Synthesis and characterization of resorcinarene‐centered amphiphilic A₈B₄ miktoarm star copolymers based on poly(ε‐caprolactone) and poly(ethylene glycol) by combination of CROP and “click” chemistry

Abstract

Well‐defined amphiphilic A8B4 miktoarm star copolymers with eight poly(ethylene glycol) chains and four poly(ε‐caprolactone) arms (R‐8PEG‐4PCL) were prepared using “click” reaction strategy and controlled ring‐opening polymerization (CROP). First, multi‐functional precursor (R‐8N3‐4OH) with eight azides and four hydroxyls was synthesized based on the derivatization of resorcinarene. Then eight‐PEG‐arm star polymer (R‐8PEG‐4OH) was prepared through “click” reaction of R‐8N3‐4OH with pre‐synthesized alkyne‐terminated monomethyl PEG (mPEG‐A) in the presence of CuBr/N,N,N′,N″,N″′‐ pentamethyldiethylenetriamine (PMDETA) in DMF. Finally, R‐8PEG‐4OH was used as tetrafunctional macroinitiator to prepare resorcinarene‐centered A8B4 miktoarm star copolymers via CROP of ε‐caprolactone utilizing Sn(Oct)2 as catalyst at 100 °C. These miktoarm star copolymers could self‐assemble into spherical micelles in aqueous solution with resorcinarene moieties on the hydrophobic/hydrophilic interface, and the particle sizes could be controlled by the ratio of PCL to PEG. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2824–2833.

Polymerization of Ethylene Oxide, Propylene Oxide, and Other Alkylene Oxides: Synthesis, Novel Polymer Architectures, and Bioconjugation

“…Click couplings, especially the copper-catalyzed azide–alkyne cycloaddition, but also thiol–ene and Diels–Alder reactions, have been identified as a convenient method to attach prefabricated PEG chains. − Since click reactions take place under mild conditions and tolerate a great amount of functional groups, they have found to be particularly useful for the preparation of miktoarm stars. − Controlled radical polymerization techniques, such as ARTP and RAFT, have also been explored extensively as a synthetic tool for arm-first star polymer synthesis. − After end functionalizing PEG with a suitable initiator group, cross-linking polymerization of divinyl monomers leads to star architectures. In analogy, ring-opening metathesis polymerization was applied using bis-norbonene monomers .…”

Precise modular synthesis and a structure–property study of acid-cleavable star-block copolymers for pH-triggered drug delivery

“…[21][22][23][24][25] As typical biomaterials approved by the United States Food and Drug Administration (FDA), 26,27 poly-(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) have been widely used to construct amphiphilic copolymers, such as diblock, 28,29 triblock, 30,31 three-armed, 32 four-armed 32,33 and multi-armed star-shaped copolymers. [34][35][36][37] In 2012, Hawker et al reported a convenient one-step way to simultaneously introduce functional acetal and azide groups in the same polymer chain, 19 which provides us more opportunities to prepare pH-responsive polymers by means of a highly efficient CuAAC "Click" reaction. Our group has recently utilized this method for preparing a pH-sensitive triblock copolymer PCL-a-PEG-a-PCL, in which the acetal groups can be rapidly acid-triggered for hydrolysis.…”

Synthesis of ultra-small branched star poly(ε-caprolactone)s and their high end group concentration effects on crystallization

“…Poly( ε ‐caprolactone)s (PCLs), which have been studied extensively over the past 20 years, are one of the most attractive biocompatible and biodegradable polyesters . PCLs low glass transition temperature, low melting temperature, and high miscibility with commercial polymers compared with other polyesters provide significant advantages to the use of PCLs in absorbable sutures, surgical fibers, artificial organs, controlled drug delivery applications, tissue regeneration approaches, food packages, and PVC plasticizers . PCLs are produced via the ring‐opening polymerization (ROP) of the cyclic ester monomer, ε ‐caprolactone (CL).…”