Facile synthesis of silica-polymer hybrids via simultaneous RAFT process and hydroxyl-alkoxysilane coupling reaction

Abstract

This study aimed at the synthesis of silica particles grafted with better-defined homopolymers and block copolymers by tandem approach. Z-functionalized Sbenzyl S'-(3-trimethoxysilyl)propyltrithiocarbonate (BTPT) was used as a couplable RAFT agent to synthesize the target inorganic-organic hybrids. Simultaneous coupling reaction and RAFT process using silica particles and BTPT as raw materials efficiently afforded homopolymers grafted silica, and RAFTsynthesized macro chain transfer agents with ω-terminal trimethoxysilane moiety were utilized to mediate graft reaction to prepare silica particles grafted with di-, tri-and tetrablock copolymers comprised of polymer segments such as polystyrene, polyacrylamides and polyacrylates. When the grafted chains had molecular weights ranging between 3920 and 24800 g/mol, the molar grafting ratios, which were dependent on reaction conditions and types and compositions of grafted chains, were estimated to be in the range of 15.2-101 μmol/g, and grafted polymers usually had polydispersity indices lower than 1.3, revealing that the grafting process was almost controllable. To the best of our knowledge, this versatile tandem approach is one of the most facile techniques to prepare silica particles grafted with polymeric chains with controlled molecular weight, low polydispersity and precise composition due to its minimal reaction steps, mild conditions, straightforward synthesis and satisfactory controllability.

Facile synthesis of silica nanoparticles grafted with quaternized linear, comblike and toothbrushlike copolymers

“…The one-pot method comprising concurrent coupling reaction and controlled radical polymerization has been proven efficient to generate well-defined polymers grafted solid substrates such as silica particles and graphene oxide. 16,[30][31][32] Our previous studies revealed that the quaternization reaction and RAFT polymerization could be simultaneously conducted to construct complex macromolecular architectures such as miktoarm star and toothbrushlike copolymers. [72][73][74] Herein tandem quaternization and RAFT processes were used to generate toothbrushlike copolymer grafted silica, in which the side chains were formed during concurrent coupling and polymerization based on BBCP, and the handle comprising linear chains was generated by chain extension polymerization mediated by the terminal dithiobenzoate moieties of PDMA grafts.…”

“…Surface-initiated controlled radical polymerization techniques involving reversible addition-fragmentation chain transfer (SI-RAFT) polymerization have been efficiently used to prepare silica-polymer hybrid materials, in which the graft reaction can be conducted via either "grafting to" or "grafting from" approach. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] The former affords a straightforward route to give the target hybrids with relatively low grafting density due to steric hindrance, whilst the latter allows the formation of silica-polymer hybrids with a higher grafting density although side reactions may lead to structural defects of grafted chains. SI-RAFT can be performed via either stepwise or tandem approach, however, the examples on tandem synthesis of polymer grafted solid substrates are very scarce thus far.…”

“…SI-RAFT can be performed via either stepwise or tandem approach, however, the examples on tandem synthesis of polymer grafted solid substrates are very scarce thus far. 16,[30][31][32][33][34][35] For example, Ranjan et al utilized tandem RAFT polymerization and click chemistry to synthesize PSt grafted silica nanoparticles with a grafting density up to 0.51-0.70 chains nm -2 , 16 and we have combined simultaneous RAFT process and linking reaction such as the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and the alkoxysilane-hydroxyl coupling reaction to synthesize silica particles 30,31 and graphene oxide 32 grafted with a series of linear polymers up to tetrablock copolymers. As compared with the traditional stepwise method, the tandem approach is more promising due to significant advantages in terms of labor, time and cost, and thus it is extremely important to further extend this method to prepare functional hybrids.…”