Scott Timothy F, Schneider Andrew D, Cook Wayne D, Bowman Christopher N
Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
Science. 2005 Jun 10;308(5728):1615-7. doi: 10.1126/science.1110505.
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.
化学交联聚合物本质上受到聚合过程中凝胶化后体积变化所引入的应力的限制。在不相应损失材料性能或产生大量应力的情况下，改变交联聚合物的形状也很困难。我们展示了一种交联聚合物，在光照下，它能表现出应力和/或应变松弛，而材料性能没有任何相应变化。通过聚合物基质中残留光引发剂的光裂解引入自由基，然后通过中链官能团的加成-断裂链转移进行扩散，从而实现这一结果。这些过程导致光致可塑性、驱动和平衡形状变化，且无残余应力。此类聚合物材料对于微器件、生物材料和聚合物涂层的开发至关重要。
