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Duas séries de copolímeros triblocos, poli (ácido lático-b-etileno glicol) (PLA-PEO-PLA), foram sintetizados a partir do éster cíclico l,l-lactideo, usando octoato de estanho como iniciador e poli (etileno glicol) (PEG) (Mn = 4000 ou 600), di-hidróxi terminado, como co-iniciador. A ligação química entre os segmentos PEG e PLA foi confirmada pelas técnicas de espectroscopia no infravermelho (FTIR) e Ressonância Magnética Nuclear de Hidrogênio (RMN-¹H) e análise térmica. O grau de polimerização do bloco PLA, DP PLA, no copolímero foi estimado por RMN-¹H e mostrou variação em função da massa molar do PEG e do aumento da concentração relativa de l,l lactídeo na mistura reacional. O aspecto dos copolímeros sintetizados variou de acordo com o tamanho dos blocos hidrofílico e hidrofóbico presentes em sua estrutura. Testes de solubilidade mostraram comportamento anfifílico para o produto sintetizado. Os segmentos de PLA formaram uma fase cristalina enquanto a fase cristalina correspondente aos segmentos PEG não foi observada.

This work seeks bringing a technological and social contribution by searching blends and composites of poly(3-hydroxybutyrate) (PHB) and polyethylene widely used in packaging films, and colloidal silica. The mixtures were prepared by extrusion using a single-screw extruder and were analyzed regarding their thermal and mechanical properties and morphology. The results have shown PHB toughness in the studied compositions, which elongation at break was in the range 5-80% compared to 2% for neat PHB. The small amount (0.2 to 0.4%) of added silica seemed to increase in 20% the tensile strength. The thermal degradation by thermogravimetry from room temperature to 800 8C revealed a mixed behavior for the composites between PHB and polyethylene.

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Two series of poly(L,L‐lactide‐b‐ethylene glycol‐b‐L,L‐lactide) copolymers, PLA‐PEO‐PLA, were synthesized by polymerization of L,L‐lactide using a dihydroxy‐terminated poly(ethylene glycol) (PEG) (Mn = 4000 or 600 g/mol) as coinitiator and stannous 2‐ethylhexanoate, Sn(Oct)2, as initiator. The synthesized copolymers have shown high stereoregularity as observed by 13C NMR analyses. The nanoparticles were prepared by using a solvent diffusion method and the self‐assemblage process and were characterized by NMR and SEM. It was possible to conclude that the self‐assembled particles presented a core‐shell structure characterized by a hydrophobic PLA core and a hydrophilic PEG shell, thus the NMR of the aqueous solutions indicated a quasi‐solid behavior for the particles' interior. The diameters of the spherical particles as observed by SEM were in the 50–250 nm range, depending on the copolymer composition and the preparation procedure. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers