Semi‐interpenetrating polymer networks composed of diisocyanate‐bridged 4‐arm star‐shaped l‐lactide oligomers and poly(ε‐caprolactone)

Semi-interpenetrating polymer networks (semi-IPNs) were prepared by reactions of 2,4-tolylene diisocyanate (TDI) and hydroxy-terminated 4-arm star-shaped l-lactide oligomers (H4LAOn's) with the degrees of polymerization of lactate unit per one arm, n = 3, 5, and 10 in the presence of poly(e-caprolactone) (PCL). Morphologies, thermal, and mechanical properties of the TDI-bridged H4LAOn (TH4LAOn)/PCL semi-IPNs were evaluated by comparing with those of poly(l-lactide) (PLA)/PCL blends. Compatibility between the two components of the TH4LAOn/PCL semi-IPN with a PCL content not more than 50 wt % was much better than those of the PLA/PCL blends with the same PCL content. All the TH4LAOn networks were substantially amorphous and their tan δ peak or glass transition temperatures increased with decreasing n value. Most of the semi-IPNs did not show clear glass transition temperature related to both the components. Tensile toughness and elongation at break for all the TH4LAOn/PCL semi-IPNs were much higher than those for the PLA/PCL blends with the same PCL content. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1420–1428