Studies of Polymerization and Ring Formation. X. The Reversible Polymerization of Six-Membered Cyclic Esters

Abstract

The nuclear synthesis of olefins through the ß-bromo ethers has been used in a systematic survey of the hexenes. Ten of the thirteen structurally possible members of this family have been prepared, including those previously unknown. The method is shown to be applicable to the synthesis of monoalkyl, symmetrical and unsymmetrical dialkyl ethylenes. It is believed the method will ultimately prove applicable also to the trialkyl and tetraalkyl ethylenes.The confusion which has existed in the physical constants of the olefins is beginning to disappear. A definite relation is shown to exist between the physical properties and molecular structure of the hexenes. Certain rules have been formulated relating the boiling points, densities and refractive indices of the hexenes to their structure.Eight bromohexyl ethyl ethers, three hexenes and five dibromohexanes are herein described for the first time.

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“…He also mentioned that lactic acid would undergo reversible polymerization i.e. characteristic of six atoms cyclic ester 17 . The polymers formed by sixmembered cyclic esters called linear polyesters and, at some instance, the chains opened and replaced by hydroxyl (OH) and carboxylic (COOH) groups.…”

Desenvolvimento da metodologia para síntese do poli(ácido lático-co-ácido glicólico) para utilização na produção de fontes radioativas

“…Neste tipo de polimerização não há a formação de subprodutos durante a reação. Os dímeros cíclicos são produzidos a partir da despolimerização de polímeros de baixa massa molecular obtidos por policondensação [9,11,14,15] .…”

Environmental-Friendly Biodegradable Polymers and Composites

“…This route was first demonstrated by Carothers in 1932(Carothers, 1932 but high molecular weights were not obtained until improved purification techniques were developed (Garlotta, 2002). The mechanism involved is ring-opening polymerization (ROP) and may be ionic or coordination-insertion depending on the catalytic system used (Auras et al, 2004;Sodergard & Stolt, 2002;Stridsberg et al, 2001;Mehta et al, 2005).…”