Towards Novel Light-Activated Shape Memory Polymer: Thermomechanical Properties of Photo-responsive Polymers

Abstract

The basic principle for the operation of a thermally stimulated shape memory polymer (SMP) is a drastic change in elastic modulus above the glass transition temperature (T g ). This change from glassy modulus to rubbery modulus allows the material to be deformed above the T g and retain the deformed shape when cooled below the T g . The material will recover its original shape when heated above the T g again. However, thermal activation is not the only possibility for a polymer to exhibit this shape memory effect or change of modulus. This paper discusses results of an alternative approach to SMP activation.It is well known that the T g of a thermosetting polymer is proportional to its crosslinking density. It is possible for the crosslinking density of a room temperature elastomer to be modified through photo-crosslinking special photo-reactive monomer groups incorporated into the material system in order to increase its T g . Correspondingly, the modulus will be increased from the rubbery state to the glassy state. As a result, the material is transformed from an elastomer to a rigid glassy photoset, depending on the crosslinking density achieved during exposure to the proper wavelength of light. This crosslinking process is reversible by irradiation with a different wavelength, thus making it possible to produce light-activated SMP materials that could be deformed at room temperature, held in deformed shape by photo-irradiation using one wavelength, and recovered to the original shape by irradiation with a different wavelength.In this work, monomers which contain photo-crosslinkable groups in addition to the primary polymerizable groups were synthesized. These monomers were formulated and cured with other monomers to form photo-responsive polymers. The mechanical properties of these materials, the kinetics, and the reversibility of the photo-activated shape memory effect were studied to demonstrate the effectiveness of using photo-irradiation to effect change in modulus (and thus shape memory effect).

Recent Advances in Functional Polymers Containing Coumarin Chromophores

“…SMPs change their shape when a particular stimulus is applied such as light [181], heat [182], electric field [183], magnetic field [184], sonic field [185], solvent ions [186], pH value [187], specific antigen-antibody interactions [188] and others. Due to this unique feature, they are successfully applied as smart medical devices [189,190], thermal sensors and actuators [191][192][193], and smart textiles [194]. In 2005, Lendlein et al have reported an approach of introducing photosensitive functional groups into a polymer matrix to prepare optically triggered SMPs [195].…”

A Brief Review of Stimulus-active Polymers Responsive to Thermal, Light, Magnetic, Electric, and Water/Solvent Stimuli

“…Light as a stimulus is exclusively efficient as it is easily available in the environment and does not include the use of seconday source of energy such as heat, electricity, or magnetic field, and hence it is environmental friendly. Light-active polymers have been proposed to be used in bioseparation (Wang et al, 2008), spring-lock truss elements for large boom structures, solar sails, morphing skins of aircrafts (Havens et al, 2005;Snyder and Tong, 2005;Dietsch and Tong, 2007), remotely triggered drug delivery systems (Wischke et al, 2009), cardiovascular therapeutic device (Maitland et al, 2002;Small et al, 2005b,c;Yakacki et al, 2007), medical stents (Small et al, 2005b(Small et al, ,c, 2007Lendlein, 2006), recordable and erasable memories (Kamenjicki et al, 2003, microrobots in medicine or optical microtweezers (Yu and Ikeda, 2005), optical storage (Chen et al, 2008), valves and switches in microdevices (Ikeda et al, 2003;Yu et al, 2003;Lendlein et al, 2005b;Jiang et al, 2006), and light-modulators and display devices (Akashi et al, 2002).…”

Responses of rings with light-activated shape memory polymers regulated by neural network and phase shift

“…Light-activated shape memory polymer (LaSMP) is a special kind of SMPs. LaSMP realizes the shape memory function through reversible photochemical reactions structures (Lendlein et al, 2005;Snyder and Tong, 2005). The photochemical reactions occur with the stimulus of ultraviolet lights and do not generate heat (Jin et al, 2011).…”