Synthesis and Properties of Aliphatic Polyester Block Copolymers Filled with Nano Layered Clay Prepared by <i>In-situ</i> Graft Polymerization

Abstract

Aliphatic polyester block copolymers poly(ε-caprolactone) -poly(butylene succinate) -poly(ε-caprolactone) (PCL-PBS-PCL) were synthesized by the ring-opening polymerization of ε-CL in the presence of the pre-polymerized PBS as the macro-initiator. LDHs-g-PCL were prepared by in-situ ring-opening polymerization of ε-CL. Then LDHs-g-PCL/PCL-PBS-PCL nanocomposites were prepared by blending PCL-PBS-PCL and LDHs-g-PCL via solution casting method. The chemical structures of PCL-PBS-PCL and LDHs-g-PCL were investigated. And crystallization behavior, mechanical properties and barrier properties of nanocomposites were also deeply studied. The results of thermal analysis confirm that the crystallization of PBS blocks is restrained markedly with the addition of LDHs-g-PCL. On the contrary, the crystallization of PCL chains is gradually increasing. The changes of crystallization for nanocomposites lead to the decrease in the high temperature melting peaks and the increase in the low temperature melting peaks. Even though a slight decrease (6%) in tensile strength, elongation at break of nanocomposites reaches to the maximum value of 772% (increased by 35%) in the presence of LDHs-g-PCL containing 20% (mass fraction). Compared with pure PCL-PBS-PCL, the O2 permeability of nanocomposites decreased by nearly 52% as LDHs-g-PCL content increase up to 50% (mass fraction). The key parameters to improve the barrier properties of nanocomposites are not only the barrier effect of the LDHs (a decrease in diffusion is expected because of a more tortuous path for diffusing molecules) but also the bulk effect that they develop in the polymer matrix.

Keywords

• layered clay
• aliphatic polyester block copolymer
• <i>in-situ</i> graft polymerization
• barrier property
• mechanical property