High Throughput Synthesis of Polyesters Using Entropically Driven Ring-Opening Polymerizations

Abstract

Copolyesters were synthesized in a high throughput (HT) manner and in high yield on ca. a 90 mg scale using entropically driven ring-opening polymerizations (ED-ROPs). This synthetic approach is a valuable addition to the HT polymer synthesis arsenal in that it allows condensation-type polymers with relatively large repeat units, such as those in poly(ethylene terephthalate) and poly(butylene terephthalate), to be obtained easily. The synthetic procedure involved taking mixtures of the appropriate macrocyclic oligoesters and heating them together under neat conditions at 250-300 degrees C for 2 h in the presence of 0.1 mol % of di- n-butyltin oxide or tetra- n-butylammonium tetrafluoroborate. In most cases Mw values were >25,000 and, as expected for ED-ROPs, the polydispersity indices were close to 2.0. Higher molecular weights could be obtained by using longer reaction times, but this might lead to product decomposition. The method worked well for esters formally derived from aliphatic or aromatic acids and alcohols, but less well for esters derived from phenols. Attempts were also made to synthesize copolymers by mixing together the two homopolymers and heating with a catalyst. These reactions were successful in a few instances, but generally, they were not. This is probably because the homopolymers did not mix well. An aluminum reaction block with 36 wells lined with Teflon cups, that fitted snugly in a cylindrical Buchi oven, was the most successful method for carrying out syntheses in an HT manner.

Recent developments in entropy‐driven ring‐opening metathesis polymerization: Mechanistic considerations, unique functionality, and sequence control

“…In this polymerization mechanism, both the nucleophile and monomer are coordinated with the catalyst for a dual activation process. ED‐ROP has been demonstrated through the coordination–insertion mechanism, for example, the ring‐opening of macrocyclic oligoesters using di‐ n ‐butyltin oxide or zinc alkoxide as catalysts . Alkene‐substituted cyclic monomers can undergo radical ROP (rROP) in the absence of added catalyst by a thermal free radical process .…”

A Possible Means to Assist the Processing of PET, PTT and PBT

“…These were carried out on ≈100 mg samples of selected polymer/MCO mixtures, with or without 1 mol‐% of dibutyltin oxide as catalyst, in Teflon cups placed in an aluminum block in a Büchi oven as described elsewhere 12. The reaction temperature was 300 °C and the reaction time was 2 h. At the end of the reaction period the product was removed, dissolved in CH 2 Cl 2 /TFA (80/20 vol.‐%) and precipitated into an excess of methanol.…”

Effect of hard segment length on the properties of poly(ether ester) elastomer prepared by one pot copolymerization of poly(ethylene glycol) and cyclic butylene terephthalate

“…A variety of cyclic polyester oligomers have been successfully prepared and researchers have used the cyclic polyester oligomers to prepare linear high molecular weight polyester [15][16][17][18][19][20][21]. Cyclic oligomers of poly(butylene terephthalate) (CBT) are now available commercially.…”