Real-Time Packing Behavior of Core-Shell Silica@Poly(N-isopropylacrylamide) Microspheres as Photonic Crystals for Visualizing in Thermal Sensing

Abstract

Abstract:We grafted thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes from monodisperse SiO 2 microspheres through surface-initiated atom transfer radical polymerization (SI ATRP) to generate core-shell structured SiO 2 @PNIPAM microspheres (SPMs). Regular-sized SPMs dispersed in aqueous solution and packed as photonic crystals (PCs) in dry state. Because of the microscale of the SPMs, the packing behavior of the PCs in water can be observed by optical microscopy. By increasing the temperature above the lower critical solution temperature (LCST) of PNIPAM, the reversible swelling and shrinking of the PNIPAM shell resulted in dispersion and precipitation (three-dimensional aggregation) of the SPM in aqueous solution. The SPMs were microdispersed in a water layer to accommodate the aggregation along two dimensions. In the microdispersion, the SPMs are packed as PCs with microscale spacing between SPMs below the LCST. When the temperature is increased above the LCST, the microdispersed PCs exhibited a close-packed arrangement along two dimensions with decreased spacing between SPMs. The change in spacing with increasing temperature above the LCST resulted in a color change from red to blue, which could be observed by the naked eye at an incident angle. Thus, the SPM array could be applied as a visual temperature sensor.

Surface-Initiated Atom Transfer Radical Polymerization for the Preparation of Well-Defined Organic–Inorganic Hybrid Nanomaterials

“…Undoubtedly, silica nanoparticles are the most common and most widely used nanoparticles modified via the SI-ATRP method with various monomers including methyl acrylate (MA) [65], methyl methacrylate (MMA) [66], 2-hydroxyethyl acrylate (HEA) [67], styrene [68,69], 2-(dimethylamino)ethyl methacrylate [70], γ-methacryloxypropyltrimethoxysilane (PMPTS) [71], ( N , N -dimethylaminoethyl methacrylate (DMAEMA) [72,73,74,75], poly(ethylene glycol) methacrylate [76,77], NIPAM [78,79,80,81], tert -butyl acrylate ( t BA) [35,82], di(ethylene glycol) methyl ether methacrylate (DEGMA) [83] and other monomers [54,80,84,85,86,87]. These hybrid nanomaterials combine the advantages of nanoparticles including its rigidity and stability and organic polymer layers characterized by flexibility, processability and functionality to enlarge the potential applications such nanohybrids.…”

“…Therefore, efficient way of obtaining modern materials responding to external stimuli are intensively sought. The most frequently proposed solution is grafting from the surface of NPs (co)polymer brushes containing thermo-sensitive PNIPAM as a building segment [78,79,80,81].…”

“…More recently, the synthesis of silica nanoparticles modified with thermo-sensitive PNIPAM brushes to produce inorganic-organic microspheres with core/shell structure (SPM) was described [79]. Then SPM was dispersed in aqueous solution and packed as photonic crystals (PC) in a dry state, thereafter using optical microscopy the packing behavior of photonic crystals was observed.…”

Conformation Study of Dual Stimuli-Responsive Core-Shell Diblock Polymer Brushes

“…Spherical polymer brushes have good stability, wettability, stimuli responsiveness, and so on [1,2,3,4,5]. Therefore, they have been widely used in the field of sensors [6,7,8], drug loading [9], protein separation [10], antifouling materials [11,12], nano-metal catalysis [13], and Pickering emulsion [14]. At present, the most widely used stimuli-responsive polymer brushes have one or more stimuli responses, such as pH [6,15], salt concentration [16], temperature [5,17], light [18], and magnetic response [4,19].…”

Selective and Colorimetric Detection of p-Nitrophenol Based on Inverse Opal Polymeric Photonic Crystals

“…Photonic crystals, consisting of periodic arrangements of dielectric materials with different refractive indexes, produce color when the photonic stop bands are located in the visible range [9][10][11][12][13][14][15][16][17][18]. Because the response process of photonic crystals can be directly expressed by light diffraction signals (the structure color "naked eye" can be seen) without any marking technology or any other analytical instruments, much attention has been paid to it in the field of sensor design and application [19][20][21][22][23][24][25][26][27][28][29][30][31]. In a previous work we prepared a novel carbonate ion sensor for detection of carbonate ions by the naked eye based on inverse opal polymeric photonic crystals (IOPPCs) [32].…”