@phdthesis{Kim2020,
  author    = {Kim, Seongjun},
  title     = {Nanoporous materials for optical applications},
  organization    = {INM - Leibniz-Institut f{\"u}r Neue Materialien},
  doi       = {10.22028/D291-32880},
  institution = {Functional Microstructures},
  school    = {Universit{\"a}t des Saarlandes},
  pages     = {VIII, 112 S.},
  year      = {2020},
  abstract  = {In this work, a new process of generating nanobubbles* in transparent polymers was developed. The azo-chemical initiators AIBN (Azobisisobutyronitrile) and ABVN (2,2'-Azobis(2,4-dimethylvaleronitrile)) were used as chemical blowing agents (CBA) that deliver nitrogen gas to form the bubbles. Specifically, the photo initiator Irgacure 819, which could be activated by a longer wavelength of UV (405 nm) than that of AIBN (345 nm), was added to the solution in order to minimize the decomposition of the azo chemicals during the first stage of sample preparation by UV-pre-curing. As a result, the CBAs remained unreacted, thus they could decompose and be used merely as a blowing agent. In addition, the post-foaming processes were conducted under the different foaming conditions to investigate critical factors affecting the nucleation and growth of bubbles. The results were discussed based on thermodynamics, mainly by conventional nucleation theory (CNT). Finally, stepwise optimization of those factors led to the generation of nanobubbles. This technique could be applicable to UV curable polymer systems in general. This novel approach was used to make prototype optical devices, such as security mark coating and light out-coupling in optical waveguide. This study also gives important information about the nucleation and growth of bubbles in meta-stable state of polymers, which could help to verify the background theories.},
  language  = {en}
}