Trifunctional cross-linking agents

Substituted aziridines have been used to form homobifunctional and trifunctional cross-linking agents, although their use has been limited (Ross, 1953 Alexander, 1954). The functional group has found use, however, in the design of the fluorescent probe dansyl aziridine (5-dimethylaminonaphthalene-2-sulfonyl aziridine) (Johnson etal., 1978 Grossman et al., 1981). 

An example of the importance of free-volume availabiUty on cross-linking has been reported in the evaluation of a trifunctional derivative of an ahphatic isocyanate which contains an aromatic ring, y -tetramethylxyUdene diisocyanate (TMXDI) [2778-42-9] C 4H N202, as a cross-linking agent for hydroxy-functional resins (15). 

Nitrile oxide precursors have been prepared by the reaction of an isocyanate and an alkyl nitroacetate. These precursors release alkanol and carbon dioxide when heated, to liberate the highly reactive nitrile oxide species. An improved synthetic procedure has been developed to afford novel cross-linking agents based on difunctional, trifunctional and aliphatic precursors. Application of these agents to polymer cross-linking has been demonstrated (527). 

Hiratsuka, T. (1988) Cross-linking of three heavy-chain domains of myosin adenosine triphosphatase with a trifunctional alkylating agent. Biochemistry 27, 4110. 

Watanabe et al. used different branching agents in order to synthesize branched/cross-linked SPIs. They introduced either melamine [110, 112] in a fully aromatic SPI (Fig. 24) or tris(aminoethyl)amine in an aro-matic/ahphatic SPI backbone [33,113]. In both cases, the proportion of trifunctional branching agent (leading to a stoichiometric proportion of amine and anhydride groups) was limited to 2 mol %. The authors studied the effect of this new polymer architecture on the membrane water uptake and maximum tensile stress at break. 

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