PIPERAZINE POLYMER

This subject has been investigated for the case of piperazine polymers and diacyl piperazines as model substances ... 

Figure 10 Transfection efficiency measurements in PC3-PSMA cells with lead polymers from the primary DNA-binding screen. Luminescence levels are normalized against total protein and reported relative to PEI. (a) Transfection measurements in the absence of serum at a polymer/plasmid ratio of 25 1. (b) Transfection of plasmid DNA with 1,4C-1,4Bis (1,4C 1,4-cyclohexanedimethanol diglycidyl ether 1,4Bis 1,4-bis(3-aminopropyl)piperazine) polymer at five different polymer/plasmid ratios, (c) Transfection in the presence of serum at a polymer/plasmid ratio of 25 1. (d) Transfection of murine osteoblasts with 1,4C-1,4Bis polymer at a polymer/plasmid ratio of 25 1 in the presence of serum. Reprinted from Barua, S. Joshi, A. Banerjee, A. etal. Mol. Pham. 2009, 6 (1), 86-97, with permission from the American Chemical Society.

This subject has been investigated for the case of piperazine polymers and diacoyl piperazines as model substances. The N—CO bond of these compounds possesses partial double-bond character. Consequently, the rotation about this bond is comparatively slow. Various absorption bands will be observed in the proton resonance spectrum according to whether neighboring groups are in the cis or the trans position about the N—CO bond. The Gibbs energy of activation AG" can be determined from the temperature dependence of the band intensities. 

A series of compounded flame retardants, based on finely divided insoluble ammonium polyphosphate together with char-forming nitrogenous resins, has been developed for thermoplastics (52—58). These compounds are particularly useful as iatumescent flame-retardant additives for polyolefins, ethylene—vinyl acetate, and urethane elastomers (qv). The char-forming resin can be, for example, an ethyleneurea—formaldehyde condensation polymer, a hydroxyethylisocyanurate, or a piperazine—triazine resin. 

Piperazine, I -diethyIcarbamyI-4-methyl-metabolism, 1, 227 Piperazine, N,JV-dimethyI-epoxy resin curative. 1, 406 Piperazine, 2,5-dioxo-occurrence, 3, 187 Piperazine-2,5-dione polymers, 1, 298... 

Piperazine attached to a polymer has also been used to cleave the Fmoc group. 

Polymers have also been prepared from cyclic amines such as piperazine and bis-(p-aminocyclohexyl)methane. An early copolymer, Igamid 1C, was based on the latter amine. This amine is also condensed with decanedioic acid, HOOC (CH2)iqCOOH, to produce to silk-like fibre Quiana (Du Pont). 

Phosphorus containing poly(maleimide-amines) were synthesized from N,N -bisdichloromaleimido-3,3 -diphenyl alkylphosphine oxides and aromatic diamines or piperazine [144]. The polymers prepared from piperazine are soluble in DMF, DM AC, DMSO, etc., but have poor thermal stability and flame retardancy. 

Figure 2 Stability of /3-poly(L-malate) measured by its activity to inhibit purified DNA polymerase a of P. polyceph-alum. The relative degree of inhibition is shown (100 rel. units refer to complete inhibition). The DNA polymerase assay was carried out in the presence of 5 /tg/ml /S-poly(L-malate) as described [4]. The polymer was preincubated for 7 days at 4°C in the following buffer solutions (50 mM) KCl/HCl (—A—). Citrate (—V—). 2-(A/-Morpholino)-ethanesulfonic acid, sodium salt (—O—). Sodium phosphate (— —). N-(2-Hydroxyethyl)piperazine-N -(2-ethanesul-fonic acid), sodium salt (— — ). N,N-b s (2-Hydroxyethyl)-glycine, sodium salt (—T—). Tris/HCl (— —). 3-(Cyclo-hexylamino)-l-propanesulfonic acid, sodium salt (— —).

A similar example is the formation of nonstoichiometric interpolymeric complexes between mutually complementary polyelectrolytes — polycation and polyanion [69,70], They behave like true polymer networks and are capable of swelling the interpolymeric complexes between PAAc and polyethylene piperazine swells, for instance, 16-18 times [70], Also advantageous in this case is the possibility to carry out this type of crosslinking in open systems, such as soil. 

As for the solid support, several polymer-supported amines were tested (Fig. 2). For either the pyrazole and isoxazole synthesis, the best results were given by aniline-functionalized cellulose, which has also the advantage of a relatively low cost. For the 2-aminopyrimidine library, polystyrene-based piperazine and piperidine gave products with a much higher purity compared with other secondary non-cyclic or primary amines, hi both cases, the resins could be reused for up to four times before degradation in their behavior was observed. This reusability could be further enhanced (up to 10 cycles for cellulose-based aniline) when the microwave-assisted protocols were used. 

The melting transition in polymers is conveniently observed by dilatometric measurements of the volume as a function of the temperature. Results thus obtained for poly-(N,N -sebacoyl piperazine) are shown in Fig. 129, and for poly-(decamethylene adipate) by the lowest curve in Fig. 130. Most of the melting, as evidenced by the abnormal increase in volume, occurs within a range of 10°, and it terminates abruptly at a temperature which may be defined within 0.5°. The data shown were obtained by raising the temperature... 

Maldotti (96) studied the kinetics of the formation of the pyrazine-bridged Fe(II) porphyrin shish-kebab polymer by means of flash kinetic experiments. Upon irradiation of a deaerated alkaline water/ethanol solution of Fe(III) protoporphyrin IX and pyrazine with a short intense flash of light, the 2 1 Fe(II) porphyrin (pyrazine)2 complex is formed, but it immediately polymerizes with second-order kinetics. This can be monitored in the UV-Vis absorption spectrum, with the disappearance of a band at 550 nm together with the emergence of a new band due to the polymer at 800 nm. The process is accelerated by the addition of LiCl, which augments hydrophobic interactions, and is diminished by the presence of a surfactant. A shish-kebab polymer is also formed upon photoreduction of Fe(III) porphyrins in presence of piperazine or 4,4 -bipyridine ligands (97). 

Scheme 7.56 One-pot Mannich reaction utilizing polymer-supported piperazine.

In contrast, liquidiliquid phase-transfer catalysis is virtually ineffective for the conversion of a-bromoacetamides into aziridones (a-lactams). Maximum yields of only 17-23% have been reported [31, 32], using tetra-n-butylammonium hydrogen sulphate or benzyltriethylammonium bromide over a reaction time of 4-6 days. It is significant that a solidiliquid two-phase system, using solid potassium hydroxide in the presence of 18-crown-6 produces the aziridones in 50-94% yield [33], but there are no reports of the corresponding quaternary ammonium ion catalysed reaction. Under the liquidiliquid two-phase conditions, the major product of the reaction is the piperazine-2,5-dione, resulting from dimerization of the bromoacetamide [34, 38]. However, only moderate yields are isolated and a polymer-supported catalyst appears to provide the best results [34, 38], Significant side reactions result from nucleophilic displacement by the aqueous base to produce hydroxyamides and ethers. 

Since acrylamide-based monoliths generally represent polar support materials, they are predominately also used for separation in normal-phase mode. For that purpose, monolithic polymers were prepared by polymerization of mixtures containing piperazine diacrylamide as cross-linking agent and methacrylamide, A-isopropylacrylamide or 2-hydroxyethyl methacrylate, and vinylsulfo-nic acid as monomers. 

Copolymers of methacrylic add and ethylene termed as ethylene ionomers have been used as the base polymer for binding alkali, alkaline earth and transition metal ions. Organic amines such as n-hexylamine, hexamethylene tetraamine, 2,2,6,6-tetramethyM-hydroxy piperazine, ethylene diamine and polymeric diamines such as silicone diamine, polyether diamine and polymeric diamines such as silicone diamine, polyether diamine and polyamide oligomers considerably enhance the complex formation characteristics of Zn(II) ethylene ionomers thereby enhancing the physico-chemical properties [13]. 

The perhydropyrazine (piperazine) heterocycle has been a favorite of the polymer chemist for the preparation of both addition and condensation polymers because of the desirable physical and chemical properties imparted by the ring. Piperazine-functional acrylate esters... 

The usefulness of piperazine and its derivatives for the preparation of polyamides has been known for some time, and it is one of the few disecondary diamines which can be employed to prepare high-melting polycondensates. Piperazine polyamides are especially useful as hot melt adhesives (68USP3377303), since they display unusually good adhesion to vinyl-based polymers such as poly(vinyl chloride). Piperazine is also the preferred diamine for the preparation of thermoplastic polyamides which exhibit the combined properties of low melt viscosity, high softening point and impact resistance at low temperatures (80USP4218351). 

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