Polycondensation interfacial

In the polycondensation step, a monofunctional phenol (such as 3-5 mol% phenol, p-tert-butylphenol, p-cumylphenol) is added as a chain terminator to control the molecular weight of the final polycarbonate. Reaction partners are now end groups (chloroformate and phenolic -OH see above) and reaction rates decrease. The final polycondensation stages are catalyzed by tertiary amines. The amines react with the chloroformate end groups to form intermediate quaternary acylium salts which then react with phenolate to form carbonate and OH ions, hydrolyzing the chloroformate end groups, or to form a urethane in a side reaction [164]. Detailed mechanistic studies of the catalyst reaction were performed by Aquino et al. [173] and Kosky et al. [174]. 

Numerous variations of the interfacial process have been published. The reactions can be carried out in batch in stirred tank reactors or continuously in series of CSTRs and tubular reactors. Intensive mixing with dispersion and redispersion is required throughout the reaction stages. After the reaction is complete, the brine phase is separated and the polymer solution washed to remove residual amine and base. Several processes for devolatilization are in use, including solventless precipitation, steam precipitation, spray drying, falling-strand devolatilization, and vacuum extrusion in devolatilizing extruders. 

Phosgenation is generally mass transfer-limited [175, 176] and its rate depends on mixing as well as on pH and the volume ratio of the organic and aqueous phases. Although the polycondensation reaction of end groups is slower, both rates still show the same dependencies due to the interfacial nature of the reaction. The following phenomena contribute to the reaction process  

Due to the low reaction temperature and the use of chain terminator, the molecular weight distribution in interfacial synthesis is kinetically controlled and may be far from thermodynamic equilibrium. In two parametric studies Mills [179] and Munjal [180] have tried to model the full molecular weight distribution of polycarbonate. Varying the ratio of mass transfer/kinetic rates, they show how mass transfer limitations can lead to a higher polydispersity or a higher oligomer content. 

A variation of solution polymerization known as interfacial polycondensation has been used in the laboratory for a long time and rumor has it that it is now being applied commercially. One monomer of a condensation pair is dissolved in one solvent, and the other member of the pair is another solvent The two solvents are insoluble in one another. The polymer is soluble in neither, and forms at the interface between them. One of the phases generally also contains an agent that reacts with the molecule of condensation to drive the reaction to completion. 

An example of such a process is the preparation of nylon 6/10 from hexa-methylene diamine and sebacoyl chloride (the add chloride form of sebadc 

The acid chloride is dissolved in, for example, CCU, and the diamine in water, along with some NaOH to soak up the HCl In the classic rope trick demonstration, the aqueous layer is gently floated on top of the organic layer in a beaker. The reactants diffuse to the interface, where they react rapidly to form a polymer film. With care, the film can be withdrawn from the interface in the form of a continuous, hollow strand which traps considerable liquid. New polymer forms at the interface as the old is withdrawn. Commercially, it is probably easier simply to stir the phases together. 

A major advantage of this technique is that these reactions usually proceed very rapidly at room temperature and atmospheric pressure, in contrast to the long times, high temperatures, and vacuums usually associated with polycondensations. This must be balanced against the cost of preparing the special monomers, such as the acid chloride above, and the need to separate and recycle solvents and unreacted monomers. 

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A polyether-amide with a heat distortion temperature of 198°C has been prepared by Hitachi by interfacial polycondensation of 2,2-bis-[4-(4-aminophen-oxy)phenyl]propane (VIII) with a mixture of isophthaloyl- and terephthaloyl-chloride (IX and X) (Figure 18.29). 

Interfacial polycondensation between a diacid chloride and hexamethylenediamine in the presence of small amounts of ACPC also yield polymeric azoamid, which is a macroazo initiator.[27] In this manner, azodicarbox-ylate-functional polystyrene [28], macroazonitriles from 4,4 -azobis(4-cyano-n-pentanoyl) with diisocyanate of polyalkylene oxide [29], polymeric azo initiators with pendent azo groups [3] and polybutadiene macroazoinitiator [30] are macroazoinitiators that prepare block and graft copolymers. 

In addition to a block copolymer, a microcapsule was made from suspension interfacial polycondensation between diacid chloride having aromatic-aliphatic azo group and aliphatic triamine [70,71]. The capsule was covered with a crosslinked structure having an azo group that was thermally stable but sensitive to light so as to be applicable to color photoprinting materials. 

PA-6,10 is synthesized from 1,6-hexamethylenediamine and sebacic acid, and PA-6,12 from 1,6-hexamethylenediamine and dodecanedioic acid. The melt synthesis from their salts is very similar to PA-6,6 (see Example 1). These diacids are less susceptible to thermal degradation.55 PA-6,10 can also be synthesized by interfacial methods at room temperature starting with the very reactive sebacyl dichloride.4 35 A demonstration experiment for interfacial polycondensation without stirring can be carried out on PA-6,10. In this nice classroom experiment, a polymer rope can be pulled from the polymerization interface.34... 

Tough, transparent, heat and flame resistant, multiblock (bisphenol fluorenone carbonate) (BPF)-dimethylsiloxane copolymers have been synthesized by interfacial polycondensation of phosgene with various mixtures of BPF end-capped siloxane oligomers and free BPF or its monosodium salt 232). Siloxane content of the copolymers were varied between 7 and 27%. Presence of two Tg s, one below —100 °C and the other as high as 275 °C, showed the formation of two-phase morphologies. 

We have put this model into mathematical form. Although we have yet no quantitative predictions, a very general model has been formulated and is described in more detail in Appendix A. We have learned and applied here some lessons from Kilkson s work (17) on interfacial polycondensation although our problem is considerably more difficult, since phase separation occurs during the polymerization at some critical value of a sequence distribution parameter, and not at the start of the reaction. Quantitative results will be presented in a forthcoming pub1ication. 

The vast majority of chemical reactions are sufficiently slow not to observe a dramatic influence of mixing on yields and selectivities. Exceptions are polymerizations, interfacial polycondensations, precipitations, and some fast reactions - usually performed in semibatch mode - such as autocatalytic reactions, neutralizations, nitrations, diazo couplings, brominations, iodinations, and alkaline hydrolysis, which are often encountered in the manufacture of fine chemicals. 

We now report a convenient method for the interfacial polycondensation of 1,1 -bis(3-aminoethyl)ferrocene (1) with a variety of diacid chlorides and diisocyanates, leading to ferrocene-containing polyamides and polyureas. In some instances, we have been able to observe film formation at the interface. Moreover, the polymerization reactions can be conveniently conducted at ambient temperatures in contrast to earlier high-temperature organometallic condensation... 

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

The condensation polymerization process, employed recently by Skourlis et al. (1993) and Duvis et al. (1993), involves immersion of carbon fibers in a solution containing hexamethylenediamine and sodium carbonate. Dried carbon fibers are then immersed in a dipolychloride solution in carbon tetrachloride where the interfacial polycondensation reaction takes place. The result is that a thin layer of polyamide (nylon 6,6) coating is deposited on the continuous carbon fiber, whose thickness is controlled though by varying the diamine concentration. 

The Schotten-Baumann reaction between dicarboxylic acid dichlorides and diamines can be performed not only in organic solvents, but also, by means of a special experimental technique known as interfacial polycondensation (see Examples 4-5 and 4-11). Both variants have the advantage of short reaction times at low temperature with simple equipment. 

The reaction between a dihydroxy compound (bisphenol) and phosgene, which is performed on an industrial scale, proceeds even at room temperature.The reaction is generally carried out in a biphasic medium consisting of methylene chloride (with dissolved phosgene) and aqueous sodium hydroxide (with dissolved bisphenol sodium salt) and a phase transfer catalyst (e.g.triethylamine).The procedure is termed interfacial polycondensation (see Sect.4.1.2.3 and Examples 4-5,4-12,and 4-13). 

Preparation of a Thermotropic, Main-Chain Liquid Crystalline (LC) Polyester by Interfacial Polycondensation... 

Fully aromatic polyamides are synthesized by interfacial polycondensation of diamines and dicarboxylic acid dichlorides or by solution condensation at low temperature. For the synthesis of poly(p-benzamide)s the low-temperature polycondensation of 4-aminobenzoyl chloride hydrochloride is applicable in a mixture of N-methylpyrrolidone and calcium chloride as solvent. The rate of the reaction and molecular weight are influenced by many factors, like the purity of monomers and solvents, the mode of monomer addition, temperature, stirring velocity, and chain terminators. Also, the type and amount of the neutralization agents which react with the hydrochloric acid from the condensation reaction, play an important role. Suitable are, e.g., calcium hydroxide or calcium oxide. 

As in the preparation of polyesters, also in the preparation of polyamides, the reaction temperature can be considerably reduced by using derivatives of dicarbo-xylic acids instead of the free acids. Especially advantageous in this connection are the dicarboxylic acid chlorides which react with diamines at room temperature by the Schotten-Baumann reaction this polycondensation can be carried out in solution as well as by a special procedure known as interfacial polycondensation (see Examples 4-11 and 4-12). 

In interfacial polycondensation, the two components are separately dissolved in two immiscible solvents. The polycondensation can now take place only at the interface of the two liquids, whereby the practically instantaneously formed thin polyamide film prevents further diffusion of the two reactants. The polycondensation can only continue when this film is pulled carefully away from the interface the process can thus be run continuously in a simple way (Fig. 4.1). 

Interfacial polycondensation can be also performed in dispersion (Example 4-13) For this purpose the solution of acid dichloride is dispersed in the aqueous solution of diamine by vigorous stirring (if necessary in the presence of a water-soluble dispersion stabilizer). The polycondensation then takes place at the surface of the droplets. Water is especially suitable as solvent for the diamine component, while aliphatic chlorinated hydrocarbons are best for the dicarbox-ylic acid dichlorides. 

Preparation of Polyamide-6,10 from Hexamethylenediamine and Sebacoyl Dichloride in Soiution and by Interfacial Polycondensation... 

The amine solution (4) is now immediately run in dropwise over a period of 30 s and the stirrer speed reduced to 2000 rpm After 2-3 min the high-speed stirrer is replaced by a normal paddle stirrer and the dispersion stirred (500 rpm) for a further 30 min at room temperature to complete the interfacial polycondensation between terephthaloyl dichloride and diethylenetriamine. 

Homopolycarbonates based on 1 and 2 have been prepared by several groups. The interfacial polycondensation typical for the synthesis of aromatic polycarbonates is not useful with alditols, including 1, because they are water-soluble and less acidic than diphenols. The 1-based homopolycarbonate was prepared by phosgena-tion of the sugar diol, with phosgene or diphosgene in pyridine-containing solvent mixtures at low temperatures. The polycondensation of the isosorbide bischloro-formate in pyridine is an alternative approach. 

Morgan PW, Kwolek SL. Interfacial polycondensation. 2. Eundamentals of polymer formation at liqud interfaces. Journal of Polymer Science Part A—Chemistry 1959 40 299-327. 

The synthetic chemistry of polyamides is briefly reviewed and illustrated with a laboratory experiment showing the interfacial polycondensation method. 

In this study, polyesters [XII] having syringyl-type biphenyl units were synthesized from 4,4 -dihydroxy-3,3, 5,5 -tetramethoxybiphenyl (XI) which was prepared from 2,6-dimethoxyphenol (11). As shown in Scheme 6, poly esterification of XI with terephthaloyl, isophthaloyl and sebacoyl chloride were carried out by the low temperature solution polycondensation and by the interfacial polycondensation. The polyterephthalate with jjinh = 1.42 dl/g was obtained by the interfacial poly condensation. The polyisophtha-late with f7 nh = 0.73 dl/g and the polysebacate with Jj nh = 0.43 dl/g were obtained by the low temperature solution polycondensation. 

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