Reversible crosslinking-decrosslinking of polymers having bicyclo orthoester moieties in the side chains

Abstract

SUMMARY: Radical polymerizations of methacrylate-and styrene-based bicyclo orthoesters (BOEs), and their copolymerization with methyl methacrylate and styrene were carried out with 2,29-azoisobutyronitrile (AIBN, 5 mol-%) as an initiator in N,N-dimethylformamide (DMF, 2 M) at 708C for 15 h to afford the corresponding polymers in 64 -96% yields having BOE moieties in the side chains. Crosslinking of the polymers was carried out in the presence of BF 3 N OEt 2 (3 mol-%) as a cationic catalyst in CH 2 Cl 2 . The yield of the crosslinked polymer increased with increasing initial concentration of the polymer and increasing crosslinking temperature. Decrosslinking of the crosslinked polymers was carried out in the presence of trifluoroacetic acid (TFA, 5 mol-%) as a cationic catalyst in CH 2 Cl 2 to regenerate the starting linear polymers. The recovery of the starting linear polymer increased with decreasing concentration of the initially crosslinked polymer and with increasing decrosslinking temperature.

Lipase-Catalyzed Degradation of Polyester in Supercritical Carbon Dioxide

“…[1] Development of chemical recycling reproducing starting materials is urgently required for global sustainability without depletion of scarce resources. [2] However, there are only a few examples of industrial chemical recycling, e.g., alcoholysis of poly(ethylene terephthalate) and poly-(bubutylene terephthalate), and their processes normally consume much energy (high temperature and/or pressure).…”

Development of materials and technologies for control of polymer recycling

“…The explained mechanism for the pyrolytic degradation was that the expected product, 2-norbornene, was not stable and therefore reproduced ethylene and cyclopentadiene as result of a following retro DA reaction. 63 Chemo-thermoreversible crosslinking-decrosslinking polymers Endo et al 64,65 synthesized copolymers having bicycle-and spiroorthoester moieties as pendant groups, which were reversibly changed between the network (ring-opening polymerization) and linear structures (ring-closing depolymerization) in the presence of cationic catalysts (Scheme 15). Crosslinking was enhanced with increases in the concentration of the polymer, whereas recovery of the starting linear polymer through decrosslinking increased with decreasing concentration of the crosslinked polymer.…”

Catalytic double ring-opening polyaddition of spiro orthoester with acid chloride for shrinkage-controlled molding

“…Generally, the double ring-opening reaction of SOE requires high temperatures of more than 100 8C [8][9][10][11]. The total polymerization of SOE proceeds in three stages: (1) the heating stage up to the polymerization temperature, (2) the isothermal polymerization stage at this temperature, and (3) the cooling stage to ambient temperature (Scheme 1).…”