Brush macro‐RAFT agent mediated dispersion polymerization of styrene in the alcohol/water mixture

Abstract

Dispersion RAFT polymerization of styrene in the alcohol/water mixture mediated with the brush macro‐RAFT agent of poly[poly(ethylene oxide) methyl ether vinylphenyl‐co‐styrene] trithiocarbonate [P(mPEGV‐co‐St)‐TTC] with similar molecular weight but different chemical composition is investigated. Well‐controlled RAFT polymerization including an initial slow homogeneous polymerization and a subsequent fast heterogeneous polymerization at almost complete monomer conversion is achieved. The molecular weight of the synthesized block copolymer increases linearly with the monomer conversion, and the polydispersity is relatively narrow (PDI < 1.3). The RAFT polymerization kinetics is dependent on the chemical composition in the brush macro‐RAFT agents, and those with high content of hydrophobic segment lead to fast RAFT polymerization. The growth of the block copolymer nano‐objects during the RAFT polymerization is explored, and various block copolymer nano‐objects such as nanospheres, worms, vesicles and large‐compound‐micelle‐like particles are prepared. The parameters such as the chemical composition in the brush macro‐RAFT agent, the chain length of the solvatophobic block, the concentration of the feeding monomer and the solvent character affecting the size and morphology of the block copolymer nano‐objects are investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3177–3190

Polymerization-induced self-assembly of block copolymer nanoparticles via RAFT non-aqueous dispersion polymerization

“…There are various studies describing dispersion polymerization syntheses conducted in water/(m)ethanol or water/1,4-dioxane mixtures [42][43][44][45][46][47][48][49][50][51]. However, in this review article we will focus on examples of RAFT dispersion polymerization in the absence of water as a cosolvent.…”

Macro-RAFT agent mediated dispersion polymerization: the monomer concentration effect on the morphology of the in situ synthesized block copolymer nano-objects

“…This shoulder is possibly ascribed to the slight bimolecular radical termination in the RAFT polymerization at the high monomer conversion as discussed elsewhere. 57 All together, these results suggest that the PEG 45 -TTC macro-RAFT mediated dispersion polymerization affords good control both on the PEG-b-PS diblock copolymer molecular weight and on the molecular weight distribution. The in situ synthesized PEG 45 -b-PS diblock copolymer nano-objects through the dispersion RAFT polymerization at different polymerization time are checked by TEM, and the TEM images are summarized in Figure 6.…”

“…By carefully checking the entrant in the vesicles, four entrapped vesicles of 1, 2, 3 and 4 as shown by the high-resolution TEM images are classified. In the general macro-RAFT agent mediated dispersion RAFT polymerization at low or moderate monomer conversion, the morphology evolution from nanospheres to worms and finally to vesicles have been found, [47][48][49][50][51][52][53][54][55][56][57][58][59][60] and the reason is ascribed to the increasing interfacial curvature between the solvophilic and solvophobic blocks with the extension of the solvophobic block during the RAFT polymerization. Clearly, the present PEG 45 -TTC macro-RAFT agent mediated dispersion polymerization at high monomer concentration affords new morphology of the PEG-b-PS diblock copolymer including the porous nanospheres, the bicontinuous nanospheres and the entrapped vesicles, which is much different from the dispersion RAFT polymerization under low or moderate monomer concentration.…”

“…First, the polymerization degree (DP) of the solvophobic block is found to be firmly correlative to the morphology of the in situ synthesized block copolymer nanoobjects, and the morphology of the block copolymer nanoobjects usually undergoes the transition from nanospheres to worms and finally to vesicles with the increasing DP of the solvophobic block during the dispersion RAFT polymerization. [47][48][49][50][51][52][53][54][55][56][57][58][59][60] Second, the chain length of the macro-RAFT agent, which forms the solvophilic block of the in situ synthesized block copolymer, also exerts great influence on the morphology of the block copolymer nano-objects. [52][53][54][55][56][57][58] It is found that, the long macro-RAFT agent leads favorably to block copolymer nanospheres and the short macro-RAFT agent leads favorably to block copolymer vesicles.…”

“…46,[56][57][58] By tuning the aforementioned parameters, block copolymer nano-objects with various morphologies such as nanospheres, nanorods, nanowires, and vesicles were prepared through dispersion RAFT polymerization. [47][48][49][50][51][52][53][54][55][56][57][58][59][60] Compared with the numerous reports on the block copolymer composition affecting the morphology of the block copolymer nano-objects, [47][48][49][50][51][52][53][54][55][56][57][58][59][60] the monomer concentration affecting the morphology of the in situ synthesized block copolymer nano-objects during the dispersion RAFT polymerization is inappropriately neglected, 56,57 although it is revealed that some interesting block copolymer morphologies such as multi-layered vesicles has been prepared at 50 wt% concentrated monomer concentration under dispersion condition. 44 In this study, the poly(ethylene glycol) trithiocarbonate macro-RAFT agent mediated dispersion polymerization of styrene in the alcoholic solvent under different monomer concentration is performed, and the monomer concentration affecting the morphology of the in situ synthesized nanoobjects of the poly(ethylene glycol)-block-polystyrene (PEG-b-PS) diblock copolymer is investigated.…”