Hybrid polymeric materials comprising clay nanotubes, photothermal agents and phase change materials for food, water and energy applications

Official URL: https://risc01.sabanciuniv.edu/record=b2579501_(Table of contents)

In this thesis, different fundamental solutions have been offered on the concepts of ''saving food'', ''saving water'' and ''saving energy'' by preparing hybrid composite systems comprising different combinations of clay nanoparticles, photothermal agents and phase change materials. For the protection of food products, two main approaches were presented to prolong the shelf life of packaged food in the marketing and transportation stages. The first solution offered was the design of active food packaging materials with halloysite nanotubes having ethylene scavenging properties for the storage of fruits and vegetables. The second solution offered was the design of a food packaging material comprising halloysite nanotubes loaded with phase change materials that can buffer temperature fluctuations during the cold-chain transportation of food products. The particle quality of halloysite nanotubes were determined to play a critical role in these studies, which has led to an in-depth investigation of the effect of homogeneous size distribution and agglomeration-free quality of halloysite nanotubes on their loading/surface functionalization capacity and efficiency as reinforcing fillers in polymer nanocomposites. A novel three-step nanoparticle separation method was developed based on the surface modification of halloysite nanotubes with polydopamine, resulting in agglomeration-free halloysite nanotubes sorted in different size ranges. The surface modification of particles with polydopamine was further extended to a new material design that utilizes the light to thermal energy conversion capability of polydopamine. Waterborne polyurethane particles synthesized in the form of aqueous dispersions were coated with polydopamine, resulting in hybrid polydopamine-polyurethane dispersions. Films cast from these dispersions intrinsically showed light to thermal energy conversion ability and were demonstrated to have a huge potential in water purification by solar driven evaporation. Promising results obtained with polydopamine-polyurethane hybrid films led us to produce a multifunctional hybrid material that has solar to thermal energy conversion, thermal energy storage and thermal buffering properties. As a preliminary work to reach this goal the shape-stable latent heat storage concept was examined by using a zeolitic shape stabilizer and phase change materials. The acquired knowledge from this study was utilized to prepare form-stable phase change films by using the photothermal polydopamine-polyurethane polymer matrix and PEG4000 as phase change materials. In this study, PEG4000 was directly integrated into the polymer matrix at different ratios by dissolving in the aqueous polydopamine-polyurethane dispersion, resulting in form-stable phase change films, which present unique energy storage properties and have strong potential as thermoregulating materials.