Monomers polycondensation

Fig. 13 Constitutional adaptation to the environment in the hydrophobically-driven component selection on formation of a rigid rod dynamer from amphiphilic monomers. Polycondensation occurs in aqueous solution with preferential incorporation of the monomer presenting the largest hydrophobic area. Selectivity is progressively lost in solutions containing increasing amounts of organic solvent, acetonitrile...

The single-monomer polycondensation scheme has also been used to synthesize hyperbranched polyethers [58], polyesters [59], polyurethanes [60], polysiloxysilanes [61], as well as polycarbonates [62], Higher order monomers including AB3, AB4, AB5, and ABg have also been applied in single-monomer polycondensation syntheses of hyperbranched polymers [63, 64]. 

Scheme 30.8 Hyperbranched polyphenylene synthesis by the single-monomer polycondensation method.

Although the properties of condensation polymers are often superior to those exhibited by vinyl addition polymerization, little attention has been directed toward the introduction of fnnctional groups by polycondensation using appropriately substituted monomer. Polycondensation polymers may contain the reactive functional groups as a part of the polymer backbone or as pendent substituents. 

Life cycle scheme of polyester (PET) fibre materials as polymer based on two monomers polycondensation. 

A-A/B-B monomers, polycondensations, 157 A-B monomers, polycondensations, 157 AB monomers, self-polymerization via benzimidazole-activated ether synthesis, 266--274 Acetophenones Ru-catalyzed addition, 67-69 Ru-catalyzed step-growth copolymerization with a,(0-dienes for high-molecular-weight polymer synthesis, 99-112 4-(Acryloxy)benzoic acid, ordered polymer synthesis, 442-450 Acyclic diene metathesis polymerization cycle, 116,118/... 

Condensation polymerization differs from addition polymerization in that the polymer is formed by reaction of monomers, each step in the process resulting in the elimination of some easily removed molecule (often water). E.g. the polyester polyethylene terephthalate (Terylene) is formed by the condensation polymerization (polycondensation) of ethylene glycol with terephthalic acid ... 

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. 

The presence of stable free radicals in the final polycondensate is supported by the observation that traces of (11) have a strong inhibiting effect on the thermal polymerization of a number of vinyl monomers. Radical polymerization was inhibited to a larger extent by a furfural resin than by typical polymerization inhibitors (34). Thermal degradative methods have been used to study the stmcture of furfural resinifted to an insoluble and infusible state, leading to proposed stmctural features (35). 

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). 

The second largest use at 21% is for unsaturated polyester resins, which are the products of polycondensation reactions between molar equivalents of certain dicarboxyhc acids or thek anhydrides and glycols. One component, usually the diacid or anhydride, must be unsaturated. A vinyl monomer, usually styrene, is a diluent which later serves to fully cross-link the unsaturated portion of the polycondensate when a catalyst, usually a peroxide, is added. The diacids or anhydrides are usually phthahc anhydride, isophthahc acid, and maleic anhydride. Maleic anhydride provides the unsaturated bonds. The exact composition is adjusted to obtain the requked performance. Resins based on phthahc anhydride are used in boat hulls, tubs and spas, constmction, and synthetic marble surfaces. In most cases, the resins contain mineral or glass fibers that provide the requked stmctural strength. The market for the resins tends to be cychcal because products made from them sell far better in good economic times (see Polyesters,unsaturated). 

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). 

The first mechanistic studies of silanol polycondensation on the monomer level were performed in the 1950s (73—75). The condensation of dimethyl sil oxanediol in dioxane exhibits second-order kinetics with respect to diol and first-order kinetics with respect to acid. The proposed mechanism involves the protonation of the silanol group and subsequent nucleophilic substitution at the siHcone (eqs. 10 and 11). 

Early studies of the condensation reaction on the monomer level did not give the full picture of this process and only in the 1980s was polycondensation of siloxanols studied by using oligomeric model compounds (76,77). These studies revealed that in the presence of strong protic acids three processes must be considered linear condensation (eq. 14), cyclization (eq. 15), and disproportionation (eq. 16). 

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... 

Interfacial polymerization is mainly used in polycondensation reactions with very reactive monomers. One of the reactants, usually an acid... 

Some of the typical conditions of polycondensations used for aliphatic and aromatic monomers are not suitable for furan derivatives, e.g., the melt polycondensation of 2,5-furan dicarboxylic acid chloride with 2,5-b/s(hydroxymethyl) furan at about 80 °C only yields a black insoluble product5. The hydrochloric acid liberated in the reaction is clearly responsible for the charring of the furanic diol which like its simpler homologue furfuryl alcohol, resinifies rapidly in acidic media (see below). 

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