiently at elevated temperatures than those of the original bis(imino)pyridine iron precatalyst 5 [166],... 

Chart 4. Polyimines and -amines used as ligands on bismuth. 

In general, the acid-sorbing resins may be classified as high molecular weight polyamines or polyimines. Thus, the original Adams and Holmes material was a polymer of m-phenylenediamine. Cation Exchange materials include synthetic resins, such as sulfonated phenol-formaldehyde or polystyrene types, and sulfonated coal. Some manufacturers have a variety of sub-types which are considered superior for particular applications. 

Pillared polyethers and polyimines have been also described, which present sorbent and ion exchange properties [7, 56]. Immobilization of crown ethers and diaza crown ethers has been carried out with the bisphosphonate pillars strategy by using the co-precipitation synthesis [44, 58]. Exchange re-... 

C=N bonds in acylhydrazone groups, which are formed by the condensation of hydrazides with carbonyl groups, exhibit reversibility under mild conditions. Like polyimines, polymers with acylhydrazone functionalities exhibit dynamic aspects through the reversibihty of the azomethine bond. Skene and Lehn have reported the synthesis of polyacylhydrazones and their dynamic features (Scheme 8.3) [23]. High molecular weight polyacylhydrazone 13 was prepared by the condensation of the corresponding dihydrazide and dialdehyde in the presence of an acid catalyst. When 13 was treated with aryl dialdehyde 14 or aryl dihydrazide 15 in... 

Figure 8.4. Template polymerization of AA along polyimine as a fnnction of [T]o/[M]o at constant [M]o in acetone/water (2/1 v/v) at 25°C. (o) Data from Bamford and Shuki. " The curve is derived from the computed rates using the constants calculated by Tan and Alberda van Ekenstein. Reprinted from Y. Y. Tan and O. R. Alberda van Ekenstein, Macromolecules, 24, 1641 (1991) with kind permission from ACS.

Dendritic polymers with enhanced amplification and interior functionality were prepared by Tomalia et al. (3) by slow step-growth polymerization techniques including polyimine formation followed by rapid ring-opening reactions. 

The importance of proper RO membrane selection has already been discussed. A review of commercially available RO membranes revealed five different basic membranes that could provide organic recovery. Cellulose acetate and cellulose acetate blends, aromatic polyamide, polyamide thin-film composite, cross-linked polyimine thin-film composite (FT-30), and polybenzimidazole were available when this work was performed. Only the first four types were commercially available. All membranes were available with excellent salt rejection (>97 sodium chloride). Two types of membranes, cellulose acetate and FT-30, have shown short-term (<2-months intermittent use) resistance... 

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