Phase behavior of biodegradable amphiphilic poly( l, l-lactide)- b-poly(ethylene glycol)- b-poly( l, l-lactide)

• Published in: Thermochimica acta 2006-06, Vol.445 (1), p.61-66
• Main Authors: Mothé, C.G., Drumond, W.S., Wang, S.H.
• Format: Article
• Language: English
• Subjects: Applied sciences; Biodegradable; Block copolymers; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; PLLA–PEG–PLLA; Properties and characterization; Thermal and thermodynamic properties; Thermal behavior
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2006.01.001

This study describes the miscibility phase behavior in two series of biodegradable triblock copolymers, poly( l-lactide)- block-poly(ethylene glycol)- block-poly( l-lactide) (PLLA–PEG–PLLA), prepared from two di-hydroxy-terminated PEG prepolymers ( M n = 4000 or 600 g mol −1) with different lengths of poly( l-lactide) segments (polymerization degree, DP = 1.2–145.6). The prepared block copolymers presented wide range of molecular weights (800–25,000 g mol −1) and compositions (16–80 wt.% of PEG). The copolymer multiphases coexistance and interaction were evaluated by DSC and TGA. The copolymers presented a dual stage thermal degradation and decreased thermal stability compared to PEG homopolymers. In addition, DSC analyses allowed the observation of multiphase separation; the melting temperature, T m, of PLLA and PEG phases depended on the relative segment lengths and the only observed glass transition temperature ( T g) in copolymers indicated miscibility in the amorphous phase.