Synthesis, structure and tunable shape memory properties of polytriazoles: dual-trigger temperature and repeatable shape recovery

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 3; no. 21; pp. 11596 - 11606
• Main Authors: Ragin Ramdas, M, Santhosh Kumar, KS, Reghunadhan Nair, CP
• Format: Journal Article
• Language: English
• Published: 01.01.2015
• Subjects: Addition polymerization; Contact angle; Monomers; Oligomers; Polymerization; Polymers; Recovery; Shape memory; Sustainability
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c5ta00616c

Thermally induced shape memory polymers (SMPs) are capable of storage, release of energy and shape recovery on the macro-scale. In this work, cross-linked SMPs were synthesized from the monomers tris(4-(1-azido 3-oxy propan-2-ol)phenyl) methane (A sub(3)), and 1,4-bis(propargyloxy) benzene (B sub(2)), and the propargyl functionalized novolac oligomer (B sub(3)). The A sub(3)B sub(2) polymer exhibited a low trigger temperature of 92 degree C, whereas A sub(3)B sub(3) registered a higher trigger temperature of 125 degree C. The extent of shape recovery of both the SMPs was above 95% and it was repeatable for at least 10 times. On repeating the shape memory cycles, the response time for shape recovery increased, but nearly a complete shape recovery was observed in both polymers. In addition, a polymer with dual trigger temperature (83 and 113 degree C) was synthesized by click polymerization between the A sub(3) monomer and stoichiometric equivalence of B sub(2) and B sub(3) monomers. The polytriazole networks bearing monophenyl and oligomer structures in tandem enabled both low and high trigger temperature in a single polymeric structure. The SMP possesses a shape recovery to an extent as high as 98% at both the trigger points even on the 10th shape memory cycle. These polymers exhibited hydrophobicity with a static water contact angle of about 90 degree and very low water absorption (<0.05 weight%). The enhanced water repellency is attributed to the inter/intra-chain hydrogen bonding characteristics of triazole bridges. The low/high/dual trigger temperature SMPs are thermally stable (T sub(10%) > 230 degree C) and are suitable for actuator applications.