Fabrication and photoactivity of a tunable-void SiO₂–TiO₂core–shell structure on modified SiO₂nanospheres by grafting an amphiphilic diblock copolymer using ARGET ATRP

Abstract

SiO₂-based composites have important applications in various technological fields. In this work, a tunablevoid SiO₂-TiO₂ core-shell structure was successfully prepared for the first time using SiO₂-polymethyl methacrylate (PMMA)-polyoligo(ethylene glycol)methyl ether methacrylate (PO(EO)nMA) (n = 2, 5, and 8). An amphiphilic copolymer was used as the template, and calcination was performed using tetrabutyl titanate (TBT) as the titanium source. SiO₂-PMMA-b-PO(EO)nMA microspheres were first synthesized through activators regenerated by electron transfer-atom transfer radical polymerization. Methyl methacrylate and O(EO)nMA were grafted with different EO unit numbers onto the surface of the halogen functional group of SiO₂. TBT was hydrolyzed along with the PO(EO)nMA chain through hydrogen bonding, and then the SiO₂-TiO₂ core-shell structure was acquired through calcination to remove the polymer. Simultaneously, amorphous TiO₂ crystallized during calcination. A series of characterizations indicated that the amphiphilic block copolymer was grafted onto SiO₂ mesoparticle surfaces, the titania samples existed only in the anatase phase, and the prepared SiO₂-TiO₂ had hierarchically nanoporous structures. The gradient hydrophilicity of the PMMA-b-PO(EO)nMA copolymer template facilitated the hydrolysis of TBT molecules along the PO(EO)nMA to PMMA segments, thereby tuning the space between the core and the shell. In addition, the space was about 6 nm when the EO number was 2, and the space was about 10 nm when the EO numbers were 5 and 8. The photocatalytic activities of the SiO₂-TiO₂ materials were tested on the photodegradation of methyl orange.

Polymer brushes grafted from graphene via bioinspired polydopamine chemistry and activators regenerated by electron transfer atom transfer radical polymerization

“…ARGET‐ATRP is a potentially more industrially attractive technique. Surface‐initiated ARGET‐ATRP has shown to be an efficient technique to graft various materials with different polymers, to give some examples: poly(acrylic acid) has been grafted to P(St‐AA)/Fe 3 O 4 composite microspheres for biology use; poly(methyl methacrylate)‐polyoligo (ethylene glycol) methyl ether methacrylate has been grafted to SiO 2 , which was used as photo‐catalyst for environmental purification . Moreover, ARGET‐ATRP has also been used in many other materials surface modification, including quantitative cell, silica, MWCNT, poly (globalide) films, wood, and so on.…”

Grafting pH‐sensitive poly[2‐(diethylamino)ethyl methacrylate] modification of vesicular silica with activator regenerated by electron transfer atom transfer radical polymerisation for controlled drug release

“…A new adsorption peak in comparison with VS at 1530 cm −1 is the typical absorption peak of NH 2 present on the surface of VS‐NH 2 (Fig. 4, spectra b ) [23, 24]. The peaks at 2900, 1280 and 1380 cm −1 (Fig.…”

Conformational transitions of a weak polyampholyte

“…One principal advantage of polyampholytes is that their association and stabilization behavior can be easily regulated by adjusting solution pH. This leads to many potential applications 5 and considerable interest in experimental, [33][34][35][36][37][38][39][40] theoretical, 2, 28, 41-45 and simulation [46][47][48][49][50][51][52][53][54][55][56] studies of polyampholytes. The conductivity, viscosity, as well as coil size of random polyampholytes have a minimum at the isoelectric conditions where there are equal numbers of positive and negative charges on the polymer backbone.…”