Polyamides polycondensation

A new class of polyamides containing dibenzo 18-crown-6-moieties and alkaline units in the main chain shows [75] varying complexing capabilities with 4-toluene sulfonates of Rb+, K+, Na+ and potassium salts of CH3C6H4SOj, SCNI-, Br-. The polyamide polycondensates are obtained from cis- or trans-4,4 -diaminodibenzo 18-crown-6-(DAC) and a 4,4 -diearboxy-a, cu-diphenoxy-alkane (DCA) (Fig. 25). 

Poly(ethylenimine S-alkyldithiocarbamate) polymers were prepared from respective poly(ethylenimine sodium dithiocarbamate) and alkyl chlorides, aralkyl chlorides, substituted alkyl esters of chloroacetic acid, p-chloroethyl esters of carbamic and carboxylic acids, and N-substituted chlorocarboxamides. The derivatives thus obtained were decomposed both physically and chemically to release sulfur and sulfur-containing substances which acted as controlled-release herbicides or fungicides. One author has proposed reactions of the pesticide 2,6-dichlorobenzaldehyde with diols and amines to form polyamide polycondensation products. ... 

Synthetic Fiber and Plastics Industries. In the synthetic fibers and plastics industries, the substrate itself serves as the solvent, and the whitener is not appHed from solutions as in textiles. Table 6 Hsts the types of FWAs used in the synthetic fibers and plastic industries. In the case of synthetic fibers, such as polyamide and polyester produced by the melt-spinning process, FWAs can be added at the start or during the course of polymerization or polycondensation. However, FWAs can also be powdered onto the polymer chips prior to spinning. The above types of appHcation place severe thermal and chemical demands on FWAs. They must not interfere with the polymerization reaction and must remain stable under spinning conditions. 

Grafting can also occur in the amide nitrogen, either through an anionic-type mechanism which is beheved to operate when ethylene oxide [75-21 -8] and similar copolymers are grafted to polyamides, or through a polycondensation mechanism when secondary amides are formed as graft copolymers (70). 

Hydrolysis and Polycondensation. One of the key properties of polyamides relates to the chemical equihbrium set up when the material is polymerized. The polymerization of nylon is a reversible process and the material can either hydrolyze or polymerize further, depending on the conditions. 

Another common polycondensation involves reaction of diamines and diacids to form polyamides, commonly called nylons ... 

Phenothiophosphine ring-containing polyamides and polyesters were also prepared by the polycondensation of 2,8-bischloroformyl-lO-phenylphenothiophos-phine 5,5, 10-trioxide with aromatic diamines such as 4,4 -diaminodiphenyl ether and 4,4 -diaminodiphenyl-methane, and bisphenols such as 4,4 -dihydroxybiphe-nyl and 4,4 -dihydroxydiphenylmethane, respectively [159]. These polymers are soluble in polar aprotic solvents and also exhibit good heat and fire resistance. Phosphorus containing high performance polymers are shown in Table 6. 

The main polymerization method is by hydrolytic polymerization or a combination of ring opening as in (3.11) and hydrolytic polymerization as in (3.12).5,7 9 11 28 The reaction of a carboxylic group with an amino group can be noncatalyzed and acid catalyzed. This is illustrated in the reaction scheme shown in Fig. 3.13. The kinetics of the hydrolytic polyamidation-type reaction has die form shown in (3.13). In aqueous solutions, die polycondensation can be described by second-order kinetics.29 Equation (3.13) can also be expressed as (3.14) in which B is die temperature-independent equilibrium constant and AHa the endialpy change of die reaction5 6 812 28 29 ... 

As is die case for odier polycondensation reactions, internal interchange reactions are possible for ADMET, similar to diat of polyesters and polyamides.16 Interchange reactions involve a catalyst molecule on a polymer chain end reacting widi an internal double bond in another polymer chain. The result is two new polymer chains however, no change in the molecular weight distribution... 

Polycondensation pol5mers, like polyesters or polyamides, are obtained by condensation reactions of monomers, which entail elimination of small molecules (e.g. water or a hydrogen halide), usually under acid/ base catalysis conditions. Polyolefins and polyacrylates are typical polyaddition products, which can be obtained by radical, ionic and transition metal catalyzed polymerization. The process usually requires an initiator (a radical precursor, a salt, electromagnetic radiation) or a catalyst (a transition metal). Cross-linked polyaddition pol5mers have been almost exclusively used so far as catalytic supports, in academic research, with few exceptions (for examples of metal catalysts on polyamides see Ref. [95-98]). 

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... 

Interfacial or solution polycondensation, with or without stirring, was the general procedure utilized for the preparation of the polyamides and polyureas.l a Details are given in Table I. An important point to be noted is that, in the unstirred interfacial condensation polymerization of 1 with sebacoyl chloride or tere-phthaloyl chloride in the organic phase and triethylamine as the proton acceptor, immediate film formation took place at the interface. The polyamide films were removed after 1 h, dried, and utilized for taking electron micrographs. 

Polyamide 6 is produced by ring opening polycondensation of e- caprolactame. If no other reactants are used, the polymer chains contain one carboxylic acid and one amine end group. 

Polycondensation, 10 189-190, 191 as an aging mechanism, 23 64 of polyamide plastics, 19 781-782 polyester formation by, 20 390-391 silicone polymerization via, 22 556-558 in the sol-gel process, 23 61-62 Polycrystalline alloys, 13 523 Polycrystalline diamond films, deposition of, 24 744-745... 

Polyamides containing thymine photodimer units in the main chain (17a,b) were prepared by polycondensation of thymine photodimer derivatives (15a,b), which were obtained by the photochemical reaction of the monomeric compound, and various diamines by the activated ester method (Figures 4 and 5) (17, 19). 

Polyamides can be obtained by the melt polycondensation between dicarboxylic acids and diamines. They have the general structure as follows ... 

Figure 5.7 Degree of polycondensation as a function of retention time and temperature [12b]. From Weger, F., Solid-state postcondensation of polyesters and polyamides, presentation given at the FrankI and Thomas Polymer Seminar, 16 June, 1994, Greenville, SC, USA, and reproduced with permission of EMS Inventa-Fischer, GmbH Co. KG...

PTT, with three methylene units in its glycol moiety, is called an odd-numbered polyester. It is often compared to the even-numbered polyesters such as PET and PBT for the odd-even effect on their properties. Although this effect is well established for many polycondensation polymers such as polyamides, where the number of methylene units in the chemical structures determines the extent of hydrogen bonding between neighboring chains and thus their polymer properties, neighboring chain interactions in polyesters are weak dispersive, dipole interactions. We have found that many PET, PTT and PBT properties do not follow the odd-even effect. While the PTT heat of fusion and glass transition temperature have values between those of PET and PBT, properties such as modulus... 

Step-growth condensation polymers, such as polyesters and polyamides, are formed by reversible reactions. In the case of PET, the commercial synthesis is essentially carried out by two reactions. The first is the formation of bishydroxyethyl terephthalate by esterification of a diacid with a glycol or by transesterification of a diester with a glycol. The second is the formation of the polymer by a polycondensation reaction. 

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 use of HMF or the corresponding dialdehyde precursors obviously applies to the synthesis of monomers for polycondensation reactions as shown by the examples given in Scheme 2. ITiese difimctional structures again mimic the corresponding well-known aliphatic and aromatic counterparts used in the preparation of polyesters, polyamides, polyurethanes, etc. 

Proposed mechanisms for polycondensations are essentially the same as those proposed in the organic chemistry of smaller molecules. Here, we will briefly consider several examples to illustrate this similarity between reaction mechanisms for small molecules and those forming polymers. For instance, the synthesis of polyamides (nylons) is envisioned as a simple Sn2 type Lewis acid-base reaction, with the Lewis base nucleophilic amine attacking the electron-poor, electrophilic carbonyl site followed by loss of a proton. 

The International Union of Pure and Applied Chemistry [IUPAC, 1994] suggested the term polycondensation instead of step polymerization, but polycondensation is a narrower term than step polymerization since it implies that the reactions are limited to condensations—reactions in which small molecules such as water are expelled during polymerization. The term step polymerization encompasses not only condensations but also polymerizations in which no small molecules are expelled. An example of the latter is the reaction of diols and diisocyantes to yield polyurethanes (Eq. 1-6). The formation of polyurethanes follows the same reaction characteristics as the formation of polyesters, polyamides, and other polymerizations in which small molecules are expelled. 

It has become the custom to name linear aliphatic polyamides according to the number of carbon atoms of the diamine component (first named) and of the dicarboxylic acid. Thus, the condensation polymer from hexamethylenedi-amine and adipic acid is called polyamide-6,6 (or Nylon-6,6), while the corresponding polymer from hexamethylenediamine and sebacoic acid is called polyamide-6,10 (Nylon-6,10). Polyamides resulting from the polycondensation of an aminocarboxylic acid or from ring-opening polymerization of lactams are indicated by a single number thus polyamide-6 (Nylon-6) is the polymer from c-aminocaproic acid or from e-caprolactam. 

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. 

In principle, the attainment of chemical equilibrium can be accelerated by catalysts however, in contrast to polyester formation, catalysts are not absolutely essential in the above-mentioned polycondensations. The first two types of reactions are generally carried out in the melt solution polycondensations at higher temperature, e.g., in xylenol or 4-fert-butylphenol are of significance only in a few cases on account of the poor solubility of polyamides. On the other hand, polycondensation of diamines with dicarboxylic acid chlorides can be carried out either in solution at low temperature or as interfacial condensation (see Sect. 4.1.2.3). 

Preparation of an Aliphatic Polyamide by Polycondensation of e-Aminocaproic Acid in the Melt... 

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