Cyanate ester and polyethylene glycol based high temperature resistant shape memory polymer development for space applications

Abstract

Cyanate Ester (CE)/Polyethylene glycol (PEG) based shape memory polymers (SMPs) offer a sustainable solution for space applications due to their high glass transition temperature and durability. PEG is a type of oligomer used as a shape memory effect modifier for CE. Due to the low toughness of CE-based polymers, they are often modified with epoxies to increase their toughness. However, the high molecular chain length of PEGs can also act as a plasticiser increasing the toughness of the CE/PEG-based SMPs instead of epoxies. This study explores the synergistic use of PEG with CE to optimise SMPs with comparable mechanical and shape memory properties, along with tailorable glass transition temperatures. During the synthesis, PEG 600, 1000, 2000 & 4000 were individually combined with CE monomers in varying stoichiometric ratios to produce a set of SMP specimens. Thermo-mechanical properties, and shape memory properties were experimentally obtained and graded as a function of different molecular weights of PEGs and their stoichiometric ratios. CE SMPs modified with PEG600 and 1000 exhibited stable storage moduli and therefore selected for further investigation. A single-parameter empirical model was developed to correlate Tg with stoichiometric ratios, enabling the prediction of Tg values for different CE: PEG600/1000 ratios or vice versa. The tensile and flexural properties at elevated temperatures were also studied. Notably, the use of lower molecular weight PEGs mitigated the storage modulus drops, while higher molecular weight PEGs significantly improved the toughness. Moreover, synthesised SMPs in the Tg range of 125–130 °C using PEG600 and PEG1000 showed improved stability of storage modulus. The SMP with PEG600 showed better thermo-mechanical properties, storage modulus stability at higher temperatures, and shape memory behaviour compared to the SMP with PEG1000. This research contributes to developing robust and adaptable SMPs for space environments, bridging the gap between mechanical performance and shape memory capabilities.