Monomeric amine reactants

Attempts to scale up the NS-300 membrane preparation from the laboratory scale to continuous machine production led to a high degree of variability in membrane properties ( ). The difference was attributed in part to the variability of machine-made polysulfone support film. Properties of the machine-made polysulfone supports differed from the laboratory cast support films. One of the major factors affecting this difference was that the machine-made support film was cast on a nonwoven polyester backing material which can vary in properties. Thus, the machine support film, which was quite adequate for NS-lOO type membranes using polymeric amine reactants, still remained a limitation for the monomeric amine reaction of NS-300. 

The initial studies by Cadotte on interfacially formed composite polyamide membranes indicated that monomeric amines behaved poorly in this membrane fabrication approach. This is illustrated in the data listed in Table 5.2, taken from the first public report on the NS-100 membrane.22 Only the polymeric amine polyethylenimine showed development of high rejection membranes at that time. For several years, it was thought that polymeric amine was required to achieve formation of a film that would span the pores in the surface of the microporous polysulfone sheet and resist blowout under pressure However, in 1976, Cadotte and coworkers reported that a monomeric amiri piperazine, could be interfacially reacted with isophthaloyl chloride to give a polyamide barrier layer with salt rejections of 90 to 98% in simulated seawater tests at 1,500 psi.4s This improved membrane formation was achieved through optimization of the interfacial reaction conditions (reactant concentrations, acid acceptors, surfactants). Improved technique after several years of experience in interfacial membrane formation was probably also a factor. 

Polymeric or monomeric complexes are formed in the reaction between zinc halides and dimethyl(aminomethyl)phosphine oxide dependent on the ratio of reactants. The ligand can bind as bidentate to one metal center or bridge two metal centers through the amine N and phosphine oxide O atoms.851... 

A solventless PMR resin became known under the designation LARC 160 (15), which could be processed as a hot melt. An exchange of MDA in PMR-15 with a liquid isomeric mixture of di- and trifunctional amines (Jeffamine 22) provided a mixture of monomeric reactants which was tacky at room temperature. In the presence of 3% methanol the resin could be processed via a hot melt process. Unfortunately, the cured resin was inferior with respect to thermal oxidative stability in comparison to PMR-15. 

Two classes of reactive secondary amines (XX and XXI) were synthesized [90] for the thermoset version of the In Situ Molecular Composite concept. The thermoset chemistry of the bisnadimide (XX) involved that of PMR systems (polymerization of monomeric reactants) [95], The secondary amine (XXI) embodied the more recent ringopening polymerization of benzocyclobutene (BCB) [96]. Polymerization exotherms for both thermoset amines occurred with an onset at 225 °C, maximizing at approximately 260 °C as evidenced by DSC at a heating rate of 10 °C/m. 

Ten years ago, good model systems were found for epoxy networks. These were polymers based on monomeric diglycidyl ethers of some bisphenols cured by simple aromatic amines (primarily w-phenylenediamine — wPhDA). Polymers based on these reactants satisfied the requirements for such a model system in several points ... 

Halodialkylamido derivatives are accessible by several methods, especially reactions between pentahalides and amines or trimethylsilyl reactants. They are obtained as dimers or as monomeric adducts in the presence of an excess of amines. A common feature of these derivatives is the hexacoordina-tion of the metal. The MNC2 units are planar with short M-N distances ( 1.86A), and thus suggest strong r-bonding by interaction of the nitrogen p orbitals and empty A orbitals of the metal. 

Two types of thermoset polyimides are currently prepared commercially. They are based on low molecular weight bis imides such as bis maleimides or bis-5-norbomene-2,3-dicarboximides. Due to unsaturations, the materials cross-link by free-radical mechanism into tight networks. Michael type additions of primary and secondary amines to the bis maleimides are often used to chain-extend them before cross-linking. This reduces the cross-linking density and the brittleness [115]. The materials are designated by the term PMR, for polymerizable monomeric reactants. 

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