Polyacetals degradation induced by BF₃‐etherates

Abstract

The degradation of polytrioxane (H, = 66,000) and copolymer of trioxane wjth 2 mole-?, of dioxolane (zn = 44,000) under the influence of BF, complexes with &ethyl ether and anisole was investigated. No differences between homo-and copolymer degradations were observed. The dependence of the rate of degradation and of the molecular weight of the degraded polymer o n BF, .ether concentration was established. The expected, linear plot of the extent of degradation us. molar ratio of [BF,-etherate]/[polyacetal] i s verified experimentally only within a narrow range of BF,-etherate concentrations.When the BF,-anisole complex was used, aromatic rings were incorporated into the degraded polymer. By using U.V-spectra a comparison between the extent of degradation and the quantity of aromatic rings incorporated was made. Under the experimental con.. ditions used (semi-open system) only 50 yo of the theoretically calculated number of macromolecules were cleaved with incorporation of anisole fragments. The role of proton-donating impurities was stressed and a reaction scheme involving the action of water was proposed. Z U S AM ME N F A S S U N G : Der -4bbau von Polytrioxan (xn = 66000) und eines Copolymeren aus Trioxan mit 2 Mol-% Dioxolan (R, = 44000) unter dem EinfluB von Komplexen des Bortrifluorids mit Diathylather und Anisol wurde untersucht. Zwischen dem Homopolymeren und dem Copolymeren wurden keine Unterschiede beim Abbau beobachtet. Die Abhangigkeit der Degradationsgeschwindigkeit und des Molekulargewichts des partiell abgebauten Polymeren von der Konzentration des BF,-Komplexes wurde ermittelt. Der erwartete lineare Zusamrnenhang zwischen dem Degradationsgrad und den1 Molverhaltnis von BF,-Atherat zu Polyacetal wurde experimentell nur in einem kleinen Konzentrationsbereich bestatigt. Beim Abbau mit dem BF,-Anisol-Komplex wurden aromatische Ringe in das Polymere eingebaut. Durch UV-Spektroskopie wurde der Zusammenhang zwischen Degradationsgrad und dem Gehalt des Polymeren an aromatischen Ringen ermittelt. Unter den gewihlten Reaktionsbedingungen (halboffenes System) enthielten nur 50 yo der durch Kettenspaltung neu entstandenen Makromolekiile ein Anisol-Bruchstiick.Der EinfluB von ionogenen Verunreinigungen wird betont, und es wird ein Reaktionsschema angegeben, welches auch die Reaktionen des Wassers einschlieRt. 157

Synthesis of copolymer from 1,3,5‐trioxane and 1,3‐dioxolane catalyzed by Maghnite‐H+

“…As depicted in Figure 8, the intrinsic viscosity (g) decreases when the duration of copolymerization increases, this is due probably to the reactions of intramolecular transesterification, i.e., ''back-biting,'' which causes degradation and formation of cyclic oligomers and consequently may cause a decrease of the intrinsic viscosity. The same results are obtained by Fejgin et al 54 when they polymerized TOX with DOX in the presence of BF 3 O (n-C 4 H 9 ) 2 .…”

“…Similar results were obtained by copolymerization TOX with DOX in presence of BF 3 complex, the yield of copolymerization was reached between 65% and 77% with low molecular weight when the proportion of DOX units increases above 2.5 mol %. 54 The rate of consumption of both comonomers (TOX, DOX) is not the same, 28,55 DOX is consumed much faster and the copolymer formed initially is considerably enriched by DOX units, and an insoluble polymer is formed composed almost entirely of TOX units.…”

Chemically recyclable thermoplastics from reversible-deactivation polymerization of cyclic acetals

“…In previous reports, residual catalyst or acid species from incomplete polymer purification prematurely catalyzed depolymerization of polyacetals owing to the thermodynamics of polymerization and depolymerization (Fig. 2E; see below) ( 51 ). With an improved purification method (see supplementary materials), all five polyacetal derivatives exhibited excellent thermal stability by thermogravimetric analysis (TGA), with degradation temperatures at 5% mass loss ( T d,5% ) above 337°C (fig.…”

Advances in the Synthesis of Chemically Recyclable Polymers

“…Continued addition of monomer M n increased linearly after 24 h during RD‐CROP of DXL, confirming the retention of active chain ends. In previous reports, residual catalysts or acids from incomplete polymer purification prematurely catalyzed the depolymerization of polyacetals, [161] which was improved by the authors. All polyacetal derivatives exhibited excellent thermal stability, with T d, 5% >337 °C.…”

“…In particular, the monomer recovery of PMMBL is 76%, and the residue is an oligomer that is not completely depolymerized, which makes it possible to achieve quantitative recovery of high‐purity monomers in a more effective depolymerization device. In addition, through DFT calculation, the author found that compared with PMMA, the recyclability of P(M)MBL is greatly improved not because of their different T c values, but because of the stability of linear and cyclic esters of primary and tertiary macromolecules and the differentiation of monomers [161] . Recently, Hong's group reported a series of methylene butyrolactone derived from biomass and synthesized polyacrylate polymers through efficient selective polymerization under the catalysis of Lewis acid‐base pairs.…”