Cross‐Linked Poly(ε‐caprolactone/D,L‐lactide) Copolymers with Elastic Properties

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Abstract
Cross‐linked ε‐caprolactone (CL) and D,L‐lactide (DLLA) copolymers with elastic properties were synthesized in three steps. First, the monomers were copolymerized in ring‐opening polymerization to obtain telechelic star‐shaped oligomers with almost completely random monomer distribution. The oligomers were methacrylated with methacrylic anhydride in the second step and cured in a third. Molar CL/DLLA compositions of 30/70, 50/50, 70/30, 90/10, and 100/0 were used to obtain elastic structures with a wide range of properties. The effect of the average length of the copolymer block on the properties of the networks was evaluated with three different co‐initiator contents (0.5, 1.0, and 2.0/100) in the oligomer synthesis. The oligomers were characterized by 13C NMR spectroscopy, size‐exclusion chromatography (SEC), and differential‐scanning calorimetry (DSC). The formation of elastic networks was confirmed by the absence of a flow region in dynamic mechanical analysis (DMA), the increase in Tg in DSC, and the full recovery of the sample dimensions after tensile testing. In addition, gel contents were high and the samples swelled in CH2Cl2. The networks possessed break stresses from 0.7–9.7 MPa with elongations from 80–350%. Networks with 100 or 90% of ε‐caprolactone retained their form in vitro for 12 weeks, but an increase in lactide content made the networks more vulnerable to hydrolysis. Water absorption of the polymers during hydrolysis. magnified image Water absorption of the polymers during hydrolysis.

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