Polymers of Carbonic Acid, 31. Cyclic Polycarbonates by Hydrolytic Polycondensation of Bisphenol-A Bischloroformate

Abstract

The hydrolytic polycondensation of bisphenol‐A bischloroformate in NaOH/CH2Cl2 was studied using triethylamine as the catalyst. Reaction conditions were optimized towards high molar masses. The isolated polycarbonates were characterized by means of SEC and MALDI‐TOF mass spectrometry. The fraction of cyclic polycarbonates strongly increased with higher molecular weights and in the best sample only cycles were detectable (up to 50 000 Da). The largest cycles can compete with cyclic DNS of microorganisms.

Cyclic polymers: Synthetic strategies and physical properties

“…Unfavorable cases MT mass spectra of virgin reaction products may cover the mass range up to 20 kDa. [20][21][22] However, a polycondensate with a M n of 10-25 kDa, as it is typical for several technical products, contains a small fraction of chains having masses above 50 kDa, which escape from any mass-spectroscopy identification at this time.…”

“…After fractionation of the crude reaction products, circular polycarbonates with masses up to 55 kDa were identified by MT mass spectroscopy and no linear chains were detectable. 21,22 For reasons discussed in ref. 30 in detail, polycondensations of bisphenol-A with (di)phosgene in homogeneous solutions gives cyclic polycarbonates with lower M n s and a higher content of linear chains.…”

“…However, these side reactions can be compensated for by an excess of phosgene (which is important in the structure of the bischloroformate), and thus, these synthetic methods may be considered as pseudoideal polycondensation methods. Reinvestigation and optimization of both methods by the author 21,22,[30][31][32][33] confirmed the results obtained by Horbach et al 29 via endgroup analyses. After fractionation of the crude reaction products, circular polycarbonates with masses up to 55 kDa were identified by MT mass spectroscopy and no linear chains were detectable.…”

“…An initiation and ring-opening polymerization process analogous to that for primary amines yields peptide chains with two reactive endgroups (Scheme 28). It is known for many decades 109 that imidazolides of carboxylic acids are several orders of magnitude more electrophilic than normal amide groups and react easily with amines at [20][21][22] C, and with alcohol or water at higher temperatures. Therefore, the imidazole-initiated peptide chains can react with each other producing chain extension by condensation steps or they can cyclize (Scheme 28).…”

“…Quite recently, a ROP of D,L-lactide catalyzed by a nucleophilic carbene at [20][21][22][23][24][25] C in solution was reported. 188 Up to 15 kDa, the MT mass spectra exclusively displayed peaks of cycles and proved total equilibration.…”