Inherent viscosity, aromatic

A polyester backbone with two HFIP groups (12F aromatic polyester of 12F-APE) was derived by the polycondensation of the diacid chloride of 6FDCA with bisphenol AF or bisphenol A under phase-transfer conditions (120). These polymers show complete solubkity in THF, chloroform, ben2ene, DMAC, DMF, and NMP, and form clear, colorless, tough films the inherent viscosity in chloroform at 25°C is 0.8 dL/g. A thermal stabkity of 501°C (10% weight loss in N2) was observed. 

Amorphous bisphenol-A polyarylates are soluble in dioxane and in chlorinated solvents such as CH2C12, 1,2-dichlororethane, 1,1,2-trichloroethane, and 1,1,2,2-tetrachloroethane while semicrystalline and liquid crystalline wholly aromatic polyesters are only sparingly soluble in solvents such as tetrachloroethane-phenol mixtures or pentafluorophenol, which is often used for inherent viscosity determinations. 

A procedure similar to that given below for wholly aromatic liquid crystalline polyesters can be used (see Section 2.4.4.2). The inherent viscosity of the resulting polymers were ca. 0.6 dL/g (0.5 g/dL in phenol-o-dichlorobenzene at... 

Poly(arylene ether l,2,4-triazole)s were synthesized from the reaction of 3,5-di(4-hydroxyphenyl)-4-phenyl-1,2,4-triazole with three different activated aromatic difluoro monomers [34,35]. The polymer from the triazole bisphenol and 1,4-di(4-fluorobenzoyl)benzene exhibited an inherent viscosity of 3.40 dL/g (0.5% solution in m-cresol at 25 °C), a Tg of 216 °C and a Tm of 377 °C [35]. Solution cast amorphous unoriented thin films of this polymer gave 23 °C tensile strength, modulus and elongation of 87.6 MPa, 2.7 GPa and 7.8% respectively. No work was performed to induce crystallinity in the film. 

Attention was then turned to aromatic heterocyclic ladder polymers other than BBL. Due to the complexities in their synthesis, ladder polymers were not reported extensively in the literature at that time. A sample of polyfluoflavine (I) having an inherent viscosity in methanesulfonic acid of 2.5 was obtained from professor C. S. Marvel at the University of Arizona. The ladder polymer was prepared [5] from the A-B polycondensation of 2,3-dihydroxy-6,7-diamino-quinoxaline hydrochloride in PPA. Transparent blue sheets were observed on precipitation of this polymer from methanesulfonic acid, and when collected and dried, it formed gold films much like the color of the BBL films. It was felt at that time that all ladder polymers of sufficient molecular weight would form precipitated films. 

The reaction temperature and time are important factors for the synthesis of the aromatic polyimide. Figure 4 shows the time dependence of inherent viscosity of aromatic polyimide P-ODPM synthesized by the polycondensation of aromatic salt monomer ODPMA at 240 °C [27]. 

Figure 5 represents the temperature dependence of inherent viscosity of the polyimide prepared by the polycondensation of salt monomer ODPMA for 1 h [27]. From the DSC and TG studies, the aromatic salt monomer was found to undergo polycondensation at the endothermic peak temperature of 220 °C. The polymerization at a temperature lower than 220 °C resulted in the polymer with low viscosity value. The inherent viscosity of the polymer increased with in-... 

In the Phillips process, polyphenylene sulfide (PPS) is obtained from the polymerization mixture in the form of a fine white powder, which, after purification, is designated Ryton V PPS. Characterization of this polymer is complicated by its extreme insolubility in most solvents. At elevated temperatures, however, Ryton V PPS is soluble to a limited extent in some aromatic and chlorinated aromatic solvents and in certain heterocyclic compounds. The inherent viscosity, measured at 206°C in 1-chloronaphthalene, is generally 0.16, indicating only moderate molecular weight. The polymer is highly crystalline, as shown by x-ray diffraction studies (9). The crystalline melting point determined by differential thermal analysis is about 285°C. 

Some all-aromatic poly (thiol esters) have also been prepared by this method (34). There is also a continuous process for interfacial condensation polymerization by which poly (thiol esters) with high inherent viscosities have been produced (27). 

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... 

Even higher glass transition temperatures are achievable if4,4 -functionalized 1,1 -binaphthyl monomers are used [28 b, 30]. For example, the homopolyester derived from 4,4 -dihydrox-1,1 -binaphthyl (BDP) and phenylterephthalic acid with an inherent viscosity of 1.90 dl/g has a Tg of 183 °C. The polyester is nematic up to its decomposition temperature and forms a nematic glass below Tg. In a similar homopolyester based on 4,4 -dicarboxy-1,1 -binaphthyl and t-butyl-hydroquinone the Tg was found to be 189 °C. In both cases, good solubility in common chlorinated solvents is maintained. This type of monomers was, for example, also used to modify wholly aromatic copolyesters based on 6-hydroxy-2-naphthoic acid (HNA) and 2,6-naphthalene dicarbox-ylic acid (NDA) [25 a]. 

The palladium-catalyzed cross-coupling of aryl halides with diamines has also been used in the preparation of polymers [6]. This reaction can be run under an atmosphere of carbon monoxide to produce aromatic polyamides with similar inherent viscosities as polymers prepared via conventional solution polymerization techniques (eq 3) [7]. 

Polymers with inherent viscosities of 1-0.25 form. Among the ofganic bases, imidazole is most effective. The reaction is applicable to both aliphatic and aromatic dicarboxylic acids and diamines. 

Direct polycondensation of various dicarboxylic acids with diamines is possible [81] under mild conditions by using a catalytic system of an enol phosphite in the presence of imidazole. One such enol phosphite is diethyl,l-methyl-3-oxo-l-butenyl phosphite. Polymers with inherent viscosities of 1-0.25 form. Among the organic bases, imidazole is most effective [84]. The reaction is applicable to both aliphatic and aromatic dicarboxylic acids and diamines. 

Linear, high molecular weight polyamides were obtained when aliphatic, aromatic, and heterocyclic diamines were reacted with aromatic and heterocyclic ortho-dicarboxylic acid dichlorides. Interfacial polymerization of an aqueous, alkaline solution of trans-2,5-dimethyIpiperazine with 3,4-furan dicarbonyl chloride in methylene chloride produced a polyamide in 97% yield with inherent viscosity of 3.71 in H SO. The polymer exhibited good stability to heat and hydrolysis and a glass transition temperature... 

In a similar way, the synthesis of aromatic polyamides from aromatic diamines m-phenylenediamine, p-phenylenediamine, bis(4-aminophenyl)methane, and bis(4-aminophenyl)ether and dicarboxylic acids such as isophthalic and tereph-thalic acid was performed in a household microwave oven [72]. The polycondensation was carried out in an JV-methyl-2-pyrrolidone (NMP) solution in the presence of triphenyl phosphite (TPP), pyridine, and lithium chloride as condensing agents to produce a series of polyamides with moderate inherent viscosities of 0.21-0.92 dL/g within 30-50 s. However, no marked differences in molecular weight distribution and inherent viscosities between the polyamides produced by conventional (60 s, 220 °C) and microwave methods were found [72]. 

The reactions were carried out in a 50-ml polyethylene (HDPE) screw-capped cylinder vessel, in which aromatic acid (1.25 mmol) together with aliphatic diamine (1.25 mmol) in an NMP (3 ml) solution were irradiated in a domestic microwave oven (30-40 s) in the presence of TPP (3.123 mmol), pyridine (0.75 ml) and lithium chloride (3.123 ml). The polyamides with inherent viscosity in the range of 0.1 to 0.8 dL/g were obtained in medium to high yield (60-100%) [74]. Temperature was not detected during these microwave experiments. The polyamides were characterized by thermal methods (TGA, DSC). However, no comparison to the polymers prepared by a conventional method was made. 

The reactions were performed in an unmodified microwave oven. Prior to the microwave irradiation, 0.1 g of diacid chloride was ground with equimolar amount of an aromatic amine or diphenol and a small amount of a polar high boiling solvent (e.g., o-cresol, 0.05-0.45 ml) that acted as a primary microwave absorber. Under microwave irradiation, the polycondensation reactions proceeded rapidly (6-12 min) while compared with a conventional solution polymerization (reflux for 12 h in chloroform then for another 12 h in dimethylacetamide solutions [79]) to give polymers with higher inherent viscosities in the range of 0.36 to 1.93 dL/g (Table 5). 

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