Synthesis polycondensation

The understanding of the SSP process is based on the mechanism of polyester synthesis. Polycondensation in the molten (melt) state (MPPC) is a chemical equilibrium reaction governed by classical kinetic and thermodynamic parameters. Rapid removal of volatile side products as well as the influence of temperature, time and catalysts are of essential importance. In the later stages of polycondensation, the increase in the degree of polymerization (DP) is restricted by the diffusion of volatile reaction products. Additionally, competing reactions such as inter- and intramolecular esterification and transesterification put a limit to the DP (Figure 5.1). 

The indirect method involves the preparation of a first block followed by a chemical change to introduce a reactive end-group. This reactive group allows the initation of the second growing-chain. In this case, the first block can be obtained by various routes of macromolecular synthesis polycondensation and ionic or radical polymerization. 

SYNTHESIS Polycondensation of a terephthalic acid with 4,6-diamino-1,3-benzenediol dihydrochloride in poly(phosphoric acid). Processing is primarily limited to variations of wet extrusion. 

ACRONYM, TRADE NAME PHBA, Ekonol (Norton) CLASS Polyesters SYNTHESIS Polycondensation STRUCTURE T O 1... 

Method of synthesis - polycondensation of m-xylenediamine with adipic acid ... 

Various inorganic, organic, and organometaUic compounds are known to cataly2e this polymerization (4,8,9). Among these, BCl is a very effective catalyst, although proprietary catalysts that signiftcandy lower polymerization temperature from the usual, sealed-tube reaction at 250°C are involved in the industrial manufacture of the polymer. A polycondensation process has also been developed for the synthesis of (4) (10—12). This involves elimination of phosphoryl chloride from a monomer prepared from (NH 2 04 and PCl. ... 

The bulk polycondensation of (10) is normally carried out in evacuated, sealed vessels such as glass ampules or stainless steel Parr reactors, at temperatures between 160 and 220°C for 2—12 d (67). Two monomers with different substituents on each can be cocondensed to yield random copolymers. The by-product sdyl ether is readily removed under reduced pressure, and the polymer purified by precipitation from appropriate solvents. Catalysis of the polycondensation of (10) by phenoxide ion in particular, as well as by other species, has been reported to bring about complete polymerisation in 24—48 h at 150°C (68). Catalysis of the polycondensation of phosphoranimines that are similar to (10), but which yield P—O-substituted polymers (1), has also been described and appears promising for the synthesis of (1) with controlled stmctures (69,70). 

Synthesis and Properties. The synthesis of (21) follows a very straightforward route based on readily accessible starting materials and on some novel reactions ia organo—inorganic sulfur chemistry (83—85), as well as on polycondensation chemistry analogous to that utilized ia the preparation of poly(alkyl/arylphosphazenes). One preparation of (21) is as follows ... 

L. B. Sokolov, Synthesis of Polymers by Polycondensation, Israel Program for Scientific Translation, Jemsalem, Israel, 1968, pp. 60—71. 

Nucleophilic Substitution Route. Commercial synthesis of poly(arylethersulfone)s is accompHshed almost exclusively via the nucleophilic substitution polycondensation route. This synthesis route, discovered at Union Carbide in the early 1960s (3,4), involves reaction of the bisphenol of choice with 4,4 -dichlorodiphenylsulfone in a dipolar aprotic solvent in the presence of an alkaUbase. Examples of dipolar aprotic solvents include A/-methyl-2-pyrrohdinone (NMP), dimethyl acetamide (DMAc), sulfolane, and dimethyl sulfoxide (DMSO). Examples of suitable bases are sodium hydroxide, potassium hydroxide, and potassium carbonate. In the case of polysulfone (PSE) synthesis, the reaction is a two-step process in which the dialkah metal salt of bisphenol A (1) is first formed in situ from bisphenol A [80-05-7] by reaction with the base (eg, two molar equivalents of NaOH),... 

An alternative synthesis route for PES involves the partial hydrolysis of dichlorodiphenyl sulfone (2) with base to produce 4-chloro-4 -hydroxydiphenylsulfone [7402-67-7] (3) followed by the polycondensation of this difimctional monomer in the presence of potassium hydroxide or potassium carbonate (7). 

As a variation on the base-catalyzed nucleopbilic displacement chemistry described, polysulfones and other polyarylethers have been prepared by cuprous chloride-catalyzed polycondensation of aromatic dihydroxy compounds with aromatic dibromo compounds. The advantage of this route is that it does not require that the aromatic dibromo compound be activated by an electron-withdrawing group such as the sulfone group. Details of this polymerization method, known as the Ullmaim synthesis, have been described (8). 

The main reactions involved in alkyd lesin synthesis are polycondensation by estetitication and ester interchange. Figure 1 uses the following symbols to... 

BALLY - SCHOLL BenzanihreneSynthesis Synthesis of polycondensed aromatics from antraquinone and tnols. 

Recently, the above mentioned model reaction has been extended to polycondensation reactions for synthesis of polyethers and polysulfides [7,81]. In recent reports crown ether catalysts have mostly been used in the reaction of a bifunctional nucleophile with a bifunctional electrophile, as well as in the monomer species carrying both types of functional groups [7]. Table 5 describes the syntheses of aromatic polyethers by the nucleophilic displacement polymerization using PTC. 

Later, Kricheldorf and coworkers [93,94] extensively demonstrated the use of 0-silylated bifunctional monomers, such as diphenols, for synthesis of a wide variety of polycondensation polymers. The silylated oxygen of difunctional phenols may be condensed with activated... 

Polyphosphonates are well-known flame-retardant materials [110] and are generally prepared by melt [111,112], interfacial [113-115] and solution polycondensation methods [116]. A typical example of synthesis is the polycondensation of bifunctional organophosphorus compounds, such as dichlorophenylphosphine oxide, with bisphenols [117,118]. 

The first polyimine was reported by Adams and coworkers [182] from terephthalaldehyde and benzidine and dianisidine. Between 1950 and 1959 Marval and coworkers [174-176] reported a number of polyimines. Suematsu and coworkers [170] reported the first successful synthesis of high molecular weight fully aromatic polyimines by solution polycondensation method using w-cresol as reaction medium. 

Scheme 7 Synthesis of HPOA and its polycondensation with para hydroxy benzoic acid.

Now, it is widely known that proline at the N-terminal position causes problems of steric hindrance by using active ester couplings in the polycondensation step as well as in the synthesis of the tri- or hexapeptides. This is often a stringent restriction also if proline or glycine are intended to be in the C-terminal position. 

The synthesis of high-molar-mass PLA and PGA by two-step polycondensations of lactic and glycolic acids, respectively, has recently been reported.374,375 It involves the formation of a low-molar-mass oligomer followed by a polycondensation step either in the solid state374 or in the melt under vacuum.375 The procedures are detailed in Section 2.4.1.5.2. 

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