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Poly(ethylene glycol)-poly(epsilon-caprolactone) diblock copolymers PEG-PCL were synthesized by ring-opening polymerization of epsilon-caprolactone using monomethoxy poly(ethylene glycol) as the macroinitiator and calcium ammoniate as the catalyst. Obvious mutual influence between PEG and PCL crystallization was studied by altering the relative block length. Fixing the length of the PEG block (Mn = 5000) and increasing the length of the PCL block, the crystallization temperature of the PCL block rose gradually from 1 to about 35 degrees C while that of the PEG block dropped from 36 to -6.6 degrees C. Meanwhile, the melting temperature of the PCL block went up from 30 to 60 degrees C, while that of the PEG block declined from 60 to 41 degrees C. If the PCL block was longer than the PEG block, the former would crystallize first when cooling from a molten state and led to obviously imperfect crystallization of PEG and vice versa. And they both crystallized at the same temperature, if their weight fractions were equal. We found that the PEG block could still crystallize at -6.6 degrees C even when its weight fraction is only 14%. A unique morphology of concentric spherulites was observed for PEG5000-PCL5000. According to their morphology and real-time growth rates, it is concluded that the central and outer sections in the concentric spherulites were PCL and PEG, respectively, and during the formation of the concentric spherulite, the PEG crystallized quickly from the free space of the PCL crystal at the earlier stage, followed by outgrowing from the PCL spherulites in the direction of right angles to the circle boundaries until the entire area was occupied.

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The purpose of this study was to use a convenient synthetic strategy to prepare a new family of biodegradable amino acid-based poly(ester amide)s (PEAs) with pendant amine groups along the polymer backbone, and investigate the applications of the new polymers in the biomedical area. Two amino acids, L-phenylalanine (Phe) and L-lysine (Lys), were used as the model amino acid compounds to illustrate the synthesis, characterization, and biological property of this new family of functional PEAs. These new PEAs were obtained by two-step reactions, the ring-opening reaction of epsilon-(benzyloxycarbonyl)-L-lysine N-carboxyanhydride (Z-LysNCA) with L-phenylalanine hexane-1,6-diol diester p-toluenesulfonate (Phe-6), and subsequently solution polycondensation with di-p-nitrophenyl sebacoyl (NS). The benzyloxycarbonyl (Z) protective groups of the resulting polymer (PEA-Z-Lys) were completely removed to produce the new functional PEAs having free pendant amine groups (PEA-Lys-NH(2)). The level of the pendant amine groups on the PEA-Lys-NH(2) could be tailored by adjusting the Phe-6 to Z-LysNCA feed ratio. Analyses of FTIR, (1)H NMR, (13)C NMR spectra, and DSC revealed the desired chemical structures and thermal property of PEA-Z-Lys as well as the final functional PEA-Lys-NH(2). The free pendant amine groups were used to chemically conjugate a fluorescent dye to demonstrate the utility of this new family of functional PEA. An in vitro cell culture study of these functional PEAs showed that they supported the proliferation of bovine aortic endothelial cell slightly better than gelatin-coated glass coverslips. This new family of biodegradable functional PEA with free amine groups may have great potential applications for biomedical and pharmacological fields.

Biodegradable poly(ester amide)s have recently been used as biomaterials due to their desirable chemical and biological characteristics as well as their mechanical properties, which are amendable for material processing. In this study, electroactive tetraaniline (TA) grafted poly(ester amide)s were successfully synthesized and characterized. The poly(ester amide)s-graft-tetraaniline copolymers (PEA-g-TA) exhibited good electroactivity, mechanical properties, and biodegradability. The biocompatibility of the PEA-g-TA copolymers in vitro was systematically studied, which demonstrated that they were nontoxic and led to favorable adhesion and proliferation of mouse preosteoblastic MC3T3-E1 cells. Moreover, the PEA-g-TA copolymers stimulated by pulsed electrical signal could serve to promote the differentiation of MC3T3-E1 cells compared with TCPs. Hence, the biodegradable and electroactive PEA-g-TA copolymers possessed the properties in favor of the long-time potential application in vivo (electrical stimulation directly to the desired area) as bone repair scaffold materials in tissue engineering.

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A biodegradable two block copolymer, poly(epsilon-caprolactone)-b- poly(gamma-benzyl-L-glutamic acid) (PCL-PBLG) was synthesized successfully by ring-opening polymerization of N-carboxyanhydride of gamma-benzyl-L-glutamate (BLG-NCA) with aminophenyl-terminated PCL as a macroinitiator. The aminophenethoxyl-terminated PCL was prepared via hydrogenation of a 4-nitrophenethoxyl-terminated PCL, which was novelly obtained from the polymerization of epsilon-caprolactone (CL) initiated by amino calcium 4-nitrobenzoxide. The structures of the block copolymer and its precursors from the initial step of PCL were confirmed and investigated by 1H NMR, FT-IR, GPC, and FT-ICRMS analyses and DSC measurements.