Biodegradable polymers based on star-shaped poly(ethylene oxide) (PEO)−poly(l-lactide)
(PLA) and PEO−poly(ε-caprolactone) (PCL) block copolymers were synthesized by a divergent synthetic
method. Multiarm PEOs with various numbers of arms with a fixed molecular weight (MW ∼ 10 000)
were synthesized by anionic polymerization of ethylene oxide initiated with metalated plurifunctional
initiators and used as a core block. The star-shaped block copolymers were prepared by ring-opening
polymerization of l-lactide or ε-caprolactone in the presence of multiarm PEOs and a catalytic amount
of stannous octoate. The equilibrium swelling and thermal and solution properties of the synthesized
star-shaped polymers were examined. The block copolymers were swollen in distilled water, and the degree
of swelling decreased as the number of arms increased. The melting point, crystallinity, and phase
separation decreased with the degree of branching. A similar tendency in solution viscosity of the star-shaped PEO and block copolymers was found. The results obtained in this study revealed unique properties
of star-shaped block polymers which could be useful in the formulation of delivery carrier for polypeptide.
Diand triblock copolymers of poly(isobutyl cyanoacrylate) and poly(ethylene oxide) have been prepared and characterized. The synthesis involved capping of monohydroxyl-and dihydroxylterminated poly(ethylene oxide) with triphenylphosphine, followed by the zwitterionic polymerization of isobutyl cyanoacrylate with the triphenylphosphine-terminated poly(ethylene oxide) macroinitiator to yield the ABor ABA-type block copolymers. The molecular weight and composition of the resulting block copolymers were close to theoretical values. Spherical nanospheres were prepared from the obtained block copolymers for potential biomedical applications.
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