Preparation And Properties Of Functionalized Photonic Crystal Hydrogel Film

In this thesis,two kinds of functionalized light-responsive hydrogel membranes were developed with carboxymethyl cellulose(CMC)hyedrogel and photonic crystals.Characteristic transmittance and reflectance spectra were used as the responsive signals.The spectra can respond fast towards different solvent systems and external forces.The self-assembly defect of photonic microspheres was analyzed,and an improved approach,i.e.,surface modification of the microspheres was proposed to enhance the self-assembly capacity and the resulting interfacial binding strength.The main research results are listed below:(1)CMC and polyvinyl alcohol(PVA)were used to construct a natural polymer based hydrogel membrane.Because of the addition of CMC,the hydrogel membrane shows excellent mechanical property and biological adhesion.Polystyrene(PS)microspheres were synthesized by emulsion polymerization,which can spontaneously assemble to exhibit characteristic transmissivity as responsive signals.Specifically,the PS microspheres were casted on the CMC/PVA membrane to form a light-responsive hydrogel device.This device can successfully work as a new rewritable substrate by using water as the trigger to tune the bandgap of photonic coatings on the hydrogel.Various transmissivity values are also achieved by adjusting the p H value and solvent environments.(2)The imperfection of the self-assembled PS photonic crystals was then analyzed.The results show that photonic crystals formed relying only on conventional interaction forces between microspheres had great defects.In order to solve this issue,an improved scheme for surface modification of photonic microspheres was studied.Carboxylated PS(PS@AA)microspheres with a special core-shell structure were synthesized.By adjusting the size of PS@AA microspheres,three kinds of photonic crystals with different characteristic visual structural colors(yellow,green and blue)were constructed.The PS@AA microspheres can be effectively assembled to form a highly reflective and ordered structure.It won’t be destroyed after water dripping,even grown on the wet hydrogel interface.(3)A mechanochromic stretchable photonic hydrogel sensor was fabricated from CMC-based hydrogel with a compression-assistant self-assembly method.The substrate of the sensor is composed of CMC and acrylamide(AAm),and the photonic core-shell structured PS@AA microspheres as the responsive units.A novel semicrystalline photonic structure(SPS)interface is obtained after compression-assistant self-assembly process.The hydrogel with a SPS interface can realize the intelligent response towards external stress or deformation,resulting in characteristic reflective changes.This thin SPS interface has lots of advantages including vivid,patch-like,noniridescent,unfading,smart and highly sensitive structural colors.