Polyureas and Polythioureas

Yamazaki et al prepared polyureas and polythioureas from carbon dioxide and disulfide with diamines via the N-phosphonium salts281. ... 

Since the reactions with phosphorus compounds give relatively high yields of carboxylic amides and esters and ureas, they have been extended to the direct polycondensations of dicarboxylic acids with diamines and bisphenols, of free a-amino acids or dipeptides, and of carbon dioxide and carbon disulfide with diamines under mild conditions to give polyamides, polyesters, polyureas, and polythioureas. 

Polyureas and polythioureas have been synthesized by Banihashemi et al. [68] by reaction of aromatic and aliphatic amines with urea and thiourea, respectively (Scheme 14.32). In a typical procedure, a solution of 10 mmol amine, 10 mmol urea, and a small amount of p-toluenesulfonic acid (1 mmol) in 5 mL N,N-dimethylacetamide was irradiated for 7 min at 220 W and then for 8 min at 400 W in a tall beaker placed in a household microwave oven. As the result, a series of polyureas and polythioureas was obtained in good yields and with moderate inherent viscosities of 0.13-0.25 dL... 

Table 3 Polyurea and Polythiourea Synthesis and Chain Length Results...

Thus while the platinum II polyureas and polythioureas exhibit some tumoral inhibition they are less active than analogous platinum polyamines. 

The previous paper describes the synthesis of platinum II polyureas and polythioureas Here we report the synthesis of palladium (II) polyamines (J ) which may be considered analogs of cis-dichlorodiamlneplatinum(II) cis-DDP (2), and the related platinum II polyamines (3). 

Pyroelectricity, piezoelectricity, and fieiroelectricity in polyurea and polythiourea have not attracted much interest until recently. Urea resins are highly cross-linked amorphous polymers and have been used as insulating plastics for many years. Polyurea and polythiourea are usually synthesized by condensation or addition polymerization, and the products are mostly in the form of powders. Owing to their insolubility, preparation of films was not possible. 

This chapter describes the most recent developments in pyroelectricity, piezoelectricity, and ferroelectricity of polyurea and polythiourea. 

Chiral amines and diamines are readily available substrates for the synthesis of ligands for transition metal-catalysed reactions since they can easily be transformed into chiral ureas and thioureas. Therefore, several groups have prepared chiral symmetrical ureas and thioureas, dissymmetrical ureas and thioureas, amino-urea and thiourea derivatives. Finally polyureas and non-soluble polythioureas were also prepared and tested as ligands for asymmetric catalysis. 

The advantages that heterogeneous catalysts have is that they are easily separable from the product, and can be recycled. A number of studies have been conducted in which ligands have been attached or bound to polymeric material to provide an immobilized ligand, and these include polyacrylate and silica [27], polyurea [28], polythiourea [29], polyether [30, 31] and dendritic [32] systems. Upon metal coordination, the immobilized catalysts have retained most of the activity and selectivity, but they now provide the advantage of simple separation and recycling. For exam-... 

As a third possibility, nanocapsules in a miniemulsion system could be achieved using different interfacial reactions in inverse miniemulsions. The formation of polyurea, polythiourea, and polyurethane nanocapsules synthesized through the polyaddition reaction has been described in detail [110-112], The size of the nanocapsules could be controlled by the amount of surfactant used and the addition time of the diisocyanate. The wall thickness was adjusted by the amount of employed monomers. dsDNA molecules were successfully encapsulated into poly-butylcyanoacrylate (PBCA) nanocapsules by anionic polymerization, which took place at the interface between the miniemulsion droplets and the continuous phase [113]. 

The thermoset polymers are usually obtained in quantitative yields. They are tough and can be molded into clear, tough films. Reaction of the polycarbodiimides with mono amines gives rise to the formation of polyguanidines. Also, conversion into polyureas with water, polythioureas with hydrogen sulfide and poly(O-alkylisoureas) with alcohols is known. ... 

The results of the preparation of polyureas under mild conditions (a pressure of less than 40 atm of carbon dioxide and a temperature around 40 °C) and of poly thioureas (using diphenyl phosphite in pyridine) are compiled in Table 1728). Although the preparation of polyureas from carbon dioxide under drastic conditions (high temperatures and high pressures) or from carbon oxysulfide has been reported, neither preparative method is operative under moderate conditions, nor have the methods for the synthesis of polythioureas from carbon disulfide been described. 

Hydrophilic materials can be encapsulated with the inverse minianulsions by using interfacial polymerization such as polyaddition and polycondensation, radical, or anionic polymerization. Crespy et al. reported that silver nitrate was encapsulated and subsequently reduced to give silver nanoparticles inside the nanocapsules. The miniemulsions were prepared by anulsilying a solution of amines or alcohols in a polar solvent with cyclohexane as the nonpolar continuous phase. The addition of suitable hydrophobic diisocyanate or diisothiocyanate monomers to the continuous phase allows the polycondensation or the cross-linking reactions to occur at the interface of the droplets. By using different monomers, polyurea, polythiourea, or polyurethane nanocapsules can be formed. The waU thickness of the capsules can be directly tuned by the quantity of the reactants. The nature of the monomers and the continuous phase are the critical factors for the formation of the hollow capsules, which is explained by the interfacial properties of the systan. The resulting polymer nanocapsules could be subsequently dispersed in water. 

As good results for the asymmetric HTR of acetophenone were obtained (conversion 100% and 91% ee) with diurea [19], not only copolymerization of diamine 18 has been performed but 1,2-cyclohexyldiamine 19 was also used. Thus pseudo-C2 polyamide 23, polyureas 24, 24 and 26 or polythioureas 27 were prepared by polycondensation with diacid chloride, diisocyanate [20] or dithioisocyanate respectively (Scheme 12) [21]. With rhodium complexes the conversions varied from 22% to 100% and ee from 0% to 60% for HTR with acetophenone at 70°C, in the presence of [Rh(cod)Cl]2 with diamine polymer imit (23-26)/Rh ratio of 10, 2-propanol and KOH. Polyamide 23 proved to be useless (only 22% conversion and 28% ee) contrary to polymea 25 which presents similar ee to those observed with diamine 18 when (Rh(cod)Cl)2 was employed as the catalytic preciu or for HTR (ie 100% conversion for both of them and 55% and 59% ee respectively). Polyureas 24a, 24b, 25 and crosslinked 26 led to better conversions, 80, 50, 97 and 100% with respectively 0, 13, 39 and 60% ee. Moreover, the chiral crosslinked polyurea 26 presented a slight increase in enantioselectivity over the monomer analog 18 (55% ee and 94% conversion under similar conditions) and the reaction rate appeared to be even higher than in the homogeneous phase. Catalytic system from 25 showed a capacity to recycle (Scheme 13) [20]. 

Polyurethane Polyurea Polythiourea Cross-linked starch Cross-linked dextran High-energy (ultrasonication) W/O IPDI Toluene diisocyanate hexamethylene diisocyanate 1,6-Hexanediol Diethylenetriamine Glycerol Starch Dextran 1,4-Diaminohexane Block opolymer emulsifier poly-[(butylene-coethylene)-b -(ethylene oxide)] Nature of reactive monomers and continuous phase 200-500 Ciespy et al. ... 

AQUEOUS SOLUTION SYNTHESIS OF PLATINUM II POLYUREAS, POLYTHIOUREAS AND POLYAMIDES... 

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