Ring‐Opening Polymerization and ring‐closing depolymerization

Abstract

Ring‐opening polymerization (ROP) of cyclic monomers is most suitable for the preparation of sequential copolymers of the type (AAB)n, the sequence being determined by the structure of the monomer. The thermodynamics and mechanisms of ROP are reviewed, including radical, cationic, anionic, and metathetical ROP, with may examples being given. As recycling becomes more important, interest in reversible polymerization, i.e., depolymerization, is increasing. The results available so far on the depolymerization of polymers obtained by ROP are discussed.

Thermal and Mechanical Properties of Diblock Copolymers Based on 2,2-Dimethyltrimethylene Carbonate andɛ-Caprolactone

“…The reaction scheme and the adopted synthetic procedure for Al(Osec-Bu) 3 as initiator in toluene solution have previously been reported. [1,9] In a typical polymerization, e. g. the one used to synthesize a diblock copolymer containing 70 wt.-% of DTC (sample 2), 100 ml of a 0.77 m solution of DTC in toluene at 20 8C was initiated with 1.14 ml of Al(Osec-Bu) 3 dissolved in the same solvent ([I] 0 = 3.38 mmol/l) and polymerized in an inert gas atmosphere. After 80 min, 1.92 g of CL (13.5 mmol) were added and the system was left to polymerize at 80 8C.…”

“…[1] It was shown that copolymerization of dimethyltrimethylene carbonate (DTC) with a variety of cyclic as well as linear comonomers yields random, tapered or block copolymers depending on initiator, comonomer nature, and reaction procedure. [2,3] Block copolymers were successfully obtained by DTC polymerization, initiated by polymeric hydroxytelechelic precursors or by living chains of the comonomer.…”

“…Poly(ethylene oxide), [7] poly(tetrahydrofuran), [8] and poly(dimethylsiloxane) [9] chains were used to initiate DTC polymerization but, under the same conditions, different polymerization rates were observed due to the nature of the polymeric initiator and its complexation mechanism. [1] The copolymerization of mixtures of DTC and e-caprolactone (CL) in toluene at 20 8C initiated by sec-BuLi and Bu2Mg yields tapered copolymers of the AXB type, [10] where A represents the poly(DTC) block, B the poly(CL) block, and X stands for a tapered block containing both monomers with a compositional gradient. On the other hand, by using initiators based on the aluminium porphyrin system TPPAl [11] or Al(Osec-Bu) 3 , [3] random copolymers were obtained.…”

Expected and unexpected reactions in ring-opening (co)polymerization

“…The ring-opening polymerization discloses an alternative route to polymers which are typically obtained by polycondensation or polyaddition polymerization following a step growth mechanism. [1,2] The present paper is devoted to the ring-opening polymerization of heterocycles like cyclic carbonates, lactones, lactams, cyclic amide-esters, urethanes, and ureas by means of ionic and insertion type initiators and covers mostly the authors' own work. Copolymerization of the above mentioned monomers results in random, sequential, block and alternating copolymers depending on the initiator used and the polymerization conditions applied.…”

“…According to time dependent1 H NMR analysis in the beginning only LLA-LLA diads are observed, i. e. first LLA is polymerized. With the elapse of time triads comprising one DTC and two LLA units are formed, then triads with two DTC and one LLA unit and finally DTClactate-DTC and DTC-homotriads are formed.…”