Anionic ring-opening polymerization kinetics

Among the more common thermoplastics from ring opening polymerization of interest in composite processing are polylactams, polyethers, polyacetals, and polycycloolefins. It has also been shown that polycarbonates can be produced from cyclic carbonates [22], Anionic ring opening polymerization of caprolactam to nylon 6 is uniquely suited to form a thermoplastic matrix for fiber-reinforced composites, specifically by the reaction injection pultrusion process [23-25]. The fast reaction kinetics with no by-products and the crystalline... 

For sodium/hexamethylene-l,6-bis-carbamidocaprolactam system, Sibal et al. [64] found the value of the constant k in Equation 1.4 to be 17.5. Note that the values of the constant k in Equation 1.4 that defines the relative complex viscosity rise during anionic ring opening polymerization of caprolactam are comparable for both caprolactam-magnesium-bromide/isophthaloyl-bis-caprolactam and sodium/hexamethylene-l,6-bis-carbamidocapro-lactam as the catalyst/initiator systems even though the kinetic constants for anionic polymerization for these systems are extremely different (see Table 1.2). 

The kinetics of anionic ring opening polymerization of caprolactam initiated by iso-phthaloyl-bis-caprolactam and catalyzed by caprolactam-magnesium-bromide satisfactorily fit Malkin s autocatalytic model below 50 percent conversion. The calculated value of the overall apparent activation energy for this system is 30.2kJ/mol versus about 70kJ/mol for Na/hexamethylene-l,6,-bis-carbamidocaprolactam as the initiator/catalyst system. 

Kinetics of anionic ring-opening polymerization has hitherto been quantitatively studied and gave for two monomers, namely ethylene oxide [IS,12] and propylene sulfide [8.20]. Studies on these systems revealed that the living conditions can be achieved, facilitating quantitative determination of rateconstants of propagation on various kinds of ionic growing species. 

Abstract. This paper reviews ring-opening polymerization of lactones and lactides with different types of initiators and catalysts as well as their use in the synthesis of macromolecules with advanced architecture. The purpose of this paper is to review the latest developments within the coordination-insertion mechanism, and to describe the mechanisms and typical kinetic features. Cationic and anionic ring-opening polymerizations are mentioned only briefly. 

Sormani PM, McGrath JE (1985) Kinetics and mechanisms of the anionic ring opening polymerization of cyclosiloxanes in the presence of bis(l,3-aminopropyl tetramethyl-disiloxane) In McGrath JE (ed) Ring opening polymerization kinetics mechanisms and synthesis. ACS Symposium Series No 286... 

Almost all fimctional silicone fluids of today s industrial production are either of a cyclic nature, containing the appropriate residues, or are linear oils bearing reactive functionalities at both ends or in the chain. The chemical nature of silicone synthesis done by equilibration and condensation is prohibitive for formation of asymmetrical silicones, in contrast to organic molecules like oleic acid or even ethanol. Currently there is only one way of preparing monofunctional silicone fluids, which is through kinetic anionic ring opening polymerization of the cyclic silicone monomer hexamethyl-cyclotrisiloxane (D3). 

Van Dyke, M. E. Clarson, S. J., Reaction Kinetics for the Anionic Ring-Opening Polymerization of Tetraphenyltetramethylcyclosiloxane Using a Fast Initiator System. J. Inorg. Organomet. Polym. 1998, 8,111-121. 

The tethered diphenyldimethylsiloxane oil was prepared by a kinetically controlled anionic ring opening polymerization of hexamethylcyclotrisiloxane (D3) and hexaphenylcyclotrisiloxane (Dj ) in the presence of n-BuLi (Figure 5) (7). Once the lithium salt of D3 and 03 6 was formed in a two step process, it was then quenched with water to give a silanol terminated diphenyldimethylsiloxane product (2). 

In another work, the kinetics of anionic ring-opening polymerization of octamethylcyclotetrasiloxane (D ) in the presence of HA fibers was studied and the properties of in situ prepared composites were excunined, in comparison with ex situ preprued composites by solution blending [104]. The in situ prepared Scunples showed a 260% increase of tensile modulus, whereris ui increcise of 210% was observed for the ex situ preprued composite at... 

Quite often in the ring-opening polymerization, the polymer is only the kinetic product and later is transformed to thermodynamically stable cycles. The cationic polymerization of ethylene oxide leads to a mixture of poly(ethylene oxide) and 1,4-dioxane. In the presence of a cationic initiator poly(ethylene oxide) can be almost quantitatively transformed to this cyclic dimer. On the other hand, anionic polymerization is not accompanied by cyclization due to the lower affinity of the alkoxide anion towards linear ethers only strained (and more electrophilic) monomers can react with the anion. 

Polymerization of racemic aziridines afforded soluble polymers, whereas the use of enantiopure aziridines provided sparingly soluble polymers. KHMDS serves to deprotonate the primary sulfonamide initiator, providing an amide anion, which then functions as a nucleophile to promote the ring-opening polymerization of the aziridine. The polymerization kinetics were shown to feature a first-order dependence on both the aziridine substrate and the anionic initiator. 

Penelle. J. Xie. T. Ring-opening polymerization of diisopropyl cyclopropane-1.1 -dicarboxylate under living anionic conditions A kinetic and mechanistic study. Macromolecules 2000.33 (13). 4667-4672... 

Penelle, J. and Xie, T, Ring Opening Polymerization of Diisopropyl Ciclopro-pane-1,1 Dicarboxylate under Living Anionic Conditions A Kinetic and Mech-anicistic Study, Macromolecules, 33, 4667, 2000. 

Macrolides have virtually no ring strain, and hence, show similar reactivities with acyclic fatty acid alkyl esters in the alkaline hydrolysis and lower anionic ring-opening polymerizabihty than e-CL. However, polymerization of the macrolides using lipase PF catalyst proceeded much faster than that of -CL. This speciflc polymerizabihty by hpase catalyst was quantitatively evaluated by Michaelis-Menten kinetics (160,168,170-172). For imsubstituted lactones in the... 

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