Research And Application Of Polymerized Microgel Colloidal Crystals

Stimuli-responsive microgels are now widely used as biomaterials.However,the large-scale production of colloidal crystal hydrogel and artificial defected colloidal crystal which are made of microgels is still a challenge.In this paper,depending on the thermoresponsive microgel poly(N-isopropylacrylamide)(PNIPAM),some efforts have been made to solve the problems of crosslinking colloidal crystal and fabricating artificial defected colloidal crystal and synthesizing stimulus responsive microgels.First of all,a facile method to crosslink microgel colloidal crystals is proposed.PNIPAM microgels with vinyl groups on their surface self-assemble into highly ordered colloidal crystals.Thenthe ordered structureislocked by light-initiated free-radical polymerization of the surface-bonded vinyl groups.The resulting polymerized microgel colloidal crystals(PMCC)can respond to both temperature andsalt reversibly,and the bandgap can be tuned in a wide range.Compared with colloidal crystals embedded in a hydrogel matrix,the swelling of the microgel particles is almost unaltered.In addition the response of PMCC is quite fast.Then,glucose sensitive PMCC is developed as a glucose colorimetric sensor.Core-shell microgels that are modified with vinyl groups on the shellself-assemble into highly ordered colloidal crystals.The ordered structure is locked by light-initiatedfree-radical polymerizations of the vinyl groups on the shell of particles,andthenthe core of microgel is modified with 3-aminophenylboronic acid.The resulting PMCC,which is also called GPMCC,can respond to temperature as well asglucose concentration reversibly,and the bandgap can be tuned in the whole visuable range.Although the response of GPMCC responding to the glucose concentration is not faster than which of PMCC responding to salt concentration,compared with ordinary glucose responsive hydrogel,the response of GPMCC is quite fast,much closer to which of microgels.In addition,a facile methodis proposedto fabricate controllable artificial defected colloidalcrystals.PNIPAM and P(NIPAM-co-AAc)microgels which have the same diameterare mixed and can self-assemble into ordered colloidal crystals.The ordered structure is embedded in acrylamide(AAm)matrix forming polymerized colloidal crystal arrays(PCCA).When pH is above the pKa of AAc,P(NIPAM-co-AAc)microgel particles swell,the defect mode appears and the pass band arises in the bandgap of the PCCA.Copmared with doping impurity colloidal spheres of different sizes,the ordered structure is not affected.Moreover,the artificial defect in colloidal crystal can be inserted and erasered by pH and temperature reversibly.Moreover,core-shell microgels are designed to synthesis photo-responsive microgels.The inner core is silver nano-prism while the middle part and the outer shell are SiO2 and PNIPAM,respectively.The silver nano-prisms have very strong surface plasmon resonances at the near infrared region,and the light energy can be absorbed and transfers into thermal energy.With the temperature increasing of the silver nano-prism in the core,the outer thermoresponsive PNIPAM deswell,which causes the diameter to decrease and the turbidityto increase.The resulting photo-responsive microgels respond to near infrared light reversibly and the responseis quite fast.