Photoinduced Plasticity in Cross-Linked Polymers

Abstract

Chemically cross-linked polymers are inherently limited by stresses that are introduced by post-gelation volume changes during polymerization. It is also difficult to change a cross-linked polymer's shape without a corresponding loss of material properties or substantial stress development. We demonstrate a cross-linked polymer that, upon exposure to light, exhibits stress and/or strain relaxation without any concomitant change in material properties. This result is achieved by introducing radicals via photocleavage of residual photoinitiator in the polymer matrix, which then diffuse via addition-fragmentation chain transfer of midchain functional groups. These processes lead to photoinduced plasticity, actuation, and equilibrium shape changes without residual stress. Such polymeric materials are critical to the development of microdevices, biomaterials, and polymeric coatings.

Molecular dynamics studying on welding behavior in thermosetting polymers due to bond exchange reactions

“…[3][4][5][6][7][8] CANs are classied into two types, where the dynamic structures are achieved either by reversible depolymerization with equilibrium shiing, as in the classic Diels-Alder (DA) reaction, [9][10][11][12][13] or through the recently developed bond exchange reactions (BERs). No matter which mechanism is chosen, CANs exhibit two features not found in traditional thermosetting polymers: malleability resulting from signicant stress relaxation, [14][15][16] and surface welding. 15,17 To further illustrate the process of BERbased surface welding effect, we drew a schematic graph as shown in Fig.…”

Photo-induced phenomena in chalcogenide glass: Comparison with those in oxide glass and polymer

“…Marked volume changes [9,10,15], anisotropic deformations [10,15,19], fluidity [20,21], and mechanical motions [22,23] can be induced commonly.…”

Understanding the Behaviour of Sulphur-Centred Radicals During Polymer Self-Healing

“…Dynamic covalent systems utilise functional groups that are capable of reacting reversibly to form cross-links. They are designed so that the equilibrium position of the cross-linking reaction can be externally manipulated by chemical stimulation [11,12], thermal stimulation [13][14][15] and photostimulation [16][17][18]. Photostimulation is especially promising for commercial applications as repair can occur at room temperature, is easy to handle, and targeted areas can be healed by limited exposure.…”