Synthesis and characterization of amphiphilic block–graft MPEG‐b‐(PαN₃CL‐g‐alkyne) degradable copolymers by ring‐opening polymerization and click chemistry

Abstract

A straightforward strategy is proposed for the synthesis of novel, amphiphilic block–graft MPEG‐b‐(PαN3CL‐g‐alkyne) degradable copolymers. First, the ring‐opening polymerization of α‐chloro‐ε‐caprolactone (αClCL) was initiated by hydroxy‐terminated macroinitiator monomethoxy poly(ethylene glycol) (MPEG) with SnOct2 as the catalyst. In a second step, pendent chlorides were converted into azides by the reaction with sodium azide. Finally, various kinds of terminal alkynes were reacted with pendent azides by copper‐catalyzed Huisgen's 1,3‐dipolar cycloaddition, and thus a “click” reaction. These copolymers were characterized by differential scanning calorimetry (DSC), 1H NMR, IR, and gel permeation chromatography. By fixing the length of the MPEG block and increasing the length of PαClCL (or PαN3CL) block, an increase tendency in Tgs was observed. However, the copolymers of MPEG‐b‐PαClCL and MPEG‐b‐PαN3CL were semicrystalline when the Mn of MPEG was above 2000 g mol−1. The block–graft copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 1.4–12.0 mg L−1 depending on the composition of polymers. The lengths of hydrophilic segment influence the shape of the micelle. The mean hydrodynamic diameters of the micelles from dynamic light scattering were in the range of 90–160 nm. In vitro hydrolytic degradation of block–graft copolymers is faster than the corresponding block copolymers. The drug entrapment efficiency and the drug loading content of micelles depending on the composition of block–graft polymers were described. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4320–4331, 2008

Synthesis and characterization of temperature‐sensitive block copolymers from poly(N‐isopropylacrylamide) and 4‐methyl‐ε‐caprolactone or 4‐phenyl‐ε‐caprolactone

“…Table I and Figure 3 show the thermal behaviors and DSC curves of the PNIPA‐ b ‐PM(B)CL block copolymers. The thermal behaviors of the block copolymers are quite complicated and strongly dependent on the molecular weights of PM(B)CL and PNIPA segments, and the composition of copolymers 23–25. According to DSC, PNIPA‐ b ‐PMCL and PNIPA‐ b ‐PBCL diblock copolymers exhibited only T g , are amorphous.…”

Recent Advances in the Functionalization of Aliphatic Polyesters by Ring-Opening Polymerization

“…Nevertheless, this polymerization of αClεCL can be successfully initiated by tin(IV) alkoxides [22] and by alcohols in the presence of tin octoate. [23] More recently, the same approach was used by Wang et al to synthesize 3-bromoooxepan-2-one but the thermal stability of this monomer was not mentioned. The synthesis of unsaturated aliphatic polyesters is highly desirable because they can be crosslinked and also the double bond can be converted into other functionalities, for instance by dihydroxilation and epoxidation reactions.…”

Smart biomaterials: the contribution of glycoscience

“…Several strategies have been proposed for the preparation of azido-functionalized polymers; among them we can mention a general strategy consisting in the (co)polymerization of halide functionalized monomers followed by nucleophilic substitution of the halide groups by sodium azide (NaN 3 ). [93][94][95] Alternatively, the azido group can be introduced via epoxide opening by NaN 3 on the co-polymerized glycidyl-containing monomers (i.e. glycidyl methacrylate).…”