Macrocyclic oligomer polymerization

Macrocyclic oligomer precursors of polycarbonates, PET, polymers of amides, etherketones, and ethersulfones are candidates for further study of macrocyclic oligomer polymerization thermodynamics [6]. Research extends to cyclic arylates (cyclic aryl-aryl esters) and cyclic alkyl aryl esters going back to isolating a cyclic trimer of poly(ethylene-terephthalate) in 1954 [13]. Much of the work on macrocyclic oligomers as precursors to high-MW macromolecules starts with spiro(bis)indane (SBI) biphenyl monomer to produce macrocyclic carbonates. 

Comparison of the chemical shift data (Table 1) reveals that the peak positions of a and 6 carbons of 20-crown-4 are quite different from the corresponding carbons of THF or the polymeric PTME. Small but distinct chemical shift differences were also found for macrocyclic oligomers of other ring sizes. 

Title Catalysts and Methods for Polymerizing Macrocyclic Oligomers... 

Tetraphenoxyl titanates such as 4-isopropyl-, 2-isopropyl-6-t-butyl-, and 2-di-t-butyl-have been prepared and used as catalysts for the rapid depolymerization and repolymerization of macrocyclic oligomers. In this manner macrocyclic co-esters consisting of (butylene terephthalate-co-ethylene terephthalate) were re-polymerized to molecular weights of up to 120,000 daltons. 

TABLE 1. Oligomer re-polymerization of macrocyclic oligomers using 0.3mol% tetraphenoxy titanates. 

The preparation and use of organotin compounds as re-polymerization agents for linear polyesters and macrocyclic oligomers is provided by Paler [1] and Winckler [2], respectively. 

Another initiator for this polymerization is (Me3CO)3W=W(OCMe3)j, but analysis of the products by MS shows that they are macrocyclic oligomers. Their ring-size distribution, as determined by GPC, conforms to the Jacobson-Stockmayer relationship see Ch. 11. It is evident that with the tungsten catalyst... 

A. Ben-Haida, H. M. Colquhoun, P. Hodge, and D. J. Williams. Synthesis of a catechol-based poly(ether ether ketone) ("o-PEEK") by classical step-growth polymerization and by entropically driven ring-opening polymerization of macrocyclic oligomers. Macromolecules, 39(19) 6467-6472, September 2006. 

When similar initiators were employed in the polymerization of 6,8-dioxa-bicyclo[3.2.1]octan-7-one (2) macrocyclic oligomers containing alternating tetrahydropyran and ester units resulted at low temperatures. At higher temperatures the lactone homopolymer was formed. The mechanism of polymerization of 2,3-dihydropyran derivatives (3) depended on the nature of the substituents, with low molecular weight polymers being formed in all cases studied. ... 

It was observed that the di-PMB protected trimer readily formed a macrocycle under polymerization conditions, as the oligomer adopted a conformation in which the two ends of the oligomer were close to each other. To avoid this problem, a mono PMB-protected trimer was synthetized in order to maintain a longer distance between the reactive centers. After PMB deprotection, the polymer was no longer soluble in chlorinated solvents. 

Normally, PEEK is a linear molecule. Chen et al synthesized PEEK single size macrocycles and macrocyclic oligomer mixtures (22). The macrocycle monomers can be ring opening polymerized into semicrystalline PEEK with the initiators of a catalytic amount... 

After getting cyclic oligomers via cyclodepolymerization, the authors polymerized them using as initiator cesium salt of 4-benzoylbenzene-l-thiol getting linear polymer of rather high dispersity (Mw= 151 000, Mn = 26 000, and a level of residual macrocyclic oligomers of 4%). Unfortunately, no studies have been performed to determine equilibrium constants of the ring-chain equilibria (Scheme 14). 

We have recently developed an effective synthetic methodology for the preparation of macrocyclic oligomers of aromatic condensation polymers and have investigated their ring opening polymerization chemistry. 

Schematic illustration of the formation of the poly(arylene disulfide)/ graphite nanocomposites via in-situ ring-opening polymerization of macrocyclic oligomers. (Adapted from ref. 58.)... 

The unique advantage of using the macrocyclics to prepare polymer-based nanocomposite is the practicable application. This is due to the fact that these macrocyclic oligomers can instantly polymerize in the melt in the absence of any catalyst or initiator at a temperature as low as 150"C, without liberation of any volatile by-products. " Therefore, they can be processed more easily compared with other polymerization processes. 

The polymerization of ethyleneimine (16,354—357) is started by a catalyticaHy active reagent (H or a Lewis acid), which converts the ethyleneimine into a highly electrophilic initiator molecule. The initiator then reacts with nitrogen nucleophiles, such as the ethyleneimine monomer and the subsequendy formed oligomers, to produce a branched polymer, which contains primary, secondary, and tertiary nitrogen atoms in random ratios. Termination takes place by intramolecular macrocycle formation. 

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