| Solvent freezing,as a simple method for preparing porous materials with highly adjustable pore structure,has received wide attention from researchers in recent years.The prepared porous materials can be used in a variety of applications such as adsorption,scaffold,etc.However,there are some issues which need to be addressed before the method can be applied for large-scale manufacturing.The materials prepared for water phase systems are usually of poor water resistance,whereas those prepared for organo-phase systems require the use of non-environment-friendly organic solvents.This thesis presents a method of preparing porous materials by emulsion lyophilization.Commercial polyacrylate emulsions was used as raw materials,in which diacetone acrylamide and adipodihydrazide act as room-temperature cross-linkers.After freezing,a cross-linking reaction occurred to fix the pore morphology,followed by lyophilization to obtain porous materials.The prepared porous materials had good mechanical properties,which provided an elongation at break of 650%and were notch insensitive.By adjusting solid content of the emulsion,porosity of the materials can be tuned from 45%to 90%.The emulsions with different glass transition temperatures(Tgs)were mixed to obtain porous materials with multi-Tg.In addition to the adjustment of the mechanical properties,multi shape-memory effect can be achieved.Moreover,these porous materials also provided a good mechanical damping property.Utilizing the slow recovery character,tissue clips with improved clamping capability were demonstrated.This thesis also explored the preparation of porous materials by drying at ambient temperature after freezing via adjusting the ratios of different emulsions and adding PVA aqueous solutions with different concentration.This method avoids the high energy-consuming process of lyophilization and may be suitable for large-scale manufacturing... |
