Synthesis And Property Research Of Responsive Janus Materials

Janus materials with two compositions distinctly compartmentalized onto the same object, have attracted considerable attention due to their anisotropic characteristics in composition and shape. It is the key to synthesize Janus materials with more functionality and precise control of composition in large scale. The functional polymer is introducted to the Janus materials. The functionalized Janus materials have excellent performance. The detailed contents are as below.1. Base on ROP and ATRP methods, hydroxide functionalized silica nanoparticles are used as sacrificial templates to graft poly(ε-caprolactone)(PCL) and poly(2-(diethylamino) ethyl methacrylate)(PDEAEMA) respectively forming bi-layers polymeric shell. After etching the silica core with HF solution, polymeric JHSs are obtained. The inner layer is the biodegradable PCL brush and the outer layer is composed of crosslinked p H-responsive PDEAEMA. Using this approach, we can well control the thickness, size and composition of the JHSs by adjusting the molecular weight of the polymers, the size of the template particles and the kinds of the as-used monomers. The hydrophobic PCL brush forms the biodegradable inner layer and the partial crosslinked PDEAEMA forms p H-responsive outer layer of the JHSs, respectively. For the hydrophobic PCL interior surface of the JHSs, it can selectively load hydrophobic materials into the cavities. Meanwhile, the transfer of materials through the PDEAEMA outer layer could be controlled by adjusting p H for its p H response. Thus these as-formed JHSs are favorable to be utilized as drug carriers.2. Silica Janus nanosheets are synthesized by crushing the Janus hollow spheres. Different from the previous alkyl/amine silica Janus ones, the other side is terminated with Si-OH group instead of alkyl- group which facilitates a second termination of ATRP agent thereby. An ATRP agent is conjugated onto the aminegroup terminated side. A thermal responsive polymer PNIPAM is selectively grafted by ATRP. Afterwards, the Br- group is de-activated with Na N3. After a second conjugation of ATRP agent onto the Si-OH side, another ATRP polymerization is performed to graft a p H responsive PDEAEMA. The dually responsive Janus nanosheets are fabricated. Wettability of the two sides can be reversibly tunable between hydrophilic and hydrophobic by either changing temperature or p H. The Janus composite nanosheets serve as a responsive solid emulsifier, type and stability of the emulsions can be adjusted by simply changing p H or(and) temperature.