Copolymers of L,L-lactide (LLA), epsilon-caprolactone (CL), trimethylene carbonate (TMC), or 1,5-dioxepane-2-one (DXO) were used to design porous tubular scaffolds with various mechanical properties, porosities, and numbers of layers in the tube wall. The mechanical properties of the tubular scaffold types showed good suitability for nerve regeneration and other nonload-bearing tissue engineering applications and were easy to handle without damaging the porous structure. A low stannous 2-ethylhexanoate-to-monomer ratio of 1:10000 did not change the tensile properties of the copolymer tubes significantly compared to those of scaffolds made using a Sn(Oct)(2)-to-monomer ratio of 1:600. The adaptability of the immersion coating and porogen leaching technique was demonstrated by creating tubes with different designs. Tubes with different wall layers were created by varying the immersion solutions, and the ease of altering the porosity, pore shape, and pore size was exemplified by using sodium chloride alone or mixed with poly(ethylene glycol) as porogen.

An unsaturated aliphatic polyester was synthesized by condensation polymerization to yield the pre-polymer, poly(but-2-ene-1,4-diyl malonate) (PBM), which is applicable as an elastomeric network and as a macroinitiator for the polymerization of cyclic ester monomers. The method of preparation was simple and straightforward with no need to purify the monomers or add a potentially harmful catalyst. The number average molecular weight of the pre-polymer could easily be increased from 5000 to 12000 by extending the reaction time. The pre-polymer PBM was successfully cross-linked with UV-radiation to form a clear, transparent, colorless, flexible, and strong film. PBM as a macroinitiator for L-lactide (LLA) and ε-caprolactone (CL) polymerizations highly increased the ductility of the LLA-polymer, while maintaining the strength, compared to PLLA polymerized with common initiators. The tensile properties of PCL were also improved. The linear PCL-PBM and PLLA-PBM polymers were easily cross-linked to give polymers with greater strength and higher modulus as the result.

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The catalytic activities of Bi(III) acetate (Bi(OAc) 3 ) and of creatinine towards the ring-opening polymerization of Llactide have been compared with those of a stannous (II) ethylhexanoate ((SnOct) 2 )-based system and with those of a system catalyzed by enzymes. All four were suitable catalysts for the synthesis of high and moderate molecular weight poly(L-lactide)s and the differences in reactivity and efficiency have been studied. Linear and branched poly(L-lactide)s were synthesized using these bio-safe initiators together with ethylene glycol, pentaerythritol, and myoinositol as coinitiators. The polymerizations were performed in bulk at 120 and 140 C and different reactivities and molecular weights were achieved by adding different amounts of coinitiators. A molecular weight of 105,900 g/mol was achieved with 99% conversion in 5 h at 120 C with a Bi(OAc) 3 -based system. This system was comparable to Sn(Oct) 2 at 140 C. The reactivity of creatinine is lower than that of Bi(OAc) 3 but higher compared with enzymes lipase PS (Pseudomonas fluorescens). A ratio of Sn(Oct) 2 M o /I o 10,000:1 was needed to achieve a polymer with a reasonable low amount of tin residue in the precipitated polymer, and a system catalyzed by creatinine at 140 C has a higher conversion rate than such a system.

An innovative type of triblock copolymer that maintains and even increases the mechanical properties of poly(l-lactide) (PLLA) and poly(ε-caprolactone) (PCL) with a controlled, predictable, and rapid degradation profile has been synthesized. Elastic triblock copolymers were formed from the hydrophobic and crystalline PLLA and PCL with an amorphous and hydrophilic middle block of poly(but-2-ene-1,4-diyl malonate) (PBM). The polymers were subjected to degradation in PBS at 37 °C for up to 91 days. Prior to degradation, ductility of the PLLA-PBM-PLLA was approximately 4 times greater than that of the homopolymer of PLLA, whereas the modulus and tensile stress at break were unchanged. A rapid initial hydrolysis in the amorphous PBM middle block changed the microstructure from triblock to diblock with a significant reduction in ductility and molecular weight. The macromolecular structure of the triblock copolymer of PLLA and PBM generates a more flexible and easier material to handle during implant, with the advantage of a customized degradation profile, demonstrating its potential use in future biomedical applications.