Polyethers solution polycondensation

Titanium-containing polyethers have been prepared by the reaction of dicyclopentadienyltitanium dichloride with aromatic and ahphatic diols via an interfacial and/or aqueous solution polycondensation technique (273). 

Polyethers and polyesters having methoxybenzalazine units with various alkylene groups (C4, C6 and Cg) in the main chain were synthesized from vanillin (7,8). The condensation reaction of 4,4 -alkylenedioxybis (3-methoxybenzaldehyde) [VI] with hydrazine monohydrate was applied to the synthesis of polyethers [VII] (Mn, 7.4 x 103 for C4, 7.3 x 103 for C6 and 4.1 x 103 for Cg derivatives), as shown in Scheme 3. Polyesters [IX] (77jnh, 0.35 dl/g for C4, 0.38 dl/g for C6 and 0.43 dl/g for Cg derivatives) were synthesized from 4,4 -dihydroxy-3,3 -dimethoxybenzalazine [VIII] and di-carboxylic acid chlorides by conventional low temperature solution polycondensation, as shown in Scheme 4. 

A series of polymers (including polysulphones, polyethers) containing the monomer fra s-l,2-diphenylcyclopropane have been synthesised [49] by solution polycondensation. CP/MAS spectroscopy was used, among other techniques, to characterise the cyclopropane ring opening reaction which had occurred in the final thermally crosslinked product. One such polymer (Fig. 15.2.45) showed characteristic peaks in its CP/MAS spectrum (Fig. 15.2.46). 

Phase-transfer catalysis (PTC) has been recently applied to the preparation of polyethers by polycondensation 1 1. This method offers several advantages over solution conducted nucleophilic displacement step-growth polymerizations. These include the substitution of inexpensive solvents for anhydrous aprotic solvents such as DMSO, DMAC etc. .., lower reaction temperatures and shorter reaction times. We wish to report our results concerning the preparation of polyethers from bisphenol A (BPA) and 1,4-dichloro-2-butene (DCB) under PTC conditions. The kinetics and the mechanism of this new type of polycondensation are described. 

Synthesis of Group IV B polyethers (2) was accomplished utilizing aqueous and nonaqueous solution polycondensations and classl l and inverse (or reverse) interfacial polycondensa-tlons. 

Polvcondensation of DHTN with dibromomethane under phase transfer conditions. The polycondensation of DHTN [13.13g, 0.080 mole] with 32mL dibromomethane was carried out in the presence of tetrabutyl ammonium bromide [2.48g or 0.008 mole] and 160mL 60 wt% aqueous KOH solution with vigorous stirring at room temperature for 24h. The polymer was precipitated in methanol and purified by reprecipitation from THF solution into distilled water to afford 13.51 g (94.8%) of the desired polyether which exhibits a reduced viscosity of 0.27 dL/g [measured at 30°C in DMF at a concentration of 0.5g/dL]. The polymer had an IR spectrum with a prominent C-O-C peak at 1210 cm". The NMR spectrum of the polyether [CDC13] showed peaks atff 1.7-2.5 (C-CH2-CH2-C), 4.6-5.3 (0-CH2-0), and 7.3-8.0 (aromatic). 

Other polycondensation reactions which lead to finely dispersed polymers in liquid polyethers are the polycondensation reactions of urea and melamine with aqueous formaldehyde [92-95]. The reaction medium is usually polyether polyols, PO homopolymers or PO-EO copolymers (random or block copolymers), with MW of 3000-5000 daltons. During the polycondensation reaction, the aminoplast polymer precipitates, being insoluble in polyether and water (water from formaldehyde solution and reaction water), is eliminated by vacuum distillation. A variant of this reaction is to develop the polycondensation in water, and water containing the aminoplast polymer (as a viscous solution) is added to a polyether polyol, under vacuum, and at high temperature (100-130 °C), water being continuously eliminated from the reaction medium. The aminoplast insoluble polymer precipitates in the form of fine particles. 

A wide variety of group 4 (Ti, Zr, Hf) metallocene-containing polyethers, polythioethers, polyesters, polyamines, polyoximes, and polyamidoximes has also been reported. Their synthesis, which is based on the polycondensation (with HCl elimination) of CP2MGI2 with difunctional organic species such as diols, dithiols, etc. (Scheme 14), was carried out either in aqueous solution or using interfacial condensation techniques, based upon the... 

Various types of condensation polymers such as aromatic polysulfonates and polysulfides, aromatic polyethers, aliphatic and aromatic polysulfides, and carbon-carbon chain polymers of high molecular weights by the phase-transfer catalyzed polycondensation fi-om combinations of aromatic disulfonyl chlorides, phosphonic dichlorides, activated aromatic dichlorides, and aliphatic dihalides, withbisphenol, aliphatic and aromatic dithiols, and active ethylene compounds. The two-phase polycondensation was generally carried out in a water-immiscible organic solvent-aqueous alkaline solution system at room temperature. The method of polycondensation offers a highly versatile and convenient synthetic method for a variety of condensation polymers. 

In this approach, AB2 type or other similar monomers such as AB (x = 4, 6, 8, etc.) monomers are polymerised by a polycondensation reaction. Gelation, a general problem in the polymerisation of multifunctional monomers, is avoided by the use of a dilute solution and the slow addition of monomer(s). Vegetable oil-based hyperbranched polyhydrocarbons, polyethers, polyesters, polyamides, and so on may be prepared by this method. 

The polyether-ester polyamic acid imidization process in a solid state under microwave irradiation was studied by Yu et al. [73]. The prepolymer, polyether-ester polyamic acid, was prepared by the polycondensation of poly(tetramethylene ether)glycol di-p-aminobenzoate (Polyamine-650, Polaroid, Co.) and pyromellitic acid dianhydride (PMDA) at room temperature in DMF solution. Later, the prepolymer solution was cast on polytetrafiuoroethylene plates to form 200 pm thin films that were imidized under microwave irradiation in a household microwave oven at 60 °C. The temperature was measured by means of a thermocouple applied to the film surface immediately after the intervals of microwave turn off It was found that microwave irradiation reduced both the reaction temperature and time. For example, during the solid phase thermal polymerization 68.3% polyamic acid was converted to polyimide at 155 °C, while under microwave irradiation 65 % of polyamic acid was reacted at 60 °C within 3 h [73]. 

There is, however, an Important practical difference between the reaction conditions required for successful operation of the routes to polyetherketones as compared with those for the polysulphones and this arises from a crucial difference between the two classes of polymers. Polyethersulphones are amorphous or only slightly crystalline and dissolve readily in polar organic solvents such as nitrobenzene or dimethyl sulphoxide at room temperature, but many polyetherketones develop considerable crystallinity and dissolve only at temperatures close to their melting points in this type of solvent. The insolubility of these polymers presented a major synthetic problan as it limits the molecular weights that could be obtained before the growing chains crystallised out from the polycondensation system and this is the main reason why commercial development of the polyetherketones lagged behind that of the polyethersulphones Solutions to this problem for the polyaroylation reactions, (1), were found first by du Pont and then by Raychem, while for the polyether syntheses the problem was solved by ICl. Raychem manufactured a polymer of structure 1, named Stilan, between 1972 and 1976, and manufacture of the ICI polymer, II, trade name Victrex PEEK", started in 1982. 

Synthesis of zirconocene polyethers was general for the interfacial systems but was effected only with aromatic diols using the aqueous systems. This suggests that the active form(s) of reactants may he different for the two synthetic systems. The lack of polymer formation in aqueous solution systems with aliphatic diols may be due to the difference in acidity between aromatic and aliphatic diols. For instance, hydro-qimone is 99% monoionized at pH s >12 and over 99% diionized at pH s >13.8. Aliphatic diols remain largely unionized even at a pH of about 14. It is possible that polycondensation is only effected in aqueous solutions containing deprotonated diols whereas other criteria and/or active species are critical for the interfacial systems. 

It is clear from these results that the application of phase transfer catalyzed synthesis to polycondensation has high potential value. With the proper choice of conditions, activated dihalides react readily with divalent nucleophiles including bisphenols, dithiols, and active methylene compounds in organic solvent-aqueous alkaline solution system to yield various types of condensation polymers such as polysulfonates, polyphosphonates, polyethers,7 polysulfides,S 10,18,19 and carbon-carbon chain polymers.14,15... 

Rausch also reported the synthesis of polyurethanes however, these polymers exhibited low solubihty and they precipitated from solution during the polymerization reactions. Polyurethanes with polyether segments in their backbones have also been synthesized. It has also been reported that polyurethanes with ferrocenyl units in their backbones exhibit enhanced thermal stability. Polyesters containing ferrocenyl units in the mainchain have been the focus of numerous studies. It has been reported that many of these organometallic polymers exhibit liquid crystalline properties. " Scheme 25 shows the synthesis of a liquid crystalline polyester (103) via polycondensation reactions. Increasing the length of the alkyl chains decreased the thermal stability and glass transition temperatures of these polymers. 

Aromatic hb polyethers were prepared from equimolar + bs polycondensations by Kricheldorf et al. [67-69], Possum et al. [70], and Long et al. [71, 72], The Kricheldorf group studied polycondensations l,l,l-tris(4.hydroxyphenyl)ethane or its trimethylsilylderivative with 4,4 -bis(4-fluorophenyl sulfone) and with 1,4-bis(4-fluorobenzoyl)benzene [68] in moderately concentrated solutions. The MALDI-TOF mass spectra revealed a high fraction of cyclic species, and even polyethers containing two cyclic elements were detectable in the mass range above... 

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