Polyesters interfacial polymerization

As with polyesters, the amidation reaction of acid chlorides may be carried out in solution because of the enhanced reactivity of acid chlorides compared with carboxylic acids. A technique known as interfacial polymerization has been employed for the formation of polyamides and other step-growth polymers, including polyesters, polyurethanes, and polycarbonates. In this method the polymerization is carried out at the interface between two immiscible solutions, one of which contains one of the dissolved reactants, while the second monomer is dissolved in the other. Figure 5.7 shows a polyamide film forming at the interface between an aqueous solution of a diamine layered on a solution of a diacid chloride in an organic solvent. In this form interfacial polymerization is part of the standard repertoire of chemical demonstrations. It is sometimes called the nylon rope trick because of the filament of nylon produced by withdrawing the collapsed film. 

Recently, many synthetic polymers such as urea/formalin resin, melamine/formalin resin, polyester, and polyurethane have been widely used as the wall material for the microcapsule, though the gelatin microcapsule is still used. Microcapsules using a synthetic polymer wall have several advantages over those using a gelatin wall (1) the preparation process is simple, (2) the size of the microcapsules is well balanced, (3) the microcapsule concentration can be increased twofold or more and (4) the microcapsules have a high resistance to water and many chemicals. Synthetic microcapsules are prepared by interfacial polymerization or in situ polymerization. 

Step-growth polymerization, 22, 24-25, 23, 84-86, 86,90-92,114-115, 261 compared with chain-growth polymerization, 88-89, 88-89 interfacial polymerization, 91-92 laboratory activities on synthesis of nylon, 228-230 synthesis of polyesters in the melt, 231-233 synthesis of polyurethane foam, 234-237 molar mass and, 86, 86 polycondensation of poly ethylene terephthalate), 90-91 polymers produced by, 86 types of monomers for, 90 Stereochemistry, 28, 37-39,41-42, 70 tacticity, 103-105 Stereoisomers, 41 Stereoregularity, 70 Stiffness, 142, 261 Strain, 142-143, 261 Strength... 

This technique can be used effectively to prepare polyesters, polyamides, and polycarbonates. The process of interfacial polymerization can best be illustrated by the reaction between a diamine and a diacid chloride to produce polyamide. The word Nykm is used to represent synthetic polyamides. The various nylons are described by a numbering system that indicates the number of carbon atoms in the monomer chains. Nylons from diamines and dibasic acids are designated by two numbers the first representing the diamine and the second the dibasic acid. Thus, nylon-6,10 is formed by the reaction of hexam-ethylenediamine and sebacoyl chloride ... 

There have been reports of the synthesis of organometallic arylidene polyesters containing ferrocene derivatives in the main chain. Interfacial polymerization of... 

Using the much more reactive acid chloride monomer allows polyester production at much lower temperatures than when using the ester, or free acid. Even under ambient conditions it is so vigorous that interfacial polymerization of diluted solutions of the monomers in an appropriate, immiscible solvent pair may be needed to control the rate. However, the high cost of the acid chloride as compared to terephthalic acid or the ester makes this route commercially unattractive. Also with this monomer pair the kinetic treatment and molecular weight distributions will differ from the general cases outlined in Chapter 20. 

Encapsulation. Immobilization of enzymes by encapsulation within semipermeable structures dates back to the 1970s. There are three fundamental variations of this approach. In coacervation, aqueous microdroplets containing the enzyme are suspended in a water-immiscible solvent containing a polymer, such as cellulose nitrate, polyvinylacetate, or polyethylene. A solid film of polymer can be induced to form at the interface between the two phases, thereby producing a microcapsule containing the enzyme. A second approach involves interfacial polymerization in which an aqueous solution of the enzyme and a monomer are dispersed in an immiscible solvent with the aid of a surfactant. A second (hydrophobic) monomer is then added to the solvent and condensation polymerization is allowed to proceed. This approach has been used extensively with nylons, but is also applicable to polyurethanes, other polyesters, and polyureas. 

Scheme 4 Interfacial polymerization to form an aromatic polyester.

Polyesters are produced commercially by melt polymerization, ester interchanges, and interfacial polymerization. Commercial poly(ethylene terephthalate) is produced traditionally by two successive ester interchange reactions. In the first step, dimethyl terephthalate is heated with ethylene glycol at temperatures near 200°C. This yields an oligomeric dihydroxyethyl terephthalate (x = 1 to 4) and methanol, which is removed. In the second step, the temperature is increased, leading to polymer formation, while ethylene glycol is distilled off. 

Polyesters were historically the first synthetic condensation polymers studied by Carothers in his pioneering work in the early 1930s. Commercial polyesters [30] were manufactured by polycondensation reactions, the methods commonly used being melt polymerization of diacid and diol, ester interchange of diester and diol, and interfacial polymerization (Schotten-Baumann reaction) of diacid chloride and diol. In a polycondensation reaction a by-product is generated which has to be removed as the reaction progresses. 

In the interfacial polymerization technique, a wall is formed from monomers that are dissolved in the two separated phases (oil and water phase) and they polymerize at the interface of emnlsion droplets. The use of these methods is limited, since the preferred matrix or coating materials are nonrenewable or nonfood grade, such as polyesters, polyamides, polyurethanes, polyacrylates, or polyureas, almost always accomplished by traces of toxic monomers (van Soest, 2007). 

In interfacial polymerization, the two reactants in a polycondensation meet at an interface and react rapidly. The substances used are multifunctional monomers. Generally used monomers include multifunctional isocyanates and multifunctional acid chlorides. The basis of this method is the classical Schottenn-Baumann reaction between an acid chloride and a compound containing an active hydrogen atom, such as an amine or alcohol, polyesters, polyurea, and polyurethane. Under the right conditions, thin, flexible waUs/sheU will be formed at or on the surface of the droplet or particle by polymerization of the reactive monomers. 

Tang, B., Huo, Z., and Wu, P. 2008. Study on a novel polyester composite nanofiltration membrane by interfacial polymerization of triethanolamine (TEOA) and trimesoyl chloride (TMC). Journal of Membrane Science 320 198-205. 

Abu Seman, M. N., Khayet, M., and Hilal, N. 2010. Nanofiltration thin-fihn composite polyester polyethersulfone-based membranes prepared by interfacial polymerization. Journal of Membrane Science 348 109-116. 

Moore reacted the acid chloride of FDCA with DHMF, yielding only low molecular weight polyesters [57], Recently, Gomes et al. described a fully furan based polyester via the acid chloride of FDCA by interfacial polymerization, with an Mn of 3800 g.mol , and a Tg of 83 °C (no Tn, is mentioned) [17], The onset of decomposition was determined to be around 205 °C. Based on these results we can conclude that DHMF is too unstable to be used as monomer in step-growth polymers. 

FIGURE 5.3 An ATR-FTIR analysis of the unmodified membrane (NFPESIO) and a modified membrane by IP using 2% w/v BPA and 60 sec reaction time. (From Journal of Membrane Science, 348, Abu Seman, M.N., Khayet, M., and Hilal, N., Nanofiltration thin-film composite polyester polyethersulfone-based membranes prepared by interfacial polymerization, 109-116, Copyright (2010), with permission from Elsevier.)... 

Interfacial polymerization was employed to produce aromatic polyesters from 2,5-furan dicarbonyl dichloride with various bis-phenols such as resorcinol, pyrocatechol, hydroquinone, and 2,2-bis(4-hydroxy-phenyl) propane. When 2,5-furan dicarbonyl dichloride was combined with 2,2-bis(4-hydroxyphenyl)propane, workers were able to obtain a maximum yield and maximum logarithmic viscosity number of 80% and 0.17, respectively, when the polymerization solvent was benzene at 25 with two equivalents of sodium hydroxide. In a more in-depth study, this same polyester 14... 

All polyesters prepared in this work were made using interfacial polymerization. To an aqueous solution containing the bis phenol and sufficient... 

Solution polymerization of the monomers is also conducted in some applications. The solvents used have to be inert to isocyanates. Highly polar solvents (DMF, etc), which are excellent solvents for polyurethanes, have to be used with caution (71). Polyurethanes are also obtained by interfacial polymerization of iso-cyanatocarboxylic chlorides and glycols to give polyester urethanes (72). 

One of the most important methods for obtaining organometallic polymers is poly condensation. In 1961 Knobloch and Rauscher reported the synthesis of polyesters and polyamides with ferrocene groups in their backbones using interfacial polymerization. 

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