Two General Methods for the Synthesis of Thiol-Functional Polycaprolactones

Abstract

We report here two different methods for preparing thiol-functional polymers. The first method consists of esterifying the hydroxyl-terminated polyesters with a thiol-protected mercaptoacetic acid. The Sangers reagent (2,4-dinitrofluorobenzene) was used to protect the mercaptoacetic acid and was removed with mercaptoethanol under mild conditions. The second technique involves the preparation of a protected thiol-functional initiator, the α-(2,4-dinitrophenylthio)ethanol, that could then be used in the polymerization of ε-caprolactone. This “functionalization from initiation” technique could also lead to the preparation of well-defined multibranched polymers with a thiol group at the focal point after the polymerization with a mercapto-initiator carrying dihydroxy or tetrahydroxy functionalities as initiating sites. The ultimate motivation in the preparation of such functional polymers is to elaborate nanocomposites by using the polymers as macroligands in the synthesis of nanoparticles.

Synthesis and Micellar Characterization of Novel Amphiphilic A−B−A Triblock Copolymers of N-(2-Hydroxypropyl)methacrylamide or N-Vinyl-2-pyrrolidone with Poly(ε-caprolactone)

“…These NMR data for PCL proton peaks are in accordance with literature reports. 31 DTPA-PCL-DTPA. This compound was synthesized by the DCC-mediated coupling of HO-PCL-OH with excess of DTPA.…”

Protected thiol strategies in macromolecular design

“…Sanger's reagent has been utilized, to a smaller extent, as a strategy of introducing thiols in a masked state into polymers [220]. The protecting group can be quantitatively removed by 2-mercaptoethanol or other thiols, using mild conditions (pH = 8 at room temperature), releasing a free thiol [221].…”

Enzymatic Continuous Flow Synthesis of Thiol‐Terminated Poly(δ‐Valerolactone) and Block Copolymers

“…Chemoselective polymerization with multifunctional initiator/monomer is one of the most challenging topics in polymer chemistry . Due to the chemical activities of thiol, a protecting group was generally employed in mercapto‐alcohol initiated ROP . Mercapto‐alcohol, such as 6‐mercpato‐1‐hexanol (MH), was utilized as the multifunctional initiator.…”