A Versatile Synthetic Platform for Discrete Oligo- and Polyesters Based on Optimized Protective Groups Via Iterative Exponential Growth

Abstract

Discrete oligo- and polyesters are highly attractive for a wide range of investigations because of their great fidelity on structure–property relationships. Even though numerous synthetic approaches have been developed, a more versatile synthetic platform with broad group tolerance is still desired. Herein, we report an iterative exponential growth strategy for efficient synthesis of discrete oligo- and polyesters, employing an optimized protective group pair, namely, TBDPS ether and t-butyl ester. The versatility of the strategy is demonstrated by facile preparation of several structurally diverse discrete oligo- and polyesters under mild, safe, and scalable reaction conditions, with the number of repeat units up to 256. Moreover, the contributions of the terminal protective groups on the melting and crystallization behaviors of discrete oligo- and poly­(ε-caprolactone)­s were investigated. With this robust synthetic platform, various functional moieties can be readily incorporated into polyester chains, and a myriad of applications of polyesters could thus be reasonably anticipated.

Local Chain Feature Mandated Self-Assembly of Block Copolymers

“…Briefly, the tert -butyldimethylsilyl (TBDMS) and benzyl (Bn) protecting groups can be selectively removed, and the activated hydroxyl/carboxyl functional groups are then coupled through esterification, generating a dimer with the same latent functional groups (Scheme S2). − Repeating the cycle leads to discrete chains with precise monomer sequence and exact chain length (Figures S1–S4). …”

Synthesis of Enantiomeric ω-Substituted Hydroxy Acids from Terminal Epoxides and Alkenes: Functional Building Blocks for Discrete and Sequence-Defined Polyesters

“…The library of enantiomeric OHAs synthesized in this study was then employed for constructing discrete poly­(ω-hydroxy acids) (POHAs) via an iterative convergent synthetic approach. This method allows for a rapid increase in the molecular weight of discrete polyesters via a minimum number of synthetic steps. − To test the scalability of the molecular weight of discrete POHAs, we employed the substituted derivatives of ε-caproic acid ( 5 , 10 , and 11 ) as building blocks. The carboxylic acid termini of these OHAs were converted to benzyl esters as protecting groups.…”

“…In addition, the stereochemistry of the monomer stereocenter and the number of carbon atoms in the monomer backbone are also determined. The resulting enantiopure OHAs are employed as building blocks for the preparation of multifunctional polyesters with defined sequences and stereoregularities via an iterative convergent approach. − These synthetic approaches allow us to control the structural parameters of the resulting polyesters, including their molecular weight, monomer sequence, stereoregularity, and functionality. We also show that the placement of functional groups can play a significant role in chemical behavior of a selective cyclization process, and we carry out an accurate determination of the topology of the intramolecularly cyclized polyester. − …”

Investigation of eight-arm tapered star copolymers prepared by anionic copolymerization and coupling reaction

“…MALDI-TOF MS was conducted on a mass spectrometer (Ultraflextreme, Bruck Dalton). 57,58 trans-2-[3-(4-tert-Butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB, >99%, Sigma-Aldrich) (20 mg mL −1 in CHCl 3 ) was used as a matrix and silver trifluoroacetate (AgTFA, >99%, Sigma-Aldrich) (10 mg mL −1 in ethanol) was used as a cationizing agent, and polymer samples were dissolved in CHCl 3 with a concentration of 10 mg mL −1 . The DCTB and AgTFA solutions were mixed in a ratio of 10/1 (v/v).…”