Synthesis and characterization of aromatic-PDMS segmented block copolymers and their shape-memory performance?

Polymer Chemistry Pub Date: 2019-08-16 DOI: 10.1039/C9PY00682F

Abstract

In this paper we will describe the synthesis and properties of two series of high molecular weight segmented block copolymers from all-aromatic amorphous (AM) or liquid crystal (LC) telechelic ester-based maleimide-functionalized oligomers (Mn = 5 kg mol?1) and telechelic thiol-terminated poly(dimethylsiloxane) (PDMS, Mn = 1, 5 and 10 kg mol?1). The multiblock copolymers were prepared via highly efficient thiol–ene click chemistry, and have Mns ranging from 22 to 58 kg mol?1. The segmented block copolymers prepared from mesogenic (LC) units show micro-phase separation and liquid crystallinity even with a PDMS content as high as 65 wt%. The AM5K-based series is completely amorphous. The multiblock copolymers with PDMS5K and 10K show two Tgs at ～?120 °C and ～120 °C, respectively, implying the presence of a (micro)phase separated system. The multiblock copolymer prepared from AM5K and PDMS1K displays excellent stress–strain behavior at 25 °C, with a tensile strength of 123.6 MPa, an elastic modulus of 3.4 GPa, an elongation at break of 31.2% and toughness of 30.7 MJ m?3. The LC5K based multiblock copolymer films exhibit poor stress–strain behavior, which is the result of a higher degree of phase separation and low phase intermixing, as confirmed by TEM measurements. The shape memory properties of the PDMS-containing segmented block copolymers in the temperature range of ?150 to 150 °C were tested using a rheometer in torsion mode. The glass transitions originating from the rigid aromatic blocks and flexible PDMS blocks were used as the reversible switches for designing Tg-based dual- and triple-shape memory polymer films. The AM5K-b-PDMS1K and LC5K-b-PDMS1K multiblock copolymers show dual-shape memory behavior in the temperature range of 20–150 °C. The PDMS5K based analogs show triple shape-memory behavior in the temperature range of ?150–150 °C.

Graphical abstract: Synthesis and characterization of aromatic-PDMS segmented block copolymers and their shape-memory performance
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