Acyllactam

Polyamide macromonomers can be made by reaction of the terminal acyllactam function with an unsaturated nucleophile such as the anion derived fromp. vinylbenzyl amine 8I). The nucleophilicity of the latter is higher than that of the lactam anion, and the reaction is straightforward. 

Griot, R. G., and A.J. Frey The Formation of Cyclols from N-Hydroxy-acyllactams. Tetrahedron [London] 19, 1661 (1963). 

The anionic polymerization of lactams proceeds by a mechanism analogous to the activated monomer mechanism for anionic polymerization of acrylamide (Sec. 5-7b) and some cationic polymerizations of epoxides (Sec. 7-2b-3-b). The propagating center is the cyclic amide linkage of the IV-acyllactam. Monomer does not add to the propagating chain it is the monomer anion (lactam anion), often referred to as activated monomer, which adds to the propagating chain [Szwarc, 1965, 1966]. The propagation rate depends on the concentrations of lactam anion and W-acy I lactam, both of which are determined by the concentrations of lactam and base. 

Initiation consists of the reaction of the A -acyllactam with activated monomer followed by fast proton exchange with monomer... 

NMR spectrum showing the presence of a 3-substituted pyridine with four nonequivalent methylene units in the substituent, and by its conversion to 2,3-bi-pyridyl with chloranil (26). Its synthesis was made by condensation of A -ben-zoylpiperidone (258) with ethyl nicotinate (259) followed by heating with concentrated hydrochloric acid, resulting in hydrolysis, decarboxylation, and ring closure (Scheme 18) 401). Application of the Mundy A-acyllactam rearrangement to A-nicotinoylpiperidone (261) has also led to a synthesis of anaba-seine (8) (Scheme 18) 402). 

Most of the work reported in the literature employs sodium lactamate salt as catalyst and isocyanate/lactam adducts as initiator. Gabbert and Hedrick [14] preferred to work with acyllactam as the initiator and Grignard salts of caprolactam as the catalyst in view of their ease of handling and fewer side reactions compared with the sodium lactamate and isocyanate system. 

The terms in Equation 1.3 (Malkin s autocatalytic model) are described in Nomenclature. In Malkin s autocatalytic model, the concentration of the activator, [A], is defined as the concentration of the initiator times the functionality of the initiator. For a difimctional initiator [e.g., isophthaloyl-bis-caprolactam, the concentration of the activator (acyllactam) is twice the concentration of the initiator]. The term [C] is defined as the concentration of the metal ion that catalyzes the anionic polymerization of caprolactam. In a magnesium-bromide catalyzed system, the concentration of the metal ion is the same as the concentration of the caprolactam-magnesium-bromide (catalyst) because the latter is monofunctional. 

Figure 1.11 Adiabatic conversion of nylon 6 Experimental data for initial polymerization temperatures of 117°C (bottom line), 136°C (middle line), and 157°C (top line) with acyllactam and caprolactam-magnesium-bromide concentrations of 70 and 108mmol/L, respectively...

The single feed composition investigated consisted of 133mmols/L of caprolactam-magnesium-bromide and 45 mmols/L of the difunctional isophthaloyl-bis-caprolactam. Note that 45 mmols/L of the difunctional isophthaloyl-bis-caprolactam contain 90 mmols/L of the active acyllactam group, which react with the monolunctional caprolactam-magnesium-bromide to initiate the polymerization reaction. 

More sophisticated functions, such as acyllactam vinyl silane , isocyanate phosphonic ester -2, etc. have been attached at the end of polymer chains, in nearly quantitative yields. Also polymers fitted with dyes or fluorescent groups at chain ends have been synthesized. ... 

Reaction (55) exhibits a higher activation energy than the addition of the caprolactam anion to acyllactam. An addition of acyllactam as activator strongly reduces the induction period and makes possible polymerization at lower temperatures. 

Initiation of e-caprolactam polymerization in the presence of acyllactam can be described by the scheme... 

With lactams, a tautomeric equilibrium is assumed to exist between the compounds formed by the addition of a simple primary cation to oxygen or nitrogen. With a proton as the cation, an acyllactam ammonium ion is finally produced [265, 266],... 

When an acyllactam is added at the beginning of polymerization, the induction period is absent (Fig. 8, curve 2). Hence, the anionic polymer-... 

As soon as polymer amide groups are formed, they can take part in both types of transacylation reactions (23) and (24). The disproportionation reactions involving polymer amide groups and/or anions produce acyllactam and diacylamine structures entering into the polymerization process... 

Transacylations between polymer amide anions and acyllactam represent either depolymerization (29) or incorporation of one monomer unit (30)... 

Acylation of the monomer activates the latter towards the nucleophilic attack by a lactam anion. Hence, it is rational to use the term activator for lactam derivatives capable of growing (e.g., A-acyllactams) or such compounds which produce the latter much faster than the initiator alone (e.g., acid chloride). In most cases, the activator or its fragments become part of the polymer molecule. Anionic polymerizations in which an activator has been added are designated as activated polymerizations, whereas in non-activated polymerizations the growth centres are produced by the initiator, reaction (23). 

A great variety of substances is capable of acting as activators. The first group comprises iV-substituted lactams with polar substituents at the nitrogen. These iV-substituted lactams must be able to acylate lactam anions with opening of the lactam ring of the activator at a rate comparable to the rate of polymerization. The main representatives of this group are acyllactams [84, 89, 107—110] (V), iV-substituted [111] (VI) or iV,Af-disubstituted [112] carbamoyllactams (VII), JV-carboxylic acid esters of lactams [112] (VIII) and salts of lactam-N-carboxylie acids [107] (IX), viz. 

Decay of imide groups (acyllactam and diacylamine structures) during anionic caprolactam polymerization 1125]... 

The open chain structure (X) is formed in the condensation of diacylamine groups. The JV-acyllactam growth centres can undergo condensation at the cyclic as well as exocyclic methylene and carbonyl groups... 

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