One-way and two-way shape memory behaviour of semi-crystalline networks based on sol–gel cross-linked poly(ε-caprolactone)

• Published in: Polymer (Guilford) Vol. 54; no. 16; pp. 4253 - 4265
• Main Authors: Pandini, S., Baldi, F., Paderni, K., Messori, M., Toselli, M., Pilati, F., Gianoncelli, A., Brisotto, M., Bontempi, E., Riccò, T.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 19.07.2013; Elsevier
• Subjects: Applied sciences; Composites; crosslinking; crystallization; Exact sciences and technology; Forms of application and semi-finished materials; melting; melting point; memory; Poly(ε-caprolactone); Polymer industry, paints, wood; polymers; Shape memory polymers; Technology of polymers; temperature; Two-way shape memory effect; X-ray diffraction; Shape memory polymers; Two-way shape memory effect; Poly(ε-caprolactone); Molecular structure; Crosslink density; Hybrid material; Mechanical properties; Experimental study; Silica; Transformation temperature; Sol gel process; Shape memory effect; Preparation; Crosslinked polymer; Polycaprolactone; Silicon polymer; Thermomechanical treatment
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2013.06.016

In this work we have explored the shape memory capabilities of a novel type of covalently cross-linked semi-crystalline polymers, prepared by exploiting the mild sol–gel chemistry, starting from alkoxysilane-terminated poly(ε-caprolactone) (PCL), and using silica-based domains as cross-link points. By adopting PCL precursors with different molecular weights, semi-crystalline networks with well defined cross-link densities and with different crystallization and melting temperatures were obtained. Beside a satisfying one-way shape memory behaviour, the materials have displayed a significant two-way shape memory response, undergoing a reversible elongation-contraction process between two distinguished strain levels when subjected to a constant load and cyclically heated/cooled on a temperature region spanning from below the crystallization temperature to above the melting temperature. The applied load and the cross-link density are revealed as key-parameters to obtain tailored actuations. Concurrent wide-angle X-ray diffraction (WAXD) and DSC analyses allowed to ascribe the effect to a structural evolution process occurring during melting and crystallization. [Display omitted]