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From nanospheres to micelles: simple control of PCL-g-PEG copolymers’ amphiphilicity through thiol-yne photografting

From nanospheres to micelles: simple control of PCL-g-PEG copolymers’ amphiphilicity through thiol-yne photografting

Polym. Chem. 6, 5093–5102 (2015)

Al Samad, A., Bakkour, Y., Fanny, C., El Omar, F., Coudane, J. & Nottelet, B

 

ABSTRACT

A simple method for the synthesis of a family of poly(ɛ-caprolactone)-g-polyethylene glycol (PCL-g-PEG) copolymers of controlled amphiphilicity and their use to generate nanospheres or micelles are reported. PCL-g-PEG with various compositions are prepared from a single strategy relying on a combination of post-polymerization modification and subsequent thiol-yne photografting. Alkyne-functional PCL (PCL-yne) are first obtained by anionic activation and reaction with propargyl bromide to yield PCL-yne with 8% alkyne groups. PEG-thiol is then reacted on PCL-yne under UV activation to yield the targeted graft copolymer by thiol-yne photoaddition. The advantage of the approach is that control over the composition is easily achieved yielding to amphiphilic graft copolymers with ethylene glycol/ caprolactone (EG/CL) ratios ranging from 0.1 to 1.3. Starting from this single strategy, it was therefore possible to obtain nanospheres (DH~55 nm) or micelles (DH~30 nm) by copolymers self-assembly depending on the ratio EG/CL. The potential of the PCL-g-PEG micelles as drug carrier was finally evaluated with curcumin that was efficiently encapsulated, protected and released over 80 days. Interestingly it was found that drug encapsulation efficiency and drug loading were higher for PCL-g-PEG copolymers compared to block PCL-b-PEG.